A Functional Study of Purified CD4+ and CD8+ Cells Isolated from Synovial Fluid of Patients with Rheumatoid Arthritis and Other Arthritides

The purpose of this investigation was to study purified synovial fluid (SF) CD4+ and CD8+ cells from patients with rheumatoid arthritis (RA) and other inflammatory joint diseases (non‐RA) with respect to the proliferative response to mitogens and recombinant interleukin 2 (rIL‐2). Highly purified cell subsets were isolated by an immunomagnetic technique, and spontaneous proliferation as well as proliferative responses to rIL‐2 and a combination of phytohaemagglutinin (PHA) and phorbol myristate acetate (PMA) (to substitute for accessory cells) were measured. Some patients had SF CD4+ and/or CD8+ cells with moderately increased spontaneous proliferation, but only the CD4+ cells of the two patient groups differed significantly from the peripheral blood (PB) T‐cell subsets of healthy individuals who served as controls. The response to rIL‐2 was variable but generally low, although about 50% of the CD4+ and 20% of the SF CD8+ cells of both patient groups expressed the Tac antigen. The response to PHA/PMA was significantly lower for RA SF CD4+ cells than for non‐RA SF CD4+ cells, which again was lower than for normal PB CD4+ cells. SF CD8+ response to PMA/PHA by both groups of patients was somewhat decreased, but not significantly lower than in the controls. Thus, the CD4+ cells seemed functionally more deviant than the CD8+ cells in both patient groups, but the abnormality was most pronounced in the RA group. The results demonstrate that the previously reported diminished response to mitogens by SF mononuclear cells is present even when SF CD4+ cells are cultured alone. This indicates that these T cells have a reduced response, probably because of prior activation.