Fibroblast-activating factor production by interleukin (IL)-2 dependent T-cell clones from rheumatoid arthritis patients and normal donors.

T cells spontaneously responsive to interleukin (IL)-2 were cloned from the peripheral blood (PBL) or synovial fluid (SFL) lymphocyte populations obtained from patients with rheumatoid arthritis (RA) or from normal PBL. The clones were compared for their capacities to produce fibroblast-activating factors (FAFs) which support the growth of RA synovial fibroblasts. Clones derived from all sources produced FAFs following mitogen stimulation, but SFL clones synthesized significantly higher levels of FAF activity. Physicochemical characterization of the FAFs suggested that SFL- and PBL-derived clones produced similar factors. It was also demonstrated that interferon-gamma and IL-2 did not contribute to the FAF activity of the clone supernatants. These results demonstrate that a subpopulation of activated lymphocytes which are present in increased numbers in the rheumatoid joint can produce factors which influence rheumatoid synovial cell growth.