CD8α+树突状细胞研究进展

根据细胞表面CD8α的表达差异,小鼠脾脏中树突状细胞(DC)可以分为2种,即CD8α-DC和CD8α+ DC,二者功能迥异.本文回顾了近年来CD8α+ DC的研究动向,重点分析了CD8α+ DC的在肿瘤免疫、移植免疫和生殖免疫等中的作用.     

重组减毒细菌运送CD8+T细胞表位的效应分析

目的:分析重组减毒菌体外运送CD8 T细胞表位的效应。方法:以表达卵清蛋白(OVA)和淋巴细胞脉络丛脑膜炎病毒(LCMV)CD8 T细胞表位的重组菌13A(ptG2F)、25A(ptG2F)和SL7207(ptG2F)感染抗原提呈细胞(APC)LKb、LLd和骨髓源树突状细胞(BMDC),应用体外抗原提呈试验检测APC对重组菌运送的CD8 T细胞表位的提呈效应。结果:感染试验证实,减毒菌13A、25A和SL7207对LKb细胞或LLd细胞均具有良好的侵袭能力,BMDC对重组菌具有很好的摄取功能。抗原提呈试验结果显示,在感染的早期(2h),LKb、LLd细胞和BMDC均可提呈重组菌13A(ptG2F)或SL7207(ptG2F)运送的T细胞表位;在感染的晚期(48h),LKb细胞对OVA257-264CD8 T细胞表位的提呈效应降低,LLd细胞对LCMV118-132CD8 T细胞表位的提呈效应增强。3种APC均不能提呈25A(ptG2F)运送的T细胞表位。另外,在同样的作用条件下,BMDC对减毒菌运送的抗原表位的提呈效应要强于LKb和LLd细胞。结论:重组菌能运送CD8 T细胞表位,为基于减毒细菌的新型基因工程疫苗的分子设计提供了有益借鉴。     

T细胞直接活化与交叉活化研究进展

T细胞介导的免疫应答在机体排斥肿瘤的过程中起核心主导作用 ,原始的CD8+ T细胞分化成效应细胞 ,在自身MHCⅠ类分子存在的条件下能识别特异性抗原肽 ,CD8+ CTL可直接识别、杀伤表达特异性抗原的肿瘤细胞。多数抗原加工通道能产生有效的CD8+ T细胞介导的免疫反应     

负载口蹄疫病毒VP1蛋白质的树突状细胞对T细胞产生IFNγ-的影响

目的:研究负载口蹄疫病毒VP1蛋白质的树突状细胞对淋巴结T细胞产生IFNγ-的影响。方法:构建pET32a-VP1原核表达载体,经IPTG诱导表达并纯化重组蛋白VP1。制备骨髓源树突状细胞(BMDC)和淋巴结T细胞,将纯化的VP1蛋白质负载BMDC后与淋巴结T细胞共培养,收集不同时间点的共培养上清液,用ELISA检测其IFNγ-的含量。结果:本实验成功构建了pET32a-VP1原核表达载体,并获得了VP1蛋白质。在负载VP1蛋白质的BMDC与T细胞共培养后,实验组各时间点上清液的IFNγ-含量均高于对照组(3小时除外),特别是在共培养后9、24和48小时,差异显著。结论:负载FMDV VP1蛋白质的BMDC可有效激活淋巴结T细胞,从而启动Th1细胞免疫应答,分泌大量IFNγ-。     

树突状细胞在调节性T细胞产生中的作用

树突状细胞（Dendritic cells，DCs）是一类重要的专职抗原提呈细胞，虽在体内的数量较少，但具有超强的抗原提呈能力，而且能够活化初始T细胞（Naive T cells），在免疫应答的诱导中具有独特的地位。DCs既能诱导有效的免疫应答，同时在诱导免疫耐受中也十分重要。在中枢耐受中，胸腺内的DCs可以通过阴性选择清除自身反应性T细胞。近年来，越来越多的证据表明，DCs在外周耐受中也起着关键性的作用，可以通过诱导效应性CD4^＋T或者CD8^＋T细胞的无能，促进调节性T细胞（T regulatory cells，Treg）的分化来调控针对自身抗原的外周耐受。DCs的来源、表型和成熟状态都具有多样性和异质性，DCs的耐受功能可能依赖于其某一成熟阶段或者是某一亚群。本文就DCs在诱导产生Treg中的作用和应用进展做一简要综述。     

树突状细胞异质性研究进展

树突状细胞(DC)是一种重要的特异性抗原递呈细胞(APC),在免疫应答的诱导和调节中起重要作用.器官移植后,异质性供体DC与受体组织发生接触,这些细胞连同宿主DC有潜在的激活同种异体反应性T细胞或使之产生耐受的倾向.在鼠及人类中,DC谱系、表型、成热及功能异常复杂,阐明其功能,有助于了解调节耐受/免疫平衡的机制.     

