Biology and Function of anti-HSV CD8 T Cells

描述(由申请人提供)：目前建立和维持长期T细胞记忆的概念提出记忆T细胞来自一小部分存活的效应性T细胞亚群。利用C57BL/6小鼠皮肤HSV-1感染模型，我们发现控制感染的能力高度依赖于HSV-1特异性CD4+和CD8+T细胞的存在，其中CD8+T细胞发挥主要作用，表达细胞溶解功能并能够合成干扰素-γ(IFN-γ)。表达CTL功能的能力与IL-2受体α链CD25的表达增加密切相关。这一观察结果得出结论，高水平的CD25表达对于HSV特异性CTL活性的表达是强制性的。然而，在感染反应的早期阶段，CD8+T细胞亚群已经被发现存在于引流区域淋巴结内和脾内。这些细胞在体外抗原刺激后合成干扰素-γ，而不表达升高的CD25水平。在所有其他方面，这些CD8+T细胞具有激活细胞的所有特征，这表明它们可能代表着一群仅能合成细胞因子而不能表达穿孔素依赖的CTL功能的效应细胞，或者它们可能是记忆性CD8+T细胞的直接祖细胞。需要解决的假设是，CD8+T细胞亚群代表了一种能够直接进入记忆池的细胞谱系，而不需要通过完整的激活程序来获得CTL功能。将研究五个具体目标。在目标1中，将详细分析在体内获得CD8+T细胞亚群的细胞溶解和细胞因子合成功能的整个感染初始反应过程。此外，定义的CD8+T细胞将被转移到受体动物，并确定后代的功能。在目标2中，这一亚群对长期记忆做出贡献的能力将通过领养转移到适当的受体小鼠来评估。这一能力将直接与从长期康复的小鼠中获得的“真正的”记忆CD8+T细胞进行比较。目的3将利用新开发的转基因模型，通过分析重要的信号媒介，以及通过测量凋亡细胞的百分比和抗凋亡分子的表达来确定细胞的持续能力，来研究不同CD8+T细胞亚群的激活状态和功能。目的4测定不同CD8+T细胞的表型特征，以了解体内迁移模式差异的分子基础。目的5将讨论不同种类的细胞因子在CD8+T细胞克隆扩增和分化中的作用，重点讨论与增殖和分化有关的细胞因子的作用。总体而言，该提案将确定CD8+CD25neg T细胞是否有助于记忆，是具有独特特征的效应细胞的一个独特亚群，还是发育的死胡同。这些研究将对CD8 T细胞生物学有更深入的了解。

DESCRIPTION (provided by applicant): Current concepts of the establishment and maintenance of long-term T cell memory propose that memory T cells are derived from a small; surviving subpopulation of effector T cells. Using a model of cutaneous HSV-1 infection in C57BL/6 mice, we have found that the ability to control infection is highly dependent upon the presence of HSV-1-specific CD4+ and CD8+ T cells, with the principal role being played by CD8+ T cells expressing cytolytic function and able to synthesize interferon-gamma (IFN-gamma). The ability to express CTL function was intimately linked with the increased expression of the IL-2 receptor alpha-chain, CD25. This observation lead to the conclusion that expression of high levels of CD25 was mandatory for the expression of HSV-specific CTL activity. However, a subpopulation of CD8+ T cells, present both within the draining regional lymph node and within the spleen during the early phase of the response to infection, has been identified. These cells synthesize IFN-gamma following antigenic stimulation in vitro without expressing elevated levels of CD25. In all other aspects, these CD8+ T cells have all of the characteristics of activated cells, suggesting that they may represent a population of effector cells able to synthesize only cytokines rather than express perforin-dependent CTL function, or may be the direct progenitors of memory CD8+ T cells. The hypothesis to be addressed is that this CD8+ T cell subpopulation represents a lineage of cells able to enter directly into the memory pool without proceeding through the full activation program to attain CTL function. Five specific aims will be studied. In Aim 1, the acquisition of in vivo cytolytic and cytokine synthetic functions of the CD8+ T cell subpopulations will be analyzed in detail throughout the course of the initial response to infection. Also, defined CD8+ T cells will be transferred to recipient animals, and the functions of the progeny determined. In Aim 2, the ability of this subpopulation to contribute to long-term memory will be assessed by adoptive transfer into appropriate recipient mice. This ability will be compared directly with "authentic" memory CD8+ T cells obtained from long-term convalescent mice. Aim 3 will address the activation status and function of the distinct CD8+ T cell subpopulations using a newly developed transgenic model, through the analysis of important signaling mediators, and the ability of the cells to persist as determined by measuring the percentage of apoptotic cells and the expression of anti-apoptotic molecules. Aim 4 will determine the phenotypic characteristics of the distinct CD8+ T cells to understand the molecular basis for differences in the migratory patterns in vivo. Aim 5 will address the role of different cytokine species in the clonal expansion and differentiation of the distinct CD8+ T cells, with focus given to the role of cytokines responsible for proliferation and differentiation. Overall, the proposal will determine whether the CD8+ CD25neg T cells contribute to memory, are a distinct subpopulation of effector cells with unique characteristics, or a developmental dead end. Greater insight into CD8 T cell biology will result from these studies.