PDCD1 and melanoma: Nonetheless, such ab binding cannot be exclusively ascribed to off-target recognition of a nuclear antigen in dead cells34 because both 29F.1A12 and RMP1-30 reacted more avidly with FVD+ WT versus PD-1 KO B16-F10 melanoma or T-cells, which differ in PD-1 but not nuclear antigen content.