TGF-β is required for high IL-17 production by TLo cells, and high latent TGF-β/LAP expression by THi cells does not inhibit Th17 responses. (A) Human CD4⁺ T cells were cultured under THi or TLo conditions for 6 days, and LAP expression was determined by flow cytometry. Plots are representative of 3 independent experiments. (B) Human CD4⁺ T cells were cultured under THi or TLo conditions with or without TGF-β in decreasing concentrations of the ALK5 inhibitor, SB505124 (5-0.05μM). Expression of IL-17 and IFN-γ were determined by flow intracellular cytometry on day 6 (n = 3). Error bars represent SEM. P values were calculated using one-way analysis of variance with Tukey correction: *P < .05.