Immune System Introduction                                   The immune system is vital for life of Human Beings and most multi-cellular organisms.  There exists a continuous war between the immune system and invaders such as bacteria and viruses.  One can easily imagine the result of a deficient immune system; however the consequences of an overactive, uncontrollable immune system range from discomforting to lethal.      The complexity of the immune system cannot be understated.  Currently there are two branches of the immune system called innate and acquired immunity.  The innate immune system is comprised of complement, granulocytes such as neutrophils, and inflammation factors such as interleukins.  Innate immunity is not specific and is a first responder.  Innate immunity also includes the basic barriers of protection such as skin, mucus membranes, lysozymes, and the acid enviroment of the GI Tract.       The other branch of the immune system is referred to as acquired immunity.  Acquired immunity is antigen specific and is triggered by antigen presenting cells, resulting in a cellular or humoral response.  The Immune System can become uncontrolled and thus a disease state.  Several autoimmune diseases have been identified and are classified based on hypersensitivity groups.      Autoimmune disease is defined by a production of antibodies or cytotoxic immunity.  Antibody responces can trigger inflammation via the antibody-antigen complexes that form.  The inflammatory responce results in increased blood supply to inflammatory site, increased capillary permeability, migration of leukocytes namely neutrophils and macrophages to the site of inflammation.  Acute phase reactions are soluble factors that are elevated during perioids of inflammation.  These reactants include C-reactive protein, serum amyloid A, complement, alpha-1 antitrypsin, haptoglobin, fibrinogen, and ceruloplasmin.   What causes the autoimmune reactions?   The causes of autoimmune reactions range from exogenous factors such as drugs and radiation to geneticic factors involving greater autoimmune risk for certain HLA type.  However there are also several autoimmune diseases that cannot be explained and thus termed idopathic.