№ 7. Immune system. AIDS. HIV.
Immune System
The body is able to defend itself against pathogens by means of a complex set of defenses. These defenses make up the body’s immune system. The reaction of the body against a foreign substance is called an immune response. Both nonspecific and specific defenses exist.
The immune system, which is made up of special cells, proteins, tissues, and organs, defends people against germs and microorganisms every day. In most cases, the immune system does a great job of keeping people healthy and preventing infections. But sometimes problems with the immune system can lead to illness and infection.
What the Immune System Does
The immune system is the body’s defense against infectious organisms and other invaders. Through a series of steps called the immune response, the immune system attacks organisms and substances that invade our systems and cause disease. The immune system is made up of a network of cells, tissues, and organs that work together to protect the body.
The cells that are part of this defense system are white blood cells, or leukocytes. They come in two basic types (more on these below), which combine to seek out and destroy the organisms or substances that cause disease.
Leukocytes are produced or stored in many locations throughout the body, including the thymus, spleen, and bone marrow. For this reason, they are called the lymphoid organs. There are also clumps of lymphoid tissue throughout the body, primarily in the form of lymph nodes that house the leukocytes.
The leukocytes circulate through the body between the organs and nodes by means of the lymphatic vessels. Leukocytes can also circulate through the blood vessels. In this way, the immune system works in a coordinated manner to monitor the body for germs or substances that might cause problems.
The two basic types of leukocytes are:
phagocytes, cells that chew up invading organisms
lymphocytes, cells that allow the body to remember and recognize previous invaders and help the body destroy them
A number of different cells are considered phagocytes. The most common type is the neutrophil, which primarily fights bacteria. If doctors are worried about a bacterial infection, they might order a blood test to see if a patient has an increased number of neutrophils triggered by the infection. Other types of phagocytes have their own jobs to make sure that the body responds appropriately to a specific type of invader.
Your Immune System.
There are two kinds of lymphocytes: the B lymphocytes and the T lymphocytes. Lymphocytes start out in the bone marrow and either stay there and mature into B cells, or they leave for the thymus gland, where they mature into T cells. B lymphocytes and T lymphocytes have separate jobs to do: B lymphocytes are like the body’s military intelligence system, seeking out their targets and sending defenses to lock onto them. T cells are like the soldiers, destroying the invaders that the intelligence system has identified. Here’s how it works.
The antibody and antigen.
Antigens are foreign substances that invade the body. When an antigen is detected, several types of cells work together to recognize and respond to it. These cells trigger the B lymphocytes to produce antibodies, specialized proteins that lock onto specific antigens. Antibodies and antigens fit together like a key and a lock.
Once the B lymphocytes have produced antibodies, these antibodies continue to exist in a person’s body, so that if the same antigen is presented to the immune system again, the antibodies are already there to do their job. That’s why if someone gets sick with a certain disease, like chickenpox, that person typically doesn’t get sick from it again. This is also why we use immunizations to prevent getting certain diseases. The immunization introduces the body to the antigen in a way that doesn’t make a person sick, but it does allow the body to produce antibodies that will then protect that person from future attack by the germ or substance that produces that particular disease.
Although antibodies can recognize an antigen and lock onto it, they are not capable of destroying it without help. That is the job of the T cells. The T cells are part of the system that destroys antigens that have been tagged by antibodies or cells that have been infected or somehow changed. (There are actually T cells that are called “killer cells.”) T cells are also involved in helping signal other cells (like phagocytes) to do their jobs.
Antibodies can also neutralize toxins (poisonous or damaging substances) produced by different organisms. Lastly, antibodies can activate a group of proteins called complement that are also part of the immune system. Complement assists in killing bacteria, viruses, or infected cells.
All of these specialized cells and parts of the immune system offer the body protection against disease. This protection is called immunity.
Nonspecific Defenses
Nonspecific defenses are those that act against all disease-causing organisms in the same way regardless of the biological nature of the organism. These defenses include the skin and the mucous membranes of the nose and mouth, which act as mechanical and chemical barriers to pathogens. Other nonspecific defenses are phagocytes, fever, and interferon, all of which act against pathogens that do enter the body.
Skin and Mucous Membranes
The layer of overlapping dead cells on the surface of the skin prevents pathogens from entering the body. A break in the skin may permit pathogens to enter body tissues. Blood clots then form a temporary barrier until new skin seals the wound.
The sweat, oils, and waxes produced by the skin contain chemical substances, such as lactic acid, that are poisonous to many bacteria and fungi. However, not all bacteria are harmful. Large populations of harmless bacteria living on the skin actually aid in protecting the body by inhibiting the growth of pathogens.
Mucous membranes defend the body against pathogens that enter through the mouth and nose. Mucus and tiny hairs in tbe-mouth and nose trap microorganisms. Enzymes in the mucus destroy pathogens. Pathogens that do reach body organs are met with other nonspecific defenses.
Phagocytes and Fever
An inflammatory response is one in which white blood cells gather and engulf the foreign substances and the body temperature rises. These white blood cells are phagocytes. Humans have two types of phagocytes—neutrophils and macrophages.
Neutrophils are small white blood cells with irregular nuclei. Neutrophils ingest small numbers of bacteria. Macrophages are large white blood cells that can engulf hundreds of bacteria. The action of the neutrophils and macrophages is usually accompanied with an increase in body temperature, or fever. If the fever is high enough, it can kill pathogens. A fever is not a disease but a symptom. It is a sign that the body is responding to an infection. However, if the infection is severe, fever itself can cause death.
A scanning electron microscope image of a single ntutrophil (yellow), engulfing anthrax bacteria (orange).
Interferon
Cells respond to a viral infection by producing a protein called interferon, which inhibits the reproduction of viruses.
Specific Defense
In a specific defense, one or more components of the immune system attack a specific pathogen. The immune system identifies specific chemicals on the surface of a pathogen and then targets that pathogen for destruction. Any substance that causes a specific immune response is called an antigen.
Specific defenses are of two types, one using cells, and the other using proteins. Both involve lymphocytes, which are special white blood cells. They exist in two primary forms—T cells and B cells. Their responses to antigens may be primary or secondary.
Immunity and Immune Disorders
A person who has a resistance to a specific pathogen is said to have immunity to it. Natural immunity is immunity that is present at birth. Acquired immunity is developed after birth.
One way of acquiring immunity is through vaccination. In vaccination an individual is exposed, usually by means of injection, to a killed or weakened form of a pathogen in order to produce immunity to the disease caused by the pathogen.
Antibiotics, drugs that fight bacterial infection, have made it possible for scientists and physicians to prevent and treat a large number of diseases. Sir Alexander Fleming (1881-1955), a British bacteriologist, discovered penicillin, one of the best-known antibiotics, in 1929.
The immune system is subject to various disorders. Normally suppressor cells prevent B cells from producing antibodies against nonpathogenic substances. In some individuals, however, the lymphocytes react to harmless antigens. These antigens, or allergens, include foods, pollen, and substances on animal fur. A reaction to an allergen is called an allergy.
At the first exposure to an allergen an individual may not have a noticeable reaction. Nevertheless, B cells may synthesize antibodies and develop memory cells. At the second exposure, the individual produces a secondary immune response. Antibodies and allergens bind together and cause the release of histamine, a chemical associated with the sneezing, watery and itchy eyes, and wheezing of allergies. Drugs called antihistamines help counteract the effect of histamines. In another type of disorder, autoimmune disease, the immune system produces antibodies against cells in the body because it fails to recognize them as self. In some cases, an antigen resembles one of the body’s own substances. Antibodies from the immune system may destroy this substance as well as the foreign antigen.
