We have previously shown that patients with antibiotic-refractory arthritis have significantly higher levels of proinflammatory cytokines and chemokines in SF, particularly IFN-γ and the IFN-inducible chemokines CXCL9 and CXCL10, than patients with antibiotic-responsive arthritis [10,37]. This evidence concerns the gene CXCL9 and arthritic joint disease.