IKK2 controls the inflammatory potential of tissue-resident regulatory T cells

Abstract Loss-of-function mutations have provided crucial insights into the immunoregulatory actions of Foxp3 + regulatory T cells (Tregs). By contrast, we know very little about the consequences of defects that amplify aspects of Treg function or differentiation. We report that mice heterozygous for an Ikbkb gain-of-function (GoF) mutation develop psoriasis. Doubling the gene dose (IkbkbGoF/GoF) results in dactylitis, spondylitis, and characteristic nail changes, which are features of psoriatic arthritis. IkbkbGoF mice exhibit a selective expansion of Foxp3 + CD25 + Tregs of which a subset express IL-17. These modified Tregs were enriched in both inflamed tissues and spleen, and their transfer was sufficient to induce disease without conventional T cells. Single-cell transcriptional and phenotyping analyses of isolated Tregs revealed expansion of non-lymphoid tissue (tissue-resident) Tregs expressing Th17-related genes, Helios, tissue-resident markers including CD103 and CD69, and a prominent NF-kB transcriptome. Thus, IKK2 regulates tissue-resident Treg differentiation, and overactivity drives dose-dependent skin and systemic inflammation.