CD43 Functions as an E-Selectin Ligand for Th17 Cells In Vitro and Is Required for Rolling on the Vascular Endothelium and Th17 Cell Recruitment during Inflammation In Vivo.

Endothelial E- and P-selectins mediate lymphocyte trafficking in inflammatory processes by interacting with lymphocyte selectin ligands. These are differentially expressed among different T cell subsets and function alone or in cooperation to mediate T cell adhesion. In this study, we characterize the expression and functionality of E-selectin ligands in Th type 17 lymphocytes (Th17 cells) and report that CD43 functions as a Th17 cell E-selectin ligand in vitro that mediates Th17 cell rolling on the vascular endothelium and recruitment in vivo. We demonstrate Th17 cells express CD44, P-selectin glycoprotein ligand (PSGL)-1, and CD43. Few PSGL-1(-/-)CD43(-/-) Th17 cells accumulated on E-selectin under shear flow conditions compared with wild-type cells. CD43(-/-) Th17 cell accumulation on E-selectin was impaired as compared with wild-type and PSGL-1(-/-), and similar to that observed for PSGL-1(-/-)CD43(-/-) Th17 cells, indicating that CD43 alone is a dominant ligand for E-selectin. Notably, this finding is Th17 cell subset specific because CD43 requires cooperation with PSGL-1 in Th1 cells for binding to E-selectin. In vivo, Th17 cell recruitment into the air pouch was reduced in CD43(-/-) mice in response to CCL20 or TNF-α, and intravital microscopy studies demonstrated that CD43(-/-) Th17 cells had impaired rolling on TNF-α-treated microvessels. Furthermore, CD43(-/-) mice were protected from experimental autoimmune encephalomyelitis and had impaired recruitment of Th17 cells in the spinal cord. Our findings demonstrate that CD43 is a major E-selectin ligand in Th17 cells that functions independent of PSGL-1, and they suggest that CD43 may hold promise as a therapeutic target to modulate Th17 cell recruitment.

Left Ventricular T-Cell Recruitment Contributes to the Pathogenesis of Heart Failure.

BACKGROUND: Despite the emerging association between heart failure (HF) and inflammation, the role of T cells, major players in chronic inflammation, has only recently begun to be explored. Whether T-cell recruitment to the left ventricle (LV) participates in the development of HF requires further investigation to identify novel mechanisms that may serve for the design of alternative therapeutic interventions. METHODS AND RESULTS: Real-time videomicroscopy of T cells from nonischemic HF patients or from mice with HF induced by transverse aortic constriction revealed enhanced adhesion to activated vascular endothelial cells under flow conditions in vitro compared with T cells from healthy subjects or sham mice. T cells in the mediastinal lymph nodes and the intramyocardial endothelium were both activated in response to transverse aortic constriction and the kinetics of LV T-cell infiltration was directly associated with the development of systolic dysfunction. In response to transverse aortic constriction, T cell-deficient mice (T-cell receptor, TCRα(-/-)) had preserved LV systolic and diastolic function, reduced LV fibrosis, hypertrophy and inflammation, and improved survival compared with wild-type mice. Furthermore, T-cell depletion in wild-type mice after transverse aortic constriction prevented HF. CONCLUSIONS: T cells are major contributors to nonischemic HF. Their activation combined with the activation of the LV endothelium results in LV T-cell infiltration negatively contributing to HF progression through mechanisms involving cytokine release and induction of cardiac fibrosis and hypertrophy. Reduction of T-cell infiltration is thus identified as a novel translational target in HF.