The immune system is made up of a complex and vital network of cells and organs that protect the body from infection by keeping infectious microorganisms out of the body (such as certain bacteria, viruses, and fungi), and by destroying any infectious microorganisms that do invade the body.
A number of problems, including allergies and hypersensitivities to certain substances, can develop when the immune system doesn’t function properly. The system also plays a role in the rejection process of transplanted organs or tissue. Autoimmune diseases, such as Juvenile Diabetes, Rheumatoid Arthritis, and anemia, as well as immunodeficiency diseases, such as acquired immunodeficiency syndrome (AIDS), and severe combined immunodeficiency (SCID) may also develop.
Autoimmune diseases are conditions in which the body makes antibodies against one's own normal body chemicals. In these diseases, antibodies cannot tell the difference between antigens located inside the cell and antigens located outside the cell. When the antibodies attack the internal cells, the reactions can be local - in just a small area - or spread throughout the whole body. While the skin and connective tissues are most affected, other tissues including nerve and muscle can also be affected.
Terms for autoimmune disease include collagen vascular disease or collagen disease. Other autoimmune diseases include: