SnRNP proteins are isolated, as by immunoaffinity chromatography, using antibodies from a serum sample of a living being affected by systemic lupus erythematosus. The Sm-B and/or Sm-B min polypeptides are in turn isolated from the snRNP protein complex as by gel electrophoresis and electroelution. The amino terminus of the Sm-B and/or Sm-B min polypeptides are then sequenced, and labelled DNA probes with nucleotide sequences complementary to that encoding the amino acid sequence are synthesized. A human cDNA library in a lambda cloning vector is transferred to appropriate filters such as nitrocellulose filters. These filters are screened as by hybidization with the labelled probes to identify the cDNA clones in the library with sequences matching those of the labelled probes. The cDNA encoding the Sm-B and/or Sm-B min proteins are then subcloned. The Sm-B and/or Sm-B min polypeptides are then isolated as by immunoaffinity chromatography and, if further desired, as by HPLC chromatography. An assay is then made with the isolated Sm-B and/or Sm-B min polypeptides by reacting the Sm-B and/or Sm-B min polypeptides with a serum sample of a living being to determine whether the living being is affected by systemic lupus erythematosus. The assay may also be made with a mixture of the isolated Sm-B and/or Sm-B min polypeptides and an isolated Sm-D polypeptide (isolated substantially as described above). The assay may be performed as by an enzyme-linked immunoabsorbant such as anti-human IgG/IgM antibodies covalently attached to an enzyme indicator. Lactoperoxidase/alkaline phosphatase are each an example of an enzyme indicator to indicate, as by a distinctive color, an affected person.
THE SM-B/B1 ANTIGENS, THE CLONING OF THE SM-B/B1 ANTIGENS AND THE DETECTION OF SYSTEMIC LUPUS ERYTHEMATOSUS BY USING THE SM-B/B1 ANTIGENS