Figure 1.

Foxp3⁺ Treg Cells Express the TGF-β-Activating Integrin β8, which Is Essential for Suppression of T Cell Expansion In Vivo

(A) TGF-β activation by naive (CD45RB^hiFoxp3⁻), effector/memory (CD45RB^loFoxp3⁻), and Treg (CD45RB^loFoxp3⁺) CD4⁺ T cell subsets isolated from the spleen of foxp3^GFP mice, detected by co-culture with an active TGF-β reporter cell line. Data (n = 4) are from two independent experiments.

(B) RNA from naive, effector/memory, and Treg cell CD4⁺ T cell subsets was isolated from the spleen of foxp3^GFP mice and analyzed for integrin β8 expression by qPCR, with levels normalized to the housekeeping gene Hprt and presented relative to naive T cells. Data (n = 2–5) are from five independent experiments.

(C) TGF-β activation by control (Itgb8^fl/flCre⁻) or Itgb8 KO (Itgb8^fl/flCd4-Cre⁺) splenic Treg cells (CD4⁺CD45RB^loCD25^hi), detected by co-culture with an active TGF-β reporter cell line as in (A). Data (n = 7) are from five independent experiments.

(D) Naive (CD4⁺CD45RB^hiCD25⁻) T cells from CD45.1⁺ congenic mice were transferred into Rag2^−/− mice at a ratio of 4:1 with control or Itgb8 KO Treg cells (CD4⁺CD45RB^loCD25^hi). Numbers of transferred CD45.1⁺ naive T cells in the spleen of recipient mice were determined 7 days later. Data (n = 8) are from six independent experiments.

(E) Representative flow cytometry plots from (D) and mean percentage Foxp3 expression of transferred Treg cell populations.

(F) Analysis of pSmad2/3 expression by flow cytometry in transferred CD4⁺ T cells (CD45.1⁺CD3⁺CD4⁺) and transferred control/Itgb8 KO Treg cells (CD45.1⁻CD3⁺CD4⁺Foxp3⁺) from spleen 7 days post transfer. Data (n = 5) are from three independent experiments.

Error bars represent SEM. See also Figure S1.