Abstract Body: Background: Atherosclerosis is driven by an autoimmune component with autoreactive T cells recognizing Apolipoprotein B (ApoB). Both experimental and clinical data suggest that antigen-specific T regulatory (Treg) cells switch to pathogenic T effector (Teff) cells during the natural course of the disease, undermining initially protective immunity. This study investigates the cellular and functional mechanisms underlying the dynamics of T-cell phenotypes in mouse models of atherosclerosis.
Methods: Female 8-week-old Apoe knockout mice were fed either a chow diet or a Western diet for up to 16 weeks. Additional Apoe knockout mice remained on a chow diet for 52 weeks to investigate aging effects. T cell phenotypes across tissues such as lymph nodes, spleen, aorta, and blood were analyzed using flow cytometry. ApoB-specific CD4 T-cell responses were quantified by triple-color fluorospot for IL-10, IFN-γ, and IL-17. Bulk RNA sequencing of CD4 T cells was used to identify transcriptional programs associated with aging and atherosclerosis. Foxp3 lineage-tracking mice fed either a chow or western diet were used to trace Tregs fate.
Results: Across all time points, Treg and CD4 T cell numbers gradually increase, indicating persistent immune activation. Atherosclerosis progression leads to decreased naïve T cells, increased central and effector memory T cells, and increased pro-inflammatory cytokines (TNF-α, IL-17) in the aortic adventitia and lymph nodes. Aging further exacerbated this immune response. Bulk RNA-seq shows inflammatory and exhaustion-associated transcriptional programmes in lymph node CD4 T cells. Tregs in lymph nodes showed a significant increase in inflammatory cytokines such as IFN-γ and IL-17, increased expression of transcription factors (T-bet and RORγt), and reduced expression of anti-inflammatory cytokine IL-10, suggesting a functional shift toward immune suppression and dysfunction. lineage-tracking mice show conversion of Foxp3 Tregs into inflammatory ex-Tregs as disease progresses. ApoB-specific responses were IL-10 dominant early but shifted toward pro-inflammatory phenotypes with disease progression.
Conclusions: Our findings suggest that atherosclerosis induces a dynamic, location-specific reprogramming of CD4 T cells and Tregs, revealing a temporal shift of Tregs from protective to pathogenic phenotype. These results provide a foundation for future therapeutic immunomodulatory approaches