Reduced percentage of immature B cells in spleens from p100^−/− mice. Splenocytes from 17- to 20-day-old wild-type, p100^−/−, and nfkb2^−/− mice were stained for CD19 and the early B-cell marker 493 (top row) or CD19 and IgM (bottom row) and analyzed by flow cytometry (lymphocyte gate). Numbers indicate percentages from indicated regions. Representative data from 3 to 4 experiments are shown.