Absence of c-Maf impairs the formation of erythroblastic islands in the fetal liver. (A) Native erythroblastic islands isolated from c-Maf^+/+ and c-Maf^−/− fetal liver were immunostained with F4/80 (green) and TER-119 (red) Abs as described in “Methods.” F4/80 is used as a macrophage-specific marker, and TER-119 is used as a marker for erythroblasts. The number of erythroblasts surrounding each macrophage was significantly reduced in c-Maf^−/− fetal liver. (B) Erythroblastic islands reconstituted with c-Maf^+/+ erythroblasts were immunostained. The number of c-Maf^+/+ erythroblasts surrounding each c-Maf^+/+ or c-Maf^−/− macrophage is shown. c-Maf^+/+ erythroblasts surrounding c-Maf^−/− macrophages were significantly reduced compared with those seen for c-Maf^+/+ macrophages. (C) Erythroblastic islands reconstituted with c-Maf^−/− erythroblasts were immunostained. The number of c-Maf^−/− erythroblasts surrounding each c-Maf^+/+ or c-Maf^−/− macrophage is shown. c-Maf^−/− erythroblasts surrounding c-Maf^−/− macrophage were significantly reduced compared with those seen for c-Maf^+/+ macrophages. Although c-Maf^−/− erythroblasts can form reconstituted erythroblastic islands with c-Maf^+/+ macrophages, c-Maf^−/− macrophages showed impaired formation of reconstituted erythroblastic islands with c-Maf^+/+ erythroblasts. Images were acquired by a Biorevo BZ microscope (Plan Apo 20×0.75 DIC N2) at room temperature and processed with the Adobe Photoshop CS4 software. The scale bar represents 20 μm; n = 4∼6 embryos per group. For each combination, ≥ 20 macrophages per embryo were analyzed. *P < .05. Data are presented as mean ± SEM.