Transitional 1 B cells are increased and Transitional 2 B cells are decreased in CD38-deficient mice. Total splenic cells were gated on B220-positive cells (100%). Percentage of each subset was calculated according to the expression of CD21 and CD24. (A) Representative dot plots from wild-type and CD38-deficient mice. (B) Percentages of each population from 10 independent experiments. Results are expressed as mean plus or minus SD (P < .05 or P < .01 as indicated, Student t test). (C) A 4-color stain was used to analyze the expression of different surface markers. Each histogram shows the mean fluorescence intensity for each marker in every subpopulation.