Here, we point out that KLRG1 expression is concentrated on the most differentiated and potent CD8 T cells, unlike PD-1, and its expression is anti-correlated to PD-1 as well as all major coinhibitory and costimulatory checkpoint receptors across tumor infiltrating (TILS) CD8 T cells in a wide variety of cancers. The gene discussed is PDCD1; the disease is neoplasm.