G-CSF administration protocol and the appearance of splenic colonies. B6 BM cells were transplanted into B6D2F1 mice, following various G-CSF administration protocols, starting at various points from day −27 to day 0 as depicted. (−) represents BM grafting without G-CSF treatment. The day of BM grafting is counted as day 0 and the splenic colonies were counted on day 8, as indicated by arrows. Colony data represent the mean ± SD of three experiments.