However, decreased PD‐1 levels may have a protective effect on cognitive function (Zhao J et al., 2021), as studies have shown that blocking the PD‐1/PD‐L1 pathway can reduce amyloid‐beta plaque deposition and enhance cognitive function in mouse models of Alzheimer's disease (Baruch et al., 2016; Rosenzweig et al., 2019). Here, PDCD1 is linked to Alzheimer disease.