MiR-29a/b Suppresses CD8⁺ T Cell Effector Function and Intestinal Inflammation

The role of CD8⁺ T cells in the pathogenesis of ulcerative colitis (UC) remains unclear. Similarly, the posttranscriptional regulation of the highly heterogenic CD8⁺ T cell populations and their effector function in IBD also remains poorly understood. Here, we find that miR-29a and -29b (miR-29a/b) regulate T cell fate, and their expression is higher near damaged colon tissue in patients with IBD compared to controls. In mice, we find that miR-29a/b suppresses the differentiation of CD8⁺ T cells and the secretion of pro-inflammatory and chemotactic factors during severe colitis by inhibiting transcriptional pathways, including those involving the T cell receptor and JAK-STAT signaling. Furthermore, we identify Ifng, an inflammatory factor that drives immune response and the reshaping of CD8⁺ T cell fate, as a potential target of the miRNAs. Finally, we show that delivery of miR-29 mimics to the colon of mice is sufficient to alleviate DSS-induced inflammation. Together, these data show that miR-29 plays an important role in suppressing T cell overactivation during inflammatory diseases.