The reactivities to individual
U1 small nuclear ribonucleoprotein (
snRNP) components and their relationship to clinical features in patients with anti-U1
snRNP antibodies were examined. We evaluated 114 patients with
connective tissue disease whose sera were positive for anti-U1
snRNP antibodies, but negative for anti-Sm
antibodies.
Antibodies to the
U1 snRNP polypeptides 70K, A, and C were detected using subunit-specific
enzyme-linked
immunosorbent assays and
antibodies to
U1 small nuclear RNA (
snRNA) were identified by an immunoprecipitation assay using deproteinized HeLa cell extracts. The clinical features were retrospectively obtained by chart review and prospectively collected after study entry. The pattern of antibody reactivities to
U1 snRNP components varied among patients. The frequency of anti-70K, anti-A, anti-C, and anti-U1
snRNA antibodies was 60%, 86%, 74%, and 46%, respectively. There was no relationship between each reactivity and the clinical findings, but the presence of reactivities to increasing numbers of
U1 snRNP components was correlated with sclerodactyly, shortness of the sublingual frenulum, esophageal dysfunction, and a lack of persistent proteinurea (p < 0.05 for all comparisons). The detection of
autoantibody reactivities to individual components of the
U1 snRNP particle is potentially useful for predicting the
clinical course in patients with
connective tissue disease and anti-U1
snRNP antibodies.