🇬🇧 The role of macrophage in health and disease

Abstract

Macrophages belong to the innate immune system and form a 3D network in all our tissues where they phagocytose bacteria, cells debris, and other waste products. At the same time, they produce growth factors and signalling molecules – not only a protection mechanism against invaders but a crucial process for organ development and homeostasis. Previously, it was thought that all macrophages develop from monocytes that act as primary contributors to inflammatory pathologies including metabolic diseases and chronic inflammation. However, since a few years we know that most tissue-resident macrophages originate from yolk-sac progenitors. Thus, especially during inflammatory conditions, tissue-resident macrophages and monocyte-derived macrophages co-exist within a tissue. But how can we follow these cells and study their distinct functions? And what does it mean if one long-lived macrophage develops together with an organ and remains there throughout life, while the other macrophage dies within a short time frame and is replaced by a new macrophage from a circulating monocyte? Here, I show examples of how these different macrophage populations can be fate-mapped and what their distinct origin means for organ development and function. Further, I show that yolk-sac derived macrophages can undergo developmental programming during embryogenesis and, thereby, serve as intergenerational transmitters of the maternal environment.