本项目将整合活体高分辨率成像、单细胞测序、多组学等前沿技术，以肺脏特殊的机械力环境对区域免疫应答的调控这一新机制作为切入点，解析生理病理条件下的肺脏区域免疫特性。肺脏具有十分特殊的解剖学结构，包含上百万个肺泡及丰富的毛细血管床。肺脏在行使呼吸的同时，也时刻受外界有害物质和病原体的侵袭。细菌感染引起的肺炎是全世界主要的公共健康问题。我们在前期工作中通过活体成像发现，作为抵御外来有害物质最重要的一类免疫细胞，中性粒细胞在肺脏中的空间位置及动态变化都呈现明显的区域特性，进一步研究发现中性粒细胞能够感知肺脏中机械力环境从而发挥其宿主免疫应答作用。在本项目中我们将整合成像技术等前沿技术手段，通过研究中性粒细胞在肺部毛细血管滞留时的机械力感知和下游因子、以及中性粒细胞与血管的相互作用对肺中性粒细胞免疫功能的决定作用，阐释肺脏固有免疫系统区域特性形成机制，为更有效的治疗呼吸系统相关疾病提供新的思路。

The proposed study will integrate intravital imaging, single cell sequencing and other techniques to understand how mechanical force in the lung environment is sensed by innate immune cells and the underlying regulatory mechanism in both physiological and pathological conditions. As a major organ of the respiratory system, the lung houses unique structures including thousands of alveoli and densed microvasculature. Innate immunity is a primordial system that has a primary role in lung antimicrobial defenses. Using intravital imaging, we have found that compared to those rapidly passing in the peripheral circulation, neutrophils are temporarily retained in pulmonary capillary bed and display different migration patterns. Further analysis revealed that neutrophils can sense the constrictive force that is generated when passing through the narrow capillaries and induce transient calcium influx. Mice with neutrophils lacking mechano-sensor piezo1 are more susceptible to pulmonary bacterial infection. We will continue to systemically profile the pulmonary neutrophils and to analyze the downstream factors underlying mechanical sensing. In addition, we will evaluate how the cross-talk between neutrophils and endothelial cells will contribute to host defense response. We believe studies from this proposal will provide insights into our deep understanding of pulmonary immunity as well as potential therapeutic strategies for the treatment of respiratory diseases.