Distinctive characteristics of germinal center B cells.

A cardinal property of the immune system is its ability to respond to an antigen that was encountered years before with an accelerated and enhanced secondary response. The property of anamnestic reactions depends upon the formation of long-lived compartments of specialized T and B lymphocytes called memory cells. While the origin of the memory T-cell compartment is not known, germinal centers are the specialized sites for memory B-cell generation and the immunoglobulin V-region hypermutation necessary for the affinity maturation of serum antibody. Interestingly, the peripheral differentiation pathway that leads to this most mature B-cell state begins with the recapitulation of many characters of immature B lymphocytes in bone marrow. This review describes the distinctive cellular basis of germinal center reaction and the characteristics of B cells in germinal centers that later enter the memory pool.