IL21 and arthritic joint disease: Supporting the anti-inflammatory role of PRL in arthritis, PRL-receptor-null mice exhibited increased joint swelling and higher joint expression of the genes encoding for TNFα, IL-1β, IL-6, IFNγ, IL-17A, IL-21, IL-22, IL-23, and IL-10 when subjected to monoarticular AIA (MAIA).