While a role for IL-21 in ICI-T1DM has not been described, we showed in mice and humans with ICI-thyroiditis that IL-21 from CD4+ cells could augment effector molecules (IFN-γ, granzyme B) and chemokine receptors on thyrotoxic CD8+ T cells (10). The gene discussed is IL21; the disease is type 1 diabetes mellitus.