Abstract
The main function of the immune system is an adequate response to a dangerous initiative and its elimination. Inadequate, either inadequate or excessive response may damage the body and illness.
In case of lack of reactivity of the organism may succumb in the fight against microorganisms and against the growth of cancer cells. In the case of inappropriately excessive reactivity is an allergic response to harmless antigens from the external environment or immunopathological response to internal autoantigens.
In either case there is damage to cells or tissues of the body immune mechanisms.