Tissue-resident macrophages: guardians of organ homeostasis

Virtually every tissue in mice and humans has one or multiple distinct tissue-resident macrophage (MTR) populations, which are crucial for the maintenance of tissue homeostasis. Dysregulated MTR function can have detrimental consequences in the context of many diseases, including cardiovascular and metabolic pathologies, obesity, cancer, amyloidosis, and infections. MTR in mammals derive from diverse origins, including yolk sac, fetal liver, and bone marrow. This differentiation stems from various embryonic precursor stages as well as bone marrow-derived monocytes. Metabolism can regulate the phenotype of MTR and profoundly impact their function. Tissue-resident macrophages (MTR) have recently emerged as a key rheostat capable of regulating the balance between organ health and disease. In most organs, ontogenetically and functionally distinct macrophage subsets fulfill a plethora of functions specific to their tissue environment. In this review, we summarize recent findings regarding the ontogeny and functions of macrophage populations in different mammalian tissues, describing how these cells regulate tissue homeostasis and how they can contribute to inflammation. Furthermore, we highlight new developments concerning certain general principles of tissue macrophage biology, including the importance of metabolism for understanding macrophage activation states and the influence of intrinsic and extrinsic factors on macrophage metabolic control. We also shed light on certain open questions in the field and how answering these might pave the way for tissue-specific therapeutic approaches. Tissue-resident macrophages (MTR) have recently emerged as a key rheostat capable of regulating the balance between organ health and disease. In most organs, ontogenetically and functionally distinct macrophage subsets fulfill a plethora of functions specific to their tissue environment. In this review, we summarize recent findings regarding the ontogeny and functions of macrophage populations in different mammalian tissues, describing how these cells regulate tissue homeostasis and how they can contribute to inflammation. Furthermore, we highlight new developments concerning certain general principles of tissue macrophage biology, including the importance of metabolism for understanding macrophage activation states and the influence of intrinsic and extrinsic factors on macrophage metabolic control. We also shed light on certain open questions in the field and how answering these might pave the way for tissue-specific therapeutic approaches. immunostimulatory component of bacterial DNA. harbors many mitochondria; specialized for thermogenesis. key hematopoietic growth factor regulating the development of monocytes and some tissue-resident macrophages. layer covering the liver surface. orphan receptors that are key regulators of signaling in metabolic responses. 3D in vitro cell aggregate model to more closely simulate physiological tissue behaviors (here, in the CNS). accumulation of proteins and lipids that are degraded under normal circumstances by AM. key biochemical process in the generation of antibody diversity and refined potent antibody responses. molecules produced by alveolar epithelial cells facilitating gas exchange in the alveolus. removal of superfluous neural connections by microglia. T cells with immunosuppressive properties. specialized in energy storage.