Demonstration of Cellular Immunity Against Urethan-Induced Lung Adenomas of Mice2

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Abstract
The tumor-specific antigenicity of urethan-induced murine lung adenomas was studied with an in vitro microassay for cell-mediated cytotoxicity. SWR mice were immunized with pooled adenomas from syngeneic animals that had been treated in infancy with 5 doses of urethan, 0.2 mg/g body weight, alone or combined with cortisone or cyclophosphamide. Direct tests on target cells from the same tumors used for immunization of the donors of effector cells were positive in 5 of 6 tumors from mice treated with urethan plus an immunodepressor, and negative in the 3 tumors from mice given urethan only. In the cross-reaction combinations, when target cells were from tumors of animals treated with urethan plus immunodepressor and effector cells from animals immunized with tumors of the same experimental group, 9 of 13 tests were positive, whereas the 4 tests with effector cells from animals immunized with tumors induced in mice given urethan only were negative. The 6 tests on tumors from mice administered urethan only, and effector cells from animals immunized with tumors from all the 3 experimental groups, were negative. In addition, the time of subcutaneous take of adenomas from the immunodepressed groups was significantly longer than that of adenomas from animals treated with urethan only. These results show that urethan-induced lung adenomas had an in vitro detectable cross-reacting antigenicity that depended on the immunological status of the tumor donors, suggesting an immunoselective process in the animals without the immunodepressive treatment.

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