Generation and characterization of an HLA-DR alpha-specific monoclonal antibody using L-cell transfectants expressing human and mouse class II major histocompatibility dimers.

Among the HLA-DR-specific monoclonal antibodies (mAbs) that have been characterized previously, there is a marked shortage of DR alpha chain-specific mAbs which stain unfixed cells. This may result from the high degree of sequence similarity between the alpha 1 domains of HLA-DR and H-2E leading to a state of cross-tolerance to DR alpha in H-2-expressing mice. BALB/b (E-negative) mice were immunized with DR1-transfected mouse L cells. The chain specificity of the resulting DR-specific mAb was determined using a panel of transfectants expressing hybrid mouse/human class II heterodimers. A DR alpha-specific mAb was generated which was capable of immunoprecipitating DR alpha beta dimers and inhibiting the anti-DR alloresponse of human T-cell clones. The present study demonstrates that, with the selection of a suitable recipient strain, transfectants can be useful in the generation and definition of chain-specific mouse mAbs.