The effect of age on the B-Cell repertoire

The antibody repertoire changes with age. This change reflects, in part, th e age-associated impairment in the production of a diverse population of na ive B cells in the bone marrow and, in parr, by the decreased diversificati on of B cells in the germinal center where affinity maturation and isotype switching takes place. B cell number is strictly regulated and despite the decreased output of B cells by the bone marrow does not decline during agin g. Self-renewal of peripheral B cells is sufficient to assure the stability of peripheral B cell number. However, when B cell production is stressed a s, for example, Following drug-induced lymphopenia, the rate of recovery of B cell number as well as of B cell diversity is compromised in old compare d to young mice. Finally, aging is associated with the appearance of B cell clonal expansions which not only limit the diversity of the B cell reperto ire but very likely give rise to monoclonal serum immunoglobulins and B cel l neoplasms.