Interleukin 6 is involved in interleukin 1‐induced activities

Abstract

Human monocytes produce a number of soluble mediators involved in regulation of inflammation and lymphocyte growth and differentiation such as interleukin 1 (IL1) and tumor necrosis factor. Recently, the cDNA of another monocyte-derived factor, interleukin 6 (IL6), was cloned. Herein we show that purified E. coli-derived recombinant IL6 (rIL6) is as active as IL 1 in the thymocyte assay. In addition, IL 1 and IL 6 synergize strongly in stimulating thymocyte proliferation. Another property shared by IL 1 and IL6 is their pyrogenicity. Human rIL6 induces a monophasic fever after i.v. injection into rabbits. Together with the observation that IL 1 induces IL6 in a variety of cells including thymocytes, our data suggest that IL6 is involved in many of the pleiotropic effects of IL1.