G-CSF-induced colony growth in vitro. BM cells were plated in methylcellulose-containing media supplemented with various quantities of G-CSF. Hematopoietic colonies containing 30 cells or more were scored after 7 to 8 days. Data are the means of four animals for each genotype and error bars represent standard deviation.gcsfr-wt/wt, (▪); gcsfr-wt/▵715, (┌);gcsfr-▵715/▵715, (□).