title: T Lymphocyte-Endothelial Interactions: Emerging Understanding of Trafficking and Antigen-Specific Immunity.
abstract: Antigen-specific immunity requires regulated trafficking of T cells in and out of diverse tissues in order to orchestrate lymphocyte development, immune surveillance, responses, and memory. The endothelium serves as a unique barrier, as well as a sentinel, between the blood and the tissues, and as such it plays an essential locally tuned role in regulating T cell migration and information exchange. While it is well established that chemoattractants and adhesion molecules are major determinants of T cell trafficking, emerging studies have now enumerated a large number of molecular players as well as a range of discrete cellular remodeling activities (e.g., transmigratory cups and invadosome-like protrusions) that participate in directed migration and pathfinding by T cells. In addition to providing trafficking cues, intimate cell-cell interaction between lymphocytes and endothelial cells provide instruction to T cells that influence their activation and differentiation states. Perhaps the most intriguing and underappreciated of these "sentinel" roles is the ability of the endothelium to act as a non-hematopoietic "semiprofessional" antigen-presenting cell. Close contacts between circulating T cells and antigen-presenting endothelium may play unique non-redundant roles in shaping adaptive immune responses within the periphery. A better understanding of the mechanisms directing T cell trafficking and the antigen-presenting role of the endothelium may not only increase our knowledge of the adaptive immune response but also empower the utility of emerging immunomodulatory therapeutics.
authors.affiliation: Center for Vascular Biology Research, Department of Medicine and Emergency Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School , Boston, MA , USA.
authors.forename: Christopher V
authors.initials: CV
authors.lastname: Carman
authors.affiliation: Center for Vascular Biology Research, Department of Medicine and Emergency Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School , Boston, MA , USA.
authors.forename: Roberta
authors.initials: R
authors.lastname: Martinelli
keywords: MHC; TCR; Trafficking; antigen presentation; endothelium; immunomodulation; lymphocyte; tolerance