Mediator and target cell variability in proliferative response of human adherent synovial cells in culture

The proliferation of cultures of adherent synovial cells was studied in response to mediators generated from several sources. Monocyte enriched cultures produced factors in the 70-80,000 and 12-16,000 molecular weight range. Both of these areas of activity also stimulate prostaglandin (PGE) from adherent synovial cells and have interleukin 1 (IL-1) activity. The 70-80,000 region appears to be the 12-16,000 molecular weight activity bound to serum components. When stimulated with the same concentration of a single preparation of this monocyte derived factor, cell lines showed great variability, with inhibition of proliferation in 2 cell lines and the remaining exhibiting stimulation. There was no correlation of proliferation with the PGE producing capacity of the cells. The proliferation response showed no correlation to PGE production by particular cell lines. Lymphocyte enriched cultures produced a factor of 36-40,000 daltons that stimulates adherent synovial cell proliferation but does not have PGE stimulating or IL-1 activity.