Abstract 127: Single Cell RNAseq Reveals Pro-inflammatory, Cytolytic T Cells Characterize Complex Human Coronary Plaques

Abstract

Background: Atherosclerosis is considered a chronic inflammatory disorder characterized by the presence of T cells and macrophages in the plaque. Given that T cells are the master regulators of the immune system, the possible role of T cells in mediating disease warrants further investigation. Objective: To map the T cell transcriptome in coronary artery plaque. Methods/Results: Using single cell RNAseq, we mapped the transcriptome of immune cells within the coronary atherosclerotic plaque in 12 patients with various disease stages. In addition to macrophages, we find an abundance of plaque T cells that appear to be enriched in plaque compared to blood ( Figure 1A ). Two plaque-enriched CD8 effector memory clusters (CD8 CTL Tem1 and CD8 CTL Tem2) display the highest proportion of activated cells (e.g., HLA-DRA+). These clusters are characterized by high expression of the pro-inflammatory cytokines (e.g., CCL3, CCL4, CCL5, and IFNG) and cytolytic markers (e.g.,GZMA, GZMH, GZMM, NKG7). CD8 CTL Tem1, however, has higher expression of GZMK, a cytolytic marker recently associated with inflammaging. CD8 CTL Tem2, on the other hand, has a higher expression of perforin and granulysin, two pore-forming proteins that mediate cell killing by enabling granzyme entry. Notably, CD8 CTL Tem2 appears to track with plaque progression, increasing as plaques mature from lipid-rich to more complex lesions then declining as plaques became more stable and calcified post-rupture. Specifically, this cluster displayed two-fold enrichment in complex plaques compared to other plaque phenotypes (12.1% vs. 6.9%, p=0.0069) ( Figure 1B ). This pro-inflammatory and cytolytic signature is also more apparent in the activated compared to nonactivated cells in this cluster. Conclusion: Taken together, our findings suggest that a pro-inflammatory CD8 T cell cluster characterized by a trifecta of cytolytic enzymes distinguishes complex plaque and deserves further investigation.