树突状细胞对外源性抗原的摄取和加工机制

树突状细胞 (dendriticcell,DC)是体内功能最强大的专职性抗原提呈细胞 (antigenpresentingcell,APC) ,因其成熟时胞体伸出许多树突状或伪足样突起而得名 ,与其它APC相比 ,DC能高效地内吞、处理及呈递抗原 ,并能激活幼稚型 (na¨lve)T淋巴细胞 ,启动初级免疫应答 ,故在免疫反应中占有极其特殊的地位[1] 。因此 ,深入了解DC对抗原的摄取、加工和MHC分子的生成及作用对揭示DC的抗原提呈机制有重要意义     

树突状细胞与趋化因子的研究进展

树突状细胞(dendritic cell,DC)是功能最强的抗原提呈细胞,广泛存在于多种器官和组织中。DC前体来源于骨髓CD34^ 细胞,随血液循环分布到抗原可能入侵的部位。这些不成熟DC能持续而有效地吞噬抗原,高表达MHC Ⅰ类、Ⅱ类分子以及协同刺激分子,随后进入脾脏或淋巴结并成熟。成熟DC吞噬作用下降,协     

树突状细胞与特异性肿瘤免疫治疗

树突状细胞 (DC)是体内功能最强的抗原提呈细胞 (APC) ,也是抗原特异性免疫应答的始动者 ,由DC激活的T细胞介导的免疫应答在机体抗肿瘤过程中起着主导作用。本文主要对DC参与抗肿瘤的机制、DC与肿瘤免疫逃逸的关系及近年来DC在肿瘤生物治疗方面的研究进展作一综述。以DC为基础的肿瘤治疗主要有两种方式 :①免疫治疗 :肿瘤抗原体外冲击致敏DC后回输体内 ;②基因治疗 :以目的基因转染DC后回输体内     

028 树突状细胞与特异性肿瘤免疫治疗

树突状细胞(DC)是体内功能最强的抗原提呈细胞(APC),也是抗原特异性免疫应答的始动者,由DC激活的T细胞介导的免疫应答在机体抗肿瘤过程中起着主导作用.本文主要对DC参与抗肿瘤的机制、DC与肿瘤免疫逃逸的关系及近年来DC在肿瘤生物治疗方面的研究进展作一综述.以DC为基础的肿瘤治疗主要有两种方式①免疫治疗肿瘤抗原体外冲击致敏DC后回输体内;②基因治疗以目的基因转染DC后回输体内.     

Bystander activation of CD8+ T lymphocytes during experimental mycobacterial infection

Infection of C57BL/6 mice with Mycobacterium avium leads to the activation of both CD4+ and CD8+ gamma interferon (IFN-gamma)-producing T cells, although the CD8+ cells play no role in protection against infection. Using transfer of different lines of transgenic T cells with T-cell receptors (TCRs) which recognize irrelevant antigens, we show here that transferred CD8+ T cells from two of the three lines were activated to the same degree as the host cells, suggesting that the majority of the IFN-gamma-producing CD8+ T cells of the host represented bystander activation. The third line, specific for the male HY antigen, showed no activation. Activation required the participation of the CD28 coreceptor on T cells and was unaffected by the removal of CD44(hi) (memory phenotype) T cells. The transferred CD8+ T cells proliferated in vivo, although this was not essential for IFN-gamma production. Taken together, these data are highly reminiscent of homeostatic proliferation of TCR transgenic T cells upon transfer to lymphopenic hosts, and suggest low-affinity stimulation through the TCR, possibly by self peptides. The findings are discussed in relation to homeostatic proliferation and their significance in the possible induction of autoimmune disease.     

