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-_, and intravital microscopy studies demonstrated that CD43(-/-) Th17 cells had impaired rolling on TNF-_-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.

Author Info: (1) Molecular Cardiology Research Institute, Tufts Medical Center, Boston, MA 02111. Sackler School of Biomedical Sciences Immunology program, Tufts University School of Medicine,

Author Info: (1) Molecular Cardiology Research Institute, Tufts Medical Center, Boston, MA 02111. Sackler School of Biomedical Sciences Immunology program, Tufts University School of Medicine, Boston, MA 02111. (2) Molecular Cardiology Research Institute, Tufts Medical Center, Boston, MA 02111. (3) Molecular Cardiology Research Institute, Tufts Medical Center, Boston, MA 02111. (4) Molecular Cardiology Research Institute, Tufts Medical Center, Boston, MA 02111. (5) Molecular Cardiology Research Institute, Tufts Medical Center, Boston, MA 02111. (6) Cardiovascular Division, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, 02115. (7) Molecular Cardiology Research Institute, Tufts Medical Center, Boston, MA 02111. Sackler School of Biomedical Sciences Immunology program, Tufts University School of Medicine, Boston, MA 02111. 800 Washington St, Box #80, Boston, MA 02111.