IL-23 tunes inflammatory functions of human MAIT cells

IL-23 signaling plays a key role in the pathogenesis of chronic inflammatory and infectious diseases, yet the cellular targets and signaling pathways affected by this cytokine remain poorly understood. We show that IL-23 receptors are expressed on the large majority of human MAIT, but not of conventional T cells, suggesting that these innate-like T cells are critical mediators of IL-23 functions. In this study, we investigated the effects of IL-23 on human MAIT cell transcriptional and chromatin accessibility profiles, using RNA- and CITE-seq and ATAC-seq, respectively. Protein and transcriptional profiling at the population and single cell level demonstrates that stimulation with IL-23 or the structurally related cytokine IL-12 drives distinct functional profiles, revealing a high level of plasticity of MAIT cells. IL-23, in particular, affects key molecules and pathways related to autoimmunity and cytotoxic functions. Integrated analysis of transcriptomic and chromatin accessibility shows that AP-1 transcription factors constitute a key regulatory node of the IL-23 pathway in MAIT cells. Overall design: PBMC were isolated from healthy donors. MAIT cells were activated for 6 days in PBMC cultures using MR1 tetramers loaded with 5-OP-RU (MR1/5-OP-RU), in the absence or presence of IL-23, or IL-12. After 6 days, MAIT cells were sorted and we performed RNA-seq, ATAC-seq, and CITE-seq. To identify the effects of IL-23 or IL-12 on MAIT cells, we compared cells activated in the presence of IL-23 or IL-12 with those stimulated with MR1/5-OP-RU only.