The Paradox of High Rates of B Cell Production in Bone Marrow and the Longevity of Most Mature B Cells

Abstract

In mammals, the bone marrow is the principal site of primary B cell generation in post-natal life (1). Studies in mice indicate the the physiological rate of B cell production in bone marrow is sufficient to replenish the peripheral B lymphocyte pool within 4 days (2). The generative potential of B cell precursors is further emphasised by the ability of rats treated from birth with anti-IgM and anti-IgD antibodies, to fully repopulate secondary lymphoid organs with B cells, within a span of eight days following the cessation of antibody-induced suppression (3). These observations alone are consistent with the view that mature B cells have a relatively short half-life of a few days (4,5). However, only 25% of recirculating and static B cells of the splenic white pulp of rats are labelled by five days of ³H-thymidine infusion, indicating that most B cells within secondary lymphoid organs are not newly formed cells (6). The studies of Sprent and Basten (7) also support such a viewpoint. These data (6, 7), taken together with the observations on the rate of B cell production in bone marrow (2), imply that only a small proportion of B cells produced in adult bone marrow become part of the mature lymphocyte pool.