The strategy for inhibiting NK cell activity by gene technology

自然杀伤（NK）细胞介导的免疫应答在异种移植排斥反应中起重要作用。利用猪内皮细胞（PEC）表面的HLA-G和HLA-E抗原，探讨了抑制NK细胞对PEC杀伤活性的策略.转染的HLA-G1基因在PEC上易于表达。表达的HLA-G1显着抑制NK介导的PEC细胞溶解，而HLA-G3在PEC上不表达。因此，在PEC中导入HLA-G3基因对人NK细胞没有保护作用.转染HLA-E基因的PEC不表达HLA分子。然而，对HLA-E基因前导序列的修饰成功地诱导了HLA-E分子的表达。此外，转染子同时表达HLA-G1和HLA-E分子，从而有效地增强了对NK介导的PEC裂解的抑制作用. HLA-G1的表达与糖基转移酶基因对糖抗原（如α-Gal表位）的改造有协同作用，HLA-G1对NK细胞介导的PEC裂解的作用低于糖基转移酶基因。在共转染的情况下，如HLA-G1 + N-乙酰氨基葡萄糖转移酶-III和HLA-G1 + α1，2岩藻糖基转移酶，显示出明显降低直接NK细胞介导的细胞毒性，与单一的HLA-G1转染子相比。

Natural killer (NK) cell mediated response plays an important role in xenograft rejection. The strategy for inhibiting NK cell activity to PEC was investigated using HLA-G and HLA-E on pig endothelial cell (PEC).1. The transfected HLA-G1 was easily expressed on PEC. The expressed HLA-G1 significantly suppressed NK-mediated PEC cell lysis.The HLA-G3 was not expressed on PEC. Therefore, the gene introduction of HLA-G3 in PEC showed no protective effect from human NK cells.2. The PEC transfectant with HLA-E genes did not expressed the HLA molecule. However, the modification of the leader sequence of the HLA-E gene successfully induced the expression of the HLA-E molecule. Furthermore, the transfectant expressed both HLA-G1 and HLA-E molecules, thus efficiently enhancing the inhibition of NK-mediated PEC lysis.3. The co-effect of HLA-G1 expression and the remodeling of glycoantigens such as the α-Gal epitope by the introduction of glycosyltransferase genes, was evaluated.The effect of HLA-G1 on NK cell-mediated PEC lysis was lower than that by the glycosyltransferases. In the case of the co-transfectants, such as HLA-G1 + N-acetylglucosaminyltransferase-III and HLA-G1 + α1,2fucosyltransferase, showed significant reductions in direct NK cell-mediated cytotoxicity, compared with the single HLA-G1 transfectant.