Lymphocyte Dynamics

淋巴细胞动力学

• 批准号: 8336169
• 负责人: William Paul
• 金额: $ 129.17万
• 依托单位: NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8336169
• 关键词: Academy; Accounting; Adjuvant; Antigens; Biological Models; Blastomyces; C-Peptide; CD4 Positive T Lymphocytes; CD8-Positive T-Lymphocytes; CD8B1 gene; Cell Count; Cell Death; Cell Fraction; Cell Proliferation; Cells; Cessation of life; Chronic Phase; Collaborations; Complex; Computational Biology; Data; Dendritic Cells; Effector Cell; Feedback; Frequencies; Genes; Goals; HIV; HIV Infections; Heating; Homeostasis; Human; IL2RA gene; Immune response; Immune system; Immunization; Immunocompetence; Immunology; Individual; Infection; Interleukin-1; Interleukin-15; Interleukin-17; Interleukin-2; Interleukin-7; Knock-out; Laboratories; Lead; Listeria monocytogenes; Lymphocyte; Lymphocyte Count; Lymphocytic choriomeningitis virus; Macaca; Measurement; Measures; Mediating; Memory; Molecular; Mus; Oregon; Pattern; Peptide/MHC Complex; Phenotype; Physiological; Play; Population; Primates; Process; Production; Proliferating; Proteins; Recording of previous events; Regulation; Regulatory T-Lymphocyte; Relative (related person); Role; SIV; Science; Scientist; Self Stimulation; Series; Specificity; Supplementation; T-Cell Depletion; T-Cell Proliferation; T-Cell Receptor; T-Lymphocyte; TNF gene; Time; Transgenic Organisms; Vaccines; Work; antigen challenge; base; cytokine; immune activation; immunogenicity; in vivo; interdisciplinary approach; killings; lymphocyte proliferation; mathematical model; memory CD4 T lymphocyte; precursor cell; professor; receptor; research study; response; tool development

Lymphocyte numbers are regulated both by responses to conventional exogenous antigens and endogenous microflora, by stimulation by self-peptide/MHC complexes and by the action of a series of cytokines. This multifaceted regulation permits individuals to maintain a broad repertoire of lymphocytes of distinctive specificities, allowing responses against a vast array of foreign substances and, at the same time, providing a pattern of memory based on the immunization history of the individual. The study of the process of lymphocyte dynamics that underlies this regulation requires a multidisciplinary approach, aimed both at the molecular underpinnings of the processes through which lymphocytes survive and proliferate and a systemics/ computational biology approach to appreciate the overall mechanisms governing total numbers of lymphocytes of distinct phenotype and distinct specificity. Emphasis has been placed on four aspects of this problem: the priming and expansion of naive CD4 T cells in response to antigen challenge, the dynamics of lymphocyte memory and of memory phenotype cells, the mechanisms underlying CD4 T cell depletion in HIV infection, and the process of homeostatic proliferation and death. Unit scientists have shown that primary responses are highly dependent upon the number of precursor cells that can respond to antigenic challenge. Using both real time PCR and flow cytometric analysis to measure the response when TCR transgenic cells are transferred to intact recipients, it has been shown that the factor of expansion (FE) of the antigen-stimulated CD4 T cells is highly dependent upon the number of specific precursors. In a model system based on responses of T cell receptor transgenic cells specific for a cyctochrome C peptide, when the frequency of precursors in the recipient is 3 or less, FE is 1500, at 300 cells it is 200 and at 30,000 it is 20. Limitation in expansion does not result from a smaller fraction of cells responding but rather, at least in part, from diminished proliferative rates of responding cells. Diminution in FE as number of precursors increase cannot be accounted for by Fas, TNF or IFNg-mediated cell death nor can it be due to limitation in numbers of dendritic cells or in amounts of antigen as increasing either DC number or amount of antigen does not alter the relationship of FE and precursor number. Furthermore, the effect is not altered by supplementation with IL-1, IL-2, IL-7 or IL-15. The relative frequency of regulatory T cells, either