天然免疫-肿瘤免疫治疗不容忽视的领域

天然免疫是机体抵御病原微生物入侵的第一道防线,因其即时性且缺乏记忆性,在抗感染免疫中被广泛研究,而在肿瘤免疫治疗中研究较少.随着对巨噬细胞和NK细胞的深入研究,天然免疫细胞的抗肿瘤作用也得到一定认可,但因效应细胞在体内的活性、数量、杀伤效率及抗瘤谱有限,使其临床应用受限.然而近年发现一种具有天然抵御肿瘤能力的小鼠,发挥抗肿瘤作用的效应细胞是以中性粒细胞、单核/E噬细胞和NK细胞为主的天然免疫细胞,且该种能力不仅能遗传还能移植,这为肿瘤的免疫治疗带来新的希望.本文将综述上述3种天然免疫中主要的效应细胞在抗肿瘤治疗中的研究进展.     

增强NK细胞肿瘤杀伤活性的研究进展

调节其他免疫细胞的功能,是机体天然免疫的主要承担者,也是获得性免疫的核心调节细胞,故NK细胞在抗肿瘤免疫中的地位越来越受到重视,随之增强NK细胞肿瘤杀伤活性的研究也逐步深入.可以通过细胞因子、单抗及多功能抗体介导NK细胞活化,通过调节抑制性信号和活化性信号传递加强NK细胞活性,通过免疫药物刺激及基因修饰提高NK细胞功能等多种途径增强NK细胞的肿瘤杀伤作用.结论:研究增强NK细胞杀伤活性的方法,将促进NK细胞在肿瘤免疫治疗中的应用.     

NKT细胞的生物特性及其在抗肿瘤免疫中的作用

[摘要] NKT细胞是一类特殊的T 淋巴细胞亚群,既表达NK 细胞受体,也表达T 细胞的相关受体。NKT细胞在多种免疫应答的调节中发挥重要作用,包括感染、自身免疫性疾病、代谢性疾病和癌症,其通过连接固有免疫系统和适应性免疫系统显示出强大的抗肿瘤活性。NKT细胞不仅能杀伤肿瘤细胞,也可激活其他抗肿瘤免疫细胞间接地发挥抗肿瘤作用,还能在肿瘤微环境中激活衰竭的免疫细胞,在抗肿瘤免疫中发挥重要的作用。本文就NKT细胞的生物学特性及其在抗肿瘤免疫中的作用作一综述。     

自然杀伤细胞治疗急性髓系白血病的研究进展

自然杀伤细胞(natural killer cell,NK)为一种存在于天然免疫系统中的淋巴细胞,具有杀伤肿瘤细胞和抗病毒感染的能力,在天然免疫和过继免疫治疗中发挥重要作用。随着NK细胞的特征和功能越来越被熟知,其已被广泛应用于临床抗肿瘤治疗,特别是血液系统恶性肿瘤如急性髓系白血病(acute myeloid leukemia,AML)、淋巴瘤等治疗。目前,基于NK细胞的免疫治疗主要包括自体NK细胞输注、异体NK细胞输注、嵌合抗原修饰NK(chimeric antigen receptor,CAR)细胞输注以及基于NK细胞的其他免疫治疗等。以NK细胞为基础的免疫治疗旨在增强NK细胞的抗肿瘤能力以及克服肿瘤免疫逃逸。随着研究进展,NK细胞将成为治疗AML的有效方法。     

NK细胞相关免疫检查点及其抑制剂的研究进展

自然杀伤(nature killer, NK)细胞为抵御病毒感染和细胞突变的第一道防线。NK细胞表面有多种激活受体和抑制受体,两者之间的动态平衡控制着NK细胞的杀伤或静止状态。其中,抑制受体作为免疫检查点发挥重要作用。肿瘤通过某些免疫检查点途径作为免疫抵抗的主要机制。在新兴的癌症免疫治疗领域探索了通过使用免疫检查点抑制剂来提高NK细胞抗肿瘤免疫的新方法,旨在使平衡向激活倾斜。近年来,针对免疫检查点的抑制剂疗法取得了巨大的成功。本文就NK细胞免疫检查点及其抑制剂的研究和应用现状进行综述。     

