Th17 cells and their effector molecule IL-17A are involved in various effector functions associated with RA pathology, and Th17 is also one of the major cell subpopulations supporting differentiation of osteoclasts during osteoclastogenesis, which is induced by RANKL and carried in combination with RANK on osteoclast precursors. The gene discussed is IL17A; the disease is rheumatoid arthritis.