title: Macrophages and regulation of erythropoiesis.
abstract: OBJECTIVE
  The nature and function of macrophages at the center of erythroblastic islands is not fully understood. This review discusses novel findings on the phenotypic and molecular characterization of erythroblastic island macrophages, and their role in regulating normal and pathological erythropoiesis.
  
  
  RESULTS
  The phenotype to prospectively isolate erythroblastic island macrophages from mouse bone marrow has been identified. In-vivo depletion of erythroblastic island macrophages causes blockade of erythroblast maturation and delays erythropoietic recovery following chemical insults. The cytokine granulocyte colony-stimulating factor arrests medullary erythropoiesis by depleting erythroblastic island macrophages from the bone marrow. In-vivo ablation of macrophages improves anemia associated with β-thalassemia and reduces red blood cell counts in the mouse model of polycythemia vera. The role of cell adhesion molecules regulating interactions between erythroblastic island macrophages and erythroblasts has been clarified, and mechanisms of pyrenocyte engulfment by erythroblastic island macrophages have been demonstrated to involve Mer tyrosine kinase receptor.
  
  
  CONCLUSIONS
  Prospective isolation of mouse erythroblastic island macrophages together with new genetic mouse models to specifically target erythroblastic island macrophages will enable molecular studies to better define their role in controlling erythroblast maturation. These studies have revealed the key role of erythroblastic island macrophages in regulating normal erythropoiesis and could be interesting targets to treat β-thalassemia or polycythemia vera.
authors.affiliation: aBlood and Bone Diseases Program, Mater Research Institute - University of Queensland, Woolloongabba bSchool of Medicine cSchool of Biomedical Sciences, University of Queensland, Saint Lucia dDepartment of Haematology, Princess Alexandra Hospital, Woolloongabba, Queensland, Australia.
authors.forename: Rebecca N
authors.initials: RN
authors.lastname: Jacobsen
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Perkins
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Levesque
mesh_terms: D000740:Anemia; D000818:Animals; D001772:Blood Cell Count; D004900:Erythroblasts / Q000502:physiology; D004920:Erythropoiesis / Q000502:physiology*; D006801:Humans; D008264:Macrophages / Q000502:physiology*; D051379:Mice; D011446:Prospective Studies