INDUCTION OF CD25 EXPRESSION IN HUMAN B-LYMPHOCYTES BY PHARMACOLOGICAL ACTIVATORS OF CELLULAR SIGNALING PATHWAYS

IL-4 promotes simultaneous expression of both the CD23 and CD25 antige ns in resting human B lymphocytes in a dose-dependent manner, Simultan eous three-colour flow cytometric analysis revealed that CD19(+)/CD23( +)/CD25(+) triple-positive cells were derived from a CD19(+)/CD23(-)/C D25(-) pool, and that induction of CD23 required lower doses of IL-4 t han did induction of CD25. Although the concentrations of IL-4 require d for half-maximal upregulation ol CD23 (35 pM) and CD25 (150 pM) expr ession were different, the capacity of IL-4 to promote expression of t he two markers could be mimicked by the same combination of pharmacolo gical agents. Thus, maximal expression of CD25 and CD25 was obtained w ith a 30 (or 120) second pulse with phorbol ester and/or ionomycin fol lowed by a sustained (20 minute) treatment with forskolin. Use of BAPT A to chelate intracellular calcium suggested that IL-4-driven CD25 exp ression required mobilization of intracellular Ca2+. Finally, downregu lation of cellular protein kinase C by chronic treatment of resting B lymphocytes with phorbol ester abolished the ability of IL-4 to elevat e CD23 and CD25 expression; phorbol ester treatment similarly abrogate d the ability of anti-CD40 and anti-Ig reagents to promote expression of CD25. The data are consistent with the proposal that IL-4 influence s CD23 and CD25 expression via a similar signal transduction pathway w hich involves both protein kinase C activation and elevation of intrac ellular cAMP levels. (C) 1996 Academic Press Limited