Bystander activation of CD4+ T cells

Bystander activation of T cells, i.e. the stimulation of unrelated (heterologous) T cells by cytokines during an Ag‐specific T‐cell response, has been best described for CD8⁺ T cells. In the CD8⁺ compartment, the release of IFN and IFN‐inducers leads to the production of IL‐15, which mediates the proliferation of CD8⁺ T cells, notably memory‐phenotype CD8⁺ T cells. CD4⁺ T cells also undergo bystander activation, however, the signals inducing this Ag‐nonspecific stimulation of CD4⁺ T cells are less well known. A study in this issue of the European Journal of Immunology sheds light on this aspect, suggesting that common γ‐chain cytokines including IL‐2 might be involved in bystander activation of CD4⁺ T cells.     

Minimal activation of memory CD8+ T cell by tissue-derived dendritic cells favors the stimulation of naive CD8+ T cells

Of the many dendritic cell (DC) subsets, DCs expressing the monomorphic coreceptor CD8 alpha-chain (CD8alpha) are localized permanently in lymphoid organs, whereas 'tissue-derived DCs' remain in nonlymphoid tissues until they 'capture' antigen and then move to local lymph nodes. Here we show that after lung infection, both naive and memory CD8+ 'killer' T cells responded to influenza virus antigens presented by lymph node-resident CD8alpha+ DCs, but only naive cells responded to antigens presented by lung-derived DCs. This difference provides a mechanism for priming naive T cell responses in conditions in which robust memory predominates. Our findings have implications for immunity to pathogens that can mutate their T cell epitopes, such as influenza virus and human immunodeficiency virus, and challenge the long-held view that memory T cells have less-stringent requirements for activation than naive T cells have.     

Circulating CD4+CD8+ T lymphocytes in patients with Kawasaki disease

We serially monitored cell surface antigen expression on mononuclear cells in peripheral blood isolated from patients with Kawasaki disease (KD), and found, for the first time, that a markedly increased number of CD4⁺CD8⁺ T lymphocytes was present in some of the patients (11 of the 24 cases). The cases of five of these 11 patients were complicated with coronary artery lesion (CAL); the 13 patients with normal numbers of CD4⁺CD8⁺ T lymphocytes did not have CAL. The patients' age, sex and grade of systemic inflammation evaluated by peripheral leucocyte count and serum C-reactive protein levels were not correlated to the number of CD4⁺CD8⁺ T lymphocytes. Other cell surface antigen characteristics of the CD4⁺CD8⁺ T lymphocytes included CD3⁺, CD45RA⁺, CD45RO⁺, CD16^?, and HLA-DR⁺. These results indicate that the surface antigen characteristics of the KD peripheral blood examined were the same as those of Epstein–Barr virus infection without CD45RA⁺. These findings provide useful information for the analysis of the pathogenesis of KD.     

Recognition of bovine respiratory syncytial virus proteins by bovine CD8+ T lymphocytes

CD8+ T lymphocytes play a major role in the clearance of bovine respiratory syncytial virus (BRSV), an important respiratory pathogen of young calves that shares many of the epidemiological and pathological features of human respiratory syncytial virus (HRSV) in infants. Recombinant vaccinia virus (rVV) and recombinant fowlpox virus (rFPV), expressing individual BRSV proteins, were used to demonstrate that the F, N and M2 proteins were the major antigens recognized by bovine CD8+ T cells in major histocompatibility complex (MHC)-defined cattle. BRSV protein recognition by CD8+ T cells was analysed using cytotoxic T lymphocyte (CTL) assays or by the production of interferon-gamma (IFN-gamma) following restimulation with BRSV proteins. Strong recognition of the G protein by CD8+ T cells was observed in cattle that had been vaccinated with rVV expressing this protein and subsequently challenged with BRSV. Although there is variation in the number of expressed MHC genes in cattle with different class I haplotypes, this did not appear to influence BRSV protein recognition by CD8+ T cells. Knowledge of the antigenic specificity of BRSV-specific CD8+ T cells will facilitate the qualitative and quantitative analysis of BRSV-specific CD8+ T-cell memory in cattle and help to ensure that potential vaccines induce a qualitatively appropriate CD8+ T-cell response.     

