PDCD1 and neoplasm: As inhibitory KIR proteins are known to be expressed in terminally differentiated CD8+ T cells and contain a cytoplasmic immunoreceptor tyrosine-based inhibitory motif (ITIM) domain, we examined whether KIR+CD8+ T cells in the tumor expressed features of T cell exhaustion (PDCD1, HAVCR2, LAG3, TIGIT, CTLA4, ENTPD1, ITGAE, CXCL13, LAYN, CXCL13, IFNG).