B cell superantigens: possible roles in immunodeficiency and autoimmunity.

Lymphocyte antigen receptors have evolved for the discrimination of self and non-self structures and consequently the unconventional binding activities of superantigens pose a special set of potential hazards and opportunities for the immune system. This review presents recent evidence that certain naturally occurring proteins have the properties of B cell superantigens by virtue of their unconventional variable-region mediated interactions with soluble and membrane-bound immunoglobulins. The implications for B lymphocyte activation and clonal selection are discussed and we speculate how superantigens may influence the development of lymphocyte repertoires and the immune responses associated with certain autoimmune and immunodeficiency diseases.