DCs directly phagocytose inhaled antigens and accumulate model antigen in airway-adjacent regions. (A) Scheme for allergen challenge includes three i.p. injections of OVA/alum and three i.n. instillations of OVA (black arrows) followed by an i.n. instillation of beads (red arrow). (B) Stills of a video from a c-fms–EGFP, Actin-CFP mouse 1 h after i.n. instillation with 1-µm fluorescent polystyrene beads. Note extension, uptake, retraction, and reextension of the indicated DC. Also note the round AM to the left of the DC, within the alveolus. Dotted lines trace the dendrite surface. (C) Migration of CD11c-EYFP cells just below the surface of an airway of an OVA-treated lung stained with Hoechst (blue) 24 h after bead inhalation. (D) Representative image of airway (AW)-associated, antigen-bearing DCs in PBS- and OVA allergen–challenged mice. Arrows indicate DCs with beads. Bars: (B and C, left) 50 µm; (B, right) 10 µm; (C, right) 20 µm; (D) 100 µm. (E) Quantification of proportion of alveolar and airway-associated DCs that contain beads immediately after and 48 h after bead inhalation corrected for the total number of beads inhaled. Error bars represent SEM. All images are representative of at least four mice per group from four independent experiments. Quantifications include data from four independent experiments.