EXPRESSION OF CD69 ANTIGEN ON SYNOVIAL-FLUID T-CELLS IN PATIENTS WITHRHEUMATOID-ARTHRITIS AND OTHER CHRONIC SYNOVITIS

Objectives-The expression of the CD69 antigen on synovial fluid and pe ripheral blood lymphocytes was studied in 12 patients with rheumatoid arthritis (RA), five subjects with other forms of chronic synovitis, a nd on the peripheral blood lymphocytes of 15 patients with systemic lu pus erythematosus (SLE) and immune vasculitis. Methods-The CD69 antige n and other activation markers (HLA-DR, interleukin 2 receptor (IL-2R) , transferrin receptor) were measured by cytometric analysis. In patie nts with RA soluble IL-2R was determined by enzyme linked immunosorben t assay (ELISA). Results-The percentage of T cells bearing CD69 was si gnificantly increased in synovial fluid from patients with RA (30.3 (1 3)%) and other chronic synovitis (18 (9)%). The expression of CD69 on peripheral blood lymphocytes of patients with RA, other chronic synovi tis, and SLE and immune vasculitis was within the normal range 2.1(1.2 )%. According to previously published work, a high proportion of synov ial fluid T cells are HLA-DR positive (64.2 (12.4)% in synovial fluid from patients with RA and 61 (1.2)% in synovial fluid from patients wi th other chronic synovitis). Transferrin receptor expression on synovi al fluid was upregulated compared with that on peripheral blood. The i ncrease of IL-2R expression on synovial fluid lymphocytes v peripheral blood was not significant; the quantitative determination of soluble IL-2R levels gave a mean value of 921 (351) U/ml in synovial fluid of patients with RA, 672 (229) U/ml in the serum of the same patients, an d 273 (100) U/ml in serum from normal subjects. Conclusions-Synovial f luid lymphocytes are in a different functional state than peripheral b lood lymphocytes. CD69 antigen is an interesting cellular marker which should be studied in patients with chronic synovitis. The unusual exp ression of the activation antigens and the sequence of their appearanc e require further study.