CD274 and Alzheimer disease: Thus, PD-1/PD-L1 blockade in mouse models of Alzheimer's disease initiates a chain of immunological events that start in the periphery and culminate within the brain's territory; beginning with the antibody recognizing its cellular targets in the periphery and transiently breaking immune tolerance, and this is followed by migration of specialized immune cell populations from the circulation to the brain (thoroughly described in: Baruch et al., 2016; Schwartz, 2017; Rosenzweig et al., 2019).