Anti-IL-17 antibody treatment reduces the splenic CD11b+ cell expansion and the systemic production of myelopoietic cytokines. Interferon-γ receptor knock-out (IFN-γR KO) mice were immunized and injected intraperitoneally with anti-IL-17 or control antibody once a week. (a to c) On day 21, spleens of individual mice were isolated and splenocytes were counted. (a) Bars represent the mean number of splenocytes ± standard error of the mean (SEM). (b) Splenocytes were characterized by flow cytometry and the percentage of CD11b+ cells, CD11b+Gr-1high cells, B220+ cells, CD4+ cells and CD8+ cells was analyzed. Bars represent the mean net numbers of three independent experiments, each consisting of three to four mice per group ± SEM. (c) The percentage of lymphocytes, (immature) neutrophils and macrophages was assessed on cytospin splenocyte preparations of six anti-IL-17- and six control-treated mice, and the net numbers were calculated. Bars represent net numbers ± SEM. (d) At day 21 post immunization, mice were challenged with 10 μg anti-CD3 antibody and serum levels of granulocyte macrophage colony-stimulating factor (GM-CSF), IL-6, IL-12 and IFN-γ were determined 1.5 hours later. Bars represent the mean of two independent experiments, each consisting of four to five mice per group ± SEM. * P < 0.05 and ** P < 0.005 for comparison with control-treated mice (Mann-Whitney U-test).