INVITRO INDUCTION OF TUMOR-SPECIFIC IMMUNITY .2. ACTIVATION OF CYTOTOXIC LYMPHOCYTES TO MURINE ONCOFETAL ANTIGENS

The presence of oncofetal antigens (OFA) on a wide variety of mouse tumor cells was demonstrated by a totally in vitro system of cellular immunity. Nonimmune spleen lymphocytes were cocultivated with irradiated syngeneic fetal liver cells and, at various times after initiation of culture, were tested for the presence of cytotoxic lymphocytes (CL) by 51Cr release assay with labeled tumor target cells. Significant cytotoxic activity was regularly detected after such culture, whereas only minor levels appeared in control cultures of spleen lymphocytes with irradiated syngeneic spleen cells. Specificity of the reaction was assessed by inhibition tests in which nonlabeled cells were admixed to the CL and 51Cr-labeled tumor targets. Fetal liver cells gave significant inhibition. No inhibition was found with adult spleen cells. Various tumor types gave inhibition, and fibrosarcomas were more effective than plasmacytomas or lymphomas. The results suggested that all tumor types tested possess such OFA, as well as their unique or virus-associated, tumor associated transplantation antigens, and the in vitro system permits a more active response to the tumor associated OFA than that observed in in vivo studies.