固相MHC Ⅰ类相关抗原A刺激的NK细胞对树突状细胞活性的影响

目的:观察固相MHC I类相关抗原A(iMICA)刺激的NK细胞对树突状细胞(DCs)活性的影响。方法:首先取新鲜分离及受固相MICA刺激的异体NK细胞,或IL-2、及IL-2联合iMICA刺激的自体NK细胞与未成熟DCs(iDCs)按5∶1比例孵育24 h后,用流式细胞术(FCM)分析HLA-DR+或CD86+频率的DCs。然后取自体NK细胞以iMICA刺激后,按1∶5的比例与iDCs孵育24 h后,FCM检测DCs上HLA-DR、CD86的表达。最后在NK细胞与DCs的共培养体系中加入抗IFN-γ抗体,观察DCs上HLA-DR、CD86表达的变化。结果:当NK细胞与iDCs孵育比例为5∶1时,异体新鲜分离的与自体活化的NK细胞均能杀伤iDCs;而iMICA无协同作用。当NK细胞与iDCs孵育的比例为1∶5时,iMICA刺激的NK细胞可促进DCs表达HLA-DR和CD86;而加入抗IFN-γ抗体可抑制NK细胞诱导DCs表面HLA-DR和CD86表达的上调。结论:异体新鲜分离的或自体活化的NK细胞杀伤iDCs时,无需iMICA的刺激;但当NK细胞的数目明显低于iDCs时,iMICA可刺激NK细胞分泌IFN-γ促进DCs成熟。     

固相MHCI类相关抗原A刺激的NK细胞对树突状细胞活性的影响

目的:观察固相MHCI类相关抗原A(iMICA)刺激的NK细胞对树突状细胞(DCs)活性的影响.方法:首先取新鲜分离及受固相MICA刺激的异体NK细胞,或IL-2、及IL-2联合iMICA刺激的自体NK细胞与未成熟DCs(iDCs)按5:1比例孵育24 h后,用流式细胞术(FCM)分析HLA-DR+或CD86+频率的DCs.然后取自体NK细胞以iMICA刺激后,按1:5的比例与iDCs孵育24 h后,FCM检测DCs上HLA-DR、CD86的表达.最后在NK细胞与DCs的共培养体系中加人抗IFN-γ抗体,观察DCs上HLA-DR、CD86表达的变化.结果:当NK细胞与iDCs孵育比例为5:1时,异体新鲜分离的与自体活化的NK细胞均能杀伤iDCs;而MICA无协同作用.当NK细胞与iDCs孵育的比例为1:5时,iMICA刺激的NK细胞可促进DCs表达HLA-DR和CD86;而加人抗IFN-γ抗体可抑制 NK细胞诱导DCs表面HLA-DR和CD86表达的上调.结论:异体新鲜分离的或自体活化的NK细胞杀伤iDCs时,无需iMICA的刺激;但当NK细胞的数目明显低于iDCs时,iMICA可刺激NK细胞分泌IFN-γ促进DCs成熟.     

重组可溶性MHC Ⅰ类相关蛋白A对NK细胞生物学活性的影响

目的:研究体外重组可溶性MHC Ⅰ类相关蛋白A(sMICA)对NK细胞杀伤靶细胞活性、分泌IFN-γ、增殖和凋亡的影响.方法:将重组sMICA蛋白与人外周血NK细胞相互作用过夜后,流式细胞仪检测NK细胞杀伤K562靶细胞的能力;ELISA检测培养上清IFN-γ浓度;MTS/PMS法检测sMICA对NK细胞增殖的影响;给NK细胞标记Annexin V和碘化丙啶检测凋亡情况.结果:可溶性MICA抑制NK细胞杀伤K562细胞的活性,下调IFN-γ的分泌,却对NK细胞的增殖和凋亡没有影响.结论:肿瘤细胞表面脱落的sMICA抗原可通过抑制NK细胞活性而逃逸机体的免疫监视功能.     

