Figure 1.

Tissue seeding. Signals and transcription factors involved in seeding of well-known tissue-resident macrophages from fetal liver p-Macs. Migration from the liver occurs in a CX3CR1 dependent manner. In the skin IL-34 and TGF-β induce the transcription factors RUNX3 and ID2 to generate Langerhans cells. In the lung GM-CSF induces the transcription factors PPARγ, BACH2, and CEBPβ to produce alveolar macrophages. In the brain/central nervous system, microglia are generated in response to the induction of the transcription factor SALL1. Red pulp macrophages in the spleen are produced in response to Heme and the transcription factor SPIC. Finally, in the liver Kupffer cells are generated in response to TGF-β and the transcription factor ID3.