Chapter 10 - Lungs—Inflammatory and respiratory system

Abstract

The exchange of oxygen and carbon dioxide between the alveoli and the bloodstream is the vital function of the lungs. While this process delivers life-requiring oxygen to the systemic circulation, particles, toxins, allergens, and microbes are also brought into the lungs. Macrophages are the most abundant immune cells in the lungs and are ideally positioned in the alveolar and interstitial spaces, where they act as guardians between the host and the outside world. However, beyond their roles in host defense and immunity, lung-resident macrophages fulfill roles specific of their host tissue and can be considered as integral components of the lungs. These tissue-specific functions are shaped by the local environmental, which allows them to adapt precisely to the demands of their anatomical niche. Here, we discuss the unique characteristics of lung-resident macrophages, their heterogeneity, specific origins, and the mechanisms that drive their adaptation, describing the direct and indirect influences of the respiratory epithelium on them. We also outline the factors that shape lung macrophage differentiation and behavior in steady state and describe how they change during injury and inflammation.