Enzyme-linked immunosorbent assay using isolated (U) small nuclear ribonucleoprotein polypeptides as antigens to investigate the clinical significance of autoantibodies to these polypeptides.

In order to investigate the clinical significance of autoantibodies to individual U small nuclear ribonucleoprotein (snRNP) polypeptides, an enzyme-linked immunosorbent assay (ELISA) using isolated 68K, A, B/B', and D polypeptides from purified U1 snRNP was developed. The ELISA levels of IgG antibodies were positively correlated with results of immunoblotting and hemagglutination. In patients positive for antibodies to ribonucleoprotein, IgG anti-68K reactivity was associated with active mixed connective tissue disease, and in particular with myositis and esophageal hypomotility. IgG B/B' and D polypeptide reactivities were associated with systemic lupus erythematosus and renal disorder. Raynaud's phenomenon was infrequent in patients with high IgG B/B' and D polypeptide reactivities. Pleuritis/pericarditis was associated with the IgG B/B' polypeptide reactivities. In longitudinal studies, ELISA levels of IgG antibodies against these polypeptides changed in parallel with disease activity.