The autoimmune system is the mechanism used by the body to protect itself from infection and limit the spread of problematic bacteria, microbes, parasites and other infection-causing agents, according to the National Institute of Allergy and Infectious Diseases. Different organs, cells and tissue compose the autoimmune system.
The cells that compose the autoimmune system include B cells, NK cells and T cells, which come from the bone marrow, according to the National Institute of Allergy and Infectious Diseases. These immune cells move throughout the body via the bloodstream and the lymphatic system. The lymphatic system alerts the immune cells of a potential infection, sending them to the affected area. Swollen lymph nodes indicate the activity of the system and immune cells in fighting off an infection. Other components of the immune system include antimicrobial proteins present in some skin cells, enhancements to immune cells provided by the spleen and the mucosal tissue located near the most likely locations of infection.
Immune deficiencies and autoimmune diseases are conditions that compromise the autoimmune system, limiting its effectiveness, according to WebMD. For example, some infections, such as the flu, can temporarily reduce the effectiveness of the immune system by lowering the amount of immune cells available to fight infection. An overly high number of immune cells can also be dangerous, causing cancers such as lymphoma and leukemia.