Interventions with agents to modulate IL‐6/IL‐6R or IL‐21/IL‐21R have been shown to confer clinical benefit in patients with autoimmune diseases including RA.[21, 24] To determine if salivaricins can suppress immune‐mediated pathological processes in vivo, we explored both prophylactic and therapeutic applications of salivaricins in collagen‐induced arthritis (CIA) model mice, a well‐characterized murine arthritis model. Here, IL21 is linked to autoimmune disease.