IL-17A sensitizes pre-osteoclasts to the receptor activator of NF-κB ligand signal. (a) CD14+ cells' representative m-RNA expression of receptor activator of NF-κB (RANK) and c-fms receptor from one donor. Representative data of five donors. (b) Surface RANK expression after treatment with macrophage colony-stimulating factor (MCSF) and/or receptor activator of NF-κB ligand (RANKL) and/or IL-17A. Representative data of two experiments. (c) Mean number of tartrate-resistant acid phosphatase (TRAP)+ multinucleated cells in the presence of IL-17A across a gradient of RANKL whilst keeping MCSF constant (left) and across a MCSF gradient whilst keeping RANKL constant (right). Data pooled from two experiments.