Studies of the mechanism for the induction of in vivo tumor immunity: By employing both in vitro and in vivo techniques, the distribution and homing of cytotoxic effector cells and precursor cells could be examined, and the interaction of various cellular had humoral elements in the immune response could be studied. Humoral and cellular regulation of cell-mediated immunity: Various humoral and cellular factors were identified to be able to suppress or augment the cell-mediated immunity. Some of then could reverse the immunosuppressive effect caused by tumor cells in vivo. Immunosuppression in cancer patients: An immuunosuppressive factor(s) was demonstrated in cancer patients' sera that could selectively suppress the T cell functions.