Human T cells and interleukin 4 inhibit the release of interleukin 1 induced by lipopolysaccharide in serumfree cultures of autologous monocytes

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Abstract
Stimulation with lipopolysaccharide (LPS) of unfractionated peripheral blood mononuclear cells in serum‐free cultures resulted in the release of lower amounts of interleukin (IL) 1 as compared with those induced in cultures of purified monocytes. In addition, a dose‐dependent decrease in IL 1 production was observed when purified autologous T cells were added to cultures of LPS‐stimulated monocytes. The inhibitory effect of T cells on IL 1 production was reproduced by adding human recombinant IL4 to monocyte cultures. IL4 optimally inhibited the generation of cell‐associated IL 1 and the extracellular release of IL 1 in monocyte cultures performed in the presence of low doses of LPS. IL 4 inhibited the generation of IL 1 activity and that of IL 1α and IL 1β antigens indicating that IL4 interfered with IL 1 transcription and/or processing rather than induced the synthesis of an IL1 inhibitor. IL2 and IL3 enhanced IL1 production by LPS‐stimulated cells whereas granulocyte‐monocyte colony‐stimulating factor had no effect. IL4 inhibited the production and the release of tumor necrosis factor α activity by monocytes stimulated with LPS. Thus, T cells and IL4 may down‐regulate the production of monokines which induce their proliferation and exert a suppressive effect on the generation of potent proinflammatory mediators.