Provided herein are compositions comprising one or more agents that inhibit or reduce the activity of IL-20. Optionally, the agents further inhibit or reduce the activity of IL-24. Kits and method of treating or preventing an inflammatory or autoimmune disease using the compositions are also provided. In addition, provided are methods of screening for agents that selectively bind the IL-20R1/IL-20R2 receptor complex or that selectively bind the IL-22R1/IL-20R2 receptor complex. The methods include contacting an agent to be screened with the receptor and determining whether the agent selectively binds to the receptor.