T细胞记忆的理论研究

基于CD8⁺ T记忆细胞的线性和逆线性分化假说分别建立了数学模型,并研究了各种T细胞亚类的动力学.发现在优化剂量抗原入侵的条件下,两个模型均能产生记忆,并可较好地模拟实验结果.通过进一步模拟发现CD8⁺ T细胞记忆与抗原的存在紧密相关,再次证实了抗原在维持T细胞记忆中的作用.另外还讨论了记忆细胞寿命的问题.认为逆线性假说具有更强的反应性和记忆性.     

病毒特异性CD8+T细胞抗病毒免疫的研究进展

病毒利用宿主细胞核酸和蛋白质装置进行增殖,并与宿主细胞表面的受体结合,感染众多靶细胞c一旦建立感染,抗原呈递细胞通过内源性抗原呈递途径加工、呈递病毒抗原,激活机体免疫应答。病毒特异性免疫主要机制是细胞毒性T淋巴细胞作用,清除病原体和感染的靶细胞．同时CD8^ T细胞分化为记忆T细胞,介导再次免疫应答。     

免疫突触的形成及其介导的分子识别

T细胞和APC细胞相互作用形成免疫突触涉及到连续发生的一系列的分子识别事件,最初APC细胞在趋化因子的作用下向T细胞移动,相遇后在抗原非依赖性的弱的黏附力作用下发生最初的黏附,同时伴随着TCR在APC表面俘获特异性抗原;抗原识别之后,由多种机制使T细胞和APC紧密接触并维持一段时间,随后分开,最终引起T细胞的增殖和分化。对免疫突触形成过程中的分子识别机制目前尚无定论,拓扑模式和数学模式的解释,脂筏和细胞骨架蛋白的重排以及接头蛋白的连接为免疫突触形成中分子的识别提供了一定的依据。     

T细胞应答的代谢特征研究进展

T细胞是参与适应性免疫应答的重要组分之一,它们通过分泌细胞因子或是直接杀伤靶细胞等发挥免疫学功能。未致敏T细胞在参与免疫应答时,会由初始T细胞活化为效应T细胞,之后则发生凋亡或转化为记忆T细胞。研究表明,T细胞的能量代谢方式与其活化与分化有着紧密的联系。不同分化阶段与不同亚群的T细胞在行使其免疫功能时具有不同的代谢特点,并由相关的信号通路调控。本文就T细胞发育、活化、分化、发挥免疫功能等阶段的代谢调节机制进行了阐述,并探讨了T细胞代谢调节在临床诊断与治疗中的应用。     

结核杆菌感染T细胞介导免疫应答研究的新进展

结核病对免疫学家构成了巨大的挑战,因为它是一种慢性传染性疾病,病原体具有持久性特点.在对人和动物进行实验时,检测到结核分枝杆菌适应性免疫应答的特点之一为感染早期T细胞免疫应答延迟.新近研究揭示了此种延迟应答的机制:通过结核杆菌抑制免疫细胞(CD4+和CD8+T细胞及DC)凋亡延迟应答,通过特异性Treg细胞抑制作用延迟应答.结核杆菌慢性感染期间存在IFNγ信号调节网络和ESAT-6抗原的慢性刺激作用,抗原特异性PD-1+ CD4+T细胞具有高度增殖分化为更多终末效应性T细胞的潜能,以此可调节和维持免疫应答.深入了解抗原特异性T细胞调节与维持适应性免疫应答的机制,有益于抗结核疫苗的设计和研制.     

CD4+T细胞免疫识别的一种新理解

获得性免疫具有抗原特异性,但同时T细胞识别却有混杂性和NHC制约等现象,这提示T细胞对抗原肽-MHC分子复合物(pMHC)识别中可能存在不同模式。本文提出了CD4 T细胞有两种特异性识别活化基础单位(具有不同的生理学意义)的模型,一种为纯TCR模式(TCR model),对pMHC(尤其是抗原肽)高特异性识别;另一种为复合受体模式(TCR-CD4 model),对MHC-Ⅱ分子特异性要求很高(NHC制约),但有可以不同亲合度结合抗原肽的混杂性;它们在免疫应答中以不同组合形式出现,可形成细胞水平区分“自我”与“非我”的效应。由此可更合理、简化地理解各种有关免疫现象以及淋巴免疫系统的起源。     

