Fig. 4.

IL-26 promotes the differentiation of peripheral blood monocytes into osteoclasts. a Human peripheral blood CD14⁺ monocytes (n = 3) were isolated and cultured with 0 (-), 10, 50, and 100 ng/mL recombinant human (rh)IL-26 or 10 ng/mL RANKL in the presence of macrophage colony-stimulating factor (25 ng/mL). Osteoclast differentiation was determined by counting tartrate-resistant acid phosphatase (TRAP)⁺ multinucleated cells with at least three nuclei. A bone-resorption assay demonstrating IL-26-induced bone-resorbing activity. Images are representative of three independent experiments. b The expression of osteoclast markers was determined using real-time polymerase chain reaction, with mRNA levels normalized against β-actin expression (n = 3). Data are presented as means ± standard error of the mean of three separate experiments. *P < 0.05; **P < 0.01; ***P < 0.005. IL interleukin, CD cluster designation, RANKL receptor activator of nuclear factor-kappaB ligand