Primary human umbilical vein endothelial cells were purchased from Lonza. Mouse brain endothelial cells (bEnd.3) were obtained from American Type Culture Collection (Manassas, VA). Human umbilical vein endothelial cell and bEnd.3 cells were cultured as described earlier.45 (link) Human peripheral blood mononuclear cells (PBMCs) were isolated from blood from healthy donors by density gradient centrifugation using Ficoll Paque (GE Healthcare, Pittsburg, PA). The Institutional Review Board at the UT Health Science Center at Tyler approved the blood donation protocol, and the participants gave written informed consent.