生命信息安全控制原理的再探讨

建立生命信息安全控制原理的理论性平台,由该平台的视野分析免疫学所涉及的诸多理论问题,譬如免疫记忆、免疫功能等方面,并针对性进行归纳以及绘制出相关图形,试图将免疫学理论中所呈现的纷繁复杂性的方面以及过于分散的条块更加条理化、清晰化及整体化。由逻辑学的层面讨论免疫学学名的形成,分析结果:免疫学学名应归结为主观是非逻辑意识产物,并主张认识论应回归自然生成逻辑的观点。免疫记忆在本质上是对遗传信息的记忆,离开了遗传信息的识别与分析就不存在免疫记忆。众多学者的系列研究资料表明,CD4+T细胞在CD8+T细胞反应的起始就辅助其发挥作用,并维持其记忆细胞功能,而CD4+T细胞的记忆是由TCR-MHCⅡ信号所决定。X线晶体衍射及三维结构图所显示MHCII类肽结合凹槽内的多肽更能显示出呈递多肽遗传信息的功能,而MHCI类分子肽结合凹槽内的多肽难以与呈递多肽遗传信息的功能联系起来。只有辅助性T细胞是决定与辅助记忆的细胞,其不仅决定B细胞胸腺依赖性抗原的记忆,而且决定CD8+T细胞的记忆性。对生命信息识别从记忆属性层面进行分类,即分为遗传信息密码识别(记忆属性)和非遗传信息密码识别(非记忆属性)2大类。通过危险因素、生命信息感应器、信息识别及应答调控这样4个相连贯环节的分析,绘制出生命信息安全控制原理图。从功能效应层面进行讨论,将生命信息安全控制的功效分类为正面功能效应和负面功能效应2大类,其中将组织修复归结为正面功能效应,创伤引起的无菌性炎症归结为负面功能效应。绘制出生命信息安全控制功效图,并讨论了生命信息安全控制功效图的建立在理论方面的重要意义。     

探究杂交瘤技术制备单克隆抗体时与骨髓瘤细胞有效融合的细胞类型

杂交瘤技术制备单克隆抗体,一般取免疫小鼠的脾细胞与骨髓瘤细胞融合,并通过筛选获得杂交瘤细胞后再生产。脾脏内含有B1细胞、Mz-B细胞、T1 B细胞、T2 B细胞、初始B细胞、致敏B细胞、短寿命浆细胞、中心母细胞、中心细胞、抗体分泌细胞等不同类型的细胞。制备单克隆抗体使用的抗原多为蛋白质,经典的免疫策略要用抗原反复刺激免疫动物,所获单克隆抗体类型多为高亲和力的免疫球蛋白G(IgG),结合近期发明的一些新技术等,可认为与骨髓瘤细胞有效融合的主要是由记忆B细胞增殖分化而来的抗体分泌细胞。     

ELISPOT检测人乳头瘤病毒特异性的记忆T细胞

应用ELISPOT方法检测人乳头瘤病毒感染后自发清除者外周血中抗原特异性的记忆T细胞。收集人乳头瘤病毒（HPV）感染后自发清除者外周血（病毒清除后74个月）,分离外周血单个核细胞（peripheralblood mononuclear cells,PBMC）。体外应用已鉴定的表位肽刺激PBMC,10 d后计数细胞,去除表位肽,继续培养。第11天,ELISPOT方法检测PBMC中HPV抗原特异性的记忆T细胞。PBMC经表位肽刺激10 d后,细胞数量有明显增加,由最初的4.1×105增加为4.2×106。第11天,细胞数量增加为4.65×106,为抗原刺激前细胞数的11.3倍。ELISPOT结果显示,PBMC中的记忆T细胞活化后,能够识别抗原递呈细胞递呈的抗原肽,并分泌IFN-γ。此HPV自发清除者外周血中抗原特异性的记忆T细胞的频数为0.007%。人乳头瘤病毒（HPV）感染后自发清除者外周血存在抗原特异性记忆T细胞,抗原肽可激活记忆T细胞,使之数量增加,分泌IFN-γ。ELISPOT可用于检测外周血中HPV特异性的记忆T细胞。     

结核分枝杆菌蛋白亚单位疫苗与疫苗诱导的T细胞免疫记忆研究进展

牛分枝杆菌减毒活疫苗--卡介苗(bacillus Calmette-Guérin,BCG)对预防严重的儿童结核病有效,但其免疫保护效率随儿童年龄增长而降低。BCG不能提供终身免疫保护可能与其诱导的记忆性T细胞主要是寿命较短的效应记忆性T细胞有关。新型结核分枝杆菌蛋白亚单位疫苗将有效的抗原有机组合起来,在适宜的疫苗佐剂辅助下诱导Th1型免疫应答。动物实验表明,增加抗原谱可有效提高亚单位疫苗的保护效率。更重要的是,亚单位疫苗在体内持续时间较短,可诱导寿命较长的中央记忆性T细胞,提供比BCG更持久的免疫保护力。记忆性T细胞的分化受抗原特性与剂量、细胞因子、转录因子及雷帕霉素等的调控。对亚单位疫苗及其诱导的免疫记忆进行研究将对新型结核分枝杆菌疫苗的设计与评价产生积极影响。     

