KLRD1 and neoplasm: Among the CD8+ T cells, the CD8_S1 cluster showed high expression levels of Bcl2, Sell (CD62L), Tcf7 and Lef1 (figure 1E, online supplemental figure S1B), indicative of a memory CD8+ T cell phenotype.34–36 The CD8_S2 cluster represented the largest fraction of tumor-infiltrating CD8+ T cells (figure 1D) and was marked by the expression of several genes associated with effector CD8+ T cells (Gzmk, Gzma, Gzmb, Klrc1, Klrd1, Ccr5 and Ccr2)37 (figure 1E, online supplemental figure S1B).