Significantly different levels of 10 proteins (IL-6, TNF-R superfamily member 9, IL-17C, IL-10, CXCL9, IL-15 receptor α [IL-15Rα], CXCL6, leukaemia inhibitory factor receptor [LIF-R], delta and Notch-like epidermal growth factor-related receptor [DNER] and hepatocyte growth factor [HGF]) between those developing arthritis and individuals not developing arthritis (Supplementary Table S5, Supplementary Fig. S3, available at Rheumatology online). The gene discussed is CXCL9; the disease is arthritic joint disease.