Stimulation of human synovial fibroblast plasminogen activator production by mononuclear cell supernatants.

Conditioned medium from concanavalin A-stimulated human peripheral blood mononuclear cells (c-MCCM) stimulates the plasminogen activator (PA) production of nonrheumatoid human synovial fibroblasts obtained from explant cultures. The effect of this synovial fibroblast-stimulating activity is observed within 2 to 4 hr and requires RNA and protein synthesis. Reversible morphological changes in the synovial cells can be observed as a result of c-MCCM action. These enzymatic and morphologic changes are similar to some of the effects of transforming viruses and tumor promoters on target cells. The possible significance of these data for an understanding of the cellular interactions involved in the formation and function of the rheumatoid "pannus" is discussed.