An antibody is made up of two heavy chains and two light chains. The unique variable region allows an antibody to recognize its matching antigen.
Immune Tolerance
Introduction
The immune system is precisely tuned to distinguish biochemical structures that belong to the body from those that do not, allowing it to swiftly deploy a potent array of defense mechanisms whenever evidence of a foreign invasion is found. However, many diseases, including autoimmune disorders, allergic diseases, and transplant rejection, are themselves caused by inappropriate immune system responses. To fight these disorders, researchers are now building on two decades of intensive basic research in immunology to develop treatments that can induce the immune system to tolerate specific antigens. Recent progress in the development of these therapies, which have the potential to be both very potent and broadly applicable, has been very encouraging.
All tolerance-induction strategies share a common goal: to selectively prevent or diminish specific harmful immune responses without disabling the immune system as a whole. In autoimmune diseases, the idea is to make the immune system tolerant to the specific, normally occurring antigens that cause it to attack the body’s own organs, tissues, or cells. In asthma and allergic diseases, the goal is to prevent responses to allergens such as cockroaches and house dust mites, which cause or exacerbate these diseases. For transplant rejection, the goal is to selectively block immune responses directed against the foreign antigens on the graft and thereby allow long-term graft survival without the heightened risks of infection, malignancy, and atherosclerosis associated with current immunosuppressive therapies.
Allergy
What does an allergy mean?
An allergy refers to an exaggerated reaction by our immune system in response to bodily contact with certain foreign substances. It is exaggerated because these foreign substances are usually seen by the body as harmless and no response occurs ion- allergic people. Allergic people’s bodies recognize the foreign substance and one part of the immune system is turned on. Allergy-producing substances are called “allergens.” Examples of allergens include pollens, dust mite, molds, danders, and foods. To understand the language of allergy it is important to remember that allergens are substances that are foreign to the body and can cause an allergic reaction in certain people.
When an allergen comes in contact with the body, it causes the immune system to develop an allergic reaction in persons who are allergic to it. When you inappropriately react to allergens that are normally harmless to other people, you are having an allergic reaction and can be referred to as allergic or atopic. Therefore, people who are prone to allergies are said to be allergic or “atopic.”
Austrian pediatrician Clemens Pirquet (1874-1929) first used the term allergy. He referred to both immunity that was beneficial and to the harmful hypersensitivity as “allergy.” The word allergy is derived from the Greek words “allos,” meaning different or changed and “ergos,” meaning work or action. Allergy roughly refers to an “altered reaction.” The word allergy was first used in 1905 to describe the adverse reactions of children who were given repeated shots of horse serum to fight infection. The following year, the term allergy was proposed to explain this unexpected “changed reactivity.”
Allergy Fact
It is estimated that 50 million North Americans are affected by allergic conditions.
The cost of allergies in the
Allergic rhinitis (nasal allergies) affects about 35 million Americans, 6 million of whom are children.
Asthma affects 15 million Americans, 5 million of whom are children.
The number of cases of asthma has doubled over the last 20 years.
What causes allergies?
To help answer this question, let’s look at a common household example. A few months after the new cat arrives in the house, dad begins to have itchy eyes and episodes of sneezing. One of the three children develops coughing and wheezing, especially when the cat comes into her bedroom. The mom and the other two children experience no reaction whatsoever to the presence of the cat. How can we explain this?
The immune system is the body’s organized defense mechanism against foreign invaders, particularly infections. Its job is to recognize and react to these foreign substances, which are called antigens. Antigens are substances that are capable of causing the production of antibodies. Antigens may or may not lead to an allergic reaction. Allergens are certain antigens that cause an allergic reaction and the production of IgE.
The aim of the immune system is to mobilize its forces at the site of invasion and destroy the enemy. One of the ways it does this is to create protective proteins called antibodies that are specifically targeted against particular foreign substances. These antibodies, or immunoglobulins (IgG, IgM, IgA, IgD), are protective and help destroy a foreign particle by attaching to its surface, thereby making it easier for other immune cells to destroy it. The allergic person however, develops a specific type of antibody called immunoglobulin E, or IgE, in response to certaiormally harmless foreign substances, such as cat dander. To summarize, immunoglobulins are a group of protein molecules that act as antibodies. There are five different types; IgA, IgM, IgG, IgD, and IgE. IgE is the allergy antibody.
In the pet cat example, the dad and the youngest daughter developed IgE antibodies in large amounts that were targeted against the cat allergen, the cat dander. The dad and daughter are now sensitized or prone to develop allergic reactions on subsequent and repeated exposures to cat allergen. Typically, there is a period of “sensitization” ranging from months to years prior to an allergic reaction. Although it might occasionally appear that an allergic reaction has occurred on the first exposure to the allergen, there must have been a prior contact in order for the immune system to be poised to react in this way.
IgE is an antibody that all of us have in small amounts. Allergic persons, however, produce IgE in large quantities. Normally, this antibody is important in protecting us from parasites, but not from cat dander or other allergens. During the sensitization period, cat dander IgE is being overproduced and coats certain potentially explosive cells that contain chemicals. These cells are capable of causing an allergic reaction on subsequent exposures to the dander. This is because the reaction of the cat dander with the dander IgE irritates the cells and leads to the release of various chemicals, including histamine. These chemicals, in turn, cause inflammation and the typical allergic symptoms. This is how the immune system becomes exaggerated and primed to cause an allergic reaction when stimulated by an allergen.
On exposure to cat dander, the mom and the other two children produce other classes of antibodies, none of which cause allergic reactions. In these non-allergic members of the family, the dander particles are eliminated uneventfully by the immune system and the cat has no effect on them.
Your immune system protects you in several ways:
· By creating a barrier that prevents bacteria and viruses from entering your body.
· By detecting and eliminating those bacteria or viruses that manage to get into the body, before they have a chance to reproduce and proliferate.
· Eliminating those viruses or bacteria that have managed to reproduce in sufficient numbers to start causing problems.
· Finding cancerous (or other unwanted cells) and eliminating them.
The most obvious parts of the immune system are the barriers we can easily see — like our skin, eyes, nose, and mouth. Skin is tough and resistant to bacteria and secretes antibacterial substances. Tears and mucus contain an enzyme that breaks down the cell walls of many bacteria. Saliva is also anti-bacterial. And if any microbes make it past the saliva, the acids in the stomach are the next level of protection.
Most bacteria and viruses do not get through the body’s first line of defenses. But some do, and once inside the body, the immune system deals with germs and microbes on a different level – the level of attack and conquer. For most people, viral and bacterial infections are the most common causes of illness. These usually run their course until the body builds up immunity to those particular microbes and recovers. But most people are most concerned with the internal workings of the immune system.
Who is at risk and why?
Allergies can develop at any age, possibly even in the womb. They commonly occur in children but may give rise to symptoms for the first time in adulthood. Asthma may persist in adults while nasal allergies tend to decline in old age.
Why, you may ask, are some people “sensitive” to certain allergens while most are not? Why do allergic persons produce more IgE than those who are non-allergic? The major distinguishing factor appears to be heredity. For some time, it has been known that allergic conditions tend to cluster in families. Your own risk of developing allergies is related to your parents’ allergy history. If neither parent is allergic, the chance that you will have allergies is about 15%. If one parent is allergic, your risk increases to 30% and if both are allergic, your risk is greater than 60%.
