PDCD1 and cholangiocarcinoma: HCC patient tumors showed higher TPEX cells expressing co-stimulatory immune checkpoint ICOS and multiple co-inhibitory immune checkpoint receptors, most frequently PD-1 and TIGIT; whereas, PDA contained more anergic PD-1+ T cells lacking co-stimulatory immune checkpoint receptors, indicating PDA as a less immune responsive tumor compared with HCC and CCA.