| Abstract: | The immune response of mice to a transplacentally induced lung tumor was investigated with the microcytotoxicity (MC) assay. The tumor, originally induced in C3Hf mice, does not grow readily when transplanted to normal syngeneic C3Hf recipients. It grows readily, however, in (A C3Hf)F1 hybrids and in strain C3H mice, which express in their normal lung tissue a component which constitutes a strong lung tumor-associated transplantation antigen (TATA) in C3Hf mice. Both lung tumor-immunized C3Hf and tumor-bearing (A X C3Hf)F1 and C3H mice possessed lymphoid cells reactive against cultured lung tumor cells in the MC assay. Reactivity was also observed against cells cultured from normal lungs of (A X C3Hf)F1 and C3H mice, but not against cells similarly cultured from C3Hf of C57BL/6 mice. Anti-tumor MC was inhibited by serum-blocking factors present in some but not all tumor-bearing and tumor-immunized mice. The MC assay and detection by it of serum-blocking factors does not distinguish the effective anti-C3Hf lung tumor immune response of immunized C3Hf mice from the ineffective immune response of tumor-bearing (A X C3Hf)F1 and C3H mice. Furthermore, in lung tumor-bearing mice cells reactive in the MC assay may be directed against a normal tissue antigen rather than a tumor-associated antigen. |