Although you may inherit the tendency to develop allergies, you may never actually have symptoms. You also do not necessarily inherit the same allergies or the same diseases as your parents. It is unclear what determines which substances will trigger a reaction in an allergic person. Additionally, which diseases might develop or how severe the symptoms might be is unknown.
Another major piece of the allergy puzzle is the environment. It is clear that you must have a genetic tendency and be exposed to an allergen in order to develop an allergy. Additionally, the more intense and repetitive the exposure to an allergen and the earlier in life it occurs, the more likely it is that an allergy will develop.
There are other important influences that may conspire to cause allergic conditions. Some of these include smoking, pollution, infection, and hormones.
Where are allergens?
Everywhere…
We have seen that allergens are special types of antigens that cause allergic reactions. The symptoms and diseases that result depend largely on the route of entry and level of exposure to the allergens. The chemical structure of allergens affects the route of exposure. Airborne pollens, for example, will have little effect on the skin. They are easily inhaled and will thus cause more nasal and lung symptoms and limited skin symptoms. When allergens are swallowed or injected they may travel to other parts of the body and provoke symptoms that are remote from their point of entry. For example, allergens in foods may prompt the release of mediators in the skin and cause hives.
We will assume that allergens are defined as: the source of the allergy producing substance (for example, cat), the substance itself (cat dander), or the specific proteins that provoke the immune response (for example, Feld1). Feld1, from the Felis domesticus (the domesticated cat), is the most important chemical allergen in cat dander.
Allergens may be inhaled, ingested (eaten or swallowed), applied to the skin, or injected into the body either as a medication or inadvertently by an insect sting.
Breathing can be hazardous if you are allergic. Aside from oxygen, the air contains a wide variety of particles; some toxic, some infectious, and some “innocuous,” including allergens. The usual diseases that result from airborne allergens are hay fever, asthma, and conjunctivitis. The following allergens are usually harmless, but can trigger allergic reactions when inhaled by sensitized individuals.
Types of allergies
People can be allergic to a wide variety of substances, the most common of which are pollen and dust mites.
Airborne allergens include:
• Pollen
Allergic rhinitis, or hay fever, is the allergic response to pollen. It causes inflammation
and swelling of the lining of the nose, as well as the protective tissue of the eyes
(conjunctiva).
Symptoms include sneezing, congestion, and itchy, watery eyes. Treatment options include over-the-counter and prescription antihistamines, nasal steroids, and nasal cromolyn. Other ways to help reduce symptoms include avoiding pollen exposure by staying indoors when pollen counts are high and closing windows and using air conditioning. Immunotherapy, or allergy shots, also may be used to treat pollen allergies.
Dust mites
Dust mites are microscopic organisms that live in dust and in the fibers of household objects not frequently laundered, such as pillows, mattresses, carpet, and upholstery. The symptoms of dust mite allergy are similar to those of pollen allergy, and also can produce symptoms of asthma such as wheezing and coughing. To help manage dust mite allergies, try using dust mite covers (airtight plastic / polyurethane covers) over pillows, mattresses, and box springs. Also, remove carpeting or vacuum frequently using a vacuum cleaner with high-efficiency filters. Treatment may include medications such as antihistamines or decongestants. Immunotherapy may be recommended for people whose symptoms are chronic.
• Molds
Molds are parasitic, microscopic fungi (like Penicillium) with spores that float in the air like pollen. Mold is a common trigger for allergies and can be found in, damp areas, such as the basement or bathroom, as well as in the outdoor environment in grass, leaf piles, hay, mulch, or under mushrooms.
Symptoms include sneezing; congestion; itchy, watery eyes; runny nose; and coughing.
Treatment options include antihistamines, nasal steroid sprays, and immunotherapy.
• Animal dander
The proteins secreted by oil glands in an animal’s skin, which are shed in dander, and the proteins present in an animal’s saliva cause allergic reactions in some people. Allergies to animals can take two or more years to develop, and symptoms may not subside until months after ending contact with the animal.
Symptoms include sneezing, congestion, and itchy, watery eyes.
Treatment involves avoiding exposure to the animals that cause your allergies.
Medications such as antihistamines or decongestants may be helpful. Immunotherapy may be recommended if you have severe symptoms from intermittent exposure.
Other allergens include:
Latex
Latex is a natural product which comes from the light milky fluid that is extracted from the rubber tree. This milky fluid is often modified during the manufacturing process to form a latex mixture. A person can be allergic to the latex or the mixture or both. Latex-containing products are many and varied (see the list below). One of two procedures is employed during the manufacturing of the latex-containing product. One procedure is “dipping,” wherein a form is dipped into a vat of latex and after drying, the latex product is washed and then peeled from the form. If the latex product is not washed well, as is the case with rushed production, more “free” latex is present on the surface. This “free” latex is responsible for a great deal of latex allergy. Dipped latex products include gloves, balloons and condoms. A much less allergic latex product is made by molding the latex. Products such as rubber stoppers and erasers are manufactured using this process. The powder of surgical gloves is a significant problem. Latex will easily stick to powder that is commonly used in surgical gloves.When the glove is placed on or taken off the hand the glove is frequently “snapped.” This snapping places the powder, with latex sticking to it, into the air. Inhaled latex can be a serious allergic problem.
Certain foods
Food allergies develop when there is an IgE antibody to a specific food. The allergens in food are those components that are responsible for inciting an allergic reaction. They are proteins that usually resist the heat of cooking, the acid in the stomach, and the intestinal digestive enzymes. As a result, the allergens survive to cross the gastrointestinal lining, enter the bloodstream, and go to target organs, causing allergic reactions throughout the body. The mechanism of food allergy involves the immune system and heredity.
The immune system, which is made up of special cells, proteins, tissues, and organs, defends people against germs and microorganisms every day. In most cases, the immune system does a great job of keeping people healthy and preventing infections. But sometimes problems with the immune system can lead to illness and infection.
About the Immune System
The immune system is the body’s defense against infectious organisms and other invaders. Through a series of steps called the immune response, the immune system attacks organisms and substances that invade body systems and cause disease.
Auto-immune diseases are those diseases in which the immune system.
The immune system is made up of a network of cells, tissues, and organs that work together to protect the body. The cells involved are white blood cells, or leukocytes, which come in two basic types that combine to seek out and destroy disease-causing organisms or substances.
Leukocytes are produced or stored in many locations in the body, including the thymus, spleen, and bone marrow. For this reason, they’re called the lymphoid organs. There are also clumps of lymphoid tissue throughout the body, primarily as lymph nodes, that house the leukocytes.
The leukocytes circulate through the body between the organs and nodes via lymphatic vessels and blood vessels. In this way, the immune system works in a coordinated manner to monitor the body for germs or substances that might cause problems.
The two basic types of leukocytes are:
1. phagocytes, cells that chew up invading organisms
2. lymphocytes, cells that allow the body to remember and recognize previous invaders and help the body destroy them
Lymphocytic infiltration in CRC tissue. CD4+ lymphocytes in CRC (A/B).
A number of different cells are considered phagocytes. The most common type is the neutrophil, which primarily fights bacteria. If doctors are worried about a bacterial infection, they might order a blood test to see if a patient has an increased number of neutrophils triggered by the infection. Other types of phagocytes have their own jobs to make sure that the body responds appropriately to a specific type of invader.
The two kinds of lymphocytes are B lymphocytes and T lymphocytes. Lymphocytes start out in the bone marrow and either stay there and mature into B cells, or they leave for the thymus gland, where they mature into T cells. B lymphocytes and T lymphocytes have separate functions: B lymphocytes are like the body’s military intelligence system, seeking out their targets and sending defenses to lock onto them. T cells are like the soldiers, destroying the invaders that the intelligence system has identified.
