Kummer et al. demonstrated that PD-1/PD-L1 signaling is an important factor in Ab phagocytosis, with PD-1 knockout resulting in increased Ab levels, amyloid plaques, and cognitive deficits in APP/PS1 mice together with an inflammatory response in PD-1-deficient microglia (103). Here, PDCD1 is linked to Cognitive impairment.