As expected, 29F.1A12 showed markedly enhanced reactivity to respective PD-1 OE (82.3 ± 3.2% vs. 14.3 ± 4.0%, n = 4, Fig. 2a) and only minimal binding to live PD-1 KO B16-F10 melanoma variant cells (0.2 ± 0.0% vs. 0.5 ± 0.1%, n = 3, Fig. 2a). The gene discussed is PDCD1; the disease is melanoma.