TNF and arthritic joint disease: In this study, by employing the arthritic hTNFtg and TNFΔARE models in combination with cell-specific inactivation of the p55TNFR, we provide novel evidence for the indispensable role of mesenchymal-specific TNF/p55TNFR signalling in the pathogenesis of modelled TNF-mediated arthritis.