Affiliations: [a] Graduate School of Genetic Resources Technology, Kyushu University, Higashi-ku, Fukuoka | [b] Morinaga Institute of Biological Science, Tsurumi-ku, Yokohama | [c] Department of Radiology, Tokyo Women's Medical College, Shinjuku-ku, Tokyo, Japan
Correspondence:
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Correspondence and reprint requests to: Hirofumi Tachibana, Department of Food Science and Technology, Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka, Japan.
Abstract: The heavy and light chain genes (μ and λ) of the human anti-adenocarcinoma monoclonal antibody HB4C5 (MAb-C5) were cloned from the human-human hybridoma cell line HB4C5 and co-expressed in Chinese hamster ovary (CHO) and COS-7 cells. ELISA assay and the RI imaging of the cancer tissue xenografted into nude mice showed that the recombinant MAb-C5 retained the original antigen binding activity. We then replaced the IgM constant region of this MAb-C5 heavy chain gene with the human IgG1 constant region gene and co-expressed it with the light chain gene. This recombination was confirmed by a complete DNA sequencing and Western-blot analysis. Despite thefact that the DNA sequence, the expressed protein size, and the assembly of heavy and light chains were indicated to be normal, the IgG1 type MAb-C5 could not bind to the original antigen. This result suggests that this antibody alters its antigen binding property upon class-switching.
Keywords: Human monoclonal antibody, HB4C5, recombinant, class switch
