Inhibition of constitutive activation of RhoA and RhoB increases surface localization of MHCII molecules and CD4⁺ T-cell activation by SWAP-70^−/− DCs. (A) FACS histograms showing the expression of surface MHCII in immature and LPS-mature CD11c⁺ BMDCs treated or not with exoenzyme C3 just before LPS treatment. The values on the histograms are the percentage of MHCII^high cells. Gray peaks correspond to isotype controls. Representative data of 3 independent experiments are shown. (B) CD11c⁺ BMDCs were treated with exoenzyme C3 before or during LPS treatment, or left alone. The average of mean of the CD11c⁺MHCII^high BMDC population is shown with plus or minus SD. Representative data of 3 independent experiments are shown. (C) MACS-isolated CD11c⁺ BMDCs—treated or not with C3—were incubated with T-cell hybridomas BO9710 and OVA_323-339 peptide (1 μg/mL). IL-2 in the culture supernatants was measured by ELISA. Representative data of 3 independent experiments are shown. □ indicates no LPS; ■, with LPS as indicated. *P < .001.