B lymphocytes and lymphoma cells from p80HT transgenic mice are resistant to certain apoptotic stimuli. (A) The numbers of total lymphocytes in the indicated lymphoid organs. Lymphocytes were stained with fluorescence-conjugated antibodies against B220, Thy-1.2, CD4, and CD8 and analyzed by flow cytometry. (B) Cell cycle analysis of splenic B cells that were either untreated or treated for 48 hours with lipopolysaccharide (20 μg/mL). Percentages of cells in each phase of the cell cycle are shown. (C-E) In vitro survival and apoptosis assays of splenic B cells and B lymphoma cells. Cells were either untreated (D) or treated with 0.5 μg/mL of doxorubicin (C) or with 20 μg/mL of lipopolysaccharide (E). Viability was determined by trypan blue dye exclusion assay. Data in panels A-E represent means (± standard deviation) of cells from 5 mice of each genotype or from 5 B lymphomas samples. **Two-tailed Student t test, P < .01.