Immunohistochemical staining of sections across the liver from a 15.5-dpc mouse embryo. (a) Section stained with anti–von Willebrand factor antibody. Cells expressing von Willebrand factor are visualized by a brown color. En, endothelial cells; M, megakaryocyte. (b) Sections stained with anti-Ship antibody. Representative Ship-expressing cells with distinctive morphology of granulocyte or monocyte/macrophage are denoted by arrows and arrowheads, respectively. (c) Section as in panel b under higher magnification. (d) Section across yolk sac of a 10.5-dpc mouse embryo stained with anti-Ship antibody. The large round cells with big nuclei are nucleated erythroblasts. Original magnifications: ×200 for a and b; ×400 for c and d.