ANTI-INTERLEUKIN-6 AUTOANTIBODIES IN RHEUMATIC DISEASES - INCREASED FREQUENCY IN THE SERA OF PATIENTS WITH SYSTEMIC-SCLEROSIS

Objective. To investigate the presence and the roles of anti-interleukin-6 (anti-IL-6) autoantibodies in rheumatic diseases, and to further elucidate clinical and pathophysiologic significance of anticytokine autoantibodies. Methods. Anti-IL-6 IgG autoantibodies were measured by the I-125-IL-6 binding activity of IgG, which was isolated from serum by protein A-Sepharose. Results. Nine of 52 sera (17.3 %) from patients with systemic sclerosis (SSc) contained anti-IL-6 antibodies, whereas only 1.9 % of sera from normal subjects and 0-5 % of sera from patients with other rheumatic diseases were positive for the antibodies. Moreover, anti-IL-6 autoantibodies were found predominantly among patients with the limited form of SSc (42.9 %), compared with those with the diffuse form (7.9 %). Conclusion. Anti-IL-6 IgG autoantibodies were detected in patients with SSc, particularly those with the limited form of the disease, at a significantly increased frequency compared with normal subjects and patients with other rheumatic diseases. These results suggest that the development of anti-IL-6 autoantibodies and IL-6 may have a role in the pathophysiology of SSc.