Reduced degranulation and cytokine production/secretion in FcϵRI-stimulated 4-1BB^-/- mast cells. (A) Wt (□) and 4-1BB^-/- (▪) BMMCs that had been sensitized overnight with 0.5 μg/mL IgE were first stimulated with antigen for 5 hours, washed, and restimulated for 45 minutes with different concentrations of antigen. Histamine released into culture media was measured. Results shown are representative of 2 experiments. (B) Wt and 4-1BB^-/- BMMCs that had been sensitized overnight with IgE were stimulated for 45 minutes with different concentrations of antigen. Histamine released into culture media was measured. Results shown are representative of 2 experiments. (C) Wt and 4-1BB^-/- BMMCs that had been sensitized overnight with IgE were stimulated for 8 hours with different concentrations of antigen. IL-6 and TNF secreted into culture media was measured. ^*P < .05 (versus wt control, Student t test). Results (mean ± SD) shown are representative of 5 experiments.