Firstly, let me introduce to you about microglia ontogeny.
Previously, Microglia has been known to originate from myeloid lineages from bone marrow, as like other monocytes. But this concept of origin of microglia is now being changed.
Ranshoff’s group showed that yolk sac macrophages are the main precursors of microglia, while most other macrophages are derived from fetal monocytes.
Both yolk sac macrophages and fetal monocytes arise from erythro-myeloid progenitors (EMPs) generated from the yolk sac hemogenic endothelium. However, in the yolk sac, microglia originates without monocytic intermediates, while other EMPs seed the fetal liver and then give rise to fetal monocoytes, then into tissue-specific macrophages.
Previously, Microglia has been known to originate from myeloid lineages from bone marrow, as like other monocytes. But this concept of origin of microglia is now being changed.
Ranshoff’s group showed that yolk sac macrophages are the main precursors of microglia, while most other macrophages are derived from fetal monocytes.
Both yolk sac macrophages and fetal monocytes arise from erythro-myeloid progenitors (EMPs) generated from the yolk sac hemogenic endothelium. However, in the yolk sac, microglia originates without monocytic intermediates, while other EMPs seed the fetal liver and then give rise to fetal monocoytes, then into tissue-specific macrophages.
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Ginhoux F, Immunity, 2015