CD16 but not CD32 enables a high phagocytic activity of slanDCs. (A) FcγR-dependent uptake of particulate antigens by slanDCs. PBMCs were incubated for 30 minutes at 37°C with untreated or IgG-coated fluorescent latex particles. Internalization of latex particles was quantified by specific staining of slanDCs and monocytes and subsequent flow cytometric analysis. Data in the histograms are 1 representative experiment, where 50 × 107 latex beads/mL were incubated with PBMCs. The numbers give the percentage of cells that contain at least 1 latex bead. (B) Quantification of the experiments over a range of bead concentrations. The upper graphs quantify the percentage of cells that have internalized at least 1 bead. The lower graphs show the MFI of the bead-containing cells as a measure of the amount of internalized beads. Data of the graphs represent mean ± SEM (N = 3). (C) CD16- and CD32-specific uptake of opsonized SRBCs by slanDCs and monocytes. slanDCs and monocytes were incubated for 30 minutes at 37°C with IgG-opsonized SRBCs. To analyze receptor-specific phagocytosis, incubation was performed in the presence of blocking mAbs for either CD16 (clone 3G8) or CD32 (clone AT10). Pappenheim-stained cytospins of cells containing SRBCs were prepared with 1 × 105 cells per microscope slide. The microscopic pictures are of 1 representative experiment. (D) The quantification is presented relative to the sample with the nonblocking isotype-matched control mAb (100%). Data represent mean ± SEM (N = 3).
