TNF and rheumatoid arthritis: Five TNF inhibitors are now available for clinical use in RA, and the following four of them (the exception being certolizumab pegol) contain the Fc (Fragment crystallizable) portion: etanercept, a TNF receptor Fc fusion protein (3); infliximab, an anti-TNFα chimeric monoclonal antibody (4); adalimumab and golimumab, anti-TNFα human monoclonal antibodies (5, 6); and certolizumab pegol, a pegylated anti-TNFα humanized antibody Fab’ fragment (7).