Here’s how it works:
When antigens (foreign substances that invade the body) are detected, several types of cells work together to recognize them and respond. These cells trigger the B lymphocytes to produce antibodies, specialized proteins that lock onto specific antigens.
Once produced, these antibodies continue to exist in a person’s body, so that if the same antigen is presented to the immune system again, the antibodies are already there to do their job. So if someone gets sick with a certain disease, like chickenpox, that person typically doesn’t get sick from it again.
This is also how immunizations prevent certain diseases. An immunization introduces the body to an antigen in a way that doesn’t make someone sick, but does allow the body to produce antibodies that will then protect the person from future attack by the germ or substance that produces that particular disease.
Although antibodies can recognize an antigen and lock onto it, they are not capable of destroying it without help. That’s the job of the T cells, which are part of the system that destroys antigens that have been tagged by antibodies or cells that have been infected or somehow changed. (Some T cells are actually called “killer cells.”) T cells also are involved in helping signal other cells (like phagocytes) to do their jobs.
Antibodies also caeutralize toxins (poisonous or damaging substances) produced by different organisms. Lastly, antibodies can activate a group of proteins called complement that are also part of the immune system. Complement assists in killing bacteria, viruses, or infected cells.
All of these specialized cells and parts of the immune system offer the body protection against disease. This protection is called immunity.
Immunity
Humans have three types of immunity — innate, adaptive, and passive:
Innate Immunity
Innate Immunity and HIV infection Pasteur
Everyone is born with innate (or natural) immunity, a type of general protection. Many of the germs that affect other species don’t harm us. For example, the viruses that cause leukemia in cats or distemper in dogs don’t affect humans. Innate immunity works both ways because some viruses that make humans ill — such as the virus that causes HIV/AIDS — don’t make cats or dogs sick.
Innate immunity also includes the external barriers of the body, like the skin and mucous membranes (like those that line the nose, throat, and gastrointestinal tract), which are the first line of defense in preventing diseases from entering the body. If this outer defensive wall is broken (as through a cut), the skin attempts to heal the break quickly and special immune cells on the skin attack invading germs.
Adaptive Immunity
The second kind of protection is adaptive (or active) immunity, which develops throughout our lives. Adaptive immunity involves the lymphocytes and develops as people are exposed to diseases or immunized against diseases through vaccination.
Passive Immunity
Passive immunity is “borrowed” from another source and it lasts for a short time. For example, antibodies in a mother’s breast milk provide a baby with temporary immunity to diseases the mother has been exposed to. This can help protect the baby against infection during the early years of childhood.
Everyone’s immune system is different. Some people never seem to get infections, whereas others seem to be sick all the time. As people get older, they usually become immune to more germs as the immune system comes into contact with more and more of them. That’s why adults and teens tend to get fewer colds than kids — their bodies have learned to recognize and immediately attack many of the viruses that cause colds.
Problems of the Immune System
Disorders of the immune system fall into four main categories:
· immunodeficiency disorders (primary or acquired)
· autoimmune disorders (in which the body’s own immune system attacks its own tissue as foreign matter)
· allergic disorders (in which the immune system overreacts in response to an antigen)
· cancers of the immune system
Immunodeficiency Disorders
Immunodeficiencies occur when a part of the immune system is not present or is not working properly. Sometimes a person is born with an immunodeficiency (known as primary immunodeficiencies), although symptoms of the disorder might not appear until later in life. Immunodeficiencies also can be acquired through infection or produced by drugs (these are sometimes called secondary immunodeficiencies).
Immunodeficiencies can affect B lymphocytes, T lymphocytes, or phagocytes. Examples of primary immunodeficiencies that can affect kids and teens are:
IgA deficiency is the most common immunodeficiency disorder. IgA is an immunoglobulin that is found primarily in the saliva and other body fluids that help guard the entrances to the body. IgA deficiency is a disorder in which the body doesn’t produce enough of the antibody IgA. People with IgA deficiency tend to have allergies or get more colds and other respiratory infections, but the condition is usually not severe.
Severe combined immunodeficiency (SCID) is also known as the “bubble boy disease” after a
DiGeorge syndrome (thymic dysplasia), a birth defect in which kids are born without a thymus gland, is an example of a primary T-lymphocyte disease. The thymus gland is where T lymphocytes normally mature.
Chediak-Higashi syndrome and chronic granulomatous disease both involve the inability of the neutrophils to function normally as phagocytes.
Acquired (or secondary) immunodeficiencies usually develop after someone has a disease, although they can also be the result of malnutrition, burns, or other medical problems. Certain medicines also can cause problems with the functioning of the immune system.
Acquired (secondary) immunodeficiencies include:
HIV (human immunodeficiency virus) infection/AIDS (acquired immunodeficiency syndrome) is a disease that slowly and steadily destroys the immune system. It is caused by HIV, a virus that wipes out certain types of lymphocytes called T-helper cells. Without T-helper cells, the immune system is unable to defend the body against normally harmless organisms, which can cause life-threatening infections in people who have AIDS. Newborns can get HIV infection from their mothers while in the uterus, during the birth process, or during breastfeeding. People can get HIV infection by having unprotected sexual intercourse with an infected person or from sharing contaminated needles for drugs, steroids, or tattoos.
Immunodeficiencies caused by medications. Some medicines suppress the immune system. One of the drawbacks of chemotherapy treatment for cancer, for example, is that it not only attacks cancer cells, but other fast-growing, healthy cells, including those found in the bone marrow and other parts of the immune system. In addition, people with autoimmune disorders or who have had organ transplants may need to take immunosuppressant medications, which also can reduce the immune system’s ability to fight infections and can cause secondary immunodeficiency.
Autoimmune Disorders
In autoimmune disorders, the immune system mistakenly attacks the body’s healthy organs and tissues as though they were foreign invaders. Autoimmune diseases include:
Lupus, a chronic disease marked by muscle and joint pain and inflammation (the abnormal immune response also may involve attacks on the kidneys and other organs)
Juvenile rheumatoid arthritis, a disease in which the body’s immune system acts as though certain body parts (such as the joints of the knee, hand, and foot) are foreign tissue and attacks them
Scleroderma, a chronic autoimmune disease that can lead to inflammation and damage of the skin, joints, and internal organs
Ankylosing spondylitis, a disease that involves inflammation of the spine and joints, causing stiffness and pain
Juvenile dermatomyositis, a disorder marked by inflammation and damage of the skin and muscles
Allergic Disorders
Allergic disorders occur when the immune system overreacts to exposure to antigens in the environment. The substances that provoke such attacks are called allergens. The immune response can cause symptoms such as swelling, watery eyes, and sneezing, and even a life-threatening reaction called anaphylaxis. Medications called antihistamines can relieve most symptoms.
Allergic disorders include:
Asthma, a respiratory disorder that can cause breathing problems, frequently involves an allergic response by the lungs. If the lungs are oversensitive to certain allergens (like pollen, molds, animal dander, or dust mites), it can trigger breathing tubes in the lungs to become narrowed and swollen, leading to reduced airflow and making it hard for a person to breathe.
Eczema is an itchy rash also known as atopic dermatitis. Although atopic dermatitis is not necessarily caused by an allergic reaction, it more often occurs in kids and teens who have allergies, hay fever, or asthma or who have a family history of these conditions.
Allergies of several types can occur in kids and teens. Environmental allergies (to dust mites, for example), seasonal allergies (such as hay fever), drug allergies (reactions to specific medications or drugs), food allergies (such as to nuts), and allergies to toxins (bee stings, for example) are the common conditions people usually refer to as allergies.
