PDCD1 and cholangitis: In addition, since the PD-1 inhibitor acts with an antitumor role through inhibiting the PD-1 expression in T cells, thus its hematological toxicity is non-neglectable: a previous study reveals that the occurrence of grade 3–4 adverse events is low, which mainly includes leukopenia, neutropenia, pneumonitis, cholangitis, neuropathy, and hypokalemia (13).