Molecular mimicry and the role of B lymphocytes in the processing of autoantigens.

The immune system has evolved several mechanisms that provide lymphocytes with the intelligence to ignore self proteins while attacking foreign pathogenic agents. Notably, B and T lymphocytes that encounter self antigen at either the inappropriate levels or affinity are usually instructed to perish or become anergized. However, the presence of autoimmune disease suggests that the induction of self tolerance is not foolproof. In fact, autoreactive cells are now found to be normal inhabitants of the B and T lymphocyte repertoire. This review examines how foreign peptides which resemble self proteins can elicit autoimmunity that is amplified to many sites on a target autoantigen. In particular, B lymphocytes initiated by foreign molecular mimics can process and present self peptides in the shaping of autoimmune T cell responses.