Expression of anti-double stranded DNA idiotype in mixed connective tissue disease and progressive systemic sclerosis.

The occurrence of anti-double stranded(ds) DNA idiotype 2C10 was studied in patients with mixed connective tissue disease (MCTD) and progressive systemic sclerosis (PSS). The 2C10-idiotype was originally identified on a dsDNA-specific monoclonal antibody from a lupus-prone MRL/Mp-lpr/lpr (MRL/l) mouse, and it has been demonstrated to be present in the sera of patients with systemic lupus erythematosus (SLE) as well as MRL/l mice. This study showed that three out of ten patients with MCTD and five out of ten with PSS had higher titers of 2C10-idiotype in their sera than the normal subjects. There was a good correlation between the anti-dsDNA activities and the idiotype levels in MCTD (r = 0.85) but not in PSS (r = -0.38). These results suggest that the 2C10-idiotype-bearing antibodies acquire the dsDNA-binding activity more easily in MCTD than in PSS.