In a murine melanoma model expressing OVA antigen, anti-PD-1 therapy could enhance responses by high affinity T-cells however SHP-1 knockdown of OT-I CD8+ T-cells, combined with anti-PD-1 ICB, mediated long-lasting suppression of tumour growth which was mediated by low-affinity T-cells. The gene discussed is PDCD1; the disease is melanoma.