Interleukin-6 expression in immunologically elicited murine macrophages.

We report the expression of both interleukin-6 (IL6) messenger RNA and biological activity in complete Freund's adjuvant-elicited peritoneal macrophages (CFA-M phi). IL6 mRNA expression peaked between 4 and 8 h of lipopolysaccharide (LPS) stimulation; biological activity was maximal at approximately 18 h of stimulation. LPS-induced IL6 mRNA was inhibited by treatment with cycloheximide (5 micrograms/ml), implicating the participation of a secondary protein mediator in the induction process, or the dependence upon protein synthesis for receptor ligand interactions. Comparison of CFA-M phi with resident peritoneal macrophages suggests that the elicited cell population makes more IL6 in response to LPS than the resident population on a per cell basis.