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

RATIONALE

Forkhead box P3 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 interferon (IFN)-γCCR5 Treg subset (Th1/Tregs) within the aorta. Importantly, Th1/Tregs arise in atherosclerosis from bona fide Tregs, rather than from 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. Finally, via single-cell RNA-sequencing and real-time -polymerase chain reaction, we show that Th1/Tregs possess a unique transcriptional phenotype characterized by coexpression of Treg and Th1 lineage genes and a downregulation of Treg-related genes, including Ikzf2, Ikzf4, Tigit, Lilrb4, and Il10. In addition, an ingenuity pathway analysis further implicates IFNγ, IFNα, interleukin-2, interleukin-7, CTLA-4 (cytotoxic T-lymphocyte-associated protein 4), 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.