Antibodies to RNA from autoimmune NZB/NZW mice recognize a similar antigenic determinant and show a large idiotypic diversity

We have identified two RNA-specific hybridoma autoantibodies in fusions of spleen cells from unimmunized NZB/NZW female with BALB/c myeloma cells. The two fusion experiments were carried out 2 years apart with different myeloma partners. Specificity analyses showed that the two monoclonal antibodies and the total RNA-binding IgG in NZB/NZW serum recognize a G,C-rich sequence of ribonucleotides. The isolated heavy and light chains of the two antibodies and their papain Fab fragments could be distinguished by NaDodSO₄/polyacrylamide gel electrophoresis. Rabbit anti-idiotypic antibodies prepared against the two monoclonal proteins showed unique specificities for the antigen-binding sites of their cognate auto-antibodies. Moreover, the anti-idiotypic antisera had little effect on the RNA-binding capacity of the total IgG from NZB/NZW serum. These results suggest that a wide range of different idiotypes is involved in the autoimmune response to a similar antigenic determinant.