Purification of the Putative TSTA of Rodent and Human Tumors

similarities to normal histocompatibility antigens (4, 7, 8, 16, 24). Although the rejection of transplantable tumors among syngeneic animals has been used profitably in the study of animal tumors, this type of experimental design has been precluded in humans by both ethical considerations and the lack of a syngeneic donor-host relationship. Thus, a num ber of in vitro assays of the host's cellular and humoral immune responses against putative TSTA have been devel oped which are applicable to both animal and human tumor systems (1, 13, 14). Because the TSTA appear to be only weakly immunogenic, the antitumor immune responses evoked on the part of the tumor host are correspondingly weak (12, 23). Nevertheless, these immune responses are apparently far more tumor specific than can be evoked by the immunization of xenogeneic animals. On the basis of the foregoing observations, the expemi ments to be described were designed with the following objectives: (a) to use the host's antitumor immune response in order to monitor the purification of the putative TSTA of rodent and human tumor tissues; (b) to determine whether any structural and/or immunochemical similarities exist be tween human and rodent TSTA; and (c) to determine whether there are any immunochemical and/or structural relationships between the TSTA and normal histocompati bility antigens in either the rat or human.