PDCD1 and neoplasm: Co-staining with the non-blocking37 anti-PD-1 ab, RMP1-30, confirmed significantly greater rPD-L1 reactivity with PD-1+ (11.4 ± 4.5%, n = 3) compared to PD-1− (1.2 ± 0.6%, n = 3) live WT B16-F10 tumor cell fractions (Fig. 6b).