Ethiopathogenesis of autoimmune diseases

Self-tolerance refers to the unresponsiveness of the immune system against autoantigens, which is acquired through mechanisms deleting or inactivating autoreactive cells. The multiple and closely linked processes responsible for self tolerance can fail or breakdown leading to an immune response against self antigens, and in some circumstances to an autoimmune disease. Several factors are involved in the development of autoimmunity. In the last years, cross reactivity between foreign antigens (viral or bacterial proteins) and self molecules, called molecular mimicry, was widely studied as a model of autoimmunity. The development of new molecular biology techniques and the progressive availability of data bases for searching of similarity have shown that several sequences of microorganisms are in common to normal cells. However, it is important to go deep into the biological meaning of these homologies in order to better elucidate the relationship between infectious microorganisms and autoimmune diseases.