Figure 2. The contact-dependent inhibitory role of T_regs on MCs degranulation depends on T_regs OX40 expression and requires OX40L on BMMCs.

(A) BMMCs sensitized with mouse IgE anti-DNP (IgE) and challenged with Ag (IgE/Ag) in the absence or presence of equal amount of WT or OX40^−/− CD4⁺CD25⁺ T_regs or separated by a transwell membrane (Transwell) were then examined for release of β-hexosaminidase. (B) Same as (A), but BMMCs were obtained from WT or OX40L^−/−mice and co-cultured with WT CD4⁺CD25⁺ T_regs. Shown are the means ± SD of three independent experiments, each performed in duplicate. (C) IgE-sensitized BMMCs were challenged with Ag in the absence or presence of membranes from K562 cells expressing OX40 (K562-OX40) or empty vector (K562). (D) IgE-sensitized BMMCs were challenged with Ag in presence of T_regs, plus blocking anti-OX40L (clone MGP34) or isotype control (rat IgG2c) antibodies.