derived from the responding cells or from the host, is not altered by precursor frequency and the difference in FE occurs even when responding cells are unable to develop into regulatory T cells. The effect is highly antigen specific in that large numbers of cells of one specificity do not effect the rate of expansion of small numbers of cells of another specificity. The advantage of smaller cell numbers is even greater oif the cells are unresponsive to IL-27, suggesting that lymphocyte expansion is innately independent of precursor number but that effect is tempered by feedback effects of IL-27. In collaboration with Professor Gennady Bocharov of the Russian Academy of Sciences, a mathematical model of the proliferation of these cells has been developed conforms very well to the observed data. In the course of analyzing the control of FE on the part of both nave and memory cells, it was observed that the most potent stimulant of FE was the cytokine IL-1. When expansion of CD4 TCR transgenic T cells in a syngeneic host in response to antigen was measured, it was found that administering IL-1 over a 3 to 5 day period caused a ten fold enhancement in FE when compared to that seen using conventional adjuvants such as LPS. This was equally true for naive and memory cells and was not mediated by other cytokines. The effect could only be partially explained by enhanced proliferation so that greater survival was also implicated. The use of recipients that were IL-1 receptor knockouts and IL-1 receptor-sufficient donors of TCR transgenic T cells showed that IL-1 could act directly on the responding CD4 or CD8 T cells to mediate expansion. The IL-1 receptor antagonist diminished the adjuvant effect of LPS indicating that a substantial portion of the effect of this conventional adjuvant was due to endogenous production of IL-1. Initial analysis of genes activated and suppressed in cells responding to antigen in the presence of LPS suggest avenues for further analysis that may lead to a mechanistic understanding of the IL-1 effect. The very robust effect of IL-1 suggests it may have a role in certain immunization strategies. IL-1 acts directly on CD4 T cells to enhance their differentiation into IL-17 producing cells. However, although IL-1 acts directly on CD8 cells to mediate their expansion, differentiation of CD8 cells requires the action of IL-1 on non T cells. Experiments involving the use weak vaccines, such as heat killed Listeria monocytogenes, the gD2 protein of H. simplex, heat killed Blastomyces or a pneumococcal protein candidate have shown that the magnitude and protective value of these agents is strikingly enhanced when IL-1 is used together with the vaccine to enhance immunogenicity. Memory CD4 T cell proliferation was shown to be quite slow. Specific T cells from mice infected with LCMV divide at a rate of 2% per day. By contrast CD44bright CD25- CD4 T cells divide much more rapidly, at 8 to 10% per day. Furthermore this rapid steady state proliferation of "memory phenotype" CD4 T cells is similar in conventional and germfree mice. Analysis of the repertoire of memory phenotype undergoing proliferation revealed no difference in receptor complexity from that of non-dividing memory phenotype cells. This implies that division is largely stochastic and probably dominantly driven by cytokines rather than by peptide/ MHC complexes, whether of exogenous or endogenous origin. Working with colleagues at the Oregon Regional Primate Center, we have analyzed lymphocyte dynamics in SIV-infected macaques and have obtained evidence for CD4 T cell populations that decay at very distinct rates in the period after their burst-like expansion. Laboratory of Immunology scientists and our colleagues have shown the critical role that aberrant immune activation in lentiviral infection plays in the decay of CD4 T cell number and in the degradation of immunocompetence in SIV-infected macaques and HIV-infected humans. The ongoing activation of the immune system caused directly or indirectly by infection appears to be of particular importance in the loss of potential effector cells during the chronic phase of the infection.

