TNFRSF11A and rheumatoid arthritis: Other mechanisms involved in the MTX effect on RA include the anti-inflammatory effect via the adenosine signalling pathway, regulation of the receptor activator for nuclear factor κ B ligand (RANKL)/receptor activator for nuclear factor κ B (RANK)/osteoprotegerin (OPG) pathway, and regulation of the number of various T cells (the reduction in Th1 and Th17 cell proportion with the increase in Th2 and regulatory T (Treg) cells) [42].