FLAG-CrmA expression in hemopoietic cells from reconstituted mice inhibits FasL-induced apoptosis but does not protect against apoptosis induced by Bcl-2–regulated death stimuli. (A) Immature thymocytes (CD4⁺CD8⁺), BM granulocytes (Mac-1⁺Gr-1⁺), BM monocytes (Mac-1⁺Gr-1^–), naive LN B cells (B220⁺), and naive LN T cells (Thy1⁺) were FACS sorted from mice reconstituted with fetal liver cells infected with a FLAG-CrmA-GFP or a control GFP retrovirus and cultured for 24 hours in medium alone or in the presence of oligomerized recombinant FasL (100 or 10 ng/mL). B cells and monocytes were activated in vitro with LPS plus IL-2, IL-4, and IL-5 or with interferon-γ (IFNγ), respectively, prior to death assays. Cells, isolated and prepared as described in panel A, were also cocultured with Neuro2A cells expressing membrane-bound FasL. (B) Bcl-2–regulated apoptosis was induced by γ-irradiation or treatment with etoposide or dexamethasone. Comparisons are made with cells from Fas-deficient Lpr mutant mice. (C) Cells were also cultured in medium alone, and viability was assessed by PI staining and FACS analysis at the specified time points. Data represent mean ± SD from 3 mice of each type.