Transgenic expression of HLA-E single chain trimer protects porcine endothelial cells against human natural killer cell-mediated cytotoxicity

Xenotransplantation. 2007 Mar;14(2):126-34. doi: 10.1111/j.1399-3089.2007.00378.x.


Background: The susceptibility of porcine endothelial cells (pEC) to human natural killer (NK) cells is related to the failure of human major histocompatibility complex (MHC)-specific killer inhibitory receptors to recognize porcine MHC class I molecules. The aims of this study were (i) to assess the protection of pEC against xenogeneic NK-mediated cytotoxicity afforded by the stable expression of HLA-E single chain trimers (SCT) composed of a canonical HLA-E binding peptide antigen, VMAPRTLIL, the mature human beta2-microglobulin, and the mature HLA-E heavy chain, and (ii) to test whether HLA-E expression on pEC and porcine lymphoblastoid cells affects the adhesion of human NK cells.

Methods: Porcine EC lines expressing different levels of HLA-E SCT were generated by Ca(2)PO(4)-transfection followed by limiting dilution cloning. Surface expression of HLA-E was measured by flow cytometry. Susceptibility of transfected pEC lines against human NK cells was tested in (51)Cr-release cytotoxicity assays. Interactions between human NK cells and HLA-E positive pEC or porcine lymphoblastoid cells were further addressed in adhesion and conjugation assays.

Results: The level of protection of pEC from human NK-mediated cytotoxicity correlated with the intensity of surface HLA-E expression. Furthermore, the HLA-E SCT-mediated protection was specifically reversed by blocking the HLA-E specific NK inhibitory receptor CD94/NKG2A. HLA-E expression does neither affect the adhesion of human NK cells to pEC nor the heteroconjugate formation between human NK and porcine 13271.10 cells.

Conclusions: Stable surface expression of HLA-E on pEC was achieved in the absence of extrinsic peptide pulsing and provided partial protection from human NK cytotoxicity. Though insufficient to inhibit xenogeneic NK cell reactivity completely, transgenic HLA-E expression on pig organs might contribute to a successful application of clinical xenotransplantation in combination with other protective strategies.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Antibodies, Heterophile / immunology
  • Cell Adhesion / physiology
  • Cell Communication / immunology
  • Cell Communication / physiology
  • Cell Line
  • Cytotoxicity, Immunologic / immunology*
  • Cytotoxicity, Immunologic / physiology
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / immunology*
  • Endothelium, Vascular / physiology
  • Gene Expression Regulation / physiology*
  • HLA Antigens / genetics
  • HLA Antigens / physiology*
  • Histocompatibility Antigens Class I / genetics
  • Histocompatibility Antigens Class I / physiology*
  • Humans
  • Killer Cells, Natural / immunology*
  • Killer Cells, Natural / physiology
  • NK Cell Lectin-Like Receptor Subfamily D / immunology
  • Swine
  • Transfection
  • Transgenes / genetics
  • Transgenes / physiology*
  • Transplantation, Heterologous / methods


  • Antibodies, Heterophile
  • HLA Antigens
  • HLA-E antigen
  • Histocompatibility Antigens Class I
  • NK Cell Lectin-Like Receptor Subfamily D