INTERLEUKIN-2 SECRETION BY SYNOVIAL FLUID LYMPHOCYTES IN RHEUMATOID ARTHRITIS

Interlcukin-2 (IL-2) receptor bearing cells and soluble IL-2,measured in a bioassay with IL-2 dependent human T-cell blasts,were recognized in synovial fluid, but not in the peripheralblood of patients with rheumatoid arthritis (RA). After stimulationin vitro with appropriate concentrations of the mitogen concanavalinA (Con-A), comparable proportions of IL-2 receptor (IL-2R) bearingcells were seen in cultures of synovial fluid lymphocytes (SFL)and in cultures of peripheral blood lymphocytes (PBL). On theother hand, higher levels of secreted IL-2 were found in SFLcultures compared to corresponding PBL cultures of RA patientsand normal donors. Specificity of the IL-2 bioassay was confirmed by blocking theT-cell blast proliferation (induced by SFL culture supernatants),by 83±4%, after addition of a monoclonal anti-IL-2R antibody.Despite the high levels of soluble IL-2, only a weak proliferativeresponse was observed in the corresponding SFL cultures. KEY WORDS: Cytokines, Reactive arthritis, Lymphocyte prohferation, Mitogen stimulation, Inhibition