The present invention relates to blocking, inhibiting, reducing, antagonizing or neutralizing the activity of IL-17F, IL-17A, or both IL-17A and IL-17F polypeptide molecules. IL-17A and IL-17F are cytokines that are involved in inflammatory processes and human disease. IL-17RC is a common receptor for IL-17A and IL-17F. The present invention includes methods of using a soluble IL-17RC receptor, IL-17RCx4 for treating inflammation.