Pathogenic Autoimmunity in Atherosclerosis Evolves From Initially Protective Apolipoprotein B <sub>100</sub> –Reactive CD4 <sup>+</sup> T-Regulatory Cells
Dennis Wolf, Teresa Gerhardt, Holger Winkels, Nathaly Anto Michel, Akula Bala Pramod, Yanal Ghosheh, Simon Brunel, Konrad Buscher, Jacqueline Miller, Sara McArdle, Livia Baas, Kouji Kobiyama, Melanie Vassallo, Erik Ehinger, Thamotharampillai Dileepan, Amal J. Ali, Maximilian Schell, Zbigniew Mikulski, Daniel Sidler, Takayuki Kimura, Xia Sheng, Hauke Horstmann, Sophie Hansen, Lucía Sol Mitre, Peter Stachon, Ingo Hilgendorf, Dalia E. Gaddis, Catherine C. Hedrick, Chris A. Benedict, Bjoern Peters, Andreas Zirlik, Alessandro Sette, Klaus Ley
Abstract
Background: Throughout the inflammatory response that accompanies atherosclerosis, autoreactive CD4 + T-helper cells accumulate in the atherosclerotic plaque. Apolipoprotein B 100 (apoB), the core protein of low-density lipoprotein, is an autoantigen that drives the generation of pathogenic T-helper type 1 (T H 1) cells with proinflammatory cytokine secretion. Clinical data suggest the existence of apoB-specific CD4 + T cells with an atheroprotective, regulatory T cell (T reg ) phenotype in healthy individuals. Yet, the function of apoB-reactive T regs and their relationship with pathogenic T H 1 cells remain unknown. Methods: To interrogate the function of autoreactive CD4 + T cells in atherosclerosis, we used a novel tetramer of major histocompatibility complex II to track T cells reactive to the mouse self-peptide apo B 978-993 (apoB + ) at the single-cell level. Results: We found that apoB + T cells build an oligoclonal population in lymph nodes of healthy mice that exhibit a T reg -like transcriptome, although only 21% of all apoB + T cells expressed the T reg transcription factor FoxP3 (Forkhead Box P3) protein as detected by flow cytometry. In single-cell RNA sequencing, apoB + T cells formed several clusters with mixed T H signatures that suggested overlapping multilineage phenotypes with pro- and anti-inflammatory transcripts of T H 1, T helper cell type 2 (T H 2), and T helper cell type 17 (T H 17), and of follicular-helper T cells. ApoB + T cells were increased in mice and humans with atherosclerosis and progressively converted into pathogenic T H 1/T H 17-like cells with proinflammatory properties and only a residual T reg transcriptome. Plaque T cells that expanded during progression of atherosclerosis consistently showed a mixed T H 1/T H 17 phenotype in single-cell RNA sequencing. In addition, we observed a loss of FoxP3 in a fraction of apoB + T regs in lineage tracing of hyperlipidemic Apoe –/– mice. In adoptive transfer experiments, converting apoB + T regs failed to protect from atherosclerosis. Conclusions: Our results demonstrate an unexpected mixed phenotype of apoB-reactive autoimmune T cells in atherosclerosis and suggest an initially protective autoimmune response against apoB with a progressive derangement in clinical disease. These findings identify apoB autoreactive T regs as a novel cellular target in atherosclerosis.