IL17A and Arthritis: Robust experimental evidence indicate that IL-17 is a strong inducer of osteoclastogenesis.73–76 In mouse models of arthritis, IL-17 appears to cause bone loss by promoting osteoclast differentiation indirectly, through the stimulation of RANKL (receptor activator of NF-kappa B ligand) expression by osteoblasts.77 RANKL is a molecule expressed mainly by cells of mesenchymal lineage and induces osteoclast differentiation by binding to the RANK receptor found on osteoclast precursor cells.