TB and Innate Immune Regulation of Lung Macrophages

描述（由申请人提供）：肺泡巨噬细胞（AM）起源于迁移到肺部的单核细胞，具有独特的生物学特性，称为替代激活状态。由于模式识别受体（如巨噬细胞甘露糖受体（MR））的活性增加，AM显示出更大的吞噬能力；改变了对微生物的氧化反应。这些特性使AM能够有效地清除肺泡内的微生物，同时最大限度地减少“附带”炎症损伤，但我们推测，AM可能使它们成为呼吸适应细胞内病原体的特别好的靶点。表面活性剂蛋白A （SP-A）在肺部病原体的先天免疫中起重要作用。我们已经确定SP-A信号人巨噬细胞增加MR功能和减少氧化反应的刺激。SP-A还可以独特地驱动单核细胞分化，上调MR功能并改变氧化反应。我们的中心假设是SP-A与常驻AM和迁移单核细胞的相互作用有助于决定AM的独特功能特性，这在处理呼吸道病原体中很重要。在这方面，SP-A通过内溶酶体途径运输，并与巨噬细胞吞噬溶酶体内的E. coil共定位。由于SP-A对大肠杆菌具有直接的抑菌活性，它可能独特地增强了AM吞噬溶酶体内的杀微生物活性。呼吸适应的细胞内病原体，如结核分枝杆菌（Mtb）破坏了几种先天宿主防御。Mtb使用MR进入巨噬细胞，其吞噬体不与溶酶体融合，因此可能限制其与SP-A在该区域的相互作用。

DESCRIPTION (provided by applicant): Alveolar macrophages (AM) originate from monocytes that immigrate into the lung and have unique biological characteristics referred to as an alternative activation state. AM display a greater phagocytic capacity due to increased activity of pattern recognition receptors [e.g. the macrophage mannose receptor (MR)]; and altered oxidative responses to microbes. These attributes allow AM to effectively clear microbes within the alveolus while minimizing "collateral" inflammatory damage, but we speculate may make them particularly good targets for respiratory-adapted intracellular pathogens. Surfactant protein A (SP-A) is important in innate immunity to lung pathogens. We have determined that SP-A signals human macrophages to increase MR function and decrease oxidative responses to stimuli. SP-A can also uniquely drive monocyte differentiation to up-regulate MR function and alter oxidative responses. Our central hypothesis is that interactions of SP-A with both resident AM and immigrating monocytes help dictate the unique functional properties of AM that are important in the handling of respiratory pathogens. In this regard, SP-A traffics through the endo-lysosomal pathway and co-localizes with E. coil within the macrophage phagolysosome. Since SP-A has direct anti-microbial activity against E. coil, it may uniquely enhance microbicidal activity within the phagolysosome of the AM. Respiratory-adapted intracellular pathogens such as Mycobacterium tuberculosis (Mtb) subvert several innate host defenses. Mtb uses the MR to enter the macrophage and its phagosome does not fuse with lysosomes, thus potentially limiting its interaction with SP-A in this locale. Our Specific Aims are to: 1) determine the mechanisms underlying SP-A-induced (A) up-regulation of MR activity and (B) inhibition of oxidative responses in macrophages; 2) determine the role of two key macrophage biochemical mediators in this process: Protein Kinase C and Phosphoinositide-3-kinases; 3) determine the effects of SP-A on monocyte differentiation; and 4) compare the impact of SP-A and other surfactant components on survival of the extracellular pathogen E. coli and the intracellular pathogen Mtb in human macrophages. We will use microscopy techniques and biochemical assays to assess SP-A's effects on MR trafficking, oxidative responses and signaling in human monocytes and macrophages, and cell culture for microbe studies. Our overall goal will be to better understand how surfactant components regulate macrophage biology to maintain the health of the individual against respiratory pathogens and how respiratory-adapted intracellular pathogens subvert this process.