三级淋巴结构（TLS）被认为可以刺激抗肿瘤免疫，并对预后和对免疫检查点阻断的反应产生积极影响。然而，在胃癌 (GC) 中，TLS 主要见于预后不良且治疗反应有限的 GC。因此，我们假设 TLS 的免疫细胞组成和功能取决于肿瘤位置和肿瘤免疫环境。利用来自 GC 原发肿瘤的档案切除标本，使用空间转录组学和免疫组织化学来表征 TLS 内部和外部的 CD45 免疫细胞的表型我们确定了 GC 中 TLS 的细胞组成和成熟状态的显着患者内和患者间多样性。肿瘤位置（原发部位与转移部位）是 TLS 成熟度差异的主要原因，因为腹膜转移灶中的 TLS 主要不成熟。与具有成熟 TLS 的肿瘤相比，这与较高水平的肿瘤浸润巨噬细胞和 Tregs 以及较少的浆细胞有关。此外，成熟的 TLS 的特点是抗肿瘤免疫途径的过度表达，例如 B 细胞相关途径、MHC II 类抗原呈递，而未成熟的 TLS 与促肿瘤途径相关，包括 T 细胞耗竭和相应癌症中 DNA 修复途径的增强。观察到GC衍生的腹膜转移通常含有不成熟的TLS，其与免疫抑制调节性肿瘤浸润白细胞相关，这与对免疫检查点阻断缺乏反应以及腹膜转移性GC的不良预后特征一致，需要采取措施在优化转移性 GC 的免疫调节策略时予以考虑。© 作者（或其雇主）2024。根据 CC BY-NC 允许重复使用。禁止商业再利用。请参阅权利和权限。英国医学杂志出版。

Tertiary lymphoid structures (TLSs) are thought to stimulate antitumor immunity and positively impact prognosis and response to immune checkpoint blockade. In gastric cancers (GCs), however, TLSs are predominantly found in GC with poor prognosis and limited treatment response. We, therefore, hypothesize that immune cell composition and function of TLS depends on tumor location and the tumor immune environment.Spatial transcriptomics and immunohistochemistry were used to characterize the phenotype of CD45+ immune cells inside and outside of TLS using archival resection specimens from GC primary tumors and peritoneal metastases.We identified significant intrapatient and interpatient diversity of the cellular composition and maturation status of TLS in GC. Tumor location (primary vs metastatic site) accounted for the majority of differences in TLS maturity, as TLS in peritoneal metastases were predominantly immature. This was associated with higher levels of tumor-infiltrating macrophages and Tregs and less plasma cells compared with tumors with mature TLS. Furthermore, mature TLSs were characterized by overexpression of antitumor immune pathways such as B cell-related pathways, MHC class II antigen presentation while immature TLS were associated with protumor pathways, including T cell exhaustion and enhancement of DNA repair pathways in the corresponding cancer.The observation that GC-derived peritoneal metastases often contain immature TLS which are associated with immune suppressive regulatory tumor-infiltrating leucocytes, is in keeping with the lack of response to immune checkpoint blockade and the poor prognostic features of peritoneal metastatic GC, which needs to be taken into account when optimizing immunomodulatory strategies for metastatic GC.© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.