IL-2 mutein promotes antigen-specific transplant acceptance in mice through expansion of ST2+ regulatory T cells.

Although transplantation is the preferred treatment for end-stage organ disease, long-term outcomes are limited by immunosuppressive drug toxicity and immune-mediated injury. Selective in vivo expansion of regulatory T cells (Tregs) using interleukin-2 (IL-2) analogs has emerged as a strategy to induce antigen-specific transplant tolerance with fewer side effects. Herein, we investigate the therapeutic efficacy of an IL-2 mutein molecule (mIL-2) with enhanced receptor specificity and extended half-life in murine models of solid organ transplantation. mIL-2 therapy significantly improves allograft survival in an antigen-specific manner, accompanied by increased Treg activation, decreased effector T cell activation and reduced donor-specific antibody production. Transcriptional profiling reveals expansion of Tregs expressing the suppression of tumorigenicity 2 (ST2) Tregs with heightened activation status and suppressive function. Accordingly, the mIL-2-induced long-term allograft survival is abrogated in Treg-specific ST2 knockout graft recipients, underscoring the critical role of ST2+ Tregs. These findings identify mIL-2 as an approach to promote long-term transplant tolerance while reducing reliance on conventional immunosuppression.