Tumor-specific immunity induced by somatic hybrids. I. Lack of relationship between immunogenicity and tumorigenicity of selected hybrids

Hybrid clones were derived from fusion of TEPC-15 plasmacytoma cells of BALB/c mice with mouse L cells of C3H origin. The morphology, tumorigenicity, and immunogenicity of three representative clones were extensively studied. One clone (LTC-1) showed a morphology intermediate to that of either parental cell and possessed the highest tumorigenic and immunogenic properties. The other two clones displayed a 'flat' morphology which differed significantly from that of either parent. One of these two, LTC-4, eventually induced tumors in some (BALB/c x C3H)F₁ mice but failed to stimulate protective immunity against TEPC-15 tumor cells in BALB/c mice. The other hybrid clone, LTC-2, has a 'very flat' morphology and did not induce tumors, although it was capable of stimulating a significant level of tumor immunity. Histologically, all the tumors induced by hybrid cells were fibrosarcomas rather than plasmacytomas. These results indicate that the morphology of hybrid cells may be correlated with the tumorigenicity as well as the histologic appearance of tumor. In addition, the degree of tumorigenicity of individual hybrid clones does not correspond to their immunogenicity in the host, suggesting that major antigens responsible for immunogenicity may not play an important role in induction of tumors.