Homeostatic Functions of Tissue-Resident Macrophages and Their Role in Tissue Maintenance.

Tissue-resident macrophages are best known for their indispensable role in immunological reactions, where they contribute to immune defense and resolution of inflammation. However, recent studies have also uncovered that they provide crucial tissue-specific functions that support organ homeostasis and maintenance. Accordingly, defects in macrophage function or development can disrupt the delicate balance of organ homeostasis, leading to pathological conditions. Therefore, understanding the functions and development of macrophages within a tissue is critical for comprehending the interplay between immune and stromal cells, which together maintain organ physiology. This knowledge has clinical implications, such as in organ transplantation or irradiation, where monocyte-derived cells with different functions may replace the original macrophage population. In this chapter, we aim to provide an overview of the tissue-specific homeostatic functions of various macrophage populations, emphasizing that macrophages are essential components of each organ and play a vital role in ensuring the organism's survival, beyond their role in immunity.