Requirements for activation of CD8+Murine T cells

Cytolytic effector function fails to develop if proliferation of allospecific cytolytic T lymphocyte precursors is inhibited, but the requirements for generation of cytolytic activity have not been fully defined. In contrast, the cytolytic effector function of cytolytic T lymphocyte clones does not change during the cell cycle, and the level of cytolytic activity is independent of cellular proliferation. The requirement for proliferation by primary responding populations may reflect the need for clonal expansion of a few inherently cytolytic effector cells in order to reach a threshold number which can readily be detected in conventional cytolytic assays. Alternatively, proliferation may be required for cytolytic T lymphocyte precursors to differentiate into mature, functional cytolytic cells. Using CD8+T cells which express an antigen-specific transgenic α/β T cell receptor, we have studied the requirements for acquisition of cytolytic capacity. Stimulation of the T cell receptor alone appears to be sufficient to render naive, CD8+ transgenic T cells sensitive to the growth effects of interleukin-2 (IL-2), and in some circumstances to interleukin-4 (IL-4), but not to induce either lymphokine production or cytolytic activity. Costimulatory molecules expressed by allogenic stimulating cells appear to be required for lymphokine production, and CD8+ transgenic T cells initially appear to secrete only IL-2 and interferon-γ. Stimulation of the T cell receptor of naive, CD8+ transgenic T cells appears to induce cytolytic activity only if cell proliferation occurs, either in response to IL-2 produced by the stimulated cells themselves when costimulatory molecules are present, or to IL-2 or IL-4 from exogenous sources if costimulatory molecules are absent.     

Collateral Bystander Damage by Myelin-Directed CD8+ T Cells Causes Axonal Loss

Permanent disability of patients suffering from central nervous system (CNS) inflammation such as multiple sclerosis, the most common chronic inflammatory disorder of the CNS, originates mainly from demyelination and axonal damage. Although many studies in the past focused on the role of CD4⁺ T cells, several recent findings postulate the relevance of autoaggressive, cytotoxic CD8⁺ T cells in the effector phase of multiple sclerosis. Yet, it remains unresolved whether axonal injury is the result of a CD8⁺ T cell-targeted hit against the axon itself or the consequence of an attack against the myelin structure. To address this issue of CD8-mediated tissue damage in CNS inflammation, we performed continuous confocal imaging of autoaggressive, cytotoxic CD8⁺ T cells in living organotypic cerebellar brain slices. We observed that loading brain slices with the cognate peptide antigen caused CD8-mediated damage of myelinated axons. To exclude the possibility that the cognate peptide loaded onto the brain slices was presented by axons directly, we restricted the cognate antigen expression exclusively to the cytosol of oligodendrocytes. Aside from vast myelin damage, extensive axonal bystander injury occurred. Using this model system of inflammatory CNS injury, we visualize that axonal loss can be the consequence from “collateral bystander damage” by autoaggressive, cytotoxic CD8⁺ T cells, targeting their cognate antigen processed and presented by oligodendrocytes.Demyelination and axonal damage are key features of multiple sclerosis (MS).¹ Mediators of both innate and adaptive immunity are thought to take part in the disease’s initiation and perpetuation.² Recently, studies investigating the pathogenic role of autoaggressive, cytotoxic CD8⁺ T cells in MS pathogenesis were intensified.³ By virtue of histological investigations on MS brain tissue, it was shown that CD8⁺ T cells outnumber CD4⁺ T cells⁴ and that they closely interact with demyelinated axons.⁵ Furthermore, CD8⁺ T cells were found clonally expanded in the cerebrospinal fluid, in the blood, and in central nervous system (CNS) lesions of MS patients.^4,6,7 Finally, CD8-mediated lysis of HLA-matched oligodendrocytes (ODCs)⁸ and transsection of dissociated single neurons⁹ provided functional evidence in vitro. In support, in vivo studies recently reported CNS injury after injecting antigen-specific CD8⁺ T cells either by using CD8-mediated experimental autoimmune encephalomyelitis,^10,11 an animal model for MS, or by using novel approaches, where mice selectively express a neo-self antigen in ODCs.^12,13Despite the concept that CD8⁺ T cells hold an active role in MS pathogenesis, neither of the studies addressed the pathogenic role of myelin-reactive CD8⁺ T cells with regard to axonal damage. To clarify whether myelin-reactive, cytotoxic CD8⁺ T cells directly attack axons or whether axonal loss may be the result of a targeted hit against myelinated structures indicating “collateral bystander damage,” we established a novel experimental system of inflammatory CNS injury: autoaggressive, cytotoxic CD8⁺ T cells were traced by continuous confocal imaging in living cerebellar brain slices, which were derived from transgenic mice expressing green fluorescent protein (GFP) in myelin (PLP-GFP mouse¹⁴). In an inflammatory environment, loading of brain tissue with the cognate peptide antigen caused CD8⁺ T cells to damage myelinated axons. To ensure that the axonal damage we observed did not just occur due to the fact that the added cognate peptide was loaded on MHC class I molecules possibly present on axons, we crossed PLP-GFP mice with ODC-ovalbumin (OVA) mice,¹⁵ thus restricting the expression of the cognate (neo-self) antigen OVA exclusively to the cytosol of ODCs. Again in an inflammatory environment, we observed in real-time cytotoxic OVA-T cell receptor CD8⁺ T cells (OT-I T cells) directly attacking myelin structures. Subsequent morphological analysis demonstrated aside from vast myelin damage significant axonal injury. Thanks to this experimental setup in which the cognate antigen was sequestered to ODCs exclusively, we could show that these autoaggressive, cytotoxic CD8⁺ T cells target their cognate antigen processed and presented by ODCs. In conclusion, axonal loss can be the consequence of “collateral bystander damage,” resulting from of a CD8-mediated attack directed against the myelin.     

