Mean RBC count of W/W^v mice implanted with sph/sph or +/+ bone marrow at 2, 6, 10, and 15 weeks posttransplantation. Results are presented as mean ± SEM. (▪) +/+→W/W^v, n = 10, except n = 8 at 15 weeks. (□)sph/sph→W/W^v, n = 10, except n = 7 at 15 weeks. Arrow on the y axis indicates mean RBC count for unmanipulated W/W^v mice.