G‑CSF stands for gra­nu­lo­cy­te-colo­ny sti­mu­la­ting fac­tor. G‑CSF is a hor­mo­ne-like sub­s­tance pro­du­ced by the body whenever an infec­tion is pre­sent. It cau­ses the stem cells to be flus­hed out of the bone mar­row and into the blood. For several years, it has been pos­si­ble to pro­du­ce this growth fac­tor syn­the­ti­cal­ly. It is admi­nis­te­red to the donor for about four days befo­re collec­ting peri­pheral stem cells.