TNFRSF18 and neoplasm: We checked the PL-L1 expression on ID8 tumor cells after in vivotreatment by anti-GITR mAb and found de novo PL-L1 expression on these tumorcells (Additional file 1: Figure S1), which may be partiallyresponsible for the resistance of ID8 tumors to treatment with single anti-GITR mAb andprovide a rationale for the synergistic effect of PD-1 blockade and GITR activation inID8 tumor inhibition.