CD274 and Alzheimer disease: PD-L1 expression levels revealed a trend for lower PD-L1 levels in AD/AIT patients compared to HC in IL1β- and IL1β/1,25(OH)2D3 co-stimulated monocytes [IL1βAD/AIT vs HC p = 0.07, IL1β/1,25(OH)2D3 AD/AIT vs HC p = 0.06] (Figure 4C).