Characteristics of T-Cells Expressing IL-37 and Its Receptors in Inflammatory Bowel Disease.

IBD pathogenesis is underpinned by an imbalance between excess inflammation caused by effector T-cells and inadequate suppression by regulatory T-cells (Tregs). Interleukin-37 (IL-37) is a potent, anti-inflammatory cytokine that signals via its receptors IL-1R5 and IL-1R8. Hence, augmenting anti-inflammatory mechanisms that drive IL-37 expression is a strategy to control IBD-associated inflammation. However, the role of IL-37 and its receptors in T-cells remains incompletely understood. Here, we investigated T-cell expression profiles of IL-37 and its receptors to understand the drivers of dysregulated T-cell responses in IBD and develop novel, more effective therapies. T-cell subsets from healthy control (HC), Crohn's disease (CD) and ulcerative colitis (UC) peripheral blood mononuclear cells (PBMC) and lamina propria mononuclear cells (LPMC) were assessed for expression of IL-37 and its receptors by flow cytometry. CD3+IL-1R8+ T-cell transcriptomes underwent RNA sequencing. The phenotype and suppressive capacity of Tregs supplemented with IL-37 was assessed in vitro. Our results indicate that IL-37 and its receptors were differentially expressed among PBMC and LPMC T-cell subsets in IBD patients compared to HC. Transcription signatures unique to IBD were revealed, particularly histone and mitochondrial pathways. Remarkably, culturing Tregs with IL-37 preserved FOXP3 expression and suppressiveness at a level comparable to treatment with the well-established Treg stabilizing agent rapamycin. Altogether, our study identified differences in T-cells expressing IL-37 and its receptors that are indicative of T-cell dysfunction in IBD. These findings highlight a novel and promising avenue for restoring immune homeostasis in IBD by targeting and boosting the IL-37 signalling pathway.