| IL17 producing T helper lymphocytes (Th17 cells) are often recruited at sites of tissue inflammation and participate in cell-mediated inflammatory reactions that involve interactions with the vascular endothelium. These interactions are quantitatively different from the Th1 T cell subset, and are highly dependent on E-selectin. T cell expressed E-selectin ligands were described before the existence of Th17 cells emerged, thus, their contribution to Th17 recruitment is unclear. One such ligand is syaloglycoprotein CD43, a protein with other pleiotropic functions but with unknown roles in Th17 cells. Chapter 3.1 of the present thesis dissertation tests the hypothesis that Th17 cells use specific E-selectin ligands that differ from other T cell subsets, and identifies CD43 as a major Th17 cell expressed E-selectin ligand in vitro and in vivo . We combine real time videomicroscopy and adhesion experiments under flow conditions in vitro, and the air pouch model of leukocyte recruitment as well as intravital microscopy of the inflamed cremaster muscle in vivo. In Chapter 3.2, we test the hypothesis that CD43 regulates antigen specific Th17 cell recruitment to sites of autoimmune reactions, using the mouse model of Experimental Autoimmune Encephalomyelitis (EAE). We find that CD43 regulates Th17 cell recruitment to the spinal cord in an E-selectin independent way, and hypothesize that CD43 regulates Th17 cell adhesion to ICAM-1. We present evidence that CD43 regulates Th17 cell adhesion and apical migration on ICAM-1, as well as ICAM-1 dependent transmigration in vitro. Lastly, in Chapter 3.3, we test the hypothesis that CD43 contributes to pathological cardiac remodeling and heart failure (HF), using the thoracic aortic constriction model (TAC) in which both E-selectin and ICAM-1 are upregulated in the heart. We demonstrate for the first time that CD43 contributes to T cell and monocyte recruitment to the heart, cardiac fibrosis and systolic dysfunction. In summary, we report several new roles for the sialoglycoprotein CD43, some of which are specific of Th17 cells, and others more broad in the context of heart inflammation in vivo. Our results identify new CD43 regulated pathways involved in Th17 cell recruitment and in inflammation associated with cardiac dysfunction. |
