PDCD1 and neoplasm: HLA class II (ligand for LAG3), PD-L1 (ligand for PD-1), HLA-E (ligand for NKG2A), and CEACAM1 (ligand for TIM3) were all expressed on tumor organoids (figure 3C, and D online supplemental figure S2B), suggesting that the opT cells were likely to be regulated by these checkpoint proteins.