Progenitor exhausted PD-1+ T cells are cellular targets of immune checkpoint inhibition in atherosclerosis

Immune checkpoint inhibitors (ICIs), targeting checkpoint receptors such as programmed cell death protein 1 (PD-1), are associated with increased risk of cardiovascular events, but the underlying mechanisms remain poorly understood. Here we show that PD-1+ T cells from murine atherosclerotic aortas mainly display a progenitor exhausted phenotype (PD-1intSlamf6+Tim3−), produce IFNγ in vivo, exhibit signs of recent proliferation and maintain polyfunctionality. PD-1 blockade induced marked changes in plaque immune phenotype, with increased PD-1high T cell accumulation, IFNγ production, formation of lymphocyte foci and neutrophil recruitment. Depletion of PD-1high T cells prior to PD-1 blockade did not impede T cell recruitment, suggesting a role for progenitor exhausted PD-1int T cells in ICI-driven T cell plaque accumulation. Human circulating PD-1+ T cells produced IFNγ and were associated with subclinical coronary atherosclerosis. Our studies highlight IFNγ-producing PD-1+ T cells as a potential key immune cell population mediating increased cardiovascular risk in patients with cancer receiving ICI. Mulholland et al. identify progenitor exhausted T cells, expressing intermediate levels of PD-1 (PD-1int), as a prominent source of pro-inflammatory cytokines in the murine atherosclerotic aorta and potential cellular targets driving checkpoint inhibition-elicited pro-atherosclerotic immune responses. They further demonstrate elevated levels of circulating PD-1-expressing T cells in individuals with subclinical cardiovascular disease.