EPITOPE MAPPING OF NEW MONOCLONAL-ANTIBODIES RECOGNIZING DISTINCT HUMAN FCRII (CD32) ISOFORMS

The class II Fc gamma receptors are widely distributed on cells of the immune system, Nevertheless, the exact cell type distribution of the FcRII isoforms is still unclear because of the lack of appropriate ant ibodies that discriminate between the various isoforms, In this study we describe the generation and characterization of three monoclonal an tibodies (MAbs) raised against recombinant human FcRIIb2 as well as a synthetic peptide (amino acids 30-39) of this receptor, Analyses of th e isoform specificity of these antibodies using ELISA and Western blot s revealed that the MAbs II1A5 (mIgG(1)) and ID2.7 (mIgM) are pan FcRI I antibodies recognizing all known FcRII isoforms, In contrast, the MA b II8D2 (mIgG(1)) specifically reacts with FcRIIb but not with FcRIIa. The observed antibody reactivities could be confirmed by examination of the exact epitopes using overlapping 15-mer peptides spanning the e ntire FcRIIb2, So far these antibodies are the only ones described tha t detect FcRII in Western blots. Moreover, they can be used to analyze the cellular FcRII isoform distribution at the protein level, which w as otherwise not possible.