Differentiation and function of intratumoral memory-phenotype CD8+ T cells

摘要 虽然大量证据表明CD8+TIL对突变或非突变的肿瘤抗原具有反应 在抗肿瘤免疫中发挥重要作用，越来越多的证据表明，真正的肿瘤反应性T细胞 在许多人类肿瘤中，细胞只占所有TIL的一小部分，这表明大多数CD8+TIL 不明确的专一性。基于这个长期存在的问题，我们检验了一种假设，即 部分TIL可能代表CD8+“记忆表型”T细胞(CD8-MP细胞)，这是一种独特的细胞群 未知的抗原特异性，在未免疫的小鼠中占CD8+T细胞的5%-10%，表现出常见的 具有先前抗原经验的特征，并有能力在 免疫反应。在初步工作中，我们发现CD8-MP细胞在 癌基因驱动的前列腺癌的免疫浸润，并表达高密度的PD-1抑制因子 受体。鉴于这些独特的见解，我们开始了平行研究，旨在进一步阐明 CD8-MP细胞的基础生物学，使用克隆方法来定义 这些细胞。我们的新数据显示，许多CD8-MP克隆的分化是由识别 通过一种可重复的、精心安排的过程在胸腺中形成自我配体，挑战了目前认为 CD8-MP细胞在动态平衡信号的响应下在外周分化。在目标1中，我们将定义 CD8-MP细胞在抗肿瘤免疫中的作用，验证了自我配体识别驱动 CD8-MP细胞早期进入发展中的肿瘤，CD8-MP细胞通过 催化更广泛的免疫细胞渗透。此外，我们还将确定可用于 鉴定瘤内CD8-MP细胞，从而使对CD8-MP细胞在小鼠癌症中的更广泛研究成为可能 模特和人类癌症患者。在目标2中，我们将阐明分子和细胞机制 直接分化CD8-MP，验证CD8-MP分化是一个两步过程的假设 由胸腺中经典树突状细胞呈现的TCR依赖的自我配体识别触发。我们 还将利用一种独特的T细胞抗原发现试验来鉴定CD8-MP识别的天然自体多肽 单元格，从而打开了以前无法进入的新的调查领域。最终，定义函数 肿瘤内CD8-MP细胞的研究和小鼠CD8-MP分化蓝图有望打开新的 研究和操纵人类这些细胞的途径。

ABSTRACT While considerable evidence demonstrates that CD8+ TILs reactive to mutated or non-mutated tumor antigens play an important role in anti-tumor immunity, expanding evidence indicates that bona fide tumor-reactive T cells comprise only a minor fraction of all TILs in many human tumors, indicating that most CD8+ TILs have undefined specificity. Based on this long-standing question, we examined the hypothesis that a substantial fraction of TILs may represent CD8+ "memory-phenotype" T cells (CD8-MP cells), a unique population of cells of unknown antigen specificity that comprise 5-10% of CD8+ T cells in unprimed mice, exhibit common hallmarks of prior antigen experience, and have the capacity to rapidly expand and produce IFN-γ during an immune response. In preliminary work, we found that CD8-MP cells make substantial contributions to the immune infiltrate of oncogene-driven prostate tumors, and express high densities of the PD-1 inhibitory receptor. Given these unique insights, we embarked on parallel studies aimed at further elucidating the fundamental biology of CD8-MP cells, using a clonal approach to define the developmental trajectories of these cells. Our new data reveal that the differentiation of many CD8-MP clones is triggered by recognition of self-ligands in the thymus via a reproducible, orchestrated process, challenging current thought suggesting that CD8-MP cells differentiate in the periphery in response to homeostatic signals. In Aim 1, we will define the function of CD8-MP cells in anti-tumor immunity, testing the hypothesis that self-ligand recognition drives the early entry of CD8-MP cells into developing tumors, and that CD8-MP cells enhance anti-tumor immunity by catalyzing broader immune cell infiltration. In addition, we will identify novel markers that can be used to identify intratumoral CD8-MP cells, thereby enabling the broader study of CD8-MP cells in murine cancer models and human cancer patients. In Aim 2, we will elucidate the molecular and cellular mechanisms that direct CD8-MP differentiation, testing the hypothesis that CD8-MP differentiation is a two-step process triggered by TCR-dependent recognition of self-ligands presented by classical dendritic cells in the thymus. We will also utilize a unique T cell antigen discovery assay to identify natural self-peptides recognized by CD8-MP cells, thereby opening new areas of inquiry that were previously inaccessible. Ultimately, defining the function of intratumoral CD8-MP cells and the blueprints of CD8-MP differentiation in mice is expected to open new avenues for the study and manipulation of these cells in humans.