Number of LSK cells and their proliferative capacity in C57BL/6 and DBA/2 mice. (A) Absolute number of LSK cells in C57BL/6 (B6) and DBA/2 mice at the ages of 8 weeks and 18 months mice as determined by flow cytometric cell sorting (mean ± SEM; n = 6 independent experiments, where the bone marrow pooled from at least 2 mice was used). (B) Proliferative capacity of purified LSK cells from C57BL/6 and DBA/2 mice at the ages of 8 weeks and 18 months in liquid cultures supported by KL, Flt3L, and TPO. Results are expressed as the number of cells obtained after 5 days of culture per 50 cells at initiation of the cultures (n = 7). ^*Significantly different (P < .05 by paired analysis) from DBA/2 at the same age. ^**Significantly different from mice at the age of 8 weeks (P < .05).