Targeting and manipulating mIgD-expressing B cells by anti-migis-δ monoclonal antibodies (52.18)

Abstract Membrane IgD and IgM double positive cells are the major population of B cells in the peripheral circulation. The δ chain of mIgD (mδ) differs from the δ chain of IgD in that mδ contains an extra C-terminal transmembrane-anchor peptide, of which the N-terminal extracellular segment of 26 a. a. residues, also referred as migis-δ segment, potentially provides as a unique antigenic site for isotype-specific targeting mIgD+ B cells. Here we report the preparation of mouse monoclonal antibodies (mAbs) specific for migis-δ using hybridoma methodology with ovalbumin conjugated with synthetic migis-δ peptide as the immunogen. The mAbs bound to recombinant IgD.Fc-migis-δ fusion protein in ELISA and to mIgD-expressing transfectants of a CHO cell line in fluorescence flow cytometric analysis. Only mAb 20E6, which binds to an epitope toward the N-terminal of migis-δ, was found to stain human B cell line MC116, which expressed surface IgD and IgM. MC116 cells could be induced to undergo apoptosis by the treatment of 20E6, in the absence or presence of crosslinking second antibody. These results encourage further investigation on the potential of anti-migis-δ mAbs to target or control mIgD+ B cells.