**7. Conclusion**

Alveolar macrophages acquire heterogeneity with other lineages by receiving unique signals in the alveolar microenvironment. The advanced phagocytosis and efferocytosis activities of alveolar macrophages enable efficient clearance of continuously inhaled pathogens and endogenous dead cells, respectively, which contributes to the prevention of uncontrolled pneumonia. Previous studies have addressed the reasons for the vulnerability of the elderly to acute LRTIs, mainly shedding light on the senescence process of alveolar macrophages from a cell-autonomous aspect. However, in addition to the knowledge gained from such studies, recent progress in experimental methods and techniques is beginning to provide insightful evidence that age-associated alterations in the alveolar microenvironment mediate reversible dysfunction of alveolar macrophages. In other words, to improve age-related dysfunction of alveolar macrophages, an approach that targets the cells is inefficient, whereas exploring methods to recover age-related alterations in the alveolar microenvironment is appropriate. As the average life expectancy is estimated to further increase in the future, exploring health promotion activities (i.e., habitual exercise, healthy diet, and regular sleep cycle) or supplements that influence the alveolar microenvironment and whether such factors can reduce the risk of acute LRTIs in the elderly is essential. We hope that this chapter will help students, trainees, and researchers in their education and research in health and life sciences.
