Atherosclerosis-Driven Treg Plasticity Results in Formation of a Dysfunctional Subset of Plastic IFNγ+ Th1/Tregs
Rationale: Foxp3+T 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.
Objective: 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.
Methods and Results: We demonstrate that atherosclerosis promotes Treg plasticity, resulting in the reduction of CXCR3+ Tregs, and the accumulation of an intermediate Th1-like IFNγ+CCR5+ 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+ Mir146a-/-Th1/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.
Conclusions: Atherosclerosis drives Treg plasticity, resulting in the accumulation of dysfunctional IFNγ+ Th1/Tregs that may permit further arterial inflammation and atherogenesis.
- Received August 10, 2016.
- Revision received September 2, 2016.
- Accepted September 15, 2016.