Indeed, NOD mice with genetic deletion of IL-21 signaling (NOD.Il21r–/–, IL-21R KO) were protected from the development of ICI-T1DM during ICI treatment (Figure 2B; P < 0.0001 for anti–PD-1 therapy in WT versus IL-21R–KO mice). Here, IL21 is linked to type 1 diabetes mellitus.