Tiam1 functions during contact hypersensitivity. (A) WT and Tiam1^−/− mice were sensitized with 0.5% FITC solution. After 6 days, 10 μL 0.5% FITC solution or control solution was applied to both ears and the thickness of each ear was measured on days 1 and 4 after challenge. Values are means ± SD (n = 10); p indicates P value. (B) Infiltrating T cells in ears of WT and Tiam1^−/− mice 1 day after FITC challenge. T-cell infiltrates are presented as the number of CD3⁺ T cells per unit surface area in the FITC-challenged ear. Values are means ± SD (n = 6). (C,D) WT and Tiam1^−/− mice were sensitized with 0.5% FITC solution. On day 3, draining LNs were isolated and single cell suspensions were stained for CD11c and counted. (C) Representative FACS analysis showing Cd11c/FITC double-positive cells in draining LNs. (D) Increased LN cell number after hapten sensitization. Results are expressed as fold increase (LN cell number of sensitized mouse/LN cell number of control mouse). Values are means ± SD (n = 4).