急性肺损伤(ALI)是体外循环(CPB)手术并发症之一，严重影响手术效果和患者预后。正常情况下，单核细胞是定居型肺巨噬细胞的主要来源。急性肺损伤时，大量单核细胞从外周血募集入肺，分化为募集型巨噬细胞，影响炎症反应的性质和程度。在国自然面上项目基金资助的前期研究中，我们发现体外循环患者外周血中幼稚单核细胞亚群比例明显增高，该亚群不仅具有影响后续亚群分化的能力，而且可参与局部组织炎性反应。因此，我们推测，幼稚单核细胞亚群可能通过影响肺内募集型巨噬细胞数目和功能影响CPB引发的ALI的发生和发展。申请人已成功建立大鼠CPB模型以及大鼠单核细胞亚群流式染色方法，拟采用体内幼稚单核细胞亚群过继移植，研究幼稚单核细胞亚群对肺内募集型巨噬细胞的数目和功能的影响及其与ALI程度的关系，通过体外趋化实验探讨其机制，进一步阐明CPB相关ALI发生机制，为临床免疫治疗提供理论参考和实验依据。

Acute lung injury (ALI), which is one of the complications induced by cardiopulmonary bypass (CPB), impacts the prognosis of the patients and the ARDS-related mortality. AS the progenitor of macrophages, mature monocytes serve as the main source of resident macrophages in the lung under the normal condition. During the process of ALI, monocytes are recruited from peripheral blood into the lung, differentiate into recruited macrophages and further impact nature and extent of local inflammation responses. In our previous study funded by NSFC, we found that the proportion of the immature monocyte subset was evidently elevated in the peripheral blood of patients undergoing CPB. More importantly, the immature monocyte subset not only impacts the differentiation of downstream subsets, but also participates local inflammatory responses. Therefore, we speculate that, the immature monocyte subset might influence the development of CPB-induced ALI by migrating into the lung and differentiating into different types of recruited macrophages. Based on a rat CPB model and flow cytomertric analysis rat monocytes, we intend to study the impact of immature monocyte subset on the recruited macrophages in the lung by cell transplantation, and explore the mechanism of the impact by ex vivo chemotaxis assay. The results of our project will improve the understanding about mechanisms of CPB-related ALI, and provide the more evidence for immunotherapy in the clinic.