LCs in WT and CD18^–/– mice. (a) Mice that were either left untreated, or were treated with topical mometasone-17-(2-furoate) 5 days or 25 days prior to assessment of LC density. Ear skin was obtained, and epidermal sheets were prepared and stained for I-A⁺ epidermal cells, as described in Methods. (b) Ears were treated with the fluorescent hapten FITC. Regional LNs were prepared 18 hours later, and LN cells were stained with phycoerythrin-labeled anti–I-A antibodies and subjected to flow cytometry. LCs were gated based on FSC/SSC characteristics. Numbers in boxes indicate the percentage of double positive cells.