Interleukin 2‐independent stimulation of rabbit chondrocyte collagenase and prostaglandin E2 production by an interleukin 1‐like factor

Abstract

In the present study, interleukin 1 (IL 1)‐containing media from different sources, namely a murine macrophage cell line (P388D₁), rabbit peritoneal macrophages, and human peripheral blood mononuclear cells, were compared for their effect on thymocyte proliferation and on collagenase and PGE₂ secretion by chondrocytes. A high correlation was found between the enhancement of thymocyte proliferation and the induction of collagenase and PGE₂ secretion by chondrocytes. Furthermore, a highly purified IL 1‐like factor, namely mononuclear cell factor (MCF) was also active on chondrocytes. The addition of highly purified IL 2 to rabbit chondrocytes had no effect on collagenase and PGE₂ secretion induced by IL 1‐containing media. Our findings suggest that the factor which induced collagenase and PGE₂ secretion by rabbit chondrocytes was an IL 1‐like factor. Thus, collagenase secretion by chondrocytes may be used as an IL 2‐insensitive assay for the detection of IL 1‐like factors.