Interleukin-21 (IL-21) has been implicated in T cell-mediated autoimmunity; however, the immunoregulatory mechanisms linking IL-21 signaling to T cell imbalance in pediatric T1D remain incompletely understood.<h4>Methods</h4>Single-cell RNA sequencing data from children with T1D were analyzed to characterize IL-21/STAT3 pathway activity across immune cell subsets. Here, IL21 is linked to type 1 diabetes mellitus.