TNF and Arthritis: Anti-citrullinated protein autoantibodies were shown to induce inflammatory TNF-α production.15–18 Anti-citrullinated protein autoantibody levels were found to correlate with enhanced NETosis (neutrophils extracellular traps) in RA.19 Autoantibodies against mutated citrullinated vimentin (i.e. MCV-ACPAs) have been shown to enhance osteoclast precursor differentiation into mature bone-resorbing cells and bone loss.20 Although ACPAs have not been shown to induce arthritis by itself in animal models, the pathogenic effect of ACPAs was shown in experimental murine models of arthritis.21,22