In vitro expansion of HSCs in STIF cytokines. (A) Freshly purified murine lineage-negative cells in the LSK gate (top panel) were analyzed for CD48 expression (bottom panel). (B) Cells expanded for 3 or 9 days in SF311 or STIF cytokines were analyzed as in panel A. (C) Percentage of stem cell markers present on SF311- and STIF-expanded cells after 3 and 9 days of cultivation. Data represent the mean of 3 cultures. Significance was tested with the Student 2-sided t test, and significance was reached with P < .001.