Roles of T-cell-derived IL-6 in BMMC effects. (A-B) CD45.2 Teffs and CD45.1 congenic Tregs, both CFSE-labeled, were cultured with BMMCs. Where indicated, IL-6Rα–blocking monoclonal antibody (clone 15A7) was added scaling the final concentration at 50, 20, 10, or 5 μg/mL. As control, no antibody or an isotype-matched antibody (Ig) was added. After 72 hours, CFSE dilution as a function of proliferation was evaluated in gated Teffs (A) or Tregs (B). Percentages of CFSE^low cells are indicated in each subset. Data are from 1 representative of 2 independent experiments. (C-D) BMMCs were left unstimulated, IgE-sensitized, or IgE-Ag–activated and cultured alone or with equal numbers of Tregs, Teffs, or both, in the presence of anti-CD3 to stimulate T cells, for 20 hours. IL-6 intracellular staining was performed on gated BMMCs (CD4⁻ cells) (C) or Teffs (D) in the coculture. Representative plots are here shown of 2 independent experiments. (E-F) WT CD45.2 Teffs and CD45.1 Tregs were CFSE labeled and stimulated in the presence of WT or il6^−/− BMMCs. Alternatively, il6^−/− CD45.2 Teffs were used. After 72 hours, CFSE dilution was evaluated by flow cytometry in gated Teffs (E) or Tregs (F). Numbers above bars indicate percentage inhibition of Tregs in each condition. *P < .05, compared with the corresponding condition with WT BMMCs and WT Teffs. Data are from 1 representative of 2 independent experiments.