The role of IL-17 in IMC-mediated enhancement of papilloma formation. (A) Papilloma development in CD4-depleted S100A9Tg;Tg.AC bitransgenic mice. CD4 antibody or IgG (control) treatment was performed as indicated on the graph. Mean and SD of papillomas per mouse are shown. Each group included five mice. Two-way ANOVA, P = 0.021. (B) The presence of CD4⁺ T cells and Gr-1⁺ IMCs in skin of C57BL/6 S100A9Tg mice treated with TPA and CD4 antibody for 5 wk. Cells were evaluated by IHC (n = 4). (C) The presence of cytokines in tissues of WT and S100A9Tg mice treated with TPA for 6 wk. Cytokines were measured in whole cell lysates using ELISA. **, P < 0.01. (D) The amount of IL-17A in skin of mice described in B measured by ELISA. (B and D) **, P < 0.01 from acetone-treated mice; #, P < 0.05 from TPA only–treated mice (n = 6). (E) Papilloma formation in S100A9Tg C57BL/6 mice was induced by DMBA application, followed by 16 wk of treatment with TPA. Mice were treated with 200 µg of either control IgG or neutralizing IL-17 antibody during the first 12 wk. Each group included five mice. Two-way ANOVA, P < 0.001. (B–E) Mean and SD are shown.