IL-26 concentrations correlated with IL-1-beta concentrations in RA serums (r = 0.95, p≤10−4) and RA SF (r = 0.6, p≤0.03) (Figure S1) but not with C-reactive protein (CRP), IL-6, TNF-alpha, and total leukocyte counts (unpublished data). Here, CRP is linked to rheumatoid arthritis.