A murine monoclonal antibody recognizes the 13,000 molecular weight polypeptide of the Sm small nuclear ribonucleoprotein complex.

Antibodies to the Sm antigen are closely associated with the rheumatic disease systemic lupus erythematosus (SLE). The Sm antigen exists in the cell as part of a ribonucleoprotein complex containing at least 10 polypeptides and five small nuclear RNA. The major immunoreactive Sm species are three polypeptides of m.w. 27,000, 26,000, and 13,000. By using an MRL/1 mouse, a strain which spontaneously produces a disease with many of the characteristics of human SLE, we have produced an anti-Sm hybridoma specific for the 13,000 m.w. Sm polypeptide. This monoclonal antibody is sufficient to allow for the rapid bulk isolation of the entire class of Sm snRNP, and can be used sequentially with an anti-(U1)RNP monoclonal antibody to subfractionate the Sm snRNP particles.