NKT细胞作为机体一种非传统型的T细胞，既发挥天然免疫功能又发挥特异性免疫的功能。传统的T细胞一般通过αβTCR识别MHC分子提呈的肽类抗原而发生激活，NKT细胞则是通过其恒定的Vα24-Jα18/Vβ11(小鼠为Vα14-Jα18)TCR识别CD1d分子提呈的糖脂类抗原而活化。在糖脂类抗原的刺激下，NKT细胞迅速活化并发挥抗感染、调节抗肿瘤免疫和调节自身免疫反应的功能。 Vα24-Jα18/Vβ11(小鼠为Vα14-Jα18)TCR NKT细胞是否识别肽类抗原仍不清楚。 在正常人群中约有90%携带EB病毒感染阳性，EB病毒感染为研究人类机体细胞毒性T淋巴细胞(CTL)提供了较多的信息，EB病毒的感染可引起机体产生高水平的细胞毒性CD8+T细胞。病毒的感染可触发机体初始及记忆性CD8+CTL反应，并形成主要针对蛋白抗原决定簇的HLA等位基因特异性的CTL。 在本项研究中我们应用了流式细胞术、HLA/EBV特异性抗原肽四聚体技术创新性的将其与NKT细胞其他抗体共同应用于EB病毒感染患者NKT细胞的的检测。应用Q-PCR、ELISPOT、细胞转染等多种生物技术对NKT细胞免疫功能进行检测。应用细胞杀伤等实验检测特异性NKT细胞对靶细胞杀伤效应，检测NKT细胞记忆性。首次检测到EB病毒抗原肽特异性的NKT细胞，也打破了以往认为NKT细胞仅能识别脂类抗原的认识。EB病毒特异性CD8+NKT细胞，既可以识别EB病毒特异性抗原，也可为α-GalCer所活化发挥功能。其次发现EB病毒特异性CD8+NKT细胞识别抗原肽具有HLA限制性。EB病毒特异性CD8+NKT细胞仅能杀伤与其HLA基因型别相同的靶细胞。再者发现NKT细胞在初次感染EB病毒后，形成了对EB病毒抗原的记忆性。当再次遇到该特异性抗原时可快速活化，发挥免疫学效应。传统认为仅特异性免疫细胞才能产生免疫记忆，但我们的研究发现NKT细胞免疫记忆的功能。 另外我们检测了EB病毒特异性CD8+NKT细胞对多种其他抗原是否存在交叉反应。观察发现EB病毒特异性CD8+NKT细胞可交叉识别禽流感病毒H5N1血凝素(H5N1HA)，特异性杀伤该抗原刺激的靶细胞，对H5N1HA存在交叉反应。鸟禽类A型流行性感冒H5N1是A型禽流感病毒的一个亚型，而A型禽流感病毒是正黏病毒科流感病毒属的一个成员。血凝素(HA)和神经氨酸苷酶(NA)是病毒表面棒状和蘑菇状两种糖蛋白结构，是病毒侵入机体引起疾病的重要成分，其中血凝素通过与上呼吸道的上皮细胞表面的唾液酸受体结合介导病毒对细胞的感染。这一发现也为解释人类抵抗H5N1病毒感染提供了一个新的可能的机制。 关键词：NKT细胞 EB病毒 特异性抗原肽 HLA限制性 H5N1HA

 NKT cells are unconventional T cells that bridge the innate and adaptive immunities. Unlike conventional T cells that are activated by peptide antigens presented by MHC molecules via αβTCR, NKT cells recognize antigenic glycolipids presented by CD1d through their semi-invariant Vα24-Jα18/Vβ11 (Vα14-Jα18 in mouse) TCR. Upon encountering antigenic glycolipids, NKT cells promptly become activated to provide protection against infection, and to regulate anti-tumour and autoimmune responses. To date, it is not clear whether semi-invariant Vα24-Jα18/Vβ11 (Vα14-Jα18/Vβ8.2, 7, 2 in mouse) TCR on NKT cells recognize antigenic peptides. Epstein-Barr virus (EBV)-infection induces high levels of cytotoxic memory CD8+ T cells. HLA allele-specific epitopes of latent EBV-infection proteins are able to elicit both primary and memory CD8+ CTL responses. EBV-specific cytotoxic memory CD8+ T cells provide one of the most informative systems to study cytotoxic T cell responses (CTL) in humans. By using flow cytometery, HLA/EBV specific tetramers, Q-PCR, ELISPOT and assays, we have mesured cytokine-production and CTL of in NKT cells from patients with latent EBV-infection. We have identified and characterised a new subset of dual- and cross-reactive EBV-epitope-peptide-specific CD8+ NKT cells. Unlike conventional αβ T cells, the EBV-specific NKT cells recognize CD1d-presented antigenic glycolipids regulating the immunity. Like the αβT cells, they also recognize HLA-molecule-presented viral epitope-peptides defending against the infection. These cells are clonally maintainable for their specificity to epitope-peptides, showing strong evidence that NKT cell progenitors have potential to develop into subsets with acquired epitope-peptide-specific immune-memory, along with their natural memory. By using same assessments, we examined the cross-reactivity towards different viral antigens. We have found that human EBV-specific CD8+ NKT cells cross-recognize the H5N1 avian influenza viral hemagglutinin (H5N1HA), an essential component for antigenic drifting and determining the pathogenesis of the virus. H5N1 avian influenza virus is a subtype of the species Influenza A virus of the Influenzavirus A genus of the Orthomyxoviridae family. The viral hemagglutinin (HA) and neuraminidase (NA), being antigenic glycoproteins found on the surface of the H5N1 influenza viruses, are responsible for binding the virus to the cell that is being infected. The finding is signifying that human beings, who are undergoing a nearly ubiquitous and life-long-persisting EBV-infections, might possess a "natural" resistance to avian H5N1 virus. Key words: NKT cell Epstein-Barr virus specific antigen peptide HLA restriction H5N1HA