IL-10 AUGMENTS CD23 EXPRESSION ON U937 CELLS AND DOWN-REGULATES IL-4-DRIVEN CD23 EXPRESSION ON CULTURED HUMAN BLOOD MONOCYTES - EFFECTS OF IL-10 AND OTHER CYTOKINES ON CELL PHENOTYPE AND PHAGOCYTOSIS

The effects of human recombinant interleukin-10 (IL-10) on the expression of several markers on U937 and human peripheral blood monocytes was studied by immunofluorescence and fluorescence-activated cell sorter (FAGS) analysis. IL-10 augmented Fc IgE receptor (Fc epsilon RII/CD23) expression on U937 cells in a concentration- and time-dependent manner. This effect was further enhanced by cotreatment with IL-4 or interferon-gamma (IFN-gamma). In contrast, the basal level of Fc epsilon RII expression on blood monocytes appeared to fall in response to IL-10, and this effect became more evident on IL-4-treated cells. Furthermore, the constitutive and IFN-gamma-triggered Fc gamma RI/CD64 expression was augmented on both monocytes and U937 cells. Thus the expression of Fc gamma RII/CD32, Fc gamma/RIII/CD16, Fc alpha R/CD89, the receptor for complement components (CR1/D35, CD3/CD11b, CR4/CD11c) and the receptor for transferrin/CD71 was not significantly influenced on IL-10-treated cells. IL-10 modestly triggered CD14 antigen expression on monocytes but not U937. The expression of intercellular adhesion molecule-1 (ICAM-1)/CD54 on monocytes was significantly inhibited by IL-10. As expected, a marked reduction of the constitutive as well as of the IFN-gamma or IL-4-driven expression of HLA-DR, HLA-DP and HLA-DQ was observed on IL-10-cultured monocytes. On the other hand, the expression of major histocompatibility complex (MHC) class I molecules was slightly and dose-dependently induced on IL-10-treated monocytes. The ability of blood monocytes to phagocytose IgG-sensitized ox erythrocytes, and to bind and ingest opsonized Escherchiacoli or latex particles, was amplified by IL-10. Our data demonstrate that IL-10 modulates the expression of a wide variety of structures on human mononuclear phagocytes, and augments their phagocytic capacity.