Abstract
The ability of dendritic cells (DCs) to activate immunity is linked to their maturation status. In prior studies, we have shown that selective antibody-mediated blockade of inhibitory FcgammaRIIB receptor on human DCs in the presence of activating immunoglobulin (Ig) ligands leads to DC maturation and enhanced immunity to antibody-coated tumor cells. We show that Fcgamma receptor (FcgammaR)-mediated activation of human monocytes and monocyte-derived DCs is associated with a distinct gene expression pattern, including several inflammation-associated chemokines, as well as type 1 interferon (IFN) response genes, including the activation of signal transducer and activator of transcription 1 (STAT1). FcgammaR-mediated STAT1 activation is rapid and requires activating FcgammaRs. However, this IFN response is observed without a detectable increase in the expression of type I IFNs themselves or the need to add exogenous IFNs. Induction of IFN response genes plays an important role in FcgammaR-mediated effects on DCs, as suppression of STAT1 by RNA interference inhibited FcgammaR-mediated DC maturation. These data suggest that the balance of activating/inhibitory FcgammaRs may regulate IFN signaling in myeloid cells. Manipulation of FcgammaR balance on DCs and monocytes may provide a novel approach to regulating IFN-mediated pathways in autoimmunity and human cancer.