Aspirate from the spleen of a dog: A central macrophage (“nurse” cell) with red circular fragments in the cytoplasm (likely degraded erythrocytes) (arrow) is surrounded by developing erythroid progenitors (basophilic erythroblasts or rubricytes). The macrophage provides adhesive support, iron, both pro-and anti-erythropoietic cytokines (depending on the context) and a “waste removal” system (expelled nuclei, organelles) for the erythroid cells.
