BM lymphocyte infiltration and Fas-mediated apoptosis in BM failure mice. Five CByB6F1 mice each received 5 Gy TBI and injections of 5 × 10⁶ B6 LN cells to induce BM failure. Two CByB6F1 mice that received 5 Gy TBI without LN cell injection were used as controls. At 14 days, all mice were bled, and serum IFN-γ concentrations were analyzed using ELISA (top left). BM cells were analyzed by flow cytometry for the proportions of CD4 (top center) and CD8 (top right) lymphocytes, for the expression of CD95 (Fas, middle row), and for the binding to annexin V (bottom row). Data in the top row are presented as means with standard error bars.