SYNERGY BETWEEN DEXAMETHASONE AND INTERLEUKIN-5 FOR THE INDUCTION OF MAJOR HISTOCOMPATABILITY COMPLEX CLASS-II EXPRESSION BY HUMAN PERIPHERAL-BLOOD EOSINOPHILS

The hematopoietic growth factors interleukin-3 (IL-3), IL-5. and granu locyte-macrophage colony-stimulating factor (GM-CSF) regulate the surv ival, maturation, and activation of eosinophils. Corticosteroids in co ntrast have a negative effect both on the hematopoietic process and th e function of eosinophils. We have unexpectedly observed synergy betwe en IL-5 and glucocorticoids such as dexamethasone and hydrocortisone f or induction of the MHC class II antigens HLA-DR and HLA-DP on eosinop hils isolated from human blood. Similarly glucocorticoids enhanced GM- CSF and IL-3, but not interferon gamma (IFN gamma), induced expression of these antigens. Expression of a third MHC class II molecule, HLA-D Q, was not induced on eosinophils by any of the cytokines alone, but i n one of three donors tested, IL-3 plus dexamethasone induced high lev els of expression. Although cytokine-induced exprc!ssion of the access ory molecule intercellular adhesion molecule 1 (ICAM-1) was partially inhibited by glucocorticoids, cytokine- and dexamethasone-treated eosi nophils presented antigen more efficiently to a hemagglutinin peptide- specific T-cell clone than eosinophils treated with cytokine alone. Th ese results highlight a potential new role for endogenous or exogenous glucocorticoid hormones in enhancing MHC class II expression by eosin ophils. (C) 1994 by The American Society of Hematology.