Circulating lymphocytes continuously enter lymph nodes for immune surveillance through specialized blood vessels named high endothelial venules1,2,3,4,5, a process that increases markedly during immune responses. How high endothelial venules (HEVs) permit lymphocyte transmigration while maintaining vascular integrity is unknown. Here we report a role for the transmembrane O-glycoprotein podoplanin (PDPN, also known as gp38 and T1α)6,7,8 in maintaining HEV barrier function. Mice with postnatal deletion of Pdpn lost HEV integrity and exhibited spontaneous bleeding in mucosal lymph nodes, and bleeding in the draining peripheral lymph nodes after immunization. Blocking lymphocyte homing rescued bleeding, indicating that PDPN is required to protect the barrier function of HEVs during lymphocyte trafficking. Further analyses demonstrated that PDPN expressed on fibroblastic reticular cells7, which surround HEVs, functions as an activating ligand for platelet C-type lectin-like receptor 2 (CLEC-2, also known as CLEC1B)9,10. Mice lacking fibroblastic reticular cell PDPN or platelet CLEC-2 exhibited significantly reduced levels of VE-cadherin (also known as CDH5), which is essential for overall vascular integrity11,12, on HEVs. Infusion of wild-type platelets restored HEV integrity in Clec-2-deficient mice. Activation of CLEC-2 induced release of sphingosine-1-phosphate13,14 from platelets, which promoted expression of VE-cadherin on HEVs ex vivo. Furthermore, draining peripheral lymph nodes of immunized mice lacking sphingosine-1-phosphate had impaired HEV integrity similar to Pdpn- and Clec-2-deficient mice. These data demonstrate that local sphingosine-1-phosphate release after PDPN–CLEC-2-mediated platelet activation is critical for HEV integrity during immune responses.

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We thank P. Kincade and L. Thompson for critical reading of the manuscript; R. Adams for providing PdgfrbCre mice; and M. Kinter and M.C. Marlin for technical assistance. Work was supported by grants from the National Institutes of Health (GM103441, GM097747, HL085607, HL093242, HL103432, HL065590, HL112788), VA Merit Award (BX001984), the American Heart Association (SDG7410022), the Deutsche Forschungsgemeinschaft (SFB688), National Natural Science Foundation of China (30928010), Jiangsu Provincial Special Program of Medical Science (BL2012005) and Jiangsu Province’s Key Medical Center (ZX201102).

Author information

Author notes

    • Brett H. Herzog
    •  & Jianxin Fu

    These authors contributed equally to this work.


  1. Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA

    • Brett H. Herzog
    • , Jianxin Fu
    • , J. Michael McDaniel
    • , Yanfang Pan
    • , Minjia Sheng
    • , Tadayuki Yago
    • , Robert Silasi-Mansat
    • , Samuel McGee
    • , Florea Lupu
    • , Rodger P. McEver
    • , Hong Chen
    •  & Lijun Xia
  2. Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA

    • Brett H. Herzog
    • , Yanfang Pan
    • , Rodger P. McEver
    • , Hong Chen
    •  & Lijun Xia
  3. Jiangsu Institute of Hematology, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, China

    • Jianxin Fu
    •  & Lijun Xia
  4. Key Laboratory of Thrombosis and Hemostasis of Ministry of Health, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, China

    • Jianxin Fu
    •  & Lijun Xia
  5. Cardiovascular Research Institute, University of California, San Francisco, California 94158, USA

    • Stephen J. Wilson
    •  & Shaun R. Coughlin
  6. Department of Medicine and Division of Cardiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA

    • Paul R. Hess
    • , Aslihan Sen
    •  & Mark L. Kahn
  7. University Hospital Wurzburg and Rudolf Virchow Center, DFG Research Center for Experimental Biomedicine, 97080 Wurzburg, Germany

    • Frauke May
    •  & Bernhard Nieswandt
  8. Division of Cardiovascular Medicine, University of Kentucky and Lexington Veterans Affairs Medical Center, Lexington, Kentucky 40502, USA

    • Andrew J. Morris


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B.H.H. and J.F. designed and performed experiments, analysed results and drafted the manuscript. J.M.M., Y.P., M.S., T.Y., R.S.-M., S.M., A.J.M. and F.L. performed experiments. S.J.W., P.R.H., A.S., F.M., B.N. and S.R.C. supplied key reagents and mice. R.P.M., H.C. and M.L.K. helped analyse results and commented on the manuscript. L.X. designed and supervised research and wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Lijun Xia.

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