Plasminogen activator activity of rheumatoid and nonrheumatoid synovial fibroblasts

Extracellular and cell associated plasminogen activator (PA) activities were measured in a series of synovial fibroblast cell lines, derived by outgrowth and passage from both rheumatoid and nonrheumatoid tissue. In early passages of these cell lines under standardized culture conditions, the enzyme activity was low for most lines but relatively high in a few. There was no significant difference in the PA levels of the cell lines from either source. In addition, cells from both groups increased their PA activity in response to conditioned medium from peripheral blood mononuclear cells. It is concluded that the presence of fibrin-like material in rheumatoid joints cannot be simply explained by a relative defect in PA production by cells obtained after outgrowth and passage from rheumatoid explant material.