Antitumor immunity after surgical removal of 3-methylcholanthrene-induced murine tumors: correlation between resistance and delayed hypersensitivity reaction.

The relationship between tumor resistance and the antitumor delayed hypersensitivity reaction (TDHR) after resection of the tumor was studied by using the syngeneic 3-methylcholanthrene-induced murine tumor, MCA-DDD. MCA-DDD was inoculated subcutaneously into the tail of DDD mice and 4 weeks later the tumor-bearing tail was resected. The tumor resistances of the mice were then determined from the diameters of the tumor that developed 14 days after subcutaneous challenge of the mice with tumor cells in the flank. It was found that the mice showed a specific resistance to the tumor until 30 days after tumor resection. In parallel with tests on tumor resistance, TDHR of the mice after tumor resection was examined by the footpad test. The cell-free fraction of sonicated MCA-DDD tumor cells was used as the preparation of tumor antigens. TDHR of the mice appeared soon after tumor resection, reached a maximum on day 7, and then decreased slowly until day 29. Mice that acquired tumor resistance showed rapid increase of TDHR after challenge with fresh tumor cells. TDHR was high on day 4 after the challenge and its level was well correlated with tumor resistance of the mice.