Cancers of the Immune System
Cancer occurs when cells grow out of control. This also can happen with the cells of the immune system. Leukemia, which involves abnormal overgrowth of leukocytes, is the most common childhood cancer. Lymphoma involves the lymphoid tissues and is one of the more common childhood cancers. With current medications most cases of both types of cancer in kids and teens are curable.
Although immune system disorders usually can’t be prevented, you can help your child’s immune system stay stronger and fight illnesses by staying informed about your child’s condition and working closely with your doctor.
Cancer immunology
Cancer immunology is the study of interactions between the immune system and cancer cells (also called tumors or malignancies). It is also a growing field of research that aims to discover innovative cancer immunotherapies to treat and retard progression of this disease. The immune response, including the recognition of cancer-specific antigens is of particular interest in this field as knowledge gained drives the development of new vaccines and antibody therapies. For instance in 2007, Ohtani published a paper finding tumour infiltrating lymphocytes to be quite significant in human colorectal cancer. The host was given a better chance at survival if the cancer tissue showed infiltration of inflammatory cells, in particular lymphocytic reactions. The results yielded suggest some extent of anti-tumour immunity is present in colorectal cancers in humans.
Over the past 10 years there has beeotable progress and an accumulation of scientific evidence for the concept of cancer immunosurveillance and immunoediting based on (i) protection against development of spontaneous and chemically induced tumors in animal systems and (ii) identification of targets for immune recognition of human cancer.
Immunosurveillance
Cancer immunosurveillance is a theory formulated in 1957 by Burnet and Thomas, who proposed that lymphocytes act as sentinels in recognizing and eliminating continuously arising, nascent transformed cells. Cancer immunosurveillance appears to be an important host protection process that inhibits carcinogenesis and maintains regular cellular homeostasis. It has also been suggested that immunosurveillance primarily functions as a component of a more general process of cancer immunoediting.
Immunoediting
Immunoediting is a process by which a person is protected from cancer growth and the development of tumour immunogenicity by their immune system. It has three main phases: elimination, equilibrium and escape. The elimination phase consists of the following four phases:
Elimination: Phase 1
The first phase of elimination involves the initiation of antitumor immune response. Cells of the innate immune system recognize the presence of a growing tumor which has undergone stromal remodeling, causing local tissue damage. This is followed by the induction of inflammatory signals which is essential for recruiting cells of the innate immune system (e.g. natural killer cells, natural killer T cells, macrophages and dendritic cells) to the tumor site. During this phase, the infiltrating lymphocytes such as the natural killer cells and natural killer T cells are stimulated to produce IFN-gamma.
Pharmacokinetic assessment of compstatin analogs ion-human primates.
Elimination: Phase 2
In the second phase of elimination, newly synthesized IFN-gamma induces tumor death (to a limited amount) as well as promoting the production of chemokines CXCL10, CXCL9 and CXCL11. These chemokines play an important role in promoting tumor death by blocking the formation of new blood vessels. Tumor cell debris produced as a result of tumor death is then ingested by dendritic cells, followed by the migration of these dendritic cells to the draining lymph nodes. The recruitment of more immune cells also occurs and is mediated by the chemokines produced during the inflammatory process.
Elimination: Phase 3
In the third phase, natural killer cells and macrophages transactivate one another via the reciprocal production of IFN-gamma and IL-12. This again promotes more tumor killing by these cells via apoptosis and the production of reactive oxygen and nitrogen intermediates. In the draining lymph nodes, tumor-specific dendritic cells trigger the differentiation of Th1 cells which in turn facilitates the development of CD8+ T cells.
Elimination: Phase 4
In the final phase of elimination, tumor-specific CD4+ and CD8+ T cells home to the tumor site and the cytolytic T lymphocytes then destroy the antigen-bearing tumor cells which remain at the site.
Equilibrium and Escape
Tumor cell variants which have survived the elimination phase enter the equilibrium phase. In this phase, lymphocytes and IFN-gamma exert a selection pressure on tumor cells which are genetically unstable and rapidly mutating. Tumor cell variants which have acquired resistance to elimination then enter the escape phase. In this phase, tumor cells continue to grow and expand in an uncontrolled manner and may eventually lead to malignancies. In the study of cancer immunoeditting, knockout mice have been used for experimentation since human testing is not possible. Tumor infiltration by lymphocytes is seen as a reflection of a tumor-related immune response.
Cancer Immunology and Chemotherapy
Obeid et al. investigated how inducing immunogenic cancer cell death ought to become a priority of cancer chemotherapy. He reasoned, the immune system would be able to play a factor via a ‘bystander effect’ in eradicating chemotherapy-resistant cancer cells. However, extensive research is still needed on how the immune response is triggered against dying tumour cells.
Professionals in the field have hypothesized that ‘apoptotic cell death is poorly immunogenic whereas necrotic cell death is truly immunogenic’. This is perhaps because cancer cells being eradicated via a necrotic cell death pathway induce an immune response by triggering dendritic cells to mature, due to inflammatory response stimulation. On the other hand, apoptosis is connected to slight alterations within the plasma membrane causing the dying cells to be attractive to phagocytic cells.
Thus Obeid et al. propose that the way in which cancer cells die during chemotherapy is vital. Anthracyclins produce a beneficial immunogenic environment. The researchers report that when killing cancer cells with this agent uptake and presentation by antigen presenting dendritic cells is encouraged, thus allowing a T-cell response which can shrink tumours. Therefore activating tumour-killing T-cells is crucial for immunotherapy success.
However, advanced cancer patients with immunosuppression have left researchers in a dilemma as to how to activate their T-cells. The way the host dendritic cells react and uptake tumour antigens to present to CD4+ and CD8+ T-cells is the key to success of the treatment.
The role of viruses in cancer development
Various strains of Human Papilloma Virus (HPV) have recently been found to play an important role in the development of cervical cancer. The HPV oncogenes E6 and E7 that these viruses possess have been shown to immortalise some human cells and thus promote cancer development.[20] Although these strains of HPV have not been found in all cervical cancers, they have been found to be the cause in roughly 70% of cases. The study of these viruses and their role in the development of various cancers is still continuing, however a vaccine has been developed that can prevent infection of certain HPV strains, and thus prevent those HPV strains from causing cervical cancer, and possibly other cancers as well.
A virus that has been shown to cause breast cancer in mice is Mouse Mammary Tumour Virus. It is from discoveries such as this and the role of HPV in cervical cancer development that research is currently being undertaken to discover whether or not Human Mammary Tumour Virus is a cause of breast cancer in humans.
What is the difference between viruses and bacteria?
Viruses and bacteria cause the majority of infections. Viruses cause most colds, flu, coughs, and sore throats. Bacteria cause most ear and sinus infections, strep throat, and urinary tract infections. Both bacteria and viruses can enter the body in many ways, including through inhalation, food, sexual contact, and skin contact.
Virus – Bacteria Differences
Viruses are the smallest and simplest life form known. They are 10 to 100 times smaller than bacteria.
The biggest difference between viruses and bacteria is that viruses must have a living host – like a plant or animal – to multiply, while most bacteria can grow oon-living surfaces.
Bacteria are intercellular organisms(i.e. they live in-between cells); whereas viruses are intracellular organisms (they infiltrate the host cell and live inside the cell). They change the host cell’s genetic material from its normal function to producing the virus itself.
There are some useful bacteria but all viruses are harmful.
Antibiotics can kill bacteria but not viruses.
