BM hematopoietic stem/progenitor cells from T-bet^tg/tg mice show impaired monocytic differentiation. (A) Experimental protocol for CFC assays. For the input cells, 25- to 30-week-old WT, T-bet^tg/wt, and T-bet^tg/tg whole BM cells were used. (B) Results of colony scoring after 9 days of culture in vitro (D.I.V.). Results are means ± SD; n = 5, 4, and 9. *P < .05, **P < .01 (1-way ANOVA, followed by Tukey’s multiple comparisons tests). (C-D) Representative cytospin images showing a terminally mature macrophage colony from a culture with WT WBMCs (C), and an immature monocytic colony from T-bet^tg/tg WBMCs (D). Hemacolor staining. Bar = 50 µm. (E) Frequencies of colonies containing immature monocytic cells. Results are means ± SD; n = 5, 4, and 9. *P < .05; ***P < .001 (1-way ANOVA, followed by Tukey’s multiple comparisons tests). (F) Effect of M-CSF addition on the frequencies of colonies containing immature monocytic cells. *P < .05 (paired Student t test). E, erythroid; G, granulocyte; GEMMk, granulocyte, erythoid, macrophage, and megakaryocyte; HSPCs, hematopoietic stem/progenitor cells; M, macrophage, Mk, megakaryocyte.