#$%^&*AU2013203707B220150115.pdf#####ABSTRACT The invention features methods and compositions for preventing or treating rheumatoid arthritis and osteoporosis by administering an antagonist of IL-20. The IL-20 antagonist may be an anti-IL-20 antibody, such as mAB 7E, that is capable of binding human IL-20 and blocking IL-20 interaction with its receptors.