Immunogenicity of methylcholanthrene-induced tumors tested by draining lymph node assay in syngeneic rats

The immunogenic properties of MC-induced and not metastasizing tumors were tested in inbred Wistar and August strains by the aid of lymphocyte stimulation in syngeneic draining lymph nodes in the comparison with the opposite ones. The lymphocyte stimulation was estimated in vitro by the spontaneous incorporation of 3HTdR. It was found that the peak of the first response of draining lymph nodes was noted on the 7th day after injection of syngeneic tumor cells. This antitumor response was specific because: 1. the second immunological response of draining lymph nodes to the same tumor cells developed earlier and was higher than the first response and 2. the rats previously immunized with MC-induced tumor, and then challenged with syngeneic sarcoma or syngeneic fibroblasts exhibited the lack of the second response and only some cross-reactivity was observed by the use of the other MC-induced sarcoma. MC-induced tumors appeared earlier and more frequently in August than in Wistar strain, the level of syngeneic draining lymph node response to immunogenic tumors was higher in August than in Wistar rats despite of the lack of difference between the percentages of immunogenic tumors arising in these two rat strains.