Reduced humoral and cellular immune response following treatment of CII/CFA immunized IFN-γR KO mice with anti-IL-17 antibodies. Interferon-γ receptor knock-out (IFN-γR KO) mice were immunized and injected intraperitoneally with 0.2 mg of neutralizing anti-IL-17 or control antibody once a week. (a, b) On day 22, sera of individual mice were analyzed for (a) total IgG, (b) anti- collagen type II (CII) IgG and (c) anti-CII IgG1, IgG2a and IgG2b. Histograms represent averages ± standard error of the mean (SEM). (d) 25 days after immunization, mice in each group were challenged with 20 μg of CII in the left ear and vehicle in the right ear. Delayed type hypersensitivity responses were measured as the percentage of swelling (i.e. 100 × the difference between the increase of thickness of the left and the right ears, divided by the thickness of the right ear) at the indicated time points. Histograms represent averages ± SEM. * P < 0.05 for comparison with control-treated mice (Mann-Whitney U-test). CFA = complete Freund's adjuvant.