Endothelial cells are indispensable elements of blood vessels and are widely recognized to influence brain development.[32] PD‐1 signaling is thought to be associated with angiogenesis, particularly in the tumor microenvironment, where the expression of PD‐1 may influence the generation and functionality of blood vessels.[33] To verify the endothelial PD‐1 expression, immunofluorescence staining was performed on mouse brain slices and cultured endothelial cells. This evidence concerns the gene PDCD1 and neoplasm.