Phenotype of CD45R⁺CD43⁺ pro–B cells following culture on S17 stromal cells or in FTOCs.

(A) 5 × 10⁴ CD45R⁺sIgM⁻ cells were seeded into FTOCs or onto S17 stroma. Cells were phenotyped 7 days later as described in Figure 1. (B) 2.5 × 10⁴fluorescence-activated cell-sorter (FACS)–purified CD45R⁺CD43⁺ pro–B cells were seeded into FTOCs. Phenotypic analysis was performed on cells harvested from lobes 7 days after initiation of cultures. Data in the figures are representative of 3 experiments.