Signal transduction via the T cell antigen receptor in naïve and effector/memory T cells

T cells play an indispensable role in immune defense against infectious agents, but can also be pathogenic. These T cells develop in the thymus, are exported into the periphery as naïve cells and participate in immune responses. Upon recognition of antigen, they are activated and differentiate into effector and memory T cells. While effector T cells carry out the function of the immune response, memory T cells can last up to the life time of the individual, and are activated by subsequent antigenic exposure. Throughout this life cycle, the T cell uses the same receptor for antigen, the T cell Receptor, a complex multi-subunit receptor. Recognition of antigen presented by peptide/MHC complexes on antigen presenting cells unleashes signaling pathways that control T cell activation at each stage. In this review, we discuss the signals regulated by the T cell receptor in naïve and effector/memory T cells.     

Macrophage T lymphocyte interactions in the anti-tumor immune response: a mathematical model

In this paper we present a model of the macrophage T lymphocyte interactions that generate an anti-tumor immune response. The model specifies i) induction of cytotoxic T lymphocytes, ii) antigen presentation by macrophages, which leads to iii) activation of helper T cells, and iv) production of lymphoid factors, which induce a) cytotoxic macrophages, b) T lymphocyte proliferation, and c) an inflammation reaction. Tumor escape mechanisms (suppression, antigenic heterogeneity) have been deliberately omitted from the model. This research combines hitherto unrelated or even contradictory data within the range of behavior of one model. In the model behavior, helper T cells play a crucial role: Tumors that differ minimally in antigenicity (i.e., helper reactivity) can differ markedly in rejectability. Immunization yields protection against tumor doses that would otherwise be lethal, because it increases the number of helper T cells. The magnitude of the cytotoxic effector cell response depends on the time at which helper T cells become activated: early helper activity steeply increases the magnitude of the immune response. The type of cytotoxic effector cells that eradicates the tumor depends on tumor antigenicity: lowly antigenic tumors are attacked mainly by macrophages, whereas large highly antigenic tumors can be eradicated by cytotoxic T lymphocytes only.     

抗独特型抗体与T细胞记忆的关系

记忆T细胞作为人体免疫系统中的一个组成部分,在免疫应答中发挥着至关重要的作用,因此利用抗独特型抗体制备诱导产生记忆T细胞的疫苗是免疫学领域的一个重要方向。抗独特型抗体Fab段具有与特异性抗原相似的抗原决定簇的结构,其作为抗原替代物制备的疫苗所激发机体产生的记忆T细胞具有特异性强和安全性高的特点,成为一种比较理想的疫苗.就抗独特型抗体与T细胞记忆之间的联系及其应用效果作一简要综述。     

A model of human immunodeficiency virus infection in T helper cell clones

We present a mathematical model of the activation and proliferation of a clone of T helper cells in response to a replicating antigen. This is able to show types of behaviour akin to persistent infection and to immune memory. This model is expanded to include the infection and destruction of activated T helper cells by human immunodeficiency virus and the growth of a population of circulating human immunodeficiency virus. The resulting model is used to investigate the circumstances under which the human immunodeficiency virus can destabilize persistent infections and destroy immune memory, and to illustrate the impact of antigenic stimulation of infected T helper cell clones upon human immunodeficiency virus replication rates.     

Induction and monitoring of active delayed type hypersensitivity (DTH) in rats

Delayed type hypersensitivity (DTH) is an inflammatory reaction mediated by CCR7- effector memory T lymphocytes that infiltrate the site of injection of an antigen against which the immune system has been primed. The inflammatory reaction is characterized by redness and swelling of the site of antigenic challenge. It is a convenient model to determine the in vivo efficacy of immunosuppressants. Cutaneous DTH can be induced either by adoptive transfer of antigen-specific T lymphocytes or by active immunization with an antigen, and subsequent intradermal challenge with the antigen to induce the inflammatory reaction in a given skin area. DTH responses can be induced to various antigens, for example ovalbumin, tuberculin, tetanus toxoid, or keyhole limpet hemocyanin (KLH).Here we demonstrate how to induce an active DTH reaction in Lewis rats. We will first prepare a water-in-oil emulsion of KLH, our antigen of interest, in complete Freund's adjuvant and inject this emulsion subcutaneously to rats. This will prime the immune system to develop memory T cells directed to KLH. Seven days later we will challenge the rats intradermally on the back with KLH on one side and with ovalbumin, an irrelevant antigen, on the other side. The inflammatory reaction will be visible 16-72 hours later and the red and swollen area will be measured as an indication of DTH severity.     

