Ribonucleoprotein (RNP) soluble nuclear antigen: demonstration of its reaction with serum antibodies by counter-immunoelectrophoresis and further partial characterization.

The soluble ribonucleoprotein nuclear antigen reactive with specific antibodies present in sera from patients with Mixed Connective Tissure disease has alpha 2-beta 1 electrophoretic mobility, thus enabling its reaction with specific serum antibodies to be studied by counter-immunoelectrophoresis. Its molecular weight determined by elution from a calibrated Sephadex G-200 gel column is about 175,000. Its purification has been attempted by successive DEAE cellulose chromatography, Sephadex G-200 gel filtration and Hydroxyapatite chromatography. Polyacrylamide gel electrophoresis of RNP antigen-containing fractions showed persistent heterogeneity which could be due either to inadequate purification or to dissociation of the RNP-antigen during electrophoresis.