EFFECT OF DIBUTYRYL-CYCLIC-AMP AND INTERFERON-GAMMA ON FC-GAMMA RECEPTOR EXPRESSION ON EOSINOPHILS

We studied the effect of dibutyryl cyclic adenosine-3',5'-monophosphat e (dbcAMP) and several cytokines on the expression of IgG Fc receptor subclasses (Fc gamma RI, Fc gamma RII, and Fc gamma RIII) and low-affi nity IgE Fc receptors (Fc epsilon RII/CD23) on peripheral eosinophils and on eosinophils differentiated in vitro from cord blood mononuclear cells by interleukin 5 (IL-5). These eosinophils expressed Fc gamma R II, and few, if any, Fc gamma RI and Fc gamma RIII as determined by fl ow cytometry with specific monoclonal antibodies. dbcAMP enhanced the Fc gamma RII expression, but did not induce the Fc gamma RI and Fc gam ma RIII expression. Interferon-gamma (IFN-gamma) enhanced Fc gamma RII expression at the same degree as did dbcAMP. IFN-gamma also induced F c gamma RIII expression on peripheral eosinophils but not on eosinophi ls grown in the presence of IL-5. Eosinophils grown in the presence of IL-5 showed a relatively immature phenotype, determined by electron m icroscopy and the low content of eosinophil cationic protein. Contrary to its enhancing effect on Fc gamma RII expression, dbcAMP suppressed the IFN-gamma-induced Fc gamma RIII expression on peripheral eosinoph ils. Other cytokines examined did not show any effects on Fc gamma R e xpression. Fc epsilon RII/CD23 expression was neither detected nor ind uced. These results indicate that expression of Fc gamma RII and Fc ga mma RIII on eosinophils is regulated differently and that cAMP and IFN -gamma play important roles in the regulation of Fc gamma R expression .