Alveolar macrophages develop from fetal monocytes that differentiate into long-lived cells in the first week of life via GM-CSF

Tissue-resident macrophages can develop from circulating adult monocytes or from primitive yolk sac-derived macrophages. The precise ontogeny of alveolar macrophages (AMFs) is unknown. By performing BrdU labeling and parabiosis experiments in adult mice, we found that circulating monocytes contributed minimally to the steady-state AMF pool. Mature AMFs were undetectable before birth and only fully colonized the alveolar space by 3 d after birth. Before birth, F4/80(hi)CD11b(lo) primitive macrophages and Ly6C(hi)CD11b(hi) fetal monocytes sequentially colonized the developing lung around E12.5 and E16.5, respectively. The first signs of AMF differentiation appeared around the saccular stage of lung development…

• ER
  European Respiratory Society
• IN
  Institut National de la Santé et de la Recherche Médicale
• FW
  Fonds Wetenschappelijk Onderzoek
• CN
  Centre National de la Recherche Scientifique
• FP
  FP7 People: Marie-Curie Actions