Fig. 1

The absence of s100a9 does not affect inflammation in the ankle joints of Il1rn^−/− mice. Arthritis incidence, based on the macroscopic score of the ankle joints, was increased in Il1rn^−/−XS100a9^−/− compared to Il1rn^−/− mice (A). However, the severity of arthritis in the positive mice was comparable (B). Representative photomicrographs of hematoxylin and eosin-stained sections showing examples of inflammation in the ankle joints of 12-week-old wild type (WT), S100a9^−/−, Il1rn^−/−, and Il1rn^−/−XS100a9^−/− mice (C, original magnification ×50). Quantification of the degree of inflammation of the ankle joints using an arbitrary score showed that the strains deficient in Il1rn developed significantly more inflammation compared to the S100a9^−/− and WT controls. However, no significant differences in inflammation were observed between Il1rn^−/−XS100a9^−/− and Il1rn^−/− mice. Line graphs are shown, representing the percentage of positive mice in A and mean ± SEM values of arthritis severity in B. Scatterplots are shown, with horizontal and vertical lines representing mean ± SEM values (C). Each data point represents the sum score of the right and left ankle joint of one mouse. ns not significant, ***P < 0.001. Results of the two-way ANOVA with interaction are presented in the table