TNF and rheumatoid arthritis: It has been shown that serum levels of Dkk-1 were significantly higher in patients with AS compared to patients with RA and healthy controls and were further increased in AS patient receiving anti-TNFα treatment [34]; the authors hypothesized that the higher levels of Dkk-1 may reflect a counter-balancing mechanism to attenuate Wnt signaling, which is turned on after resolution of inflammation following the treatment.