An example of a disease caused by bacteria is strep throat and an example of an affliction caused by a virus is the flu.
Differences in reproduction
Bacteria carry all the “machinery” (cell organelles) needed for their growth and multiplication. Bacteria usually reproduce asexually. In case of sexual reproduction, certain plasmids genetic material can be passed between bacteria. On the other hand, viruses carry mainly information – for example, DNA or RNA, packaged in a protein and/or membranous coat. Viruses harness the host cell’s machinery to reproduce. Their legs attach onto the surface of the cell, then the genetic material contained inside the head of the virus is injected into the cell. This genetic material can either use the cell’s machinery to produce its own proteins and/or virus bits, or it can be integrated into the cell’s DNA/RNA and then translated later. When enough “baby” viruses are produced the cell bursts, releasing the new viral particles. In a sense, viruses are not truly “living,” but are essentially information (DNA or RNA) that float around until they encounter a suitable living host.
Structure and contents of a typical Gram positive bacterial cell.
Living vs. Non-living
Transmission electron microscope (TEM) image of a recreated 1918 influenza virus.
Bacteria are living organisms but opinions vary on whether viruses are. A virus is an organic structures that interacts with living organisms. It does show characteristics of life such has having genes, evolving by natural selection and reproducing by creating multiple copies of themselves through self-assembly. But viruses don’t have a cellular structure or their own metabolism; they need a host cell to reproduce. It should be noted that bacterial species such as rickettsia and chlamydia are considered living organisms despite the same limitation of not being able to reproduce without a host cell. See also: Virus – Life Properties
How do antibiotics work against infections?
Antibiotics can be used to treat bacterial infections. However, antibiotics are ineffective in treating virus-related illnesses. In addition, antibiotics treat specific bacteria and overuse or misuse of antibiotics can lead to drug-resistant bacteria. It is important that antibiotics are taken properly and for the duration of the prescription. If antibiotics are stopped early, the bacteria may develop a resistance to the antibiotics.
Antibiotics are medicines used that kill or inhibit bacteria in patients without harming the patient. Some antibiotics are made from natural sources, such as Penicillin and other antibiotics are made from synthetic sources in laboratories. Different antibiotics can be classified into two different groups. The two groups are bacteriostatic and bacteriocidal. The two groups of antibiotics work in different ways.
Bacteriostatic Antibiotics
Antibiotics that are classified in the bacteriostatic group don’t actually kill bacteria. Bacteriostatic antibiotics inhibit the growth of bacteria. Inhibiting the growth of bacteria, allows the patients’ immune system to fight off the existing bacteria without becoming overwhelmed with the growth of more bacteria.
Bacteriocidal Antibiotics
Antibiotics that are classified in the bacteriocidal group do kill bacteria. Bacteriocidal antibiotics are considered more affective because they do kill all of the bacteria instead of leaving some bacteria remaining for the patients’ immune system to fight off. Patients that have weak immune systems may have trouble fighting off bacteria. For these patients, bacteriocidal antibiotics are especially beneficial.
How Antibiotics Work
There are several different ways that antibiotics work to kill or inhibit bacteria. Some antibiotics kill bacteria by attacking the outer cell wall of the bacteria. Some antibiotics kill bacteria by attacking the inner membrane of the bacteria cell. Some antibiotics kill bacteria by attacking the chemical pathways bacteria require for survival. Some antibiotics inhibit bacteria growth by attacking the chemical pathways bacteria require in order to reproduce.
Antibiotic Resistance
Sometimes bacteria develop a resistance to certain antibiotics. When bacteria survive exposure to an antibiotic, the bacteria become stronger against and more likely to survive that antibiotic in the future. The bacteria passes the resistance gene when it reproduces. Eventually, the resistant gene can be passed to large numbers of bacteria, producing an antibiotic-resistant strain of bacteria. Antibiotic resistance is exasperated by patients who don’t finish their prescription of antibiotics, not fully killing the bacteria and encouraging bacteria resistance in surviving bacteria. When bacteria develops a resistance to a certain antibiotic and stops being affective, doctors must start using a different antibiotic.
Antibiotics are not Selective in Which Bacteria is Killed
While antibiotics help a patient by killing harmful bacteria, the medicine often kills good bacteria, also. Antibiotics are not selective in what bacteria that is killed. The body has several species of good bacteria that are helpful to the body. For instance, the good bacteria acidophilus is naturally found in the body and aids digestion. Because antibiotics kill acidophilus, some doctors suggest that patients taking antibiotics, take an acidophilus supplement at the same time.
AIDS. Human Immunodeficiency Virus.
Human Immunodeficiency Virus. AIDS
Human immunodeficiency virus
Stylized rendering of a cross section of the human immunodeficiency virus.
Human immunodeficiency virus (commonly known as HIV, and formerly known as HTLV-III and lymphadenopathy-associated virus) is a retrovirus (Table 2) that is the cause of the disease known as AIDS (Acquired Immunodeficiency Syndrome), a syndrome where the immune system begins to fail, leading to many life-threatening opportunistic infections
HIV primarily infects vital components of the human immune system such as CD4+ T cells (directly and indirectly destroying them), macrophages and dendritic cells. As CD4+ T cells are required for proper functioning of the immune system, when enough of them have been destroyed by HIV it compromises the immune system, leading to AIDS. HIV also directly attacks organs such as the ‘kidneys, “heart and “brain, leading to acute renal failure, cardiomyopathy, dementia and encephalopathy. Many of the problems faced by people infected with HIV result from failure of the immune system to protect from opportunistic infections and cancers.
Infection with HIV occurs after the transfer of blood, semen, vaginal fluid, or breast milk from an infected person to an uninfected one. Within these body fluids HIV is carried as a free virus and in infected CD4+ T cells, dendritic cells, and macrophages. The three major routes of transmission are sexual intercourse, sharing of contaminated needles used for intravenous drug delivery and transmission from an infected mother to her baby at birth or through breast milk.
Transmission
|
Exposure Route |
Estimated infections per 10,000 exposures to an infected source |
|
Blood Transfusion |
9,000 |
|
Childbirth |
2,500 |
|
Needle-sharing injection drug use |
67 |
|
Receptive anal intercourse* |
50 |
|
Percutaneous needle stick |
30 |
|
Receptive penile-vaginal intercourse* |
10 |
|
Insertive anal intercourse* |
6.5 |
|
Insertive penile-vaginal intercourse* |
5 |
|
Receptive fellatio* |
1 |
|
Insertive fellatio* |
0.5 |
The picture of retrovirus.
Three main transmission routes of HIV have been identified:
· Sexual route. The majority of HIV infections are acquired through unprotected sexual relations. Sexual transmission occurs when there is contact between sexual secretions of one partner with the rectal, genital or oral mucous membranes of another.
HIV and semen.
· Blood or blood product route. This transmission route can account for infections in intravenous drug users, hemophiliacs and recipients of blood transfusions (though most transfusions are checked for HIV) and blood products. It is also of concern for persons receiving medical care in regions where there is prevalent substandard hygiene in the use of injection equipment, such as the reuse of needles in
HIV in blood.
· Mother-to-child transmission (MTCT). The transmission of the virus from the mother to the child can occur in utero during the last weeks of pregnancy and at childbirth. In the absence of treatment, the transmission rate between the mother and child is 25%. However, where treatment is available, combined with the availability of Caesarean section, this has been reduced to 1%.Breast feeding also presents a risk of infection for the baby.
Structure and genome
Diagram of HIV.
