Human autoantibodies against the 70-kd polypeptide of U1 small nuclear RNP are associated with HLA-DR4 among connective tissue disease patients.

Serum samples from patients with connective tissue disease (CTD) were characterized using a recently developed enzyme-linked immunosorbent assay for reactivity with individual specific polypeptides of U1 small nuclear ribonucleoproteins, including the U1-70-kd protein. The distribution of HLA antigens was compared in CTD patients with and in those without anti-U1-70-kd autoantibodies and in normal controls. The frequencies of HLA-DR4 and HLA-DRw53 were increased among the anti-U1-70-kd autoantibody positive CTD group compared with the frequencies in anti-U1-70-kd autoantibody negative systemic lupus erythematosus patients and compared with normal controls. We conclude that the presence of autoantibodies reactive with the anti-U1-70-kd protein antigen is associated with HLA-DR4 and HLA-DRw53.