NK细胞识别MHC Ⅰ类分子的机理

人及鼠Ｎ细胞上抑制性受体的结构功能已研究得较为清楚了。其识别ＭＨＣⅠ类分子的机理公认的“失去自己”的假说,具体作用模式为效应抑制模式和靶干扰模式,前者已越来越为实验所证实,本文对效应抑制模式的信号传导机制及ＮＫ细胞抑制性受体识别ＭＨＣ Ⅰ类分子位点的研究进行了综述。     

NK细胞识别MHC Ⅰ类分子的机理

人及鼠Ｎ细胞上抑制性受体的结构功能已研究得较为清楚了，其识别ＭＨＣⅠ类分子的机理公认的为“失去自己”假说，具体作用模式为效应抑制模式和靶干扰模式，前者已越来越为实验所证实。本文对效应抑制模式的信号传导机制及ＮＫ细胞抑制性受体识别ＭＨＣⅠ类分子位点的研究进行了综述。     

MHC Ⅰ类分子限制性抗原的加工与递呈

MHC分子限制性抗原的加工与递呈是近年基础免疫学研究热点之一。MHCⅠ类分子将加工后的抗原递呈给CD8T淋巴细胞，此路径的抗原加工与递呈由于其重要性而受到广泛重视，本文就近年来这一领域的研究成果作一综述。     

MHCⅠ类分子及与之结合的抗原肽

细胞内生性抗原需降解成抗原肽，由ＭＨＣⅠ类分子呈递给ＣＤ８￣＋Ｔ细胞识别，从而诱导特异性细胞免疫应答。ＭＨＣⅠ类分子与抗原肽之间的结合表现出ＭＨＣ等位基因特异性，根据此特点可以预测抗原的Ｔ细胞识别表位，对于阐明自身免疫病和器官移植排斥反应的机理，指导人工合成肽疫苗用于病毒感染及肿瘤的免疫防治均具有重要意义。     

弱酸洗脱提取的肿瘤抗原肽致敏的树突状细胞对CTL的体内外激活效应

弱酸洗脱提取小鼠红白血病细胞膜表面肿瘤抗原肽,用于致敏树突状细胞（ｄｅｎｄｒｉｔｉ ｃｅｌｌｓ,ＤＣ）观察其对细胞毒性Ｔ淋巴细胞（ＣＴＬ）的体内外激活效应。方法以ＰＨ３．３的枸橼酸－磷酸盐缓冲液室温下处理ＦＢＬ－３小鼠红白血病细胞５ｍｉｎ,流式细胞术检测洗脱效率,弱酸洗脱的抗原肽经ＳｅｐＰａｋＣ１８柱提取纯化,用于致敏ＤＣ,检测其体外刺激ＣＴＬ细胞株增殖的能力及体内激发特异性抗肿瘤免疫应答的能力。     

MHC I类抗原多肽致敏IL-2基因修饰的树突状细胞对小鼠 引流淋巴结T细胞亚群的影响及其免疫保护作用

目的探讨MHCI类分子限制性肿瘤抗原多肽Mutl体外冲击白细胞介素2(Interleukin-2,IL-2)基因修饰的树突状细胞(Dendrticcells,DC)对小鼠体内特异性免疫的活化机制。方法用腺病毒作为载体介导小鼠IL-2基因修饰DC,用小鼠Lewis肺癌3LL细胞株MHCI类分子限制性八肽Mutl冲击IL-2基因修饰的DC(DC-IL-2-Mutl)免疫小鼠,用流式细胞术(FACS)分析免疫保护小鼠接受3LL细胞再攻击后引流淋巴结内T细胞亚群的比例变化。结果用Mutl冲击的DC免疫的小鼠抵抗3LL细胞再攻击时,引流淋巴结内CD8     

树突状细胞与NK细胞相互作用的研究进展

树突状细胞(DC)不但参与天然免疫,而且是启动获得性免疫的关键因素。自然杀伤细胞(NK细胞)是天然免疫的重要组成部分。DC与NK细胞之间存在相互作用。DC可通过分泌IL-12和IL-18等细胞因子与细胞间直接接触而影响NK细胞功能。NK细胞不但可通过死亡受体途径促进DC凋亡溶解,还可通过所分泌的细胞因子促进DC的成熟,其作用结果取决于NK/DC的比例。     

Immobilized MHC class I chain-related protein A synergizes with IL-15 and soluble 4-1BB ligand to expand NK cells with high cytotoxicity ex vivo

