The immune system is a finely tuned system, which functions round-the-clock whole life to protect the body against various foreign cells, be it microbes or abnormal cells. Though the immune system is up and running all the time surrounded by self-antigens, it does not mount a response against them. At times, these mechanisms go awry, and this results in injury to various tissues.
Autoimmunity is a condition when the body produces auto-antibodies and immunologically competent T lymphocytes against its own tissues. Conditions where the mechanisms of self-tolerance fail are termed as autoimmune disorders and the phenomenon is called autoimmunity.
Autoimmunity literally means “protection against self”; however, in practice it leads to “injury to self.” At the clinical level, autoimmunity is apparently involved in a variety of appar-ently unrelated diseases, such as systemic lupus erythematosus (SLE), insulin-dependent diabetes mellitus, myasthenia gravis, rheumatoid arthritis, multiple sclerosis, and hemolytic anemias.
Ehrlich in 1901 first postulated the existence of tolerance to self-antigens as also those situations where this mechanism would fail, leading to “horror autotoxicus”. More recently, an understanding of the various immunological mechanisms and disorders has led to the same conclusions.