人鼻咽癌细胞株CNE2对NK细胞KIR/NKG2D受体的免疫编辑作用及其对NK细胞杀伤功能的影响

Immunoediting of natural killer cells by human nasopharyngeal carcinoma cell line: altered expression of KIRs and NKG2D receptors leads to reduction of natural killer cell-mediated cytolysis

目的探讨NK细胞与表达NKG2D配体的人鼻咽癌细胞株CNE2混合培养后4、24、48h时KIR、NKG2D的变化及其对NK细胞杀伤CNE2细胞活性的影响。方法PCR-SSP法检测CNE2细胞HLA-A、B、Cw表型、NK细胞KIR表型(选择3例健康者为试验对象),流式细胞仪检测对照组(新鲜分离的NK细胞)KIR2DL1、KIR2DL3、KIR3DL1、NKG2D的表达情况。IL2组(IL2培养的NK细胞)、CNE2组(CNE2、IL2、NK细胞混合培养)培养后4、24、48h时KIR2DL1、KIR2DL3、KIR3DL1、NKG2D的表达情况,LDH释放法测定IL2组及CNE2组培养24h后的NK细胞对CNE2细胞的杀伤活性。结果CNE2细胞表面HLA-A、B、Cw表型为A2,24;B18,35;Cw4,7。3例健康者均表达KIR2DL1、KIR2DL3、KIR3DL1。CNE2组4、24、48h时KIR2DL1、KIR2DL3表达较对照组、IL2组明显升高(P<0.01),NKG2D表达较对照组、IL2组明显降低(P<0.01),KIR3DL1表达与对照组、IL2组相比无明显变化(P>0.05)。IL2组4、24、48h时KIR2DL1、KIR2DL3、KIR3DL1及NKG2D表达与对照组相比无明显变化(P>0.05)。IL2组、CNE2组培养24h后的NK细胞对CNE2细胞的杀伤活性在效靶比10∶1时分别为(26.96±1.47)%和(2.74±1.64)%,两者相比差异有统计学意义(P<0.01);效靶比20∶1时分别为(35.74±3.59)%和(4.57±2.41)%,两者相比差异有统计学意义(P<0.01)。结论NK细胞与NKG2D配体阳性的肿瘤细胞持续性接触,下调NK细胞表面NKG2D表达,上调NK细胞表面与HLAI类分子相结合的KIR表达,导致NK细胞对靶细胞杀伤活性减低。本研究阐明了编辑后的NK细胞杀伤活性减低的分子基础,同时提示阻断HLAI类分子与KIR的结合或者增强NK细胞表面NKG2D的表达将有利于提高NK细胞杀伤肿瘤细胞的活性。

Objective To analyze the changes of inhibitory killer cell immunoglobulin-like receptors （KIRs）, NKG2D receptor and the cytotoxicity of natural killer （NK） cells induced by persistent exposure to CNE2 cells. Methods The HLA-class I genotypes of CNE2 cells and KIR genotypes were determined by PCR with sequence-specific primers （PCR-SSP）. The expressions of KIR2DL1, KIR2DL3, KIRBDL1, and NKG2D by the NK cells （fleshly isolated NK cells, NK cells cocultured with 100 U/ml IL2 or with 100 U/ml IL2 and CNE2 cells as the control, IL2 and CNE2 groups, respectively） were analyzed by flow cytometry. Cytotoxicity of NK cells against CNE2 cells were detected by LDH releasing assay. Results The HLA genotypes of CNE2 cells were A2, 24, B18, 35, Cw4, 7. NK cells isolated from 3 healthy donors expressed KIR2DL1, KIR2DL3, and KIR3DL1. After 4, 24 and 48 h of culture, NK cells in CNE2 group displayed higher KIR2DL1, KIR2DL3 but lower NKG2D expression than those in the control and IL2 groups （P〈0.01）, whereas the latter two groups showed no significant difference in KIR2DL1, KIR2DL3, and NKG2D expressions （P〉0.05）, and no difference in KIR3DL1 expression was found between the 3 groups （P〉0.05）. After 24 h of culture, the cytotoxicity against CNE2 cells mediated by the NK cells in IL2 and CNE2 groups were （26.96 ±1.47）% and （2.74±1.64）% at E：T ratios of 10：1, and （35.74±3.59）% and （4.57±2.41）% at E：T ratio of 20：l, respectively. NK cells in CNE2 group displayed lower cytotoxicity than those in IL2 group （P〈0.01）. Conclusions Persistent exposure to tumor cells expressing NKG2D ligands can lead to downregulated expression of NKG2D receptor, increased expression of KIRs and reduction of NK-mediated cytolysis. These results elucidate the molecular mechanism of reduced cytotoxicity mediated by the edited NK cells and indicate that blocking HLA-class I-bound KIRs orenhancing the expression of NKG2D may promote NK cell-mediated cytolysis.