Two's company but three's a blast!

In this issue of Blood, Romano et al discover that in murine bone marrow, both granulocyte and erythroid precursors develop around a single central macrophage, within a specialized niche termed erythromyeloblastic islands (EMBI).1 Although it is well established that mammalian erythropoiesis occurs in erythroblastic islands (EBI), comprising 5 to 30 maturing red blood cell precursors surrounding a macrophage,2 like an orchestra around a conductor, Romano et al identify that the orchestra constitutes granulocyte as well as erythroid precursors. Furthermore, they introduce a new concept in hematopoietic cell homeostasis: an inverse relationship between erythroid and granulocyte lineage cell numbers in EMBI that vary in response to microenvironmental cues. These findings provide insight into disorders such as anemia of inflammation/chronic disease.

Automated summary

Research in murine bone marrow has discovered the presence of erythromyeloblastic islands (EMBI) where granulocyte and erythroid precursors develop around a central macrophage. This finding reveals an inverse relationship between the numbers of erythroid and granulocyte lineage cells in EMBI, which can vary in response to microenvironmental cues. These findings have important implications for understanding anemia of inflammation/chronic disease.