Cartilage depletion in the joints of mice with antigen-induced arthritis (AIA). Arthritis was induced in WT and DR3−/− mice, and the joints were prepared, sectioned, and stained as described in Materials and Methods. A, Representative Safranin O–fast green–stained joint sections from WT and DR3−/− mice, 21 days after generation of AIA. B, Quantification of cartilage depletion in WT and DR3−/− mice on day 21. C, Representative Safranin O–fast green–stained (top row) and toludine blue–stained (bottom row) joint sections from WT and DR3−/− mice, 3 days after generation of AIA. D, Quantification of cartilage depletion in WT and DR3−/− mice on day 3, as measured by Safranin O–fast green staining. In A and C, bars = 60 μm. In B and D, each data point represents a single mouse; horizontal lines show the mean. P values were determined by Mann-Whitney U test. See Figure 1 for other definitions.