Fig. 4.From: Tissue macrophages: heterogeneity and functionsF4/80+ stromal macrophages in the bone marrow play a trophic role in haemopoiesis. Haemopoietic stem cells (HSC) associate with mesenchymal stromal cells in a specialised niche in the bone marrow during the early stages of haemopoiesis. After proliferation and differentiation, erythroblasts and myeloblasts associate with stromal F/80+ macrophages, forming haemopoietic islands with central macrophages. These stromal macrophages express non-phagocytic adhesion molecules, a divalent cation-dependent haemagglutinin and the sialic acid recognition receptor Siglec1 (CD169), which retain these committed haematopoietic cells for poorly defined trophic support, before they are ready for release into the circulation. In addition these stromal macrophages ingest erythroid nuclei and recycle FeBack to article page