PDCD1 and neoplasm: More importantly, we observed enrichment of potentially exhausted and suppressive immune subsets in tumours: Foxp3+CD152+TIGIT+CD4+ regulatory T cells (Treg) (C4), PD1+CD103+CD45RO+CD8+ resident memory T cells (TRM) (C7) and PD1+ CD45RO+CD4+ memory T cells (C19) (Fig. 1d).