IL18 and rheumatoid arthritis: Of these, the levels of nine proteins (IL–8, CCL20, IL–17A, IL–17C, IL–18, 4E–BP1, caspase 8, sCD40 and sOPG) correlated with a cumulative GC dose (r ≥ 0.40, p ≤ 0.01, Supplementary Figure S2) in active RA.