Centre for Haematology, Department of Immunology and Inflammation, Imperial College London, London, United Kingdom.
Department of Medical Microbiology and Immunology, Taibah University, Medina, Saudi Arabia.
Blood. 2023 May 18;141(20):2417-2429. doi: 10.1182/blood.2022018380.
Immune thrombocytopenia (ITP) is traditionally considered an antibody-mediated disease. However, a number of features suggest alternative mechanisms of platelet destruction. In this study, we use a multidimensional approach to explore the role of cytotoxic CD8+ T cells in ITP. We characterized patients with ITP and compared them with age-matched controls using immunophenotyping, next-generation sequencing of T-cell receptor (TCR) genes, single-cell RNA sequencing, and functional T-cell and platelet assays. We found that adults with chronic ITP have increased polyfunctional, terminally differentiated effector memory CD8+ T cells (CD45RA+CD62L-) expressing intracellular interferon gamma, tumor necrosis factor α, and granzyme B, defining them as TEMRA cells. These TEMRA cells expand when the platelet count falls and show no evidence of physiological exhaustion. Deep sequencing of the TCR showed expanded T-cell clones in patients with ITP. T-cell clones persisted over many years, were more prominent in patients with refractory disease, and expanded when the platelet count was low. Combined single-cell RNA and TCR sequencing of CD8+ T cells confirmed that the expanded clones are TEMRA cells. Using in vitro model systems, we show that CD8+ T cells from patients with ITP form aggregates with autologous platelets, release interferon gamma, and trigger platelet activation and apoptosis via the TCR-mediated release of cytotoxic granules. These findings of clonally expanded CD8+ T cells causing platelet activation and apoptosis provide an antibody-independent mechanism of platelet destruction, indicating that targeting specific T-cell clones could be a novel therapeutic approach for patients with refractory ITP.
免疫性血小板减少症（ITP）传统上被认为是一种抗体介导的疾病。然而，许多特征表明存在替代的血小板破坏机制。在这项研究中，我们采用多维方法来探讨细胞毒性 CD8+T 细胞在 ITP 中的作用。我们对 ITP 患者进行了特征描述，并与年龄匹配的对照进行了比较，使用免疫表型分析、T 细胞受体（TCR）基因的下一代测序、单细胞 RNA 测序以及功能 T 细胞和血小板测定。我们发现，慢性 ITP 成人患者存在表达细胞内干扰素 γ、肿瘤坏死因子 α 和颗粒酶 B 的多功能、终末分化效应记忆 CD8+T 细胞（CD45RA+CD62L-）增多，将其定义为 TEMRA 细胞。这些 TEMRA 细胞在血小板计数下降时会扩增，并且没有表现出生理性耗竭的证据。对 TCR 的深度测序显示 ITP 患者存在扩增的 T 细胞克隆。T 细胞克隆持续多年存在，在难治性疾病患者中更为明显，并且在血小板计数低时会扩增。对 CD8+T 细胞进行单细胞 RNA 和 TCR 联合测序证实，扩增的克隆是 TEMRA 细胞。使用体外模型系统，我们表明来自 ITP 患者的 CD8+T 细胞与自身血小板形成聚集体，通过 TCR 介导的细胞毒性颗粒释放释放干扰素 γ，并触发血小板激活和凋亡。这些发现表明，克隆扩增的 CD8+T 细胞导致血小板激活和凋亡，提供了一种非抗体依赖的血小板破坏机制，表明针对特定 T 细胞克隆可能是治疗难治性 ITP 患者的一种新方法。
