Characterization of mouse-human hybridoma as a useful fusion partner for the establishment of mouse-human-human hybridoma secreting anti-tetanus toxoid human monoclonal antibody of IgM or IgG class

We succeeded in establishing a mouse-human (M-H) heterohybridoma clone which provides parental cells useful for human monoclonal antibody (hMoAb) production. Electron micrographs show that the M-H hybridoma cells retain characteristics of murine origin with regard to chromatin patterns, small granules, granular endoplasmic reticulum and Golgi apparatus. The human DNA incorporated into the M-H hybridoma is estimated to be about 1% of the total human chromosomal DNA. Mouse-human-human (M-H-H) hybridomas obtained by hybridization of the M-H hybridoma cells with Epstein-Barr virus(EBV)-transfected human B cells secrete immunoglobulin (Ig) in amounts comparable to those of murine hybridomas. Also the M-H-H hybridomas grow in nude mice and are capable of producing ascites containing large quantities of Ig. The Ig class switching takes place in the M-H-H hybridomas at a much higher frequency than in the original EBV transformant and the M-H hybridoma. Cells secreting specific monoclonal antibody of different Ig classes could be separated and concentrated by the use of fluorescence activated cell sorter (FACS).