Quantitation of precipitating antibodies to certain soluble nuclear antigens in SLE.

Electrophoresis in polyacrylamide gels in the presence of sodium dodecyl sulfate was used to separate and quantitate the components of a washed immune precipitate. Serum was from patients with systemic lupus erythematosus known to have antibodies to soluble nuclear ribonucleoprotein (RNP) or to a soluble nuclear non-nucleic acid protein (Sm). Amounts of antibody that was predominantly IgG ranged from 0.2 to 8 mg/ml of patients' serum, and in some cases accounted for over 20% of the total serum IgG. Results demonstrate that some patients respond to the disease by producing large amounts of a specific antibody, and that these antibodies can contribute significantly to hypergammaglobulinemia.