PDCD1 and melanoma: Next, we subcutaneously inoculated 1 × 105 B16F10 melanoma cells, which are tumour cells that are insensitive to PD-1 antibody treatment, into Rig-I+/+ and Rig-I−/− mice and intraperitoneally injected 250 μg of cIg or PD-1 antibody into each mouse on days 4, 6 and 8 (Fig. 7D).