Diversity in the fine specificity and idiotypic profile of mouse anti-HLA-DR monoclonal antibody elicited with the syngeneic anti-idiotypic monoclonal antibody F5-830.

Four hundred and sixty-six hybridomas were generated from a BALB/c mouse immunized with the syngeneic anti-idiotypic mAb F5-830 that recognizes an idiotope in the Ag-combining site of mAb AC1.59. At an appropriate concentration, the latter reacts with a determinant expressed by HLA-DR1, DRw8, and DRw9 Ag and subtypes of HLA-DR4 and DRw6 allospecificities. Serologic and immunochemical assays identified eight anti-HLA-DR anti-anti-idiotypic mAb. They are heterogeneous in their reactivity with a panel of HLA-typed B lymphoid cells: like mAb AC1.59, the anti-anti-idiotypic mAb MA1/38, MA1/40, MA1/47, and MA1/98 recognize the determinant shared by HLA-DR1, DRw8, and DRw9 Ag and subtypes of HLA-DR4 Ag. On the other hand, the anti-anti-idiotypic mAb MA1/52, MA1/157, MA1/281, and MA1/285 have a more restricted reactivity, inasmuch as the corresponding determinant(s) is detectable on only some of the allospecificities recognized by mAb AC1.59. Each anti-anti-idiotypic mAb varies in its extent of reactivity with HLA-DR allospecificities. These results suggest differences in the fine specificity of anti-HLA-DR anti-anti-idiotypic mAb and in the structural characteristics of the mAb AC1.59 defined determinant shared by HLA-DR1, DRw8, and DRw9 Ag and subtypes of DR4 allospecificities. Furthermore, the anti-anti-idiotypic mAb are heterogeneous in terms of expression of idiotopes and of their spatial relationship with their Ag-combining site. The heterogeneity in the characteristics of anti-HLA-DR antibodies elicited with anti-idiotypic mAb F5-830 suggests that the Id cascade triggered by immunization with incompatible HLA allospecificities may account for the changes in the anti-HLA antibody specificity that have been observed in the course of an immune response to mismatched HLA alloantigens.