Surveillance, latency and the two levels of MCA-induced tumor immunogenicity.

Among 154 different, MCA-induced mouse sarcomas, the immunogenicities of those tumors that had had the shortest original latencies in their autochthonous hosts were of an intermediate level with relatively little scatter. This fact is not predicted by the theory of immunological surveillance, but does fit the predictions of the immunological facilitation theory of oncogenesis. The frequency distribution of the tumor immunogenicities showed 2 peaks; the cluster of higher immunogenicity had a shorter latency than did the cluster of lower immunogenicity. The data for tumors initiated within in vivo diffusion chambers also showed 2 immunogenicity clusters, suggesting that the discrete clusters were not caused by host immunity. However, immunity apparently reduced the mean latency of the more immunogenic cluster and/or lengthened the mean latency of the less immunogenic, a result also inconsistent with the theory of immunological surveillance.