Major histocompatibility complex (MHC) class I chain-related protein A (MICA), which is a ligand for human NKG2D, is expressed by a variety of epithelial tumor cells and promotes the activation of natural killer (NK), CD8⁺ and γδ-T cells. Although ectopic expression of MICA on tumor cells elicits anti-tumor responses, soluble MICA downregulates the activities of lymphocytes. In this study, we showed that recombinant, immobilized MICA (iMICA) molecules coated on plastic wells weakly promote peripheral NK cell activation, secretion of interferon (IFN)-γ and degranulation without inducing apoptosis. In addition, iMICA synergized with IL-15 and soluble 4-1BB ligand (s4-1BBL) to expand NK cells 25- to 42-fold in a 13-day culture, whereas NK cells stimulated only with IL-15 and s4-1BBL expanded 10- to 16-fold. In contrast to NK cells expanded by IL-15 and s4-1BBL stimulation, NK cells expanded long term in the presence of iMICA exhibited increased cytotoxicity against leukemia cells. These results suggest that large numbers of NK cells with high cytotoxicity can be generated by stimulation with IL-15 and s4-1BBL in the presence of iMICA and that these cells can be used for adoptive cancer immunotherapy.     

A bird's eye view of NK cell receptor interactions with their MHC class I ligands

The surveillance of target cells by natural killer (NK) cells utilizes an ensemble of inhibitory and activating receptors, many of which interact with major histocompatibility complex (MHC) class I molecules. NK cell recognition of MHC class I proteins is important developmentally for the acquisition of full NK cell effector capacity and during target cell recognition, where the engagement of inhibitory receptors and MHC class I molecules attenuates NK cell activation. Human NK cells have evolved two broad strategies for recognition of human leukocyte antigen (HLA) class I molecules: (i) direct recognition of polymorphic classical HLA class I proteins by diverse receptor families such as the killer cell immunoglobulin-like receptors (KIRs), and (ii) indirect recognition of conserved sets of HLA class I-derived peptides displayed on the non-classical HLA-E for recognition by CD94-NKG2 receptors. In this review, we assess the structural basis for the interaction between these NK receptors and their HLA class I ligands and, using the suite of published KIR and CD94-NKG2 ternary complexes, highlight the features that allow NK cells to orchestrate the recognition of a range of different HLA class I proteins.     

结肠癌患者单核或树突状细胞MICA的表达及其与NK细胞活性的关联

目的:观察结肠癌患者单核或树突状细胞是否表达MHCⅠ类相关抗原A(MICA),并分析MICA+单核细胞的频率是否与患者体内NK细胞的活性相关联。方法:首先利用流式细胞仪检测MICA在外周血单核细胞和由单核细胞诱导而来树突状细胞(DCs)上的表达;并用IL-15和IFNα-刺激树突状细胞,观察MICA表达的变化;然后检测患者外周血NKG2D+、CD16+、CD69+NK细胞的频率及NK细胞的杀伤活性;最后分析MICA+单核细胞的频率是否与NK细胞表达NKG2D及其杀伤活性关联。结果:与健康个体相比,结肠癌患者MICA+单核细胞的频率无显著变化。未成熟DCs表达MICA,但受IL-15和IFNα-刺激后,结肠癌来源的DCs表面MICA的表达无显著上调。结肠癌患者外周血NKG2D+、CD69+NK细胞的频率显著降低,NK细胞的杀伤活性显著降低,而CD16+NK细胞的频率无明显变化。结肠癌患者MICA+单核细胞的频率与NK细胞表达NKG2D无明显关联,但与NK细胞杀伤靶细胞时CD107a的表达正相关。结论:结肠癌患者体内单核细胞表达MICA与NK细胞表达NKG2D无关,但高频率MICA阳性的单核细胞与NK细胞的抗肿瘤活性正相关。     

MHC class I chain-related gene A transmembrane polymorphism in Spanish women with breast cancer

The NKG2D–major histocompatibility complex class I-related chain A (MICA) system plays a key role in the antitumoral immune response. We studied five alleles of a microsatellite in the MICA transmembrane region; one of which ( MICA-A5.1 ) gives rise to a truncated protein. The MICA-A5 allele was reduced in breast cancer patients compared with healthy controls ( P  = 0.04). Given the association between the HLA-B7 allele and the susceptibility to breast cancer in our area, we also analyzed the distribution of the frequency of the MICA alleles in human leukocyte antigen (HLA)-B7 patients compared with patients with the other alleles. The MICA-A5.1 allele was increased in HLA-B7 patients ( P  = 0.0003). These results suggest that the MICA-A5 allele appears to confer protection against human breast cancer and that the MICA-A5.1 appears to increase the susceptibility to breast cancer in HLA-B7 patients in our area.     

