CX3CR1 was stably expressed on differentiated CD8+ T cells in the effector phase [19,20], and increased frequency of circulating CX3CR1+CD8+ T cells correlated with response to anti-PD-1 therapy in patients with renal cell carcinoma, melanoma, and non-small cell lung cancer [20,32,33]. The gene discussed is PDCD1; the disease is renal cell carcinoma.