To identify easily obtainable biomarkers, which might predict the development and therapeutic consequences of anti-TNFi Ab, we investigated early appearance of circulating anti-TNFi Ab and corresponding levels of TNFi in RA patients, and related the anti-TNFi Ab and drug levels to serum levels of IL-6, sTNF-R1 and sTNF-R2. Here, IL6 is linked to rheumatoid arthritis.