Efficient differentiation of p100^−/− pre–pro-B cells into myeloid cells. (A) Lin⁻B220⁺CD19⁻c-Kit^low pre–pro-B cells were sorted from bone marrow of 18- to 20-day-old wild-type and p100^−/− mice and cultured as described in “Methods.” After 14 days, cells were collected, stained for CD19 and Mac-1 expression, and analyzed by flow cytometry. Numbers represent mean values (± SD) from 3 mice. (B) Efficient uptake of E coli-FITC bioparticles by in vitro–differentiated Mac-1⁺p100^−/− myeloid cells. Cultured p100^−/− B220⁺CD19⁻ pre-pro-B cells were incubated after 14 d with FITC-labeled E coli and uptake by CD19⁺ (----) or Mac-1⁺ cells (—) was measured by flow cytometry.