Fig. 2

Early serum S100A8/A9 levels are prognostic for development of increased joint swelling. a Serum levels of S100A8/A9 in IL-1Ra^–/– mice (n = 37) were increased compared to BALB/c mice (n = 8) at week 8 of age (P = 0.029) and at weeks 10, 12, 14, and 16. b At week 8, serum levels of S100A8/A9 in IL-1Ra^–/– mice correlated with the combined macroscopic score for joint swelling, and continued to be correlated with joint swelling at weeks 10, 12, 14, and 16 (data not shown). c IL-1Ra^–/– mice were stratified for macroscopic joint swelling at week 16 in severe (score 2.25–4), mild (score 0.75–2), and low (0–0.5) joint swelling. Serum S100A8/A9 levels were increased in severe arthritic mice as early as week 10 compared to mild (P = 0.004) and low arthritic mice (P = 0.009). Serum levels of S100A8/A9 in severe arthritic mice continued to be increased compared to mild and low arthritic mice at weeks 12, 14, and 16. d Serum levels of S100A8/A9 at week 10 correlated with joint swelling at week 16, indicating that early serum S100A8/A9 levels are prognostic for disease outcome at a later stage. *P < 0.05, **P < 0.01, ***P < 0.001. IL-1Ra interleukin-1 receptor antagonist