Macrophage populations and self-renewal: Changing the paradigm

Table 1 Approaches to dissect the origins of macrophage lineages

Methods and tools	Results
Membrane markers	CX3CR1hi/F4/80hi/CD11blo: YS macrophages
	CX3CR1lo/F4/80lo/CD11bhi: HSC macrophages
Transcription factors	MYB+: HSC macrophages
	MYB-: YS macrophages
Depletion (clodronate, Abs)	Non-specific depletion with clodronate. The CCR2-/- mice that are depleted from circulating monocytes exhibit normal tissue macrophage populations
Genetic fate mapping techniques: RUNX1	Early expression of RUNX1 in YS derived macrophages and identification of embryonic macrophages in adulthood (microglia, Langerhans cells)
Genetic fate mapping techniques: FLT3	Identification of a HSC stage in differentiation: + for monocytes and - for tissue macrophages
Genetic fate mapping techniques: CSF1R	Labeling of 30% YS derived macrophages in the embryo and similar persistence in adult microglia
Genetic fate mapping techniques: CX3CR1	labeling of monocytes and miocroglia
Parabiosis	Replacement of resident macrophages by chimeric monocytes
Sublethal irradiation and bone marrow transplant	Chimerism in blood monocytes without eradicating resident macrophages. Risk of inflammation and membrane leakage

YS: Yolk sac; HSC: Hematopoietic stem cell. This Table describes the methods to identify the origin of mononuclear phagocytes and the major results. It refers to recent reviews[16-18].