CD8+ T-cells protect against experimental atherosclerosis through antigen specific interactions in the plaque

Abstract

Atherosclerosis is a chronic inflammatory disease with a significant adaptive immune component. CD8+ T cells accumulate in plaques and display signatures of antigen-specific activation. However, whether this accumulation is driven by local antigen recognition and what functional consequences follow, remains poorly understood. Here we address this gap of knowledge using loss- and gain-of-function experiments. Atherosclerotic Rag-/-Ldlr-/- mice received adoptively transferred wildtype or antigen-restricted CD8+ T cells alongside CD4+ T cells to distinguish antigen-specific from antigen-independent responses. In a complementary model, ApobOVA-TGxLdlr-/- mice, expressing an ovalbumin-tagged variant of the atherosclerosis-associated ApoB100 protein, enabled OT-I CD8+ T cells to function as atherosclerosis-antigen-specific CD8+ T cells. T-cell distribution, activation and phenotype were assessed systemically and within lesions, plaque burden and composition were quantified histologically. Wildtype CD8+ T cells accumulated significantly more in aortic lesions compared to antigen-restricted CD8+ T cells, and exhibited increased activation, exhaustion and cytokine secretion, indicating that plaque-infiltrating T cells are predominantly antigen-specific. Perturbing antigen-specific CD8+ T-cell interactions significantly decreased plaque stability index, suggesting a protective role for antigen-specific CD8+ T cells. In ApobOVA-TGxLdlr-/- mice, OT-I T cells accumulated at high frequency in the liver, consistent with hepatic ApoB100-expression, and were found in circulation and aorta. Histological analysis revealed reduced plaque burden in OT-I recipients, reproducing an atheroprotective effect of antigen-specific CD8+ T-cell responses. Plaque reduction coincided with reduced TUNEL, but similar Caspase 3 staining, suggesting OT-I transfer results in reduced secondary necrosis. In line with this, CD47 expression in OT-I recipient mice was reduced and in vitro, OT-I but not antigen non-specific CD8+ T cells reduced expression of CD47 on OVA-presenting foam cells. CD8+ T-cell accumulation in experimental atherosclerosis is driven primarily by antigen-specific interactions and such responses are associated with plaque stabilization and reduced lesion formation, potentially through induction of apoptosis and prevention of secondary necrosis