Expansion of immature erythroid cells in Lyn^-/- spleen and increased erythroid CFU-e numbers in BM and spleen of Lyn^-/- mice. (A) A 3-color flow cytometric analysis of 8-week-old Lyn^+/+ and Lyn^-/- spleen populations stained with CD71 and Ter119. Propidium iodide (PI)-positive and mature RBCs were excluded from the analysis. Relative percentages (± SD) of immature erythroid (upper right quadrant) and more mature erythroid (lower right) cells of 3 mice of each genotype are indicated. Erythropoiesis in (B) spleen, (C) BM of 8- and 16-week-old Lyn^+/+ and Lyn^-/- mice, and (D) embryonic day-14 fetal liver was assessed by methylcellulose culture. Mature erythroid (CFU-e) and immature erythroid (BFU-e) progenitors were determined at day 2 and day 10, respectively. (E) Relative percentages (± SD) of annexin-FITC-positive erythroid cells in fetal liver (n = 7-8/genotype) and adult bone marrow (n = 5/genotype) are indicated.