Immunochemical analysis of an arginine-rich systemic lupus erythematosus autoepitope.

The MRL mouse strain spontaneously produces antinuclear autoantibodies that recognize DNA and the small nuclear ribonucleoprotein (snRNP) antigens. The monoclonal antibody 2.73 was derived from the lupus prone MRL/n line and is reactive with the 70K protein of the U1 snRNP particle. The epitope recognized by 2.73 was characterized by peptide and inhibition ELISA analysis. Several arginine/aspartic acid (RD) repeats of varying lengths are found in the carboxyl terminus of the 70K protein and are responsible for immunoreactivity with 2.73. We investigated the contribution of charge and found that the immunoreactivity of 2.73 and the 70K protein is specific for the RD repeats. The presentation of the epitope may also contribute to the epitopes immunoreactivity with the 2.73 mouse monoclonal autoantibody.