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Human NK cells can lyse porcine endothelial cells independent of their expression of Galα(1,3)‐Gal and killing is enhanced by activation of either effector or target cells
Author(s) -
HorvathArcidiacono Judith A.,
Porter Cynthia M.,
Bloom Eda T.
Publication year - 2006
Publication title -
xenotransplantation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.052
H-Index - 61
eISSN - 1399-3089
pISSN - 0908-665X
DOI - 10.1111/j.1399-3089.2006.00316.x
Subject(s) - xenotransplantation , biology , microbiology and biotechnology , tumor necrosis factor alpha , major histocompatibility complex , immunology , antigen , transplantation , medicine , surgery
Background: Xenotransplantation of pig organs may provide an approach to alleviate the severe shortage of human organs. Natural antibodies against Gal α (1,3)‐Gal ( α Gal) epitopes cause hyperacute rejection of pig organs in primates. However, evidence for the role of α Gal in the natural killer (NK) cell‐mediated xenoresponse has been contradictory. Methods: We investigated the recognition of α Gal by human NK cells using endo‐ β ‐galactosidase C, an enzyme that cleaves α Gal, and endothelial cells (EC) from α 1,3‐galactosyltransferase null pigs that do not synthesize α Gal. Endo‐ β ‐galactosidase C treatment variably reduced the susceptibility of porcine EC to lysis by fresh human NK cells. Results: Removal of α Gal from porcine EC using endo‐ β ‐galactosidase C, produced variable results, i.e. cytotoxicity was decreased in half of the human NK cell donors tested. The two EC strains from α Gal−/− pigs were marginally, and not significantly, less susceptible to lysis by naïve human NK cells compared with α Gal‐expressing cells obtained from animals from the same herd, but these differences were not statistically significant ( P > 0.10). Treatment of porcine EC with recombinant human tumor necrosis factor (TNF)‐ α , which is known to activate porcine EC, enhanced the susceptibility of all target cells to lysis by fresh human NK cells. Surface expression of MHC or adhesion molecules on α Gal−/− cells, compared with wild type cells, showed no consistent difference in either MHC or adhesion molecules CD106 (VCAM‐1), CD31 (PECAM) or CD62E (E‐selectin), either with or without TNF‐ α stimulation, that could explain the differential susceptibility to lysis. Strikingly, all α Gal−/− and wild type EC exhibited similar susceptibility to human NK cells that had been cultured for 5 days with or without interleukin‐2. Conclusions: These findings demonstrate that human NK cells can kill porcine targets in the absence of α Gal, and donor variability plays a major role in whether α Gal has a role in determining susceptibility of porcine EC to lysis. Moreover, susceptibility to lysis of α Gal null EC is enhanced to the level of wild type EC by activation of either effector or target cells. Elimination of α Gal alone from source pigs will be insufficient to circumvent the NK cell mediated destruction of porcine EC.