The EPOR is not required for gp55-mediated erythroid proliferation. GFP-positive Fv2^s/s;Epor^-/- fetal liver cells were transplanted into Fv2^r/r recipients. (A) Flow cytometry was performed 4 weeks after transplantation to assess bone marrow reconstitution. Three subpanels correspond to granulocytes (i), platelets (ii), and erythrocytes (iii). The percentage of GFP-positive cells is indicated by the number above the line. (B-G) Photomicrographs of FVA-infected spleens. The sections in panels B, D, and F were stained with hematoxylin and eosin. The sections in panels C and E were stained with anti-GFP antibody and counterstained with hematoxylin. The section in panel G was stained with Rauscher anti-gp69/71 antibody. Original magnifications × 20 (B-C), × 400 (D-E), and × 100 (F-G).