In vivo PGE2 treatment preferentially increases early but not late CFU-S. (A) Representative photographs of spleens removed from mice transplanted with bone marrow from PGE2- or vehicle-treated donor mice at day 8 and day 10 after transplantation. (B) Quantification of splenic colonies in transplanted mice at days 8, 10, 11, and 12 after transplantation. **P ≤ .05 (3 separate experiments are included for days 8 and 12).