In rheumatoid arthritis (RA), T cells have been proposed either as a main actor or as an epiphenomenon in such a primarily synoviocyte-driven disease. A major issue remains the remarkable paradox between the T cell infiltrate and the relative failure to detect definite markers of their activity. To determine the Th1/Th2 cytokine profile in RA synovium, we used a single cell flow cytometric assay for interleukin-2 (IL-2), interferon-γ (FN-γ), IL-4 and IL-10 in paired peripheral blood (PB) and synovial tissue (ST) lymphocytes from RA and osteoarthritis (OA) patients and PB lymphocytes from healthy controls. Cytokines were undetectable in unstimulated PB and ST lymphocytes. More stimulated PB arm ST CD4+ lymphocytes produced IFN-γ than IL-4, for all individuals tested. RA PB CD4+ lymphocytes showed the same Th1 cytokine pattern as normal controls. No increase of such a Th1 profile was observed for ST lymphocytes. A specific recruitment of T CD4+ lymphocytes in the rheumatoid inflamed synovium could not be concluded on the basis of these results
