Unique epitopes on C epsilon mX in IgE-B cell receptors are potentially applicable for targeting IgE-committed B cells.
Membrane-bound IgE (mIgE) is part of the IgE-BCR and is essential for generating isotype-specific IgE responses. On mIgE(+) B cells, the membrane-bound epsilon-chain (mepsilon) exists predominantly in the long isoform, mepsilon(L), containing an extra 52 aa CepsilonmX domain between CH4 and the C-terminal membrane-anchoring segment; the short isoform of mepsilon, mepsilon(S), exists in minor proportions. CepsilonmX thus provides an attractive site for immunologic targeting of mIgE(+) B cells. In this study, we show that nine newly prepared CepsilonmX-specific mAbs, as well as the previously reported a20, bound to mIgE.Fc(L)-expressing CHO cells, while only 4B12 and 26H2 bound to mIgE.Fc(L)-expressing B cell line Ramos cells. The mAb 4B12 bound to the N-terminal part, 26H2 the middle part, and all others the C-terminal part of CepsilonmX. Expression of Igalpha and Igbeta on the mIgE.Fc(L)-CHO cells reduces the binding of a20 to CepsilonmX as compared with that of 4B12 and 26H2. The chimeric mAbs c4B12 and c26H2, when cross-linked by secondary antibodies, lysed mIgE.Fc(L)-Ramos cells by apoptosis through a BCR-dependent caspase pathway. Using PBMCs as the source of effector cells, c4B12 and c26H2 demonstrated Ab-dependent cellular cytotoxicity toward mIgE.Fc(L)-Ramos cells in a dose-dependent fashion. In cultures of PBMCs from atopic dermatitis patients, c4B12 and c26H2 inhibited the synthesis of IgE driven by anti-CD40 and IL-4. These results suggest that 4B12 and 26H2 and an immunogen using the peptide segments recognized by these mAbs are potentially useful for targeting mIgE(+) B cells to control IgE production.
Chen
Jiun-Bo
JB
Institute of Molecular Medicine, National Tsing Hua University, Hsinchu, Taiwan.
Wu
Pheidias C
PC
Hung
Alfur Fu-Hsin
AF
Chu
Chia-Yu
CY
Tsai
Tsen-Fang
TF
Yu
Hui-Ming
HM
Chang
Hwan-You
HY
Chang
Tse Wen
TW
D000595:Amino Acid Sequence; D000818:Animals; D000920:Antibody-Dependent Cell Cytotoxicity / Q000235:genetics; D017209:Apoptosis / Q000235:genetics / Q000276:immunology; D016175:B-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism*; D001666:Binding Sites, Antibody / Q000235:genetics; D016466:CHO Cells; D002460:Cell Line; D045744:Cell Line, Tumor; D002999:Clone Cells; D006224:Cricetinae; D003412:Cricetulus; D018985:Epitopes, B-Lymphocyte / Q000235:genetics* / Q000378:metabolism*; D018390:Gene Targeting; D006801:Humans; D007073:Immunoglobulin E / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D007139:Immunoglobulin epsilon-Chains / Q000096:biosynthesis* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism*
D018985:Epitopes, B-Lymphocyte; D007139:Immunoglobulin epsilon-Chains; D020033:Protein Isoforms; D011947:Receptors, Antigen, B-Cell; D007073:Immunoglobulin E