Stimulation of mouse bone marrow cells by rIL-7 and/or scIL-7/HGFβ in vitro. Freshly harvested BM cells from IL-7^-/- mice were cultured in RPMI-1640 containing 2-ME in the presence of 10 ng/mL rIL-7 or 30 ng/mL scIL-7/HGFβ, or both. Nonadherent cells were harvested at day 17 and analyzed by flow immunocytometry. Top row shows representative histograms of B220⁺ and B220^- cells in each culture. The vertical standards indicate the peaks (or theoretical peak; dashed line) of florescence intensity and are used to eliminate most of the overlap regions between the peaks. Middle row shows the contour plots for CD43 and HSA of the B220^- and B220⁺ cells to the left and right of the peaks in the top row. The various fractions of developing B-lineage cells and their relative proportions in the B220^- and B220⁺ cell subsets are indicated for each quadrant. Bottom row shows the relative proportions of fractions Ao (CLPs), A₁ (early pre-pro-B cells) and A2 (late pre-pro-B cells).