Immune checkpoint inhibitors are widely used anticancer therapies¹ that can cause morbid and potentially fatal immune-related adverse events such as immune-related myocarditis (irMyocarditis)^2,3,4,5. The pathogenesis of irMyocarditis and its relationship to antitumour immunity remain poorly understood. Here we sought to define immune responses in heart, tumour and blood in patients with irMyocarditis by leveraging single-cell RNA sequencing coupled with T cell receptor (TCR) sequencing, microscopy and proteomics analyses of samples from 28 patients with irMyocarditis and 41 unaffected individuals. Analyses of 84,576 cardiac cells by single-cell RNA sequencing combined with multiplexed microscopy demonstrated increased frequencies and co-localization of cytotoxic T cells, conventional dendritic cells and inflammatory fibroblasts in irMyocarditis heart tissue. Analyses of 366,066 blood cells revealed decreased frequencies of plasmacytoid dendritic cells, conventional dendritic cells and B lineage cells but an increased frequency of other mononuclear phagocytes in irMyocarditis. Fifty-two heart-expanded TCR clones from eight patients did not recognize the putative cardiac autoantigens α-myosin, troponin I or troponin T. Additionally, TCRs enriched in heart tissue were largely nonoverlapping with those enriched in paired tumour tissue. The presence of heart-expanded TCRs in a cycling blood CD8 T cell population was associated with fatal irMyocarditis case status. Collectively, these findings highlight crucial biology driving irMyocarditis and identify putative biomarkers.

免疫检查点抑制剂是广泛使用的抗癌疗法¹，可导致病态和可能致命的免疫相关不良事件，例如免疫相关心肌炎 （irMyocarditis）^2,3,4,5。irMyocarditis 的发病机制及其与抗肿瘤免疫的关系仍然知之甚少。在这里，我们试图通过利用单细胞 RNA 测序结合 T 细胞受体 （TCR） 测序、显微镜和蛋白质组学分析来定义 irMyocarditis 患者心脏、肿瘤和血液中的免疫反应来自 28 名irMyocarditis 患者和 41 名未受影响的个体的样本。通过单细胞 RNA 测序结合多重显微镜对 84,576 个心肌细胞的分析表明，细胞毒性 T 细胞、常规树突状细胞和炎性成纤维细胞在 irMyocarditis 心脏组织中的频率和共定位增加。对 366,066 个血细胞的分析显示，浆细胞样树突状细胞、常规树突状细胞和 B 系细胞的频率降低，但其他单核吞噬细胞在 irMyocard炎中的频率增加。来自 8 例患者的 52 个心脏扩增的 TCR 克隆未识别推定的心脏自身抗原 α-肌球蛋白、肌钙蛋白 I 或肌钙蛋白 T。此外，在心脏组织中富集的 TCR 与在配对肿瘤组织中富集的 TCR 基本不重叠。循环血液 CD8 T 细胞群中存在心脏扩增的 TCR 与致死性 irMyocarditis 病例状态相关。总的来说，这些发现突出了驱动 irMyocarditis 的关键生物学因素，并确定了推定的生物标志物。