Associations of IgA and IgA-rheumatoid factor with disease features in patients with rheumatoid arthritis

In previous studies we have shown that levels of IgM-rheumatoid factor (RF) in plasma and peripheral blood mononuclear cell supernatants are correlated with disease activity and response to second-line therapy in patients with rheumatoid arthritis (RA). The present studies were designed to examine whether IgA-RF levels are also correlated with clinical features of this disease. Two groups of RA patients were studied. Group I consisted of 87 patients in whom extensive clinical data had been collected. Group II included nine patients beginning treatment with gold or methotrexate who were studied during the first year of therapy. Measurement of IgM, IgA, IgM-RF and IgA-RF in culture supernatants and plasma was done by an ELISA method. These data were examined for correlations with clinical and laboratory features. Levels of IgA-RF in supernatants and plasma were found not to be correlated with disease features in the cross-sectional analysis of Group I patients, while IgM-RF and total IgA levels did show significant clinical correlation. Treatment of Group II patients with gold or methotrexate was associated with significant decreases in plasma levels of total IgA and IgM-RF as well as a small but statistically significant decrease in plasma IgA-RF. Plasma levels of total IgM were not altered during therapy. These findings suggest that production of IgA but not IgA-RF is correlated with disease status in patients with RA.