Therapeutics that inhibit IL-6 at different points in its signaling pathway are in clinical use, yet whether the immunological effects of these interventions differ based on their molecular target is unknown. We performed short-term interventions in individuals with type 1 diabetes using anti–IL-6 (siltuximab) or anti–IL-6 receptor (IL-6R; tocilizumab) therapies and investigated the impact of this in vivo blockade on T cell fate and function. Immune outcomes were influenced by the target of the therapeutic intervention (IL-6 versus IL-6R) and by peak drug concentration. Tocilizumab reduced ICOS expression on T follicular helper cell populations and T cell receptor–driven (TCR-driven) STAT3 phosphorylation. Siltuximab reversed resistance to Treg-mediated suppression and increased TCR-driven phosphorylated STAT3 and production of IL-10, IL-21, and IL-27 by T effectors. Together, these findings indicate that the context of IL-6 blockade in vivo drives distinct T cell–intrinsic changes that may influence therapeutic outcomes.


Cate Speake, Tania Habib, Katharina Lambert, Christian Hundhausen, Sandra Lord, Matthew J. Dufort, Samuel O. Skinner, Alex Hu, MacKenzie Kinsman, Britta E. Jones, Megan D. Maerz, Megan Tatum, Anne M. Hocking, Gerald T. Nepom, Carla J. Greenbaum, Jane H. Buckner


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