blood-brain barrier; Ig-superfamily cell adhesion molecules (IgCAMs); T cell diapedesis; endothelial junctions; experimental autoimmune encephalomyelitis; intraluminal T cell crawling; endothelial cells;
Moretti Federico, Lyck Ruth, Abadier Michael, Engelhardt Britta, Fässler Reinhard (2013), Kindlin-3 regulates integrin activation and adhesion reinforcement of effector T cells., in PNAS
Engelhardt Britta, Ransohoff Richard M (2012), Capture, crawl, cross: the T cell code to breach the blood-brain barriers., in Trends in immunology
Lyck Ruth, Engelhardt Britta (2012), Going against the tide - how encephalitogenic T cells breach the blood-brain barrier., in Journal of vascular research
, 49(6), 497-509.
Stolp Bettina, Imle Andrea, Coelho Fernanda Matos, Hons Miroslav, Gorina Roser, Lyck Ruth, Stein Jens V, Fackler Oliver T (2012), HIV-1 Nef interferes with T-lymphocyte circulation through confined environments in vivo., in Proceedings of the National Academy of Sciences of the United States of America
, 109(45), 18541-6.
Muldoon Leslie L, Alvarez Jorge I, Begley David J, Boado Ruben J, Del Zoppo Gregory J, Doolittle Nancy D, Engelhardt Britta, Hallenbeck John M, Lonser Russell R, Ohlfest John R, Prat Alexandre, Scarpa Maurizio, Smeyne Richard J, Drewes Lester R, Neuwelt Edward A (2012), Immunologic privilege in the central nervous system and the blood-brain barrier., in Journal of cerebral blood flow and metabolism : official journal of the International Society of Cer
Wyss Lena, Schäfer Julia, Liebner Stefan, Mittelbronn Michel, Deutsch Urban, Enzmann Gaby, Adams Ralf H, Aurrand-Lions Michel, Plate Karl H, Imhof Beat A, Engelhardt Britta (2012), Junctional Adhesion Molecule (JAM)-C Deficient C57BL/6 Mice Develop a Severe Hydrocephalus., in PloS one
, 7(9), 45619-45619.
Steiner Esther, Enzmann Gaby U, Lin Shuo, Ghavampour Sharang, Hannocks Melanie-Jane, Zuber Benoît, Rüegg Markus A, Sorokin Lydia, Engelhardt Britta (2012), Loss of astrocyte polarization upon transient focal brain ischemia as a possible mechanism to counteract early edema formation., in Glia
, 60(11), 1646-59.
Ransohoff Richard M, Engelhardt Britta (2012), The anatomical and cellular basis of immune surveillance in the central nervous system., in Nature reviews. Immunology
, 12(9), 623-35.
Pfeiffer Friederike, Schäfer Julia, Lyck Ruth, Makrides Victoria, Brunner Sarah, Schaeren-Wiemers Nicole, Deutsch Urban, Engelhardt Britta (2011), Claudin-1 induced sealing of blood-brain barrier tight junctions ameliorates chronic experimental autoimmune encephalomyelitis., in Acta neuropathologica
, 122(5), 601-14.
Steiner O, Coisne C, Engelhardt B, Lyck R (2011), Comparison of immortalized bEnd5 and primary mouse brain microvascular endothelial cells as in vitro blood-brain barrier models for the study of T cell extravasation, in JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM
, 31(1), 315-327.
Engelhardt Britta (2011), Neuroscience. Blood-brain barrier differentiation., in Science (New York, N.Y.)
, 334(6063), 1652-3.
Greenwood J, Heasman S J, Alvarez J I, Prat A, Lyck R, Engelhardt B (2011), Review: leucocyte-endothelial cell crosstalk at the blood-brain barrier: a prerequisite for successful immune cell entry to the brain., in Neuropathology and applied neurobiology
, 37(1), 24-39.
Döring Axinia, Engelhardt Britta (2011), TET inducible expression of the α4β7-integrin ligand MAdCAM-1 on the blood-brain barrier does not influence the immunopathogenesis of experimental autoimmune encephalomyelitis., in European Journal Immunology
Coisne Caroline, Engelhardt Britta (2011), Tight junctions in brain barriers during central nervous system inflammation., in Antioxidants & redox signaling
, 15(5), 1285-303.
Engelhardt Britta (2011), β1-integrin/matrix interactions support blood-brain barrier integrity., in Journal of cerebral blood flow and metabolism : official journal of the International Society of Cer
, 31(10), 1969-71.
