Regulatory T cells (Treg) are a critical immune component guarding against excessive inflammatory responses, but current understanding of Treg heterogeneity and function in non-lymphoid tissue in humans is limited. In this project we are characterising unique types of Treg signatures in the context of tissue-confined inflammatory responses in human skin and gut. We hypothesize that impairment in tissue-specific immune regulation leads to exacerbated T cell responses and chronic inflammation in these diseases. To investigate this, we are utilizing transcriptomic, phenotypic and metabolomic methods, using an integrative bioinformatical approach of single-cell (sc) sequencing data and metabolomic screens of Tregs from blood and tissue of patients with chronic inflammatory diseases. ScRNA-sequencing data from patients diagnosed with psoriasis, chronic cutaneous sarcoidosis, and ulcerative colitis have shown that diseased tissue-Tregs have a strong, specific, tissue-resident signature. We identified a skewed expression of polyamine catabolic genes linked to a more activated, Th17-like Treg phenotype in inflamed tissue. We confirmed these findings on metabolite and protein level, using skin-derived Tregs to describe a functional defect linked to polyamine metabolism in chronically inflamed skin. Together, our results indicate a novel interface of polyamine catabolism and Treg function in non-lymphoid tissues which leads to impaired control of effector T cell responses. Ultimately, our findings significantly contribute to basic understanding of Treg function and shed light on immune regulation during chronic inflammation in human tissue.