HIV is different in structure from other retroviruses. It is about 120 nm in diameter (120 billionths of a meter; around 60 times smaller than a red blood cell) and roughly spherical. It is composed of two copies of positive single-stranded RNA that codes for the virus’s nine genes enclosed by a conical capsid composed of 2,000 copies of the viral protein p24.
HIV has been found at low concentrations in the saliva, tears and urine of infected individuals, but the risk of transmission by these secretions is negligible. The use of physical barriers such as the latex condom is widely advocated to reduce the sexual transmission of HIV. Current research is clarifying the relationship between male circumcision and HIV in differing social and cultural contexts.
Early Symptoms of HIV
The earliest symptoms of HIV infection occur while your body begins to form antibodies to the virus (known as seroconversion) between six weeks and three months after infection with the HIV virus. Those who do show early HIV symptoms will develop flu-like symptoms. This can include: fever, rash, muscles aches and swollen lymph nodes and glands. However, for most people, the first symptoms of HIV will not be apparent.
Although the infection is slowly taking hold of your body, the majority of those infected with HIV will be asymptomatic. Only by being tested for HIV can you know for sure if you have been infected. Yet, despite the absence of HIV symptoms, you are still highly contagious during this time making it very much a possibility to infect others, including your baby.
HIV/AIDS Symptoms
As the infection progresses, people with HIV grow increasingly susceptible to illnesses and infection that don’t normally affect the healthy population. Even though many of these illnesses can easily be treated, those with HIV often have such weakened immune systems that typical cures fail.
Without treatment, people infected with HIV can expect to develop AIDS eight to ten years after HIV infection. Taking HIV medications, however, can slow down this progression. With treatment, it can take ten to 15 years or more before you develop AIDS. In the later stages of HIV, before it progresses to full blown AIDS, signs of HIV infection can involve more severe symptoms. These include:
chronic yeast infections or thrush (yeast infection of the mouth)
Fever and/or night sweats
Easy bruising
Bouts of extreme exhaustion
Unexplained body rashes
Appearance of purplish lesions on the skin or inside mouth
Sudden unexplained weight loss
Chronic diarrhea lasting for a month or more
HIV Treatment
HIV and AIDS can be treated through various medications and drugs. Because HIV causes AIDS, treatment for HIV is generally the same as AIDS treatment. HIV medications are used to combat the virus by either preventing it from copying itself or by blocking its access to cells. HIV AIDS treatments may also include medications to help deal with any opportunistic infections you may have become infected with. Currently, there is neither an AIDS cure nor an HIV cure.
HIV Medications
There are four different groups of antiretroviral drugs used to deal with HIV/AIDS. The first group of medications are known as nucleoside reverse transcriptase (RT) inhibitors and aim to interrupt the virus’ ability to copy itself. Using these drugs should help reduce the amount of infection in your system, ideally to undetectable levels, while increasing your CD4 cell count.
Nucleoside RT inhibitors attempt to interrupt the HIV from copying itself during the early stages of the process. Nucleoside analog medications for HIV include AZT (Azidothymidine); ddC (zalcitabine); ddl (dideoxyinosine); d4T (stavudine) and Abacavir (ziagen) among others.
Non-nucleoside reverse transcriptase inhibitors also slow down the replication process during the early stages of HIV copying. This group of HIV medication includes Delavridine (Rescriptor); Nevirapine (Viramune) and Efravirenz (Sustiva).
The third group of AIDS and HIV treatment is known as protease inhibitors. Like nucleoside RT inhibitors, protease inhibitors attempt to interrupt the reproduction of the virus. However, these drugs do so at a later stage of the HIV life cycle. Some of the drugs that fall into this group include Ritonavir (Norvir), Saquinivir (Invirase), and Amprenivir (Agenerase).
The final group of drugs currently only has one drug (Fuzeon) approved for use. This group is known as fusion inhibitors and work by stopping the virus from entering your CD4 cells thereby preventing the joining of the virus with the cell membranes. This type of treatment should be used in conjunction with another form of treatment.
Which group of drugs is best varies from person to person. Discuss with your health care provider which you should use.
When Should You Start HIV Treatments?
It is difficult to know exactly when an individual should begin taking medication for their HIV. Unlike other infections, starting treatment early on is not necessarily beneficial. However, waiting until your HIV infection has progressed to late-stage HIV may also not be ideal. Depending on the state of your immune system, some people may be better off to prolong starting antiretroviral treatment while others may benefit from starting early.
If you are HIV positive, it is important to work closely and talk openly with your health care provider. Because HIV symptoms are ofteot noticeable until the infection has really advanced, regular monitoring of your immune system can help determine just how much of your system the infection has taken over. Regular CD4 tests (which indicate how many cells per cubic millimeter are in your blood) can give valuable insight as to the state of your immune system. The lower the CD4 cell count, the more reason you have to start drug therapy since your immune system is weakening.
Alternatively, you can also have regular viral load tests. These tests indicate just how much of the virus is in your system. Depending on the amount (whether it is low, medium or high), you may be advised to start or hold off on treatment.
Some people with an HIV infection choose to compliment their drug treatment with alternative therapies. Although these treatments do not combat the virus itself, they can help you to feel better about yourself, improve your immune system, reduce your stress levels and alleviate side effects. Some of these alternative therapies include acupressure, massage and vitamins.
Committing to a Regime
Taking HIV medications requires a large commitment on your part. There is no cure for HIV so once treatment is started; it needs to be continued for the rest of your life. Additionally, your medications need to be taken according to a strict timetable anywhere from one to three times a day. Some drugs need to be refrigerated while others have side effects.
Once you have started treatment, regular testing will still be necessary to make sure your viral load is decreasing while your CD4 count is increasing. If this does not happen, or if your viral load begins to increase after a period of effective treatment, it may indicate that your drug regime is failing or that your infection is starting to become resistant to treatment. Changing your drug regime may be necessary.
AIDS and HIV Resistance to Drugs
Overtime, some people taking treatment for AIDS or HIV may develop a resistance to the drugs they are using. This occurs because the HIV virus reproduces itself in your system, often mutating in the process. Since mutations of the HIV strain’s DNA occasionally occur in areas that the drugs target, the virus becomes resistant and is able to copy itself unhindered.
While changing your drug regime can help, it is possible for you to become resistant to an entire group of drugs. To reduce the likelihood of your body becoming resistant to HIV medications, it is necessary to take your drugs on time and every day. By doing this, the virus does not have a chance to copy itself.
It is also possible for you to be infected with a strain of HIV that is already resistant to certain drugs or an entire drug group. This will limit your treatment possibilities.
Treatment Side Effects
Like many other types of medications, HIV treatment often causes unwanted side effects in users. In general, the most common side effects include nausea, fatigue and diarrhea. However, some side effects may severely limit your daily activities, require hospitalization or even be life threatening, although this is rare.
Common side effects in those using nucleoside RT inhibitors include a decrease in red or white blood cells and possibly an inflamed pancreas or nerve damage. Protease inhibitors user often experience nausea, diarrhea as well as other gastrointestinal problems. The drug may also interact with other drugs causing an allergic reaction. Using Fuzeon has also been known to cause an allergic reaction as well pneumonia, low blood pressure, vomiting, fever or chills, rash and difficulties breathing.
Most people find that their body adjusts to the drugs after a period of time causing their side effects to subside. Those who don’t find any relief from their side effects may want to discuss the issue with their health care provider, especially if the side effects are so severe that they make it difficult for you to follow your drug regime. Changing your HIV treatment may help reduce the severity of your side effects and make it easier to take your medications. It is important to note, though, that repeated changes to your medication combinations can actually increase the likelihood that your body will develop a resistance.
