Flow cytometry analysis of an Eμ-ret (Tg+) early pro-B cell culture. Early pro-B cells from the day-17 fetal liver of an Eμ-ret mouse were sorted and cultured for 17 days in standard media with IL-7 (100 U/mL). The shaded histogram represents the Tg+ culture, whereas the bold outline represents a bone marrow control. In the left histogram, the bone marrow control was resolved into CD45R⁻ and CD45R⁺ (B-lineage) populations. In the middle histogram, the bone marrow CD45R⁺ B-lineage cells were gated and resolved into a CD43⁻ (late pre-B and B cell) and a CD43⁺ (pro and early pre-B) population. In the right histogram, the bone marrow CD45R⁺CD43⁺ B-lineage cells were gated and resolved into a BP-1⁻ (early pro-B) and BP-1⁺ (late pro-B and early pre-B) population.