The induction of Bim expression during human T-cell blast generation is abolished in an ALPS-Ic patient but not in ALPS-Ia patients. Sensitivity to death by IL-2 deprivation. Anti–Mcl-1, anti–Bcl-2, anti–Bcl-x_S, anti-Bim, or anti–β-actin immunoblots were performed on extracts from fresh peripheral-blood mononuclear cells (PBMCs) (day 0) or from day-6 T-cell blasts (day 6), obtained from healthy donors (Control) or from the ALPS-Ic patient 1 (A) or ALPS-Ia patients 2 and 3 (B), as indicated. The positions of Mcl-1, Bcl-2, Bcl-x_S, Bim_EL, Bim_L, Bim_S, and β-actin are indicated on the left of the corresponding blots. The extracts used correspond to 1 × 10⁶ cells, and expression levels of the proteins analyzed were quantified in a densitometer and normalized to the same amount of β-actin. The results obtained for the Bim_EL/β-actin ratios in fresh PBMCs and in day-6 T-cell blasts from the same donors allowed the calculation of the fold induction of Bim in each case, and results are depicted in panel C. Results are the mean ± SD from 10 different healthy controls and from at least 2 different experiments performed with the individual ALPS patients 1, 2, or 3, as indicated. (D) Day-6 T-cell blasts were incubated at 2 × 10⁶ cells/mL for 24 or 48 hours in the absence of IL-2. Apoptosis was estimated by analyzing ΔΨm loss by DiOC₆³ staining and flow cytometry, and results were expressed as the percentage of DiOC₆³-low cells. Results are the mean ± SD of duplicate determinations using T cells from 4 different healthy controls and of 2 different experiments using T cells from the patients. The samples shown in each immunoblot were run in the same gel.