整合多组学分析揭示免疫抑制宿主中肺巨噬细胞转录组特征的改变。

INTRODUCTION: With the extensive use of immunosuppressants, immunosuppression-associated pneumonitis including (PCP) has received increasing attention. Though aberrant adaptive immunity has been considered as a key reason for opportunistic infections, the characteristics of innate immunity in these immunocompromised hosts remain unclear. METHODS: In this study, wild type C57BL/6 mice or dexamethasone-treated mice were injected with or without . Bronchoalveolar lavage fluids (BALFs) were harvested for the multiplex cytokine and metabolomics analysis. The single-cell RNA sequencing (scRNA-seq) of indicated lung tissues or BALFs was performed to decipher the macrophages heterogeneity. Mice lung tissues were further analyzed via quantitative polymerase chain reaction (qPCR) or immunohistochemical staining. RESULTS: We found that the secretion of both pro-inflammatory cytokines and metabolites in the -infected mice are impaired by glucocorticoids. By scRNA-seq, we identified seven subpopulations of macrophages in mice lung tissues. Among them, a group of Mmp12 macrophages is enriched in the immunocompetent mice with infection. Pseudotime trajectory showed that these Mmp12 macrophages are differentiated from Ly6c classical monocytes, and highly express pro-inflammatory cytokines elevated in BALFs of -infected mice. , we confirmed that dexamethasone impairs the expression of , , and , as well as the fungal killing capacity of alveolar macrophage (AM)-like cells. Moreover, in patients with PCP, we found a group of macrophages resembled the aforementioned Mmp12 macrophages, and these macrophages are inhibited in the patient receiving glucocorticoid treatment. Additionally, dexamethasone simultaneously impaired the functional integrity of resident AMs and downregulated the level of lysophosphatidylcholine, leading to the suppressed antifungal capacities. CONCLUSION: We reported a group of Mmp12 macrophages conferring protection during infection, which can be dampened by glucocorticoids. This study provides multiple resources for understanding the heterogeneity and metabolic changes of innate immunity in immunocompromised hosts, and also suggests that the loss of Mmp12 macrophages population contributes to the pathogenesis of immunosuppression-associated pneumonitis.

简介：随着免疫抑制剂的广泛应用，免疫抑制相关肺炎，包括卡氏肺孢子虫肺炎（PCP），越来越受到关注。尽管异常的适应性免疫被认为是机会性感染的一个关键原因，但这些免疫功能低下宿主固有免疫的特征尚不清楚。

方法：在这项研究中，野生型 C57BL/6 小鼠或地塞米松处理的小鼠注射或不注射。采集支气管肺泡灌洗液（BALF）进行多重细胞因子和代谢组学分析。对指定的肺组织或 BALF 进行单细胞 RNA 测序（scRNA-seq），以解析巨噬细胞异质性。进一步通过定量聚合酶链反应（qPCR）或免疫组织化学染色分析小鼠肺组织。

结果：我们发现糖皮质激素抑制感染小鼠中促炎细胞因子和代谢物的分泌。通过 scRNA-seq，我们在小鼠肺组织中鉴定出 7 种巨噬细胞亚群。其中，一组 Mmp12 巨噬细胞在免疫功能正常的感染小鼠中富集。拟时轨迹显示，这些 Mmp12 巨噬细胞来源于 Ly6c 经典单核细胞，并且高度表达 BALF 中升高的促炎细胞因子在感染小鼠中。通过体外实验，我们证实地塞米松抑制了 AM 样细胞中、、、和的表达以及真菌杀伤能力。此外，在 PCP 患者中，我们发现了一组类似于上述 Mmp12 巨噬细胞的巨噬细胞，这些巨噬细胞在接受糖皮质激素治疗的患者中受到抑制。此外，地塞米松同时损害了常驻 AM 的功能完整性，并下调了溶血磷脂酰胆碱的水平，导致抗真菌能力下降。

结论：我们报道了一组 Mmp12 巨噬细胞在感染中赋予保护作用，而糖皮质激素可以抑制其作用。本研究为理解免疫功能低下宿主固有免疫的异质性和代谢变化提供了多种资源，也提示 Mmp12 巨噬细胞群体的丧失可能导致免疫抑制相关肺炎的发病机制。