IL-17A increases bone resorption in synergy with receptor activator of NF-κB ligand. CD14+ cells cultured on dentine slices for 18 days in the presence of macrophage colony-stimulating factor (MCSF) and receptor activator of NF-κB ligand (RANKL) and/or IL-17A showing (a) increased cell fusion and (b) increased bone resorption. Bars (left to right): upper panel, 45, 45 and 60 μm; lower panel, 70, 100 and 100 μm. (c) Mean percentage dentine erosion of control versus IL-17A-stimulated CD14+ cells, P < 0.01. Data pooled from four individual experiments performed in triplicate.