Differential isotype recognition of two centromere associated polypeptides by immunoblotting in connective tissue disease.

On investigating the immunoblotting profile of 65 systemic sclerosis patients, a 140 kD polypeptide was recognised by sera from 16, when immunoblotted against a nuclear-enriched K562 cell sonicate. All 16 sera contained anticentromere antibodies (ACA) detected by immunofluorescence (IF) and 15 of 16 also recognized a 19 kD polypeptide on immunoblotting. Two ACA positive sera failed to recognize the 140 kD polypeptide but one of these recognized the 19 kD polypeptide. The 140 kD polypeptide identified a group with more limited skin involvement (P less than 0.05) and all 16 had Raynaud's phenomenon. The sera from three of 100 systemic lupus erythematosus (SLE) patients also recognized both polypeptides. On investigating the isotype specificity, the 140 kD polypeptide was strongly detected by an IgM autoantibody and the 19 kD polypeptide by an IgG autoantibody.