Characterization of murine CD160+ CD8+ T lymphocytes

CD160 is an Ig-like glycoprotein expressed on NK, NKT and TCRgammadelta T cells, as well as intestinal intraepithelial T lymphocytes. In addition, a minor subset of CD8(+) but not CD4(+) T cells in the periphery is also known to express CD160, but the subset has not been fully characterized. In this study, we prepared anti-murine CD160 mAbs and investigated the expression profile of CD160 on various subsets of CD8(+) T cells. The amount of CD160 on almost all CD8(+) T cells was increased upon CD3-mediated stimulation in vitro, and soluble CD160 was found to be released. Flow cytometric analysis revealed most CD8(+) T cells expressing CD160 to show a CD44(high) phenotype in vivo. On further analysis, both CD44(high)CD62L(low) effector memory T cells (T(EM)) and CD44(high)CD62L(high) central memory T cells (T(CM)) expressed CD160 at an intermediate level. High levels were evident with recently activated CD8(+) T(EM). Na?ve CD8(+) T cells presumably immediately after stimulation (CD44(low)CD62L(low)CD69(+)) also expressed CD160, but only at a low level. Purified CD160(+) CD8(+) T cells from OT-1 transgenic mice expressing TCR against OVA residues 257-264 presented by H-2K(b) produced IFN-gamma more rapidly than CD160(-) CD8(+) T cells upon antigen stimulation. These results together show that CD160 is expressed on the majority of CD8(+) memory T cells as well as recently activated CD8(+) T cells.     

Inhibitory CD8+ T cells in autoimmune disease

Rheumatologists have long been focused on developing novel immunotherapeutic agents to manage such prototypic autoimmune diseases as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). The ultimate challenge in providing immunosuppressive treatment for patients with RA and SLE has derived from the dilemma that both protective and harmful immune responses result from adaptive immune responses, mediated by highly diverse, antigen-specific T and B cells endowed with powerful effector functions and the ability for long-lasting memory. As regulatory/suppressor T cells can suppress immunity against any antigen, including self-antigens, they emerge as an ideal therapeutic target. Several distinct subtypes of CD8(+) suppressor cells (Ts) have been described that could find application in treating RA or SLE. In a xenograft model of human synovium, CD8(+)CD28(-)CD56(+) T cells effectively suppressed rheumatoid inflammation. Underlying mechanisms involve conditioning of antigen presenting cells (APC). Adoptively transferred CD8(+) T cells characterized by IL-16 secretion have also exhibited disease-inhibitory effects. In mice with polyarthritis, CD8(+) Ts suppressed inflammation by IFNgamma-mediated modulation of the tryptophan metabolism in APC. In SLE animal models, CD8(+) Ts induced by a synthetic peptide exerted suppressive activity mainly via the TGFbeta-Foxp3-PD1 pathway. CD8(+) Ts induced by histone peptides were found to downregulate disease activity by secreting TGFbeta. In essence, disease-specific approaches may be necessary to identify CD8(+) Ts optimally suited to treat immune dysfunctions in different autoimmune syndromes.