Mycobacterium tuberculosis antigen, interleukin 2 and interleukin 2 inhibitor in patients with rheumatoid arthritis

IL-2 production by the phytohemaglutinin (PHA)-stimulated mononuclear cells (MNC) of peripheral blood (PB) and synovial fluid (SF) from patients with rheumatoid arthritis (RA), other arthritic diseases (OAD) and age-matched normal controls were studied, and the activity of IL-2 inhibitor in sera of studied subject was examined. The significant decreased IL-2 production by PB MNC from the patients with RA (p < 0.05) and OAD (p < 0.05) were observed when compared with normal controls, and no statistical difference was found although IL-2 levels in RA PB were lower than in OAD PB. However, significant statistical difference (p < 0.01) was found when the IL-2 production by RA SF was compared with OAD SF. Serum IL-2 inhibitory factor was examined by IL-2-dependent mouse helper T cell line (HT-2). Significantly higher inhibitory activity was found in RA patients (p = 0.001) compared to OAD and normal control patients. Mycobacterium tuberculosis (MT) antigen was also examined from patients with RA and OAD, and 55.5% of SF from RA patients were positive for MT antigens and none was detected in OAD by a highly specific and sensitive double-antibody sandwich ELISA. However, no correlation between MT antigens, IL-2 levels and IL-2 inhibitory activities were found in patients with RA. Our results and other indicate that rheumatoid SF MNC, IL-2 inhibitor and MT antigen may play important roles in the pathogenesis of RA.