Viral Escape Mutant Epitope Maintains TCR Affinity for Antigen yet Curtails CD8 T Cell Responses

T cells have the remarkable ability to recognize antigen with great specificity and in turn mount an appropriate and robust immune response. Critical to this process is the initial T cell antigen recognition and subsequent signal transduction events. This antigen recognition can be modulated at the site of TCR interaction with peptide:major histocompatibility (pMHC) or peptide interaction with the MHC molecule. Both events could have a range of effects on T cell fate. Though responses to antigens that bind sub-optimally to TCR, known as altered peptide ligands (APL), have been studied extensively, the impact of disrupting antigen binding to MHC has been highlighted to a lesser extent and is usually considered to result in complete loss of epitope recognition. Here we present a model of viral evasion from CD8 T cell immuno-surveillance by a lymphocytic choriomeningitis virus (LCMV) escape mutant with an epitope for which TCR affinity for pMHC remains high but where the antigenic peptide binds sub optimally to MHC. Despite high TCR affinity for variant epitope, levels of interferon regulatory factor-4 (IRF4) are not sustained in response to the variant indicating differences in perceived TCR signal strength. The CD8+ T cell response to the variant epitope is characterized by early proliferation and up-regulation of activation markers. Interestingly, this response is not maintained and is characterized by a lack in IL-2 and IFNγ production, increased apoptosis and an abrogated glycolytic response. We show that disrupting the stability of peptide in MHC can effectively disrupt TCR signal strength despite unchanged affinity for TCR and can significantly impact the CD8+ T cell response to a viral escape mutant.     

Understanding original antigenic sin in influenza with a dynamical system

Original antigenic sin is the phenomenon in which prior exposure to an antigen leads to a subsequent suboptimal immune response to a related antigen. Immune memory normally allows for an improved and rapid response to antigens previously seen and is the mechanism by which vaccination works. I here develop a dynamical system model of the mechanism of original antigenic sin in influenza, clarifying and explaining the detailed spin-glass treatment of original antigenic sin. The dynamical system describes the viral load, the quantities of healthy and infected epithelial cells, the concentrations of naïve and memory antibodies, and the affinities of naïve and memory antibodies. I give explicit correspondences between the microscopic variables of the spin-glass model and those of the present dynamical system model. The dynamical system model reproduces the phenomenon of original antigenic sin and describes how a competition between different types of B cells compromises the overall effect of immune response. I illustrate the competition between the naïve and the memory antibodies as a function of the antigenic distance between the initial and subsequent antigens. The suboptimal immune response caused by original antigenic sin is observed when the host is exposed to an antigen which has intermediate antigenic distance to a second antigen previously recognized by the host''s immune system.     

A Role for Rebinding in Rapid and Reliable T Cell Responses to Antigen

Experimental work has shown that T cells of the immune system rapidly and specifically respond to antigenic molecules presented on the surface of antigen-presenting-cells and are able to discriminate between potential stimuli based on the kinetic parameters of the T cell receptor-antigen bond. These antigenic molecules are presented among thousands of chemically similar endogenous peptides, raising the question of how T cells can reliably make a decision to respond to certain antigens but not others within minutes of encountering an antigen presenting cell. In this theoretical study, we investigate the role of localized rebinding between a T cell receptor and an antigen. We show that by allowing the signaling state of individual receptors to persist during brief unbinding events, T cells are able to discriminate antigens based on both their unbinding and rebinding rates. We demonstrate that T cell receptor coreceptors, but not receptor clustering, are important in promoting localized rebinding, and show that requiring rebinding for productive signaling reduces signals from a high concentration of endogenous pMHC. In developing our main results, we use a relatively simple model based on kinetic proofreading. However, we additionally show that all our results are recapitulated when we use a detailed T cell receptor signaling model. We discuss our results in the context of existing models and recent experimental work and propose new experiments to test our findings.     

Contributions of memory B cells to secondary immune response

The secondary immune response is one of the most important features of immune systems. During the secondary immune response, the immune system can eliminate the antigen, which has been encountered by the individual during the primary invasion, more rapidly and efficiently. Both T and B memory cells contribute to the secondary response. In this paper, we only concentrate on the functions of memory B cells. We explore a model describing the memory contributed by the specific long-lived clone which is maintained by continued stimulation with a small amount of antigens sequestered on the surfaces of the follicular dendritic cells (FDC). The behavior of the secondary response provided by the model can be compared with experimental observations. The model shows that memory B cells indeed play an important role in the secondary response. It is found that a single memory cell in a long-lived clone may not be long-lived. In the present note, the influences of relevant parameters on the secondary response are also explored.