DC和NK细胞诱导的抗肿瘤CTL反应

细胞毒性T淋巴细胞(CTL)介导的细胞毒效应能够高效、特异性杀伤肿瘤细胞而不损伤周围组织。树突细胞(DC)是已知体内抗原提呈功能最强的抗原提呈细胞,能摄取各种抗原,体内外能激发T细胞增殖,诱导特异性CTL生成。自然杀伤(NK)细胞在由DC引起的抗肿瘤免疫中发挥重要作用。近年来NK-DC细胞的相互作用在CTL反应中的作用引起关注。现综述DC、NK 细胞在诱导抗肿瘤CTL反应中作用的研究进展。     

DC和NK细胞诱导的抗肿瘤CTL反应

细胞毒性T淋巴细胞（CTL）介导的细胞毒效应能够高效、特异性杀伤肿瘤细胞而不损伤周围组织。树突细胞（DC）是已知体内抗原提呈功能最强的抗原提呈细胞，能摄取各种抗原，体内外能激发T细胞增殖，诱导特异性CTL生成。自然杀伤（NK）细胞在由DC引起的抗肿瘤免疫中发挥重要作用。近年来NK-DC细胞的相互作用在CTL反应中的作用引起关注。现综述DC、NK细胞在诱导抗肿瘤CTL反应中作用的研究进展。     

白细胞介素和肿瘤免疫治疗

在肿瘤免疫治疗中,提高抗肿瘤活性的特异细胞毒 T 杀伤细胞(Specific CytotoxicT Lymphocytes,CTL)和其它具有杀伤功能的细胞的活性是至关重要的,并且已发现某些免疫促进剂或药物具有诱导 CTL 和 NK 细胞活性的作用,但是它们往往不能够成为对肿瘤有明显抑制效应的免疫杀伤细胞。此外有许多种类的肿瘤细胞并不具有免疫原性,这些条件限制了它们在肿瘤治疗中对癌细胞的杀伤效果。     

NK细胞在肿瘤过继性免疫治疗中的临床应用与研究进展

目的 自然杀伤(natural killer,NK)细胞是固有免疫细胞,是机体抗肿瘤的第一道防线.NK细胞无需预先致敏即可杀伤肿瘤细胞,具有良好的安全性和抗肿瘤作用.NK细胞作为抗肿瘤过继免疫细胞治疗制剂在世界范围内广泛应用.本文总结NK细胞在肿瘤过继性免疫治疗中的临床应用与研究进展.方法 应用PubMed、Elsevier、Springer、Wiley Online Library和CNKI文献检索系统,以“NK细胞,NK细胞与肿瘤生物治疗,NK细胞与肿瘤过继性免疫治疗”为关键词,检索1964-06-2015-12的有关文献.纳入标准:1)与NK细胞生物学相关的文献;2)与NK细胞体外扩增相关的文献;3)与NK细胞过继治疗血液性肿瘤及实体瘤的Ⅰ期及Ⅱ期临床研究相关的文献;4)与未来NK细胞临床应用研究方向相关的文献.根据纳入标准分析文献81篇.结果 NK细胞对肿瘤的杀伤活性主要取决于细胞表面活化性受体和抑制性受体间的动态平衡.目前,广泛认为基于NK细胞的过继性免疫治疗是具有良好潜力的肿瘤治疗方案.能否在GMP水平体外激活、扩增获得大量的NK细胞对肿瘤的过继治疗至关重要.用于体外扩增的NK细胞的来源包括外周血、脐带血以及干细胞.用于刺激NK细胞扩增的方法也不尽相同,包括可溶性细胞因子、抗体以及其他分子等.目前,自体或同种异体NK细过继疗法在血液或实体肿瘤治疗中广泛应用,但国外更倾向于应用同种异体NK细胞过继治疗.结论 NK细胞在肿瘤的过继性免疫治疗中具有重要临床意义和应用潜力,同时也面临诸多技术难题有待突破.     

