Anti‐idiotypic antibodies specific for a pathologic anti‐Pr2 cold agglutinin

The heterogeneity of human red cell (RBC) autoantibodies may be assessed by using anti‐idiotypic antibodies. In this study, mouse monoclonal anti‐idiotypic antibodies were produced against a pathologic RBC autoantibody with anti‐Pr2 specificity. Epstein‐Barr virus‐transformed B‐cell clones were established from a patient who had splenic lymphoma and associated immune hemolysis due to an anti‐Pr2 cold autoantibody. Two of the eight clones producing this autoantibody were used to immunize mice for the establishment of hybridomas, and four monoclonal anti‐idiotypic antibodies were isolated (2 IgG1 kappa and 2 IgM kappa). By the use of these anti‐idiotypic antibodies, strong cross reactivity was seen on enzyme‐linked immunosorbent assay with other anti‐Pr2‐producing clones from the same patient, but no cross‐reactivity was seen with RBC autoantibodies from other individuals having anti‐Pr or different specificities. Each of the anti‐idiotypic antibodies inhibited hemagglutination (HA) by the patient's anti‐Pr2 but failed to inhibit HA by antisera of a different RBC specificity. Cross‐competition experiments indicated that all of the anti‐idiotypic antibodies may recognize the same or a closely related idiotope on the anti‐Pr2 autoantibody. These studies suggested that the four anti‐idiotypic antibodies are directed against the same (or closely related) idiotypic determinant(s), unique to this patient's anti‐Pr2 and located at or near the antigen‐binding site. These anti‐idiotypic antibodies may be useful tools for the study of this autoimmune response or for the development of immune therapeutic agents. Additional panels of anti‐idiotypic antibodies will be necessary to elucidate further the idiotypic diversity of RBC autoantibodies occurring both in healthy individuals and in patients with immune hemolysis.