膜型/分泌型MICA对NK细胞受体NKG2D的相反调节效应及其对NK细胞受体谱的影响

目的　观察膜型和分泌型MICA对NK细胞受体表达的影响 ,以探讨NK细胞抗肿瘤活化机制及肿瘤细胞表达MICA分子的意义。方法　用MTT法测定人NK细胞系 (NK92 )的细胞毒活性 ;用RT PCR或FACS检测NK细胞受体 (NKG2D ,NKG2A B ,KIR2DL1,KIR2DS1)及NKG2D的识别配体MICA的表达。结果　肿瘤细胞表面的MICA分子可上调NKG2D的表达 ,下调抑制性受体NKG2A B和KIR2DL1的表达 ;而分泌型MICA (sMICA)分子对NKG2D及抑制性受体的表达均有抑制作用。结论　膜型MICA分子可上调NKG2D的表达 ,激发NK细胞对肿瘤细胞的细胞毒效应 ;分泌型MICA分子则通过降低NKG2D的表达下调机体的抗肿瘤免疫效应 ,肿瘤细胞分泌sMICA分子为肿瘤发生免疫逃逸的机制之一。     

MHC class I chain-related molecules induced on monocytes by IFN-gamma promote NK cell activation

NKG2D receptor-ligand interaction triggers NK cell-mediated cytolysis and IFN-gamma secretion. IFN-gamma produced by NK cells has been found to promote the interaction between NK cells and monocytes; however, the underlying mechanism remains elusive. We demonstrate here that IFN-gamma exclusively induced or upregulated the expression of MHC class I chain-related (MIC) molecules, which are ligands of the NKG2D receptor, on the surface of human monocytes of the PBMC population. The IFN-gamma-induced MIC molecules on monocytes played an essential role in triggering the activation of NK cells because mAb-mediated masking of the MIC molecules and the inhibition of cell-to-cell contact using transwell inserts significantly abolished NK cell activation. Meanwhile, membrane-bound IL-15 (mIL-15) was concomitantly induced with MIC molecules on IFN-gamma-treated monocytes and played an essential role in protecting NK cells cocultured with monocytes from MIC-induced NKG2D down-modulation. Therefore, we conclude that the IFN-gamma-induced MIC molecules participated in monocyte/NK cell interaction and that this interaction also involved mIL-15.     

MHC class I expression protects target cells from lysis by Ly49-deficient fetal NK cells

Using appropriate conditions natural killer (NK) cells can be cultured from the liver and thymus of day 14 fetal mice. These fetal NK cells are phenotypically and functionally indistinguishable from adult NK cells with the exception that they lack measurable expression of all of the Ly49 molecules that can currently be detected with antibodies. Despite this, they preferentially kill tumor cells and blast cells deficient in the expression of major histocompatibility complex class I molecules, although the degree of discrimination is usually weaker than that shown by adult NK cells and varies depending on the particular combination of effector and target cells used. Polymerase chain reaction analysis revealed that although fetal NK cells are severely deficient in the expression of mRNA for Ly49A, B, C, D, G, H, and I they express high levels of Ly49E mRNA, raising the possibility that Ly49E may have an important and special function in the early development of the NK lineage.     

Dendritic cell/macrophage precursors capture exogenous antigen for MHC class I presentation by dendritic cells

Presentation of MHC class I antigens by professional antigen-presenting cells (APC) is an important pathway in priming cytotoxic T lymphocyte responses in vivo. This study sought to identify the nature of the professional APC responsible for indirect class I presentation by examining a special feature of professional APC, namely their ability to process exogenous forms of antigen for class I presentation. Incubation of highly purified bone marrow-derived precursor cells with chicken ovalbumin (OVA) led to the efficient presentation of the major class I-restricted OVA determinant by mature dendritic cells (DC), but not by macrophages (Mϕ) derived from the precursor population. DC as well as macrophages were, however, able to mediate class II presentation of OVA, suggesting that macrophages were deficient in class I processing but not in capturing exogenous OVA. The majority of mature DC, i.e. over 80 %, generated from the precursor cells pulsed with OVA, presented the class I OVA epitope. Upon maturation, class I presentation of OVA by DC was greatly reduced, suggesting that class I processing of exogenous antigen is modulated during DC maturation in a manner similar to class II antigen processing. This study shows that bone marrow-derived DC/Mϕ progenitors capture exogenous antigen for class I presentation, and that cells of the DC lineage can be functionally distinguished from cells of the macrophage lineage based on their ability to process exogenous antigen for class I presentation.