(A) Thymic cellularity and weight in bcl-2–deficient mice. The bcl-2−/− mice (closed bars) and their LM (open bars) were killed at 4 weeks of age, and the total cell number in the thymus, total body weight, and the thymus weight were measured. The average and standard deviation of 12 bcl-2−/− and 15 LMs are shown. (B) Flow cytometric analysis of thymocytes from 4-week-old bcl-2−/− and +/− mice. Single cell suspension of thymocytes from a bcl-2+/− mouse (left) and a bcl-2−/− mouse (right) were stained with anti-CD4, CD8, and TCRαβ MoAb. Representative two-color immunofluorescence contour plots of CD4 and CD8 expression (upper) and histograms of TCRαβ expression (lower) are shown.