Absence of infiltration of neutrophils and bone destruction in the joints of anti-IL-17-treated mice. In experiment 1 of Figure 1d, histological analysis of the joints was performed. On day 25, four mice of each group were sacrificed and sections of the fore limbs, hind limbs and ankles were scored for three parameters of arthritis following hematoxylin staining. (a) Histograms represent averages ± standard error of the mean (SEM). * P < 0.005 for comparison with control-treated mice (Mann-Whitney U-test). (b, c) Pictures of the hematoxylin-stained paraffin sections of the joints of control-treated (b, a representative mouse) and anti-IL-17-treated (c, mice with the most severe symptoms) mice are shown. In control-treated mice, a severe hyperplasia and infiltration of immunocompetent cells in the synovium and pannus formation that penetrates into the bone can be seen. (b1, 2) Detail of the area indicated by respectively the left and right box in b. Note the presence of osteoclast-like multinucleated giant cells (arrows in b1), and the presence of polymorphonuclear cells in b2. (c1) Detail of the area indicated by the right box in c showing a moderate infiltration of mononuclear cells and hyperplasia. Scale bars represent (b, c) 50 μm and (b1, b2 and c1) 500 μm.