Production of mononuclear cell factor by mononuclear phagocytes from rheumatoid synovial fluid.

Collagenase-and PGE1-stimulating activities (mononuclear cell factor or MCF) have been found in culture supernatants from synovial fluid macrophages (SF-M phi) of patients wih rheumatoid arthritis. The apparent molecular weight of the MCF activity present in SF-M phi supernatants was between 15-20,000 daltons, which is similar to interleukin I. All the SF-M phi supernatants from patients tested showed the MCF activity. Our study presents evidence for MCF production by monocyte-macrophages at the local site of the lesion.