TNF and rheumatoid arthritis: Based on the pivotal role of TNF-α in the pathogenesis of RA [4], two classes of biologic drugs to block this cytokine have been developed: a soluble TNF-α receptor (etanercept) and TNF-binding monoclonal antibodies (mAbs) such as infliximab, adalimumab, golimumab, or certolizumab [5,6].