肿瘤免疫微环境中的NK 细胞及免疫治疗

自然杀伤（NK）细胞是一类具有强大抗肿瘤功能的固有淋巴细胞,能够快速识别和杀伤肿瘤细胞,其功能受活化性受 体和抑制性受体的多种信号所调控。但是,肿瘤浸润NK 细胞的杀伤功能由于免疫抑制性肿瘤微环境而失调,甚至会促进肿瘤细胞的免疫逃逸,导致多种免疫疗法临床治疗的效果不佳。肿瘤细胞上调表达抑制性配体、肿瘤微环境中大量抑炎因子及异常的 低氧、低pH 等,都诱导肿瘤浸润NK 细胞杀伤功能受损。近年来,关于肿瘤微环境与肿瘤浸润NK 细胞的研究正处于肿瘤免疫领 域的前沿,已经取得了很多临床研究成果。多项研究表明,肿瘤浸润NK 细胞通常表现为抑制性受体上调、活化性受体下调和代 谢异常等特征,基于此,研究者开发了多种针对性治疗方案,以恢复NK 细胞的杀伤能力。本文在阐述NK 细胞功能活化和抑制 相关机制的基础上,论述了肿瘤浸润NK 细胞的特征及其相应的肿瘤免疫治疗方案。     

Memory type 2 helper T cells induce long-lasting antitumor immunity by activating natural killer cells

Functionally polarized helper T cells (Th cells) play crucial roles in the induction of tumor immunity. There is considerable knowledge about the contributions of IFN-producing Th1 cells that supports the role of cytotoxic cluster of differentiation (CD8) T cells and natural killer (NK) cells, but much less is known about how IL-4-producing Th2 cells contribute to tumor immunity. In this study, we investigated the cellular and molecular mechanisms employed by memory Th2 cells in sustaining tumor immunity by using a mouse model system wherein ovalbumin (OVA) is used as a specific tumor antigen. In this model, we found that OVA-specific memory Th2 cells exerted potent and long-lasting antitumor effects against NK-sensitive OVA-expressing tumor cells, wherein antitumor effects were mediated by NK cells. Specifically, NK cell cytotoxic activity and expression of perforin and granzyme B were dramatically enhanced by the activation of memory Th2 cells. Interleukin 4 (IL-4) produced by memory Th2 cells in vivo was critical for the antitumor effects of the NK cells, which IL-4 directly stimulated to induce their perforin- and granzyme-B-dependent cytotoxic activity. Our findings show that memory Th2 cells can induce potent antitumor immunity through IL-4-induced activation of NK cells, suggesting potential applications in cellular therapy for cancer patients.     

Human natural killer cells promote cross‐presentation of tumor cell‐derived antigens by dendritic cells

Dendritic cells (DCs) cross‐present antigen (Ag) to initiate T‐cell immunity against most infections and tumors. Natural killer (NK) cells are innate cytolytic lymphocytes that have emerged as key modulators of multiple DC functions. Here, we show that human NK cells promote cross‐presentation of tumor cell‐derived Ag by DC leading to Ag‐specific CD8⁺ T‐cell activation. Surprisingly, cytotoxic function of NK cells was not required. Instead, we highlight a critical and nonredundant role for IFN‐γ and TNF‐α production by NK cells to enhance cross‐presentation by DC using two different Ag models. Importantly, we observed that NK cells promote cell‐associated Ag cross‐presentation selectively by monocytes‐derived DC (Mo‐DC) and CD34‐derived CD11b^negCD141^high DC subsets but not by myeloid CD11b⁺ DC. Moreover, we demonstrate that triggering NK cell activation by monoclonal antibodies (mAbs)‐coated tumor cells leads to efficient DC cross‐presentation, supporting the concept that NK cells can contribute to therapeutic mAbs efficiency by inducing downstream adaptive immunity. Taken together, our findings point toward a novel role of human NK cells bridging innate and adaptive immunity through selective induction of cell‐associated Ag cross‐presentation by CD141^high DC, a process that could be exploited to better harness Ag‐specific cellular immunity in immunotherapy.     

