Ex vivo growth of myeloid bone marrow cells. (A) Experimental schema. (B) Colony formation and serial replating. Bone marrow cells from littermate-matched mice at 8 weeks of age were plated in duplicate in methylcellulose containing IL-3, IL-6, and SCF, and after 7 days, colonies and total cells per duplicate plates were counted. Cells were then replated in duplicate and 7 days later, colonies were counted and replated. Replating continued for 4 weeks or until colony formation failed. (C) Methylcellulose colony growth. On day 7 of week 1, total colonies and total cells on duplicate were counted to assess the average number of cells per colony. (D) Immunophenotype of day-7, week-1 total cells from duplicate methylcellulose plates.