The measurement of antibodies to extractable nuclear antigen.

By the use of a combination of Ouchterlony immunodiffusion and hemagglutination, it was found that 30 of 81 sera (37%) from patients who had systemic lupus erythematosus (SLE) had antibodies to the ribonucleoprotein component of extractable nuclear antigen, and 37 (46%) had antibody to the Sm antigen. Immunodiffusion was more sensitive for detection of anti-ribonucleoprotein, while hemagglutination detected more anti-Sm. Both technics are necessary to define qualitatively the types of antibodies present in SLE sera.