DC-targeted TLRLs enhance maturation and activation of human DCs in vitro. Human monocyte–derived DCs were cultured in the presence of various concentrations of poly I:C and R848, either in soluble form (soluble TLRL) or encapsulated within NPs carrying αDC-SIGN (NP-DC-SIGN-TLRL) or isotype control (NP-Isotype-TLRL) Abs for 48 hours. DCs cultured in medium without TLRLs were included as iDCs. (A) DC maturation was checked by analyzing CD80 and CD83 expression by flow cytometry. Representative flow cytometric histograms of a single donor are shown in the left panels. Relative expression levels were determined for each donor by dividing mean fluorescent intensities of experimental samples by those of iDCs. Right panels show mean relative expression levels of 6 independent donors ± SEM, with the x-axis representing the concentration of the respective soluble or encapsulated TLRLs present in the culture medium. (B) TNF-α, IL-6, and IL-12 production by the DCs were determined in the culture supernatant. Values represent mean cytokine production levels of DCs from 6 independent donors ± SEM. The x-axis represents the concentration of the respective soluble or encapsulated TLRLs present in the culture medium. *P < .05, **P < .01, and ***P < .001 for the significant difference between soluble TLRL and NP-Isotype-TLRL.