Compositions for cancer or infection treatment via immunopotentiation caused by inhibition of immunosuppressive signal induced by PD-1, PD-L1, or PD-L2 and therapies using them, immunopotentiative substrates included as the active ingredient, screening methods of the substrates for cancer or infection treatment, cell lines used for the screening methods, evaluation methods that selects the substrates for cancer treatment, and carcinoma cell transplanted mammals used for the evaluation methods. The compositions of the present invention that inhibits the function of PD-1, PD-L1, or PD-L2 are useful for cancer or infection treatment.