While HIV treatments have come a long way over the years, they still leave much to be desired at least as far as side effects are concerned. Currently, researchers are looking for new ways of treating HIV and AIDS as well trying to create an HIV vaccine.
AIDS
Acquired Immunodeficiency Syndrome or Acquired Immune Deficiency Syndrome (AIDS or Aids) is a collection of symptoms and infections in humans resulting from the specific damage to the immune system caused by the human immunodeficiency virus (HIV). The late stage of the condition leaves individuals prone to opportunistic infections and tumors.
In 1990, the World Health Organization (WHO) grouped these infections and conditions together by introducing a staging system for patients infected with HIV- 1 .
Stage I: HIV disease ia asymptomatic and not categorized as AIDS
Stage II: includes minor mucocutaneous manifestations and recurrent upper respiratory tract infections
Stage III: includes unexplained chronic diarrhea for longer than a month, severe bacterial infections and pulmonary tuberculosis
Stage IV: includes toxoplasmosis of the brain, candidiasis of the esophagus, trachea, bronchi or lungs and Kaposi’s sarcoma; these diseases are indicators of AIDS.
The symptoms of AIDS are primarily the result of conditions that do not normally develop in individuals with healthy immune systems. Most of these conditions are infections caused by bacteria, viruses, fungi and parasites that are normally controlled by the elements of the immune system that HIV damages. Opportunistic infections are common in people with AIDS. HIV affects nearly every organ system. People with AIDS also have an increased risk of developing various cancers such as Kaposi sarcoma, cervical cancer and cancers of the immune system known as lymphomas.
Additionally, people with AIDS often have systemic symptoms of infection like fevers, sweats (particularly at night), swollen glands, chills, weakness, and weight loss. After the diagnosis of AIDS is made, the current average survival time with antiretroviral therapy is estimated to be now more than 5 years, but because new treatments continue to be developed and because HIV continues -to evolve resistance to treatments, estimates of survival time are likely to continue to change. Without antiretroviral therapy, death normally occurs within a year. Most patients die from opportunistic infections or malignancies associated with the progressive failure of the immune system.
The rate of clinical disease progression varies widely between individuals and has been shown to be affected by many factors such as host susceptibility and immune function health care and co-infections, as well as factors relating to the viral strain. The specific opportunistic infections that AIDS patients develop depend in part on the prevalence of these infections in the geographic area in which the patient lives.
Treatment
There is no cure for AIDS at this time. However, a variety of treatments are available that can help keep symptoms at bay and improve the quality of life of those who have already developed symptoms.
Antiretroviral therapy suppresses the replication of the HIV virus in the body. A combination of several antiretroviral agents, termed highly active antiretroviral therapy (HAART), has been highly effective in reducing the number of HIV particles in the blood stream, as measured by the viral load (how much virus is found in the blood). Preventing the virus from replicating can help the immune system recover from the HIV infection and improve T-cell counts.
HAART is not a cure for HIV, and people on HAART with suppressed levels of HIV can still transmit the virus to others through sex or sharing of needles. But HAART has been enormously effective for the past 10 years. There is good evidence that if the levels of HIV remain suppressed and the CD4 count remains high (above 200 cells/mcl), life can be significantly prolonged and improved.
However, HIV may become resistant to HAART in patients who do not take their medications on schedule every day. Genetic tests are now available to determine whether a particular HIV strain is resistant to a particular drug. This information may be useful in determining the best drug combination for each individual, and adjusting the drug regimen if it starts to fail. These tests should be performed any time a treatment strategy begins to fail, and prior to starting therapy.
When HIV becomes resistant to HAART, other drug combinations must be used to try to suppress the resistant strain of HIV. There are a variety of new drugs on the market for the treatment of drug-resistant HIV.
Treatment with HAART has complications. HAART is a collection of different medications, each with its own side effects. Some common side effects are nausea, headache, weakness, malaise (a general sick feeling), and fat accumulation on the back (“buffalo hump”) and abdomen. When used for a long time, these medications increase the risk of heart attack, perhaps by increasing the levels of fat and glucose in the blood.
Any doctor prescribing HAART should carefully watch the patient for possible side effects associated with the combination of medications the patient takes. In addition, routine blood tests measuring CD4 counts and HIV viral load (a blood test that measures how much virus is in the blood) should be taken every 3 – 6 months. The goal is to get the CD4 count as close to normal as possible, and to suppress the HIV amount of virus in the blood to an undetectable level.
Other antiviral medications are being investigated. In addition, growth factors that stimulate cell growth, such as erthythropoetin (Epogen) and filgrastim (G-CSF or Neupogen) are sometimes used to treat anemia and low white blood cell counts associated with AIDS.
Medications are also used to prevent opportunistic infections (such as Pneumocystis jiroveci pneumonia) if the CD4 count is low enough. This keeps AIDS patients healthier for longer periods of time. Opportunistic infections are treated when they happen.
Prevention
1. Abstain from sex. This obviously has limited appeal, but it absolutely protects against HIV transmission by this route.
2. Have sex with a single partner who is uninfected. Mutual monogamy between uninfected partners eliminates the risk of sexual transmission of HIV.
3. Use a condom in other situations. Condoms offer some protection if used properly and consistently. Occasionally, they may break or leak. Only condoms made of latex should be used. Only water-based lubricants should be used with latex condoms.
4. Do not use injected drugs. If IV drugs are used, do not share needles or syringes. Many communities now have needle exchange programs, where you can get rid of used syringes and get new, sterile ones for free. These programs can also provide referrals to addiction treatment.
5. Avoid contact with another person’s blood. Protective clothing, masks, and goggles may be appropriate when caring for people who are injured.
6. Anyone who tests positive for HIV can pass the disease to others and should not donate blood, plasma, body organs, or sperm. An infected person should tell any prospective sexual partner about their HIV-positive status. They should not exchange body fluids during sexual activity, and should use whatever preventive measures (such as condoms) will give the partner the most protection.
7. HIV-positive women who wish to become pregnant should seek counseling about the risk to unborn children, and medical advances that may help prevent the fetus from becoming infected. Use of certain medications can dramatically reduce the chances that the baby will become infected during pregnancy.
8. Mothers who are HIV-positive should not breast feed their babies.
The riskiest sexual behavior is unprotected receptive anal intercourse — the least risky sexual behavior is receiving oral sex. Performing oral sex on a man is associated with some risk of HIV transmission, but this is less risky than unprotected vaginal intercourse. Female-to-male transmission of the virus is much less likely than male-to-female transmission. Performing oral sex on a woman who does not have her period carries low risk of transmission.
HIV-positive patients who are taking anti-retroviral medications are less likely to transmit the virus. For example, pregnant women who are on effective treatment at the time of delivery, and who have undetectable viral loads, give HIV to the infant less than 1% of the time, compared with about 20% of the time if medications are not used.
The
If you believe you have been exposed to HIV, seek medical attention IMMEDIATELY. There is some evidence that an immediate course of antiviral drugs can reduce the chances that you will be infected. This is called post-exposure prophylaxis (PEP), and has been used to treat health care workers injured by needlesticks, to prevent transmission.
There is less information available about how effective PEP is for people exposed to HIV through sexual activity or IV drug use. However, if you believe you have been exposed, you should discuss the possibility with a knowledgeable specialist (check local AIDS organizations for the latest information) as soon as possible. Anyone who has been raped should be offered PEP and should consider its potential risks and benefits.
Estimated number of people in the world living with HIV/AIDS in 2008.
VIDEO
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