Steiner Oliver, Coisne Caroline, Cecchelli Roméo, Boscacci Rémy, Deutsch Urban, Engelhardt Britta, Lyck Ruth (2010), Differential roles for endothelial ICAM-1, ICAM-2, and VCAM-1 in shear-resistant T cell arrest, polarization, and directed crawling on blood-brain barrier endothelium., in Journal of immunology (Baltimore, Md. : 1950)
, 185(8), 4846-55.
In multiple sclerosis (MS) and in its animal model, experimental autoimmune encephalomyelitis (EAE), autoaggressive T cells get access to the central nervous system (CNS), causing inflammation, edema and demyelination, which all set the stage for the clinical manifestations of this disabling disease. Therapeutic targeting of a4-integrin mediated immune cell trafficking across the highly specialized endothelium of the blood-brain barrier (BBB) is a validated and successful treatment to ameliorate symptoms of MS. Nevertheless, the multistep recruitment of circulating T cells across the the BBB and especially the roles of the endothelial adhesion molecules involved are not yet fully understood. Additional complexity has been added to this process by the recent discovery of post-arrest T cell polarization and crawling on the BBB in vivo, which is a pre-requisite for T cells to efficiently scan the BBB for permissive sites for diapedesis. These findings point to an additional window of opportunity for improved therapy. By live cell imaging we could demonstrate in an in vitro BBB model that endothelial ICAM-1 but not ICAM-2 and VCAM-1 mediates the directed crawling of T cells against the direction of flow. Considering that this additional step in T cell migration across the BBB is now recognized to be mediated by ICAM-1, the previously assigned role of ICAM-1 to T cell diapedesis across the BBB may not hold true. Furthermore, availability of sites suited for diapedesis is directly influenced by the barrier characteristics of the BBB. We therefore propose that the BBB actively controls T cell arrest, polarization and crawling and directs T cells preferentially to sites suited for transcellular diapedesis. To test this hypothesis in detail we will focus on investigating the individual contributions of the BBB-expressed Ig superfamily cell adhesion molecules (IgCAMs) ICAM-1, ICAM-2, VCAM-1, PECAM-1, JAM-A, JAM-B and JAM-C in T cell polarization, arrest and crawling on the BBB and in T cell diapedesis across the BBB in vitro and in vivo. In light of the dominant role of ICAM-1 in T cell interaction with the BBB, Specific Aim 1 is dedicated to clarify, if endothelial ICAM-1 besides its promintent role in T cell crawling additionally mediates T cell diapedesis across the BBB. By means of live cell imaging we will compare the dynamics and the localization of T cell diapedesis across wild-type and ICAM-1null in vitro BBB models. Re-introduction of RFP-tagged ICAM-1 mutants into the ICAM-1null in vitro BBB endothelium will allow to visualize ICAM-1 during this process and to distinguish, if ICAM-1 triggered signalling pathways are required for T cell crawling on or T cell diapedesis across the BBB. Specific Aim 2 is designed to delineate, if the special barrier characteristics of the BBB favor transcellular over paracellular T cell diapedesis and to determine, which IgCAMs are involved in the respective processes. To this end, we will use in vitro BBB models, in which endothelial junctions are visualized by VE-cadherin-GFP to observe T cell diapedesis in the absence or presence of individual IgCAMs (see above) and under non-inflammatory and inflammatory conditions using life cell imaging. Finally, under Specific Aim 3 we seek to understand, if the uncovered molecular pathways that mediate T cell interaction with the BBB are amenable to therapeutic inhibition. We will therefore investigate the role of individual IgCAMs in EAE pathogenesis by studying disease development in the respective gene deficient mice. Where appropriate, we will study T cell interaction with the spinal cord microvasculature by means of (2-Photon) intravital microscopy (IVM) in the respective IgCAM mouse mutants or proceed to unravel the possible involvement of individual IgCAMs in autoimmune processes beyond T cell interaction with the BBB, such as T cell activation, differentiation, proliferation and cytokine production. We propose that the highly specialized BBB endothelium imposes BBB specific roles onto invididual IgCAMs during the multi-step T cell extravasation into the CNS. Therefore, therapeutic targeting of IgCAM-mediated T cell migration across the BBB needs to be more thoroughly explored in order to create new opportunities for improving the safety of this validated treatment strategy for MS.