An autoantibody reactive with a 72,000 dalton centromeric antigen was detected by immunoblotting with the use of a nuclear enriched HeLa cell preparation in 42 of 77 patients with progressive systemic sclerosis (PSS). Reactivity with the 72,000 dalton polypeptide was associated with anti-centromere autoantibodies (ACA) detected by immunofluorescence (IF), and the antigen was highly conserved, being present in both human cells and Leishmania tropica. Thirty-five (83%) of the 42 sera reactive with the 72,000 dalton polypeptide also reacted with a 19,500 dalton polypeptide, and antibodies eluted from both the 72,000 dalton and the 19,500 dalton polypeptides reacted with the centromere when retested by IF on intact HEp2 cells, demonstrating that both polypeptides are antigenic components of the centromere. Only one of the 42 sera had precipitating antibodies to the Scl-70 antigen detected by counterimmunoelectrophoresis, indicating that the 72,000 dalton polypeptide was not related to the previously described Scl-70 antigen. The other 35 of the 77 sera tested were negative for ACA, although all had ANA, with the main patterns of IF being fine speckling of the nucleus (18 sera) and homogeneous or speckled staining of the nucleolus (17 sera). Anti-Scl-70 antibodies were detected in 17 of these 35 patients, 15 (88%) of whom reacted with an 89,000 dalton polypeptide, one with a 140,000 dalton polypeptide, and one with a 74,000 dalton polypeptide. Ten of the 15 sera reacting with the 89,000 dalton polypeptide also reacted with a 74,000 dalton polypeptide, and 2-D gel analysis suggested a relationship between the two molecules. Clinically defined types of scleroderma tended to associate with antibodies to particular molecular antigenic specificities. Thirty-seven (88%) of the 42 patients reactive with the 72,000 dalton polypeptide had sclerodactyly and features of the CREST syndrome, whereas patients reactive with the 89,000 dalton polypeptide and with Scl-70 tended to have more extensive cutaneous and visceral involvement.

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