The invention pertains to the generation and utility of antibodies that can bind effectively to CepsilonmX domain on membrane-bound IgE (mIgE) expressed on the surface of human B lymphocytes. The CepsilonmX domain of 52 amino acid residues, located between the CH4 domain and the C-terminal membrane-anchor peptide on human membrane-bound epsilon chain, had been suggested as an antigenic site for immunological targeting of B cells expressing mIgE. Previous reported monoclonal antibodies, including a20, which bind to RADWPGPP (SEQ ID NO:1) peptide at the C-terminal of CepsilonmX, have now been found to bind poorly to mIgE on human B cells. We have discovered that only monoclonal antibodies specific for certain segments, such as GLAGGSAQSQRAPDRVL (SEQ ID NO:2) and HSGQQQGLPRAAGGSVPHPR (SEQ ID NO:3), of CepsilonmX can bind effectively to mIgE on human B cells and hence have the utility for targeting those B cells for the treatment of diseases mediated by IgE.
