CLPs from IL-7 knockout mice are deficient in B-lymphoid commitment but retain their B-lymphoid potential. (A) Representative FACS plots of reporter gene expression within the LIN⁻Flt-3⁺IL-7R⁺Sca1^lowKit^low CLP/Fraction A compartments. LIN cocktail contains antibodies against CD11b, GR1, TER119, CD3, CD11c, LY6C, and NK1.1. (B) Summary of the FACS data analyzing reporter gene expression in CLP/Fraction A cells or CD19⁺ cells collected from 6 IL^+/+ and 6 IL^−/− mice. Each dot represents one IL^+/+ (white) or IL^−/− (black) mouse, and the horizontal line represents the mean in each group. (C) Color-coded bar with data collected by single-cell multiplex RT-PCR analysis from CLPs sorted from normal and IL-7–deficient mice. Each horizontal line of boxes represents a single investigated cell collected from 2 independent sorting experiments. A colored box indicates that an RT-PCR product from a given gene could be detected on an ethidium bromide–stained agarose gel. (D) Top: Lymphoid cell cloning frequency of seeded single CLPs collected from normal (IL-7^+/+) or IL-7–deficient mice (IL-7^−/−; white bars), and the frequency of clones that contain cells expressing CD19 as analyzed by flow cytometry (black bars) after 8 days of incubation on OP9 stroma cells under B-cell–promoting culture conditions. Bottom: Data from cocultures of single sorted wt or IL-7–deficient CLPs incubated on OP9DL stroma cells to stimulate the development of THY1.2⁺ T-lineage cells. White bars represent total lymphoid cell cloning frequency, striped bars the frequency of T-cell clones, and black bars the frequency of CD19⁺ B-cell clones. The data are presented as mean + SEM from 3 independent experiments. Cells in both panels have been cultured in the presence of 10 ng/mL KL, 10 ng/mL IL-7, and 10 ng/mL FLT3L.