Antibodies to DEC205 and MR are accumulated more efficiently by DCs than anti-CD40. (A) BDCA1⁺ DCs or (B) MoDCs were continuously incubated with 1 μg/mL fluorescently labeled anti-MR, anti-CD40, or anti-DEC205 for the indicated times, washed, counterstained, and fixed (top panels). Middle and bottom panels show data from the top panel, together with matched samples treated with leupeptin and NH₄Cl (inh) during the continuous incubation. MuIso is the isotype for anti-CD40, and huIso is the isotype for anti-MR and anti-DEC205. Graphs depict the mean ± SEM normalized MFI from ≥ 3 independent donors. Normalized MFI indicates amount of accumulation; MFI was calculated by removing the contribution of surface fluorescence (4°C control) and normalizing the MFI for the number of fluorophores per antibody. Differences in antibody accumulation in the absence or presence of inhibitors were assessed with the paired t test, and statistically significant differences are depicted, *P < .05.