Taken together with findings in other autoimmune diseases [11], there is genetic and immunological rationale for the initiation of clinical trials to investigate the safety and efficacy of anti-IL-21 therapy in RA patients (www.clinicaltrials.gov - NCT01565408 and NCT01647451) and in other diseases, including type 1 diabetes. Here, IL21 is linked to type 1 diabetes mellitus.