However, the release of proinflammatory cytokines by microglia in PD-related conditions upregulates the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) by endothelial cells of the BBB, which are counter receptors for cell surface proteins in T cells and monocytes [22]. This evidence concerns the gene ICAM1 and Parkinson disease.