Specific immunoglobulin production and enhanced tumorigenicity following ascites growth of human hybridomas

Human × human hybridomas constructed with the B6 lymphoblastoid clone, which produces antitetanus toxoid (TT) antibody, and the lymphoblastoid cell line KR-4 or human hybrid myeloma KR-12, were adapted to growth as ascites in pristane-treated BALB/c nude mice by a single prior passage as a solid subcutaneous (s.c.) tumor in irradiated nude mice followed by in vitro culture. Both B6 × KR-4 and B6 × KR-12 hybrids produced anti-TT antibody and phenotypically resembled the lymphoblastoid KR-4, or the hybrid myeloma KR-12 parent, respectively. Growth as ascites increased the tumorigenicity of both hybrids in nude mice as measured by tumor incidence and rate of tumor growth. The observed increase in tumorigenicity of these hybrid cells after ascites growth was associated with a substantial loss of chromosomes. Passage of the B6 × KR-4 lymphoblastoid hybrid resulted in several reversible morphological changes characteristic of myeloma cells. These changes correlated with increased human Ig production. These observations provide a system for greatly amplifying human monoclonal antibody production.