Department of Immunology, University of Toronto, Toronto, Ontario M5S 1A8, Canada;
J Immunol. 2014 Jan 15;192(2):782-91. doi: 10.4049/jimmunol.1302663. Epub 2013 Dec 13.
CD8(+) CTLs are adept at killing virally infected cells and cancer cells and releasing cytokines (e.g., IFN-γ) to aid this response. However, during cancer and chronic viral infections, such as with HIV, this CTL response is progressively impaired due to a process called T cell exhaustion. Previous work has shown that the glycoprotein T cell Ig and mucin domain-containing protein 3 (Tim-3) plays a functional role in establishing T cell exhaustion. Tim-3 is highly upregulated on virus and tumor Ag-specific CD8(+) T cells, and antagonizing Tim-3 helps restore function of CD8(+) T cells. However, very little is known of how Tim-3 signals in CTLs. In this study, we assessed the role of Tim-3 at the immunological synapse as well as its interaction with proximal TCR signaling molecules in primary human CD8(+) T cells. Tim-3 was found within CD8(+) T cell lipid rafts at the immunological synapse. Blocking Tim-3 resulted in a significantly greater number of stable synapses being formed between Tim-3(hi)CD8(+) T cells and target cells, suggesting that Tim-3 plays a functional role in synapse formation. Further, we confirmed that Tim-3 interacts with Lck, but not the phospho-active form of Lck. Finally, Tim-3 colocalizes with receptor phosphatases CD45 and CD148, an interaction that is enhanced in the presence of the Tim-3 ligand, galectin-9. Thus, Tim-3 interacts with multiple signaling molecules at the immunological synapse, and characterizing these interactions could aid in the development of therapeutics to restore Tim-3-mediated immune dysfunction.
CD8(+) CTLs 擅长杀死病毒感染细胞和癌细胞，并释放细胞因子（例如 IFN-γ）来辅助这种反应。然而，在癌症和慢性病毒感染（如 HIV）期间，这种 CTL 反应由于一种称为 T 细胞耗竭的过程而逐渐受损。先前的工作表明，糖蛋白 T 细胞免疫球蛋白和粘蛋白结构域包含蛋白 3（Tim-3）在建立 T 细胞耗竭方面发挥功能作用。Tim-3 在病毒和肿瘤 Ag 特异性 CD8(+) T 细胞上高度上调，拮抗 Tim-3 有助于恢复 CD8(+) T 细胞的功能。然而，关于 Tim-3 在 CTLs 中的信号传递知之甚少。在这项研究中，我们评估了 Tim-3 在免疫突触中的作用及其与原发性人 CD8(+) T 细胞中近端 TCR 信号分子的相互作用。Tim-3 在免疫突触中的 CD8(+) T 细胞脂筏内被发现。阻断 Tim-3 导致 Tim-3(hi)CD8(+) T 细胞与靶细胞之间形成的稳定突触数量显著增加，表明 Tim-3 在突触形成中发挥功能作用。此外，我们证实 Tim-3 与 Lck 相互作用，但与磷酸化形式的 Lck 不相互作用。最后，Tim-3 与受体磷酸酶 CD45 和 CD148 共定位，这种相互作用在 Tim-3 配体半乳糖凝集素-9 的存在下增强。因此，Tim-3 在免疫突触处与多个信号分子相互作用，表征这些相互作用可能有助于开发恢复 Tim-3 介导的免疫功能障碍的治疗方法。
