INCREASED B-LYMPHOPOIESIS IN GENETICALLY SEX STEROID-DEFICIENT HYPOGONADAL (HPG) MICE

Interleukin 7 (IL-7) responsive B lineage precursors were greatly expa nded in genetically hypogonadal female (HPG/Bm-hpg/hpg) mice that have a secondary deficiency in gonadal steroidogenesis. Estrogen replaceme nt in these mice resulted in a dose-dependent reduction in B cell prec ursors. More modest increases were documented in genetically normal mi ce that were surgically castrated. These findings complement other rec ent observations that B lymphopoiesis selectively declines in pregnant or estrogen-treated animals. Sex steroids have long been known to inf luence such disparate processes as bone physiology and tumor growth, i n addition to their importance for reproductive function. We now show that these hormones are important negative regulators of B lymphopoies is.