PDCD1 and Alzheimer disease: We analyzed GSK3β as a downstream target molecule of PD1/PDL1 based on the following findings: 1) PDL1 interacts with GSK3β in tumor cells and GSK3β regulates PD1 level in CTL (Li et al., 2016); 2) GSK3β phosphorylates tau mainly at Thr231, Ser262, and Ser396 in the AD brain; and 3) GSK3β activity is closely associated with learning/memory impairment in AD.