Essay --

In normal cases the immune system's white blood cells protect the body from harmful substances, called pathogens. A pathogen is anything that tries to harm the body. Some examples of pathogens are fungi, bacteria, protozoans, and viruses , and blood or tissues from another species or person. The immune system produces antibodies that destroy these harmful substances. An antibody is like a protein marker produced by B-Cells to identify foreign objects. Unfortunately, as useful the immune system is for our bodies, there are many disorders and diseases related to it. Immune system disorders cause low immune activity or over immune activity in the immune system. During immune system over activity cases, the body damages and attacks its own tissues; these diseases are known as autoimmune diseases. Immune deficiency decreases the body's ability to fight pathogens, causing a higher chance for infection. Allergies are an example of the immune systems over-activity diseases. Allergies occur when the immune system reacts to foods or substances that are not harmful. The most common allergens are pets and pollen. When the immune system senses an allergen, it releases unneeded chemicals. Histamine for example, is one of the chemicals that are released after the immune system senses an allergen; it triggers an inflammatory response. Allergic reactions like this have many symptoms that can include breathing problems, eye irritation, rash, even nausea and vomiting. Asthma is a condition where the immune system becomes over-active in the bronchi. Many people with asthma suffer constriction in their bronchial tubes, which make it harder to breath. An asthma infected persons airways are almost always under inflammation. There is no total cure f... ...rittle bones, and death; 20% of people who have a thyroid storm die. The final immune disorder I want to mention is immunodeficiency. Immunodeficiency is the failure of the immune system to protect the body from harmful substances and infection. Most of the time it is caused by the absence of some components needed. The main cause of immunodeficiency around the world is the Human immunodeficiency Virus (HIV). HIV attacks and kills a crucial part of the immune system; T helper cells. T Helper-Cells kills infected cells. And without T-Cells many other immune cells cannot work properly, including B-Cells that make antibodies. A person infected with HIV may not show any signs or symptoms for years. But as HIV kills more and more T-Cells die the body becomes more vulnerable to infection. And when infected cells outnumber uninfected cells, then the patient will have AIDS.