EZH2 identifies the precursors of human natural killer cells with trained immunity

Objective:Trained immunity of natural killer (NK) cells has shown great potential in the treatment of cancers by eliciting enhanced effector responses to restimulation by cytokines or cancer cells for long time periods after preactivation. However, the human NK cells responsible for the generation and maintenance of trained immunity are largely unknown. We hypothesized that heterogeneous human NK cells would respond differentially to stimulation with a combination of IL-12, IL-15, and IL-18, and that an NK cell subset might exist that is mainly responsible for the induction of trained immunity. On the basis of our hypothesis, we aimed to identify the subset from which cytokine-trained human NK cells originate and to explore possible regulatory targets for drug intervention.Methods:Flow cytometry assays were performed to analyze the functions of cytokine-trained NK cells and examine cell division and protein expression in NK cell subsets. Single-cell RNA sequencing (scRNA-seq) plus TotalSeq™ technology was used to track the heterogeneity of NK cells during the induction of trained immunity.Results:Traditional developmental markers for peripheral NK cells were unable to identify the precursors of human NK cells with trained immunity. Therefore, we used scRNA-seq plus TotalSeq™ technology to track the heterogeneity of NK cells during the induction of trained immunity and identified a unique cluster of CD57⁻NKG2A⁺EZH2⁺IFNG⁺MKI67⁺IL12R⁺IL15R⁺IL18R⁺ NK cells. Enrichment and pseudotime trajectory analyses suggested that this cluster of NK cells contained the precursor of trained NK cells. We then used flow cytometry to further investigate the role of EZH2 in trained NK precursors and found that CD57⁻NKG2A⁺EZH2⁺ NK cells had faster cell cycles and an enhanced trained phenotype, and EZH2 inhibition significantly impaired the induction of trained immunity in NK cells. These results suggested that EZH2 is a unique epigenetic marker of precursors of human NK cells with trained immunity.Conclusions:Our work revealed human NK heterogeneity in the induction of trained immunity, identified the precursor subset for trained NK cells, and demonstrated the critical role of EZH2 in the induction of trained immunity in human NK cells.     

Human breast tumor cells induce self-tolerance mechanisms to avoid NKG2D-mediated and DNAM-mediated NK cell recognition

Breast cancer is the leading cause of death for women between the ages of 35 to 65. This is mostly due to intertumor heterogeneity and the lack of specific therapies for all subtypes. However, some breast cancers with an unexpected good prognosis are associated with enhanced antitumor immunity in situ. We studied whether breast cancer subtypes might have different susceptibilities to natural killer (NK) cells' antitumor immunity. We collected a large public set of microarray data for primary breast tumors and determined NK cell ligand expression. We found that despite heterogeneous levels of inhibitory HLA members, NKG2D ligands and DNAM ligands are expressed in virtually all breast tumor subtypes. Functional experiments in breast cancer subtypes expressing various levels of NK cell ligands showed that NK-mediated cytotoxicity is mainly HLA, NKG2D, and DNAM dependent. In parallel, we showed that cell lines and primary breast tumor cells secrete soluble inhibitory factors that alter NK cell functions. Finally, we showed that these mechanisms of escape occur in vivo in the MMTV-Neu model of spontaneous murine breast cancer. Our study shows that breast cancer cells, independent of the subtype, have developed different mechanisms to escape from NK cells' antitumor immunity. These results emphasize the role of NK cells in breast tumor clearance and underlie the importance of devising future therapy aiming at enhancing NK cell-mediated recognition in parallel with the prevention of the tumor-editing process.     

The role of NK cell recognition of nectin and nectin-like proteins in tumor immunosurveillance

Natural killer (NK) cells have important functions in the innate immunity to tumors. Recognition of tumor cells by NK cells is mediated by the interaction of activating and inhibitory NK cell receptors with ligands expressed on the tumor target. In addition, NK cell-target cell interactions require the engagement of adhesion molecules that stabilize the cell-cell conjugate. Recently, several novel NK cell receptors have been reported to regulate NK cell adhesion and activation through interaction with ligands of the nectin and nectin-like (Necl) family of adhesion molecules. We here review current knowledge on these receptors, CD226, CD96 and CRTAM, and their role in tumor immunosurveillance.     

