MPP potential changes between the fetal, neonatal, and adult stages of development. (A) CFU assays for single LT-HSC, ST-HSC, MPP2, MPP3, and MPP4. Across several populations, CFU-M frequency decreased between birth and adulthood, and CFU-G and CFU-GM frequency increased. Error bars show standard deviations from 3 independent experiments performed with at least 60 cells per population per experiment. ∗∗∗P < .001; ∗∗P < .01 in either E16 or P0 mice relative to adult. ∗∗∗P < .001; ∗∗P < .01 in adult relative to both E16 and P0. P values were calculated by one-way ANOVA with Holm-Sidak post hoc test. (B) Limiting dilution curves for B-cell production from MPP2, MPP3, and MPP4. (C) Fractions of each MPP subtype that gave rise to B cells based on limiting dilution curves in panel B. Frequencies were calculated and compared using ELDA. (D) Fraction of individually plated MPPs that gave rise to T cells. The data reflect 3 independent experiments with at least 20 individually plated MPP per experiment. ∗∗∗P < .001 using Fisher exact test. (E) Schematic overview of dynamic changes in MPP potential between E16 and adulthood. Lymphoid potential is shown in the top panel, and the balance between monocyte and mixed granulocyte-monocyte output is shown in the bottom panel. ANOVA, analysis of variance; ELDA, extreme limiting dilution analysis.