EFFECTS OF INVITRO CORTICOSTEROIDS ON B-CELL ACTIVATION, PROLIFERATION, AND DIFFERENTIATION

The graded effect of in vitro corticosteroids (CS) on the different phases of B cell activation, proliferation and differentiation was examined. Early events such as activation and proliferation of high-dose anti-.mu. or Staphylococcus aureus-stimulated B cells are profoundly suppressed by the presence of in vitro CS. The suppressed proliferative response may be mediated by a direct effect on B cells and/or modulation of accessory cell function. Later events in the B cell cycle such as the proliferative response to B cell growth factor after either in vivo or in vitro activation are less sensitive to the suppressive effects of in vitro CS. The final events in the B cell cycle, namely, the differentiation to the Ig-producing state, is not suppressed by in vitro CS. Indeed, depending on the systems employed, there is either no effect or enhancement of Ig secretion by the presence of in vitro CS. The graded effect of in vitro CS on the discrete phases of the B cell activation, proliferation and differentiation cycle provide new insights into the complex nature of CS-induced modulation of human B cell responses.