淋巴细胞数量通过对常规外源抗原和内源微生物群的反应、自肽/MHC复合物的刺激以及一系列细胞因子的作用来调节。这种多方面的调节使个体能够维持具有独特特异性的广泛淋巴细胞库，从而能够对大量外来物质做出反应，同时提供基于个体免疫史的记忆模式。对作为这一调节基础的淋巴细胞动力学过程的研究需要采用多学科方法，既针对淋巴细胞生存和增殖过程的分子基础，又针对系统学/计算生物学方法，以了解控制不同表型和不同特异性的淋巴细胞总数的总体机制。重点关注该问题的四个方面：初始 CD4 T 细胞响应抗原挑战的启动和扩增、淋巴细胞记忆和记忆表型细胞的动态、HIV 感染中 CD4 T 细胞耗竭的机制以及稳态增殖和死亡的过程。 单位科学家表明，初级反应高度依赖于能够对抗原攻击做出反应的前体细胞的数量。使用实时 PCR 和流式细胞术分析测量 TCR 转基因细胞转移至完整受体时的反应，结果表明，抗原刺激的 CD4 T 细胞的扩增因子 (FE) 高度依赖于特定前体细胞的数量。在基于对细胞色素C肽特异的T细胞受体转基因细胞的反应的模型系统中，当受体中前体细胞的频率为3或更少时，FE为1500，在300个细胞时为200，在30,000个细胞时为20。扩增的限制不是由于响应细胞的比例较小，而是至少部分由于响应细胞的增殖率降低而导致。 FE 随着前体细胞数量增加而减少，不能用 Fas、TNF 或 IFNg 介导的细胞死亡来解释，也不能归因于树突细胞数量或抗原量的限制，因为增加 DC 数量或抗原量不会改变 FE 和前体细胞数量的关系。此外，补充 IL-1、IL-2、IL-7 或 IL-15 不会改变其效果。调节性 T 细胞（无论是来自应答细胞还是来自宿主）的相对频率不会因前体频率而改变，即使当应答细胞无法发育为调节性 T 细胞时，FE 也会出现差异。该效应是高度抗原特异性的，因为一种特异性的大量细胞不会影响另一种特异性的少量细胞的扩增速率。如果细胞对 IL-27 无反应，则较小细胞数量的优势甚至更大，这表明淋巴细胞扩增本质上独立于前体细胞数量，但该效应受到 IL-27 反馈效应的缓和。 与俄罗斯科学院的根纳季·博恰洛夫教授合作，开发了这些细胞增殖的数学模型，该模型与观察到的数据非常吻合。 在分析 FE 对幼稚细胞和记忆细胞的控制过程中，观察到 FE 最有效的刺激物是细胞因子 IL-1。当测量同系宿主中 CD4 TCR 转基因 T 细胞响应抗原的扩增时，发现与使用 LPS 等传统佐剂相比，在 3 至 5 天的时间内施用 IL-1 导致 FE 增强十倍。对于幼稚细胞和记忆细胞来说同样如此，并且不受其他细胞因子介导。这种效应只能通过增殖增强来部分解释，因此生存率也更高。使用IL-1受体敲除的受体和IL-1受体充足的TCR转基因T细胞供体表明，IL-1可以直接作用于响应的CD4或CD8 T细胞以介导扩增。 IL-1受体拮抗剂减弱了LPS的佐剂作用，表明这种常规佐剂的作用的很大一部分是由于IL-1的内源性产生。对 LPS 存在下响应抗原的细胞中激活和抑制的基因的初步分析表明了进一步分析的途径，这可能导致对 IL-1 效应的机制理解。 IL-1 的强大作用表明它可能在某些免疫策略中发挥作用。 IL-1 直接作用于 CD4 T 细胞，增强其分化为产生 IL-17 的细胞。 然而，尽管IL-1直接作用于CD8细胞以介导其扩增，但CD8细胞的分化需要IL-1对非T细胞的作用。 涉及使用弱疫苗（例如热灭活单核细胞增生李斯特氏菌、单纯螺杆菌的 gD2 蛋白、热灭活芽生菌或肺炎球菌蛋白候选物）的实验表明，当 IL-1 与疫苗一起使用以增强免疫原性时，这些药物的强度和保护价值显着增强。 记忆 CD4 T 细胞增殖速度相当缓慢。 感染 LCMV 的小鼠的特定 T 细胞每天以 2% 的速度分裂。 相比之下，CD44bright CD25-CD4 T 细胞的分裂速度要快得多，每天为 8% 至 10%。 此外，“记忆表型”CD4 T 细胞的这种快速稳态增殖在传统小鼠和无菌小鼠中是相似的。对正在增殖的记忆表型的全部成分的分析表明，受体复杂性与非分裂记忆表型细胞的受体复杂性没有差异。 这意味着分裂在很大程度上是随机的，并且可能主要由细胞因子驱动，而不是由肽/MHC复合物驱动，无论是外源性还是内源性的。 我们与俄勒冈地区灵长类动物中心的同事合作，分析了感染 SIV 的猕猴的淋巴细胞动态，并获得了 CD4 T 细胞群在爆发式扩张后以非常明显的速率衰减的证据。免疫学实验室的科学家和我们的同事已经证明，慢病毒感染中的异常免疫激活在 SIV 感染的猕猴和 HIV 感染的人类中 CD4 T 细胞数量的衰减和免疫能力的退化中发挥着关键作用。由感染直接或间接引起的免疫系统的持续激活似乎对于感染慢性期潜在效应细胞的损失特别重要。