Corticosteroid-Induced Modulation of Immunoglobulin Secretion by Human B Lymphocytes: Potentiation of Background Mitogenic Signals

Abstract

The modulation of immunoglobulin (Ig) secretion of human peripheral blood mononuclear cells by in vitro hydrocortisone (HC) was evaluated. A marked enhancement of Ig secretion was observed in unstimulated cultures in the presence of HC as compared to cultures without HC. The augmented response was not due to a direct induction of Ig secretion by HC, but resulted from an enhancement or unveiling of the background mitogenic signal provided by the supplemental serum used in culture. HC-induced augmentation of Ig secretion was only seen in unstimulated cultures performed in fetal calf serum (FCS) which is known to possess mitogenic properties. In contrast, HC had no significant effect on Ig secretion of cultures performed in human serum, which provides little or no background mitogenic signal. On the other hand, no enhancement of Ig Secretion by HC was seen in cultures maximally stimulated with pokeweed mitogen regardless of whether FCS or human A serum was used. The mechanisms of this modulation of Ig secretion are unclear at present and may include a synergy between corticasteroids and background mitogenic signals (such as FCS) indirectly triggering B cells and/or the dampening of a negative immunoregulatory effect of an accessory cell.