The overexpression of IL-4 reduced bone formation by osteoblasts and caused osteoporosis of both cortical and trabecular bones [64]; although, IL-4 inhibited the receptor activator of nuclear factor kappa-Β ligand (RANKL)-induced osteoclastogenesis mediated by c-Fos and NFATc1 expression in osteoclasts [65]. The gene discussed is IL4; the disease is osteoporosis.