BMMCs expand both Teffs and Tregs and inhibit Treg suppression. CD45.2⁺ Teffs and CD45.1⁺ Tregs were CFSE-labeled and polyclonally activated in the presence of unstimulated, IgE-sensitized, or IgE-Ag–challenged BMMCs. After 72 hours, CFSE dilution in gated Teffs or Tregs was evaluated by flow cytometry as a function of proliferation. (A) Percentage of proliferating (CFSE^low) Teffs. Numbers above bars indicate percentage inhibition of Tregs in each condition. (B) Representative histogram plots showing CFSE dilution in Teffs in the absence (filled areas) or presence (solid lines) of Tregs. (C) Percentages of proliferating (CFSE^low) Tregs. (D) Representative histogram plots showing CFSE dilution in Tregs in the absence (solid lines) or presence (filled areas) of Teffs. *P < .05, compared with the corresponding condition in the absence of BMMCs. °P < .05, compared with the corresponding condition in the absence of Ag stimulation to BMMCs. All data are from 1 representative of 3 independent experiments.