CD274 and ischemic stroke: PD-L1 participates in the progression of hypoxia-induced multiple organ injuries, such as injury caused by ischemic stroke, AKI, and obstructive sleep apnea.284 Hypoxia upregulates PD-L1 expression via HIF-1α, and PD-L1 is overexpressed in the spleen and central nervous system (CNS) post-stroke.