Helper and suppressor roles of CD8+ T cells

描述（由申请方提供）：效应CD 8 + T细胞对携带抗原的树突状细胞（携带Ag的DC）的清除被认为是限制细胞毒性T淋巴细胞（CTL）应答的一种机制。然而，在长期暴露于Ag的情况下，例如慢性感染或癌症，DC被慢性活化的CD 8 + T细胞消除可能导致免疫抑制。我们的初步观察结果表明，在预先存在的肿瘤特异性免疫的情况下，将肿瘤无关（LCMV-gp 33）肽添加到肿瘤裂解物负载的DC中可以增加在治疗环境中施用的癌症疫苗的功效。这种有益效果依赖于记忆型LCMV-gp 33特异性CD 8 + T细胞的存在;而效应型LCMV-gp 33特异性CD 8 + T细胞消除了疫苗的功效。这些数据表明，CD 8 + T细胞活化的连续阶段与CD 8 + T细胞的不同免疫调节活性相关。因此，我们建议描绘的机制，抑制和辅助功能的效应和记忆阶段的CD 8 + T细胞，分别。此外，我们将研究如何分别避免或利用这些免疫调节功能来改善癌症免疫疗法。本提案中概述的工作将遵循三个具体目标-（1）确定效应CD 8 + T细胞的免疫抑制机制;（2）确定记忆CD 8 + T细胞的辅助活性机制;（3）比较CD 8+辅助与抑制对预防与治疗环境中携带疫苗的DC存活的影响。我们将在体外试验中使用小分子抑制剂、阻断抗体和转基因小鼠，检查效应期CD 8 + T细胞对DC的杀伤以及记忆期CD 8 + T细胞对DC成熟和IL-12分泌的诱导。使用体内DC迁移试验，我们将使用转基因小鼠来确定参与预免疫小鼠中的辅助和抑制功能的途径，分别携带记忆或效应阶段的反应。最后，这些实验也将在荷瘤小鼠中进行，以描绘影响基于DC的免疫疗法的途径。相关性：治疗性基于DC的疫苗通常在外周施用，其中肿瘤特异性效应细胞占主导地位并且可以杀死疫苗。通过确定CD 8 + T细胞免疫调节功能的机制，我们可以设计出对抑制功能有抵抗力的疫苗，并且更能够接受记忆细胞来源的帮助，前瞻性地允许我们为癌症患者设计有效的治疗性疫苗。

DESCRIPTION (provided by applicant): The clearance of antigen-carrying dendritic cells (Ag-carrying DC) by effector CD8+ T cells has been postulated as a mechanism for limiting cytotoxic T lymphocyte (CTL) responses. However, in situations of prolonged Ag exposure, such as chronic infection or cancer, DC elimination by chronically-activated CD8+ T cells may lead to immune suppression. Our preliminary observations indicate that the addition of a tumor-irrelevant (LCMV-gp33) peptide to tumor-lysate loaded DC can increase the efficacy of cancer vaccines administered in therapeutic settings in the presence of pre-existing tumor-specific immunity. Such beneficial effects of rely on the presence of memory-type LCMV-gp33-specific CD8+ T cells; whereas effector-typeLCMV-gp33-specific CD8+ T cells abolished the efficacy of the vaccine. These data suggest that the sequential phases of CD8+ T cell activation are associated with different immunoregulatory activities of CD8+ T cells. Therefore, we propose to delineate the mechanisms underlying the suppressive and helper functions of effector and memory-stage CD8+ T cells, respectively. Additionally, we will examine how these immunoregulatory functions can be, respectively, avoided or exploited for improved cancer immuno-therapies. The work outlined within this proposal will follow three specific aims- (1) To determine the mechanism of immunosuppression by effector CD8+ T cells; (2) to determine the mechanism of helper activity of memory CD8+ T cells; and (3) compare the impact of CD8+ help versus suppression on the survival of vaccine-carrying DC in preventative vs. therapeutic settings. We will use small molecule inhibitors, blocking antibodies and transgenic mice in in vitro assays examining killing of DC by effector-stage CD8+ T cells and the induction of DC maturation and IL-12 secretion by memory-stage CD8+ T cells. Using a DC migration assay in vivo, we will use transgenic mice to determine the pathways involved in helper and suppressor functions in pre-immunized mice carrying memory or effector stage responses, respectively. Lastly, these experiments will also be performed in tumor-bearing mice to delineate the pathways that effect DC-based immunotherapies. Relevance: Therapeutic DC-based vaccines are typically administered in the periphery, where the tumor-specific effector cells predominate and can kill the vaccine. By determining the mechanisms underlying CD8+ T cell immunoregulatory functions, we can design vaccines that are resistant to the suppressive functions and are more capable of receiving the memory cell-derived help, prospectively allowing us to design effective therapeutic vaccines for cancer patients.