(A) The percentage of IMs (F4/80⁺CD11c^–), AMs (F4/80⁺CD11c⁺), and DCs (F4/80^–CD11c⁺) in whole lung from BALB/c mice was determined by flow cytometry. IMs, AMs, and DCs were also stained for MHC II and CD68. (B) The percentage of F4/80⁺CD11c^–, F4/80⁺CD11c⁺, and F4/80^–CD11c⁺ cells in BALF from BALB/c mice. (C–E) Lung cryosections were double stained for CD11c (blue) and F4/80 (red). IMs (F4/80⁺CD11c^–) are stained red, DCs (F4/80^–CD11c⁺) are stained blue, and AMs (F4/80⁺CD11c⁺) are double stained. (C) Representative photographs showing some IMs, AMs, and DCs (original magnification, ×100). The average number of IMs and AMs per field was calculated. (D) Image of IMs in the vicinity of DCs (original magnification, ×100). (E) Photographs at higher magnification showing IMs, AMs, interstitial F4/80⁺CD11c⁺ macrophages, and DCs (original magnification, ×200). (F and G) Alternatively, F4/80 was stained pink rather than red. (F) Representative photographs showing some IMs (pink), DCs (blue), and AMs (purple) (original magnification, ×100). (G) Photographs at higher magnification (original magnification, ×200). (H) FACS-sorted APCs were cocultured with FITC-labeled dextran in the absence or presence of sodium azide. After 45 minutes, the uptake of fluorescent dextran was determined by flow cytometry. (I) FACS-sorted APCs (1 × 10⁴ or 4 × 10⁴ cells/well) were loaded with the DO11.10 OVA peptide and cocultured for 3 days with naive DO11.10 CD4⁺ T cells. DO11.10 T cell proliferation was assessed by [³H]thymidine uptake in a 16-hour pulse. *P < 0.05 (H and I).