Alterations in peripheral B cells and B cell progenitors following androgen ablation in mice

The production of B lymphocytes is regulated in part by physiologic levels of androgens and estrogens, While these sex hormones down-regulate B lympho poiesis, augmentation of B lymphopoiesis occurs under conditions where andr ogen or estrogen levels are decreased. In this study we examine the effect of androgen ablation of male mice on B lymphopoiesis and on the phenotypic composition of peripheral B lymphocyte populations. Spleen and thymic weigh ts are significantly increased following castration, as is the total number of peripheral blood lymphocytes. However, the absolute numbers of a cells in the periphery are selectively increased following castration; the number s of T cells, NK cells and granulocytes remain unchanged. The increase in c irculating B cells is due largely to increases in the numbers of recent bon e marrow emigrants expressing a B220(Io+) CD24(hi+) phenotype and these cel ls remain significantly elevated in castrated mice for up to 54 days post-c astration. Similar increases in the percentages of newly emigrated B cells are observed in mice that lack a functional androgen receptor (Tfm), Finall y, assessments of B cell progenitors in the bone marrow revealed significan t increases in the relative numbers of IL-7-responsive B cell progenitors, including cells in Hardy fractions B (early pro-B cells), C (late pro-B cel ls), D (pre-B cells) and E (immature B cells). These findings demonstrate t hat androgen ablation following castration significantly and selectively al ters the composition of peripheral B cells in mice. Further, these alterati ons result from the potentiating effects of androgen ablation on IL-7-respo nsive pro-B cell progenitors.