VSIR and acute myeloid leukemia: To determine whether PD-1H on AML cells suppresses T cells and PD-1H blockade reverses AML PD-1H–mediated T cell inhibition, we transplanted C1498FF–mPD-1H into PD-1H-KO mice and treated them with either PD-1H–blocking antibody (13F3) or isotype control.