The results of this SF biomarker study revealed that only 6 of 16 proteins (TNF-α, IL-1-β, IL-7, MMP-1, MMP-2 and MMP-3) were significantly higher in active RA patients than OA patients, whereas levels of IL-1 ra, IL-2, IL-4, IL-6, IL-15, IL-18, MMP-3, G-CSF, IGFBP-3 and ILGFBP-4 did not different statistically. Here, IL15 is linked to rheumatoid arthritis.