FcϵRI activation enhances BMMC apoptosis and is required for optimal induction of T-cell activation. (A) Anti-OVA IgE or (B) anti-DNP IgE pretreated BMMCs were incubated with or without OVA (50 μg/mL) or DNP-OVA (0.5 μg/mL), respectively, for the indicated time periods. Data are represented as mean plus or minus SEM of 3 independent experiments (*P < .05 between the 2 groups by paired t test). (C) Anti-OVA IgE pretreated MigR1- (vector) or BCL-XL–transduced BMMCs were incubated with OVA (50 μg/mL) with or without IL-3 (10 ng/mL) for the indicated time periods. BMMC death was measured by examining the proportion of annexin V–positive cells by flow cytometry. (D) Anti-OVA IgE pretreated MigR1- (left) or BCL-XL–transduced (right) MHC class II^−/− BMMCs were incubated for 48 hours with OVA (50 μg/mL), washed, and cocultured with unsorted splenocytes from OT-II mice. (E) Anti-OVA IgE pretreated MHC class II^−/− BMMCs were incubated for 48 hours with OVA (50 μg/mL), washed, and cocultured with unsorted splenocytes from OT-II mice in the presence (right) or absence (left) of IL-3 (10 ng/mL). CD69 was detected 48 hours later on CD4⁺ T cells by flow cytometry. The number in the upper right corner indicates the percentage of CD69⁺CD4⁺ T cells.