[A study of anti-D'E polypeptide in the diagnosis of mixed connective tissue disease].

By using immunoblotting technique (IBT) and salt extracts of rabbit thymus powder as antigen, we detected autoantibodies against polypeptides of extractable nuclear antigen (ENA) in 358 patients with different rheumatic diseases. It was found that antibodies against polypeptides with molecular weights of 13,900 dalton (designated as D') and 11,500 dalton (designated as E) could be detected only in mixed connective tissue disease (MCTD) with a positive rate of 19.1%. These antibodies were termed collectively as anti-D'E polypeptide in this paper and shown to have high specificity for the diagnosis of MCTD (P < 0.001).