B2M and Alzheimer disease: Based on recent scRNA-seq studies of Alzheimer’s disease (AD) and vascular dementia (VaD) in humans and mice, some of the genes that were upregulated in healthy aged BECs were also upregulated in AD- or VaD-associated ECs (e.g., APOE, ALPL, B2M, HSPA4 and VWF) [18, 48, 49].