Differential recognition of MHC class I molecules of xeno-/allo-endothelial cells by human NK cells

Using human umbilical vein endothelial cells (HUVEC) and porcine aortic end othelial cells (PAEC) as target cells, human peripheral blood NK cells (PBN K) and NK92 cells as effector cells, the differential cytotoxicities of NK cells to allo- and xeno-endothelial cells were studied. The influence of MH C class I molecules on the cytotoxicity of human NK cells was assayed using acid treatment, and blockades of MHC class I antigens, CD94 and KIR (NKB1) . The results indicated that the killing of PAEC by the two kinds of NK cel ls is higher than that of HUVEC. After acid-treatment, the cytotoxicity of the two kinds of NK cells to PAEC and HUVEC is significantly enhanced, but the magnitude of the enhancement is different. The enhancement of NK killin g to acid treated HUVEC is much greater than that to PAEC. Blockade of CD94 mAb did not alter the NK cytotoxicity, while blockade of NKB1 mAb enhanced the cytotoxicity of PBNK to HUVEC and PAEC by 95% and 29% respectively. Th e results above suggested that the differential recognition of MHC I molecu les of xeno-endothelial cells by human NK cells could be the major reason f or higher NK cytotoxicity to PAEC. KIR might be the primary molecule that t ransduced inhibitory signals when endothelial cells were injured by NK cell s.