Downregulation of the NK cell activity on xenograft

HLA-E/GHLA-E的α 1结构域完全丧失细胞表面表达，而α 2结构域的表达与HLA-G1相同。α 3和跨膜结构域的取代没有改变。我们接下来成功地鉴定了位置-147作为HLA-E表达的最关键点。此外，在11或66处的点取代导致细胞表面表达的增强。然而，双取代（11，147）和三取代（11，66，147）在表达上优于取代147，但对人NK细胞的抑制作用并不明显。Δ-SCR2-β和Δ-SCR3-β不能抑制补体介导的和NK介导的PEC裂解。然而，delta-SCR4-CR4显示出明显的补体调节作用，但对NK细胞没有影响。结果表明，FasL对NK细胞有直接的抑制作用，其作用机制可能与SCR 2 - 4有关。用FasL-TM的转染子在PEC上高表达。接下来，将转染子分子对PEC上NK细胞介导的溶解的改善作为不一致异种移植物的体外延迟型排斥模型进行测试。Fas L-TM对NK细胞介导的PEC裂解有明显的抑制作用。猪α 1，3GT转染K562细胞。由于K562转染子增加了α-Gal表位的表达，因此NK细胞依赖的直接K562裂解上调。结果表明，α-Gal抗原表位的NK细胞受体的存在。

HLA-E/GThe substitution of α1 domain of HLA-E completely lost the cell surface expression, however, the α2 domain was expressed very high as same as HLA-G1. The substitution of α3 and transmembrane domain showed no alteration. We next successfully identified position-147 as the most critical point for HLA-E expression. In addition, the point substitution at 11 or 66 led to a enhancement in cell surface expression. However, a dual substitution (11, 147) and a triple substitution (11, 66, 147) are better in expression but not in inhibitory function against human NK cell than the substitution 147.DAF function for NK cellWe report on an investigation of the effect of DAF on NK cell-mediated cytolysis. Delta-SCR2-DAF and delta-SCR3-DAF failed to suppress both complement-mediated and NK-mediated PEC lyses. However, delta-SCR4-DAF showed a clear complement regulatory effect, but had no effect on NK cells. The data suggest DAF has the direct inhibitory function on NK cells via SCR2-4.The Synthesized Type I Membrane Protein of FasLcDNA of the extra cellular portion of the FasL gene with a transmembrane (TM) of HLA-G1 was constructed. The transfectant with FasL-TM was high expressed on PEC.The amelioration of NK cell-mediated lysis by the transfectant molecules on PEC was next tested as an in vitro delayed-type rejection model of a discordant xenograft. The FasL-TM indicated a clear inhibitory effect on NK cell-mediated PEC lysis.pig-α1,3GTThe cDNA of pig-α1,3GT was subcloned. And transfected into K562 human cell. As the K562 transfectants increased the expression of the α-Gal epitope, so the NK cell-dependent direct K562 lysis was up-regulated. The data indicated the existance of the NK cell receptor responsible for the α-Gal epitope.