Glucocorticoids Enhance the in Vitro Ig Synthesis of Pokeweed Mitogen‐Stimulated Human B Cells by Inhibiting the Suppressive Effect of T8+ T Cells

Abstract

The in vitro effects of three potent glucocorticoids (GC) (dexamethasone, prednisolone, cortisone) on human lymphocyte functions were investigated. In pharmacological concentrations GC strongly suppressed lymphocyte transformation induced by T-cell mitogen (concanavalin A and phytohaemagglutinin). After pokeweed mitogen (PWM) stimulation GC enhanced the number of immunoglobulin (Ig)-producing cells without affecting the proliferative response. Mineralocorticoid aldosterone showed no effect. Addition of 3 X 10(-8)-3 X 10(-6) mol/l of different GC to PWM cultures significantly increased the number of Ig-secreting cells, measured by the plaque-forming cell assay. Experiments conducted with fractionated defined lymphocyte subpopulations showed that the T8+, a radiosensitive T suppressor cell, is more sensitive than the T4+ T helper cell to GC effects. It is concluded that GC in pharmacological concentrations display a dual effect on human lymphocyte functions in vitro: an inhibition of lectin-induced T lymphocyte proliferation and a rather selective inhibition of T suppressor cell function which leads to an enhanced B-cell maturation and Ig synthesis in PWM-stimulated cultures. No measurable direct effect on the B lymphocytes was noticed.