The distal EPOR and STAT5 are not required for Friend virus-induced erythroblastosis. (A) Photograph of spleens from FVA-infected mice. Mouse strains are indicated at the top. Infection with Friend virus is indicated at the bottom (FVA). (B) Photomicrograph of spleen from Friend virus-infected EporHM mouse, stained with hematoxylin and eosin. Original magnification × 400. (C) Spleen weights of FVA-infected mice in grams. The mouse strains are indicated at the bottom. Stat5 (-/-) denotes the Stat5a^-/-;Stat5b^-/- strain. The spleen weights of uninfected mice are provided as a control (no FV). Error bars represent standard deviation (Stat5 (-/-), EporH, EporHM, P < .001). (D) Percent transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL)-positive cells in the spleens of FVA-infected mice (Stat5 (-/-), P = .07; EporH, P > .10; EporHM, P = .10).