Complementary activation of peripheral natural killer cell immunity in nasopharyngeal carcinoma

NK cells and alphabeta- and gammadelta-CTL play important roles in cellular immunity against tumors. We previously demonstrated that NPC patients have a quantitative and qualitative deficit in gammadelta-CTL and EBV-specific alphabeta-CTL when compared to normal subjects and NPC long-term survivors. In this study we report further observations of a complementary activation of peripheral NK cells in NPC patients. The NK cells in these patients, compared to those of healthy subjects and NPC survivors, were preferentially activated in response to the stimulation of myeloma cell line XG-7 and expanded in the presence of exogenous IL-2. The production of IFN-gamma was lowest in the patient group, whereas IL-12, IL-15 and TNF-alpha were produced in higher levels in patients than in the donors and survivors. The cytolytic effect of the NK cells against NPC cells in the patient group was also higher than that of the donors and survivors. Furthermore, the patients at later stages of NPC had lower gammadelta-CTL activity but higher NK cytotoxicity towards NPC targets, with higher production of IL-12, IL-15 and TNF-alpha but lower production of IFN-gamma than in patients at earlier stages. This might be part of a triggered compensatory re-activation of the innate immunity, believed to be mediated through various cytokines and chemokines when adaptive T cell immunity is breached. Together, these data suggest complementary roles of innate and adaptive immune response in tumor immunity where NK cells, gammadelta- and alphabeta-CTL compensate for the deficits of one another at different stages of tumor invasion.     

NK Cells: Key to Success of DC-Based Cancer Vaccines?

The cytotoxic and regulatory antitumor functions of natural killer (NK) cells have become attractive targets for immunotherapy. Manipulation of specific NK cell functions and their reciprocal interactions with dendritic cells (DCs) might hold therapeutic promise. In this review, we focus on the engagement of NK cells in DC-based cancer vaccination strategies, providing a comprehensive overview of current in vivo experimental and clinical DC vaccination studies encompassing the monitoring of NK cells. From these studies, it is clear that NK cells play a key regulatory role in the generation of DC-induced antitumor immunity, favoring the concept that targeting both innate and adaptive immune mechanisms may synergistically promote clinical outcome. However, to date, DC vaccination trials are only infrequently accompanied by NK cell monitoring. Here, we discuss different strategies to improve DC vaccine preparations via exploitation of NK cells and provide a summary of relevant NK cell parameters for immune monitoring. We underscore that the design of DC-based cancer vaccines should include the evaluation of their NK cell stimulating potency both in the preclinical phase and in clinical trials.     

Genealogical memory to perinatal iodine-131 exposure in rats: I. Alteration in natural immunity

A heritable alteration in the natural immunity as measured by changes in the natural killer (NK) cell activities of peripheral blood lymphoid-cells was found to occur in rats upon an in utero exposure to iodine-131. The model that was employed for the measurements consisted of Fischer F344 inbred rats exposed to iodine-131 (sodium) during their 16th to 18th day of gestation. The natural immunity of the animals was evaluated by determining the NK cell activities of peripheral blood lymphoid cells of the offsprings when they reached 2 months of age. Immediately following determination of the natural immunity, brother and sister matings were carried out for evolution of the families. Study of these pedigrees revealed an impairment in the natural immunity to persist through two generations (F1, and F2) of the male animals. The hematological profiles of the animals suggest that the insult may alter the numbers of red and white blood cells in the succeeding generations, but has little noticeable effect upon the percentage of lymphocytes. The interpretation of the results indicate that a perinatal insult by iodine-131 during late gestation can result in both somatic and germ cell changes in the immunological system. Thus, there appears to be a genealogical memory to an in utero radionuclide insult which may adversely affect the offspring's immunological competency to respond to subsequent insults.