DEFINITION OF AUTOIMMUNE DISEASES

The autoimmune reactions are all immunological responses towards intact self-antigens, which are normally presented in the body. As it has already been mentioned earlier, not all endogenous antigens belong to autoantigens, hence not all immune responses against self cells in fact belong to autoimmunity. Self-tolerance or lack of immune responsiveness to individual�s own tissue antigens exists normally only for true autoantigens (normal constituents of healthy body). But, normally, there is no tolerance of viral of tumor neoantigens, antigens of senescent cells altered self-constituents and other similar endogenous �non-auto� antigens. Moreover, self-tolerance is not absolute, and some manifestations of anti-self response are inherent to normal function of healthy immune system and even essential for autoregulation of immunity.

This section of interactive textbook refers to autoimmunity (natural physiological immune response against self-antigens) and autoallergy (excessive pathological immune response towards autoantigens).

According to modified E. Witebsky�s criteria (1957), a disease is supposed to be autoimmune, if autoreactive Ig and/or lymphocytes render pathogenetic (destructive either dysregulatory) action over the organism. In true autoimmune disease the following conditions fulfilled:

• A disorder mast be reproducible in recipients of patient�s serum or T cells
• Autoreactive elements of immune system have to be revealed in majority of cases.
• The target autoantigen (s) have to be isolated and characterized
• For clinical logic, an additional important witness of probable autoimmune mechanism of disease is the effectiveness of immunosuppressive therapy
• For experimental pathophysiology a strong witness for autoimmune nature of a disorder is the existence of its animal model, achieved either by spontaneous or by induced violation of self-tolerance.

Broader interpretation of the term �Autoimmune diseases� includes into this category all disorders in which autoantibodies and/or autoreactive lymphocytes are involved as etiologic or pathogenetic factors, both in primary or secondary links.

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