A recombinant extracellular domain of the human interleukin 4 receptor inhibits the biological effects of interleukin 4 on T and B lymphocytes

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Abstract
Human interleukin 4 (IL 4) acts on various hematopoietic cell types through interaction with a specific cell surface receptor (IL 4R), whose cDNA has been cloned. We have produced a cDNA encoding a soluble form of the extracellular domain of the human IL 4R (sIL 4R) and describe here the capacity of sIL 4R to antagonize the in vitro activities of IL 4 on normal B and T lymphocytes. sIL 4R inhibited IL 4‐induced proliferation of both phytohemagglutinin‐preactivated peripheral blood mononuclear cells (PBMC) and anti‐IgM co‐stimulated tonsil B cells with similar efficiency. This inhibitory activity was specific since sIL 4R did not affect IL 2‐dependent proliferation of these cells. sIL 4R also blocked IL 4‐dependent induction of the low‐affinity receptor for IgE on B cells and inhibited IgE production by IL 4‐activated PBMC. Thus, in contrast to the IL 6R extracellular domain which stimulates IL 6 biological activity, the IL 4R extracellular domain is a powerful antagonist of its specific ligand.