Mota Castro Dias, MarianaMarianaMota Castro Dias0000-0001-7077-1407Odriozola Quesada, AdolfoAdolfoOdriozola QuesadaSoldati, Sasha Giulio NataleSasha Giulio NataleSoldatiBösch, FabioFabioBöschGruber, Isabelle ManuelaIsabelle ManuelaGruberHildbrand, TobiasTobiasHildbrandSönmez, DeryaDeryaSönmezKhire, TejasTejasKhireWitz, Guillaume RobertGuillaume RobertWitzMcGrath, James L.James L.McGrathPiontek, JörgJörgPiontekKondoh, MasuoMasuoKondohDeutsch, UrbanUrbanDeutschZuber, BenoîtBenoîtZuber0000-0001-7725-5579Engelhardt, BrittaBrittaEngelhardt0000-0003-3059-98462024-10-052024-10-052021https://boris-portal.unibe.ch/handle/20.500.12422/56804The migration of activated T cells across the blood-brain barrier (BBB) is a critical step in central nervous system (CNS) immune surveillance and inflammation. Whereas T cell diapedesis across the intact BBB seems to occur preferentially through the BBB cellular junctions, impaired BBB integrity during neuroinflammation is accompanied by increased transcellular T cell diapedesis. The underlying mechanisms directing T cells to paracellular versus transcellular sites of diapedesis across the BBB remain to be explored. By combining in vitro live-cell imaging of T cell migration across primary mouse brain microvascular endothelial cells (pMBMECs) under physiological flow with serial block-face scanning electron microscopy (SBF-SEM), we have identified BBB tricellular junctions as novel sites for T cell diapedesis across the BBB. Downregulated expression of tricellular junctional proteins or protein-based targeting of their interactions in pMBMEC monolayers correlated with enhanced transcellular T cell diapedesis, and abluminal presence of chemokines increased T cell diapedesis through tricellular junctions. Our observations assign an entirely novel role to BBB tricellular junctions in regulating T cell entry into the CNS. This article has an associated First Person interview with the first author of the paper.en600 - Technology::610 - Medicine & health500 - Science::510 - MathematicsBrain endothelial tricellular junctions as novel sites for T cell diapedesis across the blood–brain barrierarticle10.48350/1562463391291410.1242/jcs.253880