CHARACTERIZATION OF NEW RAT ANTI-MOUSE IGE MONOCLONALS AND THEIR USE ALONG WITH CHIMERIC IGE TO FURTHER DEFINE THE SITE THAT INTERACTS WITH FC-EPSILON-RII AND FC-EPSILON-RI

Three rat monoclonal antibodies specific for mouse IgE (C12B9, 23G3, and B1E3) were established by using monoclonal anti-DNP mouse IgE (mIgE) as immunogen. These antibodies, as well as a fourth, (R1E4) were characterized. It was found that one antibody (C12B9) recognizes an allotypic determinant (Igh-7a) found on the C-epsilon chain of mIgE. Antibody cross-blocking studies and epitope mapping studies using recombinant mIgE indicated that 3 antibodies (C12B9, R1E4 and 23G3) were directed against the C-epsilon-3 domain while one (B1E3) was directed against the C-epsilon-4 domain. A highly specific sandwich RIA for mIgE was developed using these antibodies. Use of these monoclonal anti-mIgE antibodies in conjunction with recombinant chimeric mIgE-human IgG1 molecules, demonstrated that the C-epsilon-3 domain is important in the binding of mIgE to the murine B cell Fc-epsilon-RII as well as to the murine mast cell Fc-epsilon-RI. The presence of the C-epsilon-4 domain influenced the binding of the recombinant IgE to the Fc-epsilon-RII; in contrast to the C-epsilon-4 domain had no effect on binding to the Fc-epsilon-RI.