High affinity receptor for IgG (Fc gamma RI/CD64) gene and STAT protein binding to the IFN-gamma response region (GRR) are regulated differentially in human neutrophils and monocytes by IL-10

Since IL-10 has been shown to up-regulate the expression of the high affinity receptor for IgG (FcgammaRI/CD64) in human monocytes, we examined whether the cytokine exerts a similar action toward polymorphonuclear neutrophils (PMN). Unexpectedly, we found that in neutrophils, IL-10 failed to induce either the mRNA accumulation or the surface expression of FcgammaRI. Consistent with these findings, stimulation of PMN with IFN-gamma, but not with IL-10, resulted in the induction of specific DNA-binding activities to the IFN-gamma response region (GRR), a regulatory element located in the FcgammaRI gene promoter, required for transcriptional activation. In electrophoretic mobility shift assays (EMSAs), we confirmed that in PBMC, IL-10 induces the binding to the GRR of both STAT1 and STAT3, two members of the STAT family. In neutrophils, however, these activators did not bind to the GRR in response to IL-10, despite the fact that both STAT1 and STAT3 are expressed in these cells. On the other hand, IFN-gamma