[Antitumor defense mechanisms in mice with progressively growing murine bladder tumor (MBT-2)].

MBT-2 in C3H/HeN mice was used as a model to examine cytotoxic activity. The cytotoxic activities examined were those of natural killer cells (NK), lymphokine activated killer cells (LAK), and tumorcidal macrophage (M psi). NK activity increased in early tumor bearers, but LAK and M psi activities increased in middle tumor bearers. NK activity was inhibited in late tumor bearers, but LAK and M psi activities were not inhibited. Cell surface markers and production of various cytokines were examined in order to analyze the changes in each activity.