Epitope analysis and primary structures of variable regions of anti-human Fc epsilon RI monoclonal antibodies, and expression of the chimeric antibodies fused with human constant regions

The structural analysis of monoclonal antibodies (mAbs) against the alpha s ubunit of the high affinity IgE receptor (Fc epsilon RI alpha) is an altern ative approach to obtaining information for the design of inhibitors that w ill block complementary interaction between IgE and Fc epsilon RI alpha and to analyzing the various biological effects induced by anti-Fc epsilon RI alpha autoantibodies in chronic urticaria. In this study, epitopes for mous e anti-human Fc epsilon RI alpha mAbs and primary structures of variable re gions of the mAbs mere analyzed. Three mAbs inhibitory for IgE-binding reac ted to the deletion mutants of Fc epsilon RI alpha containing the whole sec ond immunoglobulin-like domain as well as IgE did. On the other band, two u ninhibitory mAbs reacted to those containing the whole first immunoglobulin -like domain. The cDNAs for variable regions of the five mAbs mere cloned a nd sequenced. Two inhibitory mouse/human chimeric antibodies mere expressed in COS7 cells and bound to Chinese hamster ovary transfectant cells expres sing Fc epsilon RI (CHO/alpha beta gamma), and these inhibited the binding of IgE to CHO/alpha beta gamma cells.