ABSTRACT
Unlike T lymphocytes, which recognize processed (partially digested) antigens, antibodies recognize antigens in their natural configuration. For an individual to make antibodies against the full range of pathogens continually encountered, B-lymphocytes expressing a diverse repertoire of immunoglobulins must be generated continually. Each B cell expresses immunoglobulin against a single antigenic epitope, with the immunoglobulin expressed at the cell surface where it acts as a specific receptor for that antigen. The diversity of specificities in different B cells is generated largely by gene rearrangements in new B cells, which continue to be generated throughout life. In their early development, B cells with immunoglobulins against ubiquitous selfantigens are eliminated. This elimination of B cells reactive to autoantigens is not absolute, however, as a broad array of mAbs and serum antibodies against autoantigens have been derived from experimental animals and humans. Peripheral blood B cells consist of these naive and relatively short-lived B cells, long-lived memory B cells resulting from maturation in response to antigenic stimulation, and a small population of B cells expressing germ line specificities, also termed CD5 B cells (Fearon et al., 1997).
