Studies of rheumatoid synovial fluid lymphocytes. III. Phenotypic and functional analysis of natural killer-like cells.

Synovial fluid and peripheral blood lymphocytes from patients with rheumatoid arthritis have been compared in terms of phenotypic and functional expression of natural killer (NK) activity. Following pretreatment with the monoclonal antibodies anti-HNK-1 (anti-Leu-7) or anti-Leu-11b and complement, NK activity against K562 cells was assessed in 4-hr chromium release assays. Rheumatoid peripheral blood lymphocytes resembled those of normal individuals, in that complement-mediated lysis of Leu-11b+ cells virtually eliminated all NK activity. Complement-mediated lysis of Leu-7+ cells resulted in only a modest reduction in NK activity. Rheumatoid synovial fluid lymphocytes differed from autologous peripheral blood lymphocytes: the overall cytotoxicity was generally less and only a fraction of the NK-like activity appeared to be mediated by Leu-11b+ cells. This apparent lack of Leu-11b expression by rheumatoid synovial fluid NK-like cells could not be accounted for by blockage or alteration of the Leu-11b antigen by factors present in synovial fluid. These observations support and extend previous data showing a discordance of phenotype and function of lymphocytes in rheumatoid synovial fluid possibly representing activation of such cells within the rheumatoid joint.