Atherosclerosis-Driven Treg Plasticity Results in Formation of a Dysfunctional Subset of Plastic IFNγ+ Th1/Tregs.

Foxp3T regulatory cells (Tregs) are key players in maintaining immune homeostasis. Evidence suggests that Tregs respond to environmental cues to permit or suppress inflammation. In atherosclerosis, Th1-driven inflammation affects Treg homeostasis, but the mechanisms governing this phenomenon are unclear.,Here, we address whether atherosclerosis impacts Treg plasticity and functionality in Apoe mice, and what effect Treg plasticity might have on the pathology of atherosclerosis.,We demonstrate that atherosclerosis promotes Treg plasticity, resulting in the reduction of CXCR3 Tregs, and the accumulation of an intermediate Th1-like IFNγCCR5 Treg subset (Th1/Tregs) within the aorta. Importantly, Th1/Tregs arise in atherosclerosis from bona fide Tregs, rather than T effector cells. We show that Th1/Tregs recovered from atherosclerotic mice are dysfunctional in suppression assays. Using an adoptive transfer system and plasticity-prone Mir146a Tregs, we demonstrate that elevated IFNγ Mir146aTh1/Tregs are unable to adequately reduce atherosclerosis, arterial Th1, or macrophage content within Apoe mice, in comparison to Mir146a Tregs. Lastly, via single cell RNA-sequencing and RT-PCR we show that Th1/Tregs possess a unique transcriptional phenotype characterized by co-expression of Treg and Th1 lineage genes, and a down-regulation of Treg-related genes, including Ikzf2, Ikzf4, Tigit, Lilrb4, and Il10 Additionally, an ingenuity pathway analysis further implicates IFNγ, IFNα, IL-2, IL-7, CTLA4, T cell receptor, and Csnk2b-related pathways in regulating Treg plasticity.,Atherosclerosis drives Treg plasticity, resulting in the accumulation of dysfunctional IFNγ Th1/Tregs that may permit further arterial inflammation and atherogenesis.