When the Immune System Malfunctions
Given the numbers of pathogens in the environment, the rearrangement of genes of the immune system, and the screenings that occur, it is surprising that more doesn’t go wrong with the immune system. However, evolution has tested the efficiency of this highly complex system of protection for your body. Even so, immune system disorders occasionally occur. The following are some of the best known.
AIDS/HIV
Acquired immunodeficiency syndrome (AIDS) occurs when one’s immune system is infected by the human immunodeficiency virus (HIV), which takes advantage of the immune system to survive and reproduce. HIV utilizes helper T cells as a host that can replicate and further infect other helper T cells. At first, the individual feels symptoms not unlike that of a common cold, which dissipate in a few weeks. Thinking the disease and danger have passed, the individual typically does not seek clinical intervention and does not display any symptoms for possibly as long as 7–10 years. This is the clinically asymptomatic period of HIV infection, when the virus is slowly increasing in numbers as the helper T cells are slowly destroyed. In the end, the immune system is rendered nonfunctional and the individual succumbs to any of a myriad of opportunistic pathogens. These late-stage symptoms are what we generally consider AIDS.
AIDS/HIV is spread mainly through sexual contact, although it can also be spread through blood transfusions, by use of contaminated needles, and from mother to child. Because the asymptomatic period can last for years, one person can infect many others without realizing it.
Allergies
Allergies are not mutations or disruptions of the immune system, but instead are instances of the immune system mounting a response to a common antigen (allergen) that stimulates a massive release of inflammatory cytokines (type I hypersensitivity). This immediate type of allergy is particularly dangerous if the allergen is inhaled or otherwise consumed into the body. The vast numbers of mast cells with their attached IgE molecules flood the system with histamine and heparin, causing a massive drop in blood pressure and systemic edema (which include the lungs and airways). This is called anaphylactic shock, and if clinical intervention isn’t immediately available, death could result in a matter of minutes.
Treating anaphylactic shock
To reverse an anaphylactic response, epinephrine (adrenaline) should be administered. Anyone who suffers from severe type I hypersensitivity, especially to food allergies and insect stings, must have an EpiPen (epinephrine autoinjector) readily available at all times.
T cells are also involved in allergic responses. These are referred to as delayed (type IV) hypersensitivity. Most commonly these are observed as rashes, hives, or welts that appear on the surface of the skin as a result of contact. However, this is also the mechanism responsible for tissue transplant rejection if the tissue isn’t a close enough match for the patient.
Preventing transplant rejection
The major histocompatibility complex antigens (MHC) molecules between donor and recipient are being matched at this point. Since siblings (especially identical twins) have the most similar MHC molecules, they make the best donors.
Autoimmune Disorders
Almost daily the list of human autoimmune disorders grows longer. With the numbers of cells produced, invariably and by chance, autoimmune diseases will result. A few of these better known disorders include:
· Crohn’s disease of the gastrointestinal tract
· Lupus, a systemic inflammatory condition
· Hashimoto’s thyroiditis, which is the most common cause of goiter in females