title: Lipopolysaccharide and interleukin 1 inhibit interferon-gamma-induced Fc receptor expression on human monocytes.
abstract: The objectives of these studies were to study the effects of bacterial lipopolysaccharide (LPS) on interferon-gamma (IFN-gamma)-induced Fc receptor expression on human monocytes and to examine whether these effects were mediated through stimulation of interleukin 1 (IL-1) production. Fc receptor expression was determined by binding of monomeric monoclonal murine immunoglobulin (Ig)G2a and cytofluorographic analysis. IL-1 activity in monocyte supernatants and lysates was assayed by augmentation of mitogen-induced murine thymocyte proliferation. IFN-gamma induced the expression of Fc receptors on human monocytes that were specific for murine IgG2a. This induction was inhibited by the addition of LPS in amounts as low as 2 to 8 pg/ml. LPS inhibition of IFN-gamma-induced Fc receptor expression was paralleled by the appearance of IL-1 in monocyte lysates and supernatants. The addition of purified human or recombinant IL-1 beta at the initiation of culture similarly inhibited the expression of IFN-gamma-induced Fc receptors on the monocytes. LPS also inhibited Fc receptor expression on the human myelomonocytic cell line THP-1 after induction with IFN-gamma or phorbol myristate acetate alone or with both agents together. This inhibition also was paralleled by the production of IL-1 but the addition of exogenous IL-1 to the THP-1 cells had no effect on IFN-gamma-induced Fc receptor expression. Tumor necrosis factor (TNF) inhibited IFN-gamma-induced Fc receptor expression on human monocytes but was much less potent than comparable amounts of IL-1. TNF also did not inhibit Fc receptor expression on THP-1 cells. In fact, IL-1 or TNF led to an enhancement in IFN-gamma-induced Fc receptor expression on THP-1 cells. These results indicate that LPS can inhibit IFN-gamma-induced Fc receptor expression on human monocytes and that IL-1 and TNF may mediate these effects of LPS. Thus, an autocrine or paracrine role is suggested for these cytokines. The possibility exists that intracellular IL-1 resulting from LPS stimulation may be at least in part responsible for inhibition of Fc receptor expression.
mesh_terms: D002460:Cell Line; D006023:Glycoproteins / Q000494:pharmacology; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000037:antagonists & inhibitors*; D007375:Interleukin-1 / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D009000:Monocytes / Q000502:physiology*; D011961:Receptors, Fc / Q000378:metabolism*; D017452:Receptors, IgG; D011994:Recombinant Proteins / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha
chemical_list: D006023:Glycoproteins; D007074:Immunoglobulin G; D007375:Interleukin-1; D008070:Lipopolysaccharides; D011961:Receptors, Fc; D017452:Receptors, IgG; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D013755:Tetradecanoylphorbol Acetate