Figure 1.

Summary of the origin, lineage, and population dynamics of main macrophage populations. Some macrophages, such as microglia, originate exclusively from an early, c-Myb-negative erythromyeloid precursor (EMP) in the yolk sac, while others, such as Langerhans and Kupffer cells, have a mixed yolk sac-fetal liver origin. Many macrophage populations originate from c-Myb-positive hematopoietic stem cells (HSC) after traveling through the main prenatal hematopoietic location, the fetal liver. Note that for the sake of simplicity, arrows indicate the main site of origin of macrophages, although for some HSC-derived macrophage populations, some contribution from the yolk sac has also been reported. Weighted arrows next to each tissue-specific macrophage population indicate the relative contribution of self-renewal (circular arrows) vs. exchange with circulating monocytes (double-sided arrows) to that particular population. Microglia and Langerhans cells for instance are mainly self-renewing, whereas cardiac and colonic macrophages do exchange significantly with circulating monocytes. Some vector graphics were obtained from Vecteezy.com with permission.