Ag-specific CD4⁺ T cell activation. Human CD1c⁺ mDCs, CD16⁺ mDCs, BDCA3⁺ mDCs, and pDCs were incubated overnight with soluble TT peptide or with PLGA particles containing TT peptide in the presence of TLR ligands (4 μg/mL R848 for pDCs, 4 μg/mL R848, and 2 μg/mL poly(I:C) for mDC subsets). Subsequently, autologous TT-responsive PBLs were added. After 4 days, T-cell proliferation was measured by (³H)–thymidine incorporation. Data are mean values ± SEM of 1 representative experiment performed in triplicate. Significance was determined by ANOVA and Newman-Keuls testing (*P < .05; **P < .01; ***P < .001) compared with PBLs only.