Phenotypic and transcriptional heterogeneity of memory CXCR5+ CD8+ T cells in human blood and lymphoid tissue

Abstract

Abstract CXCR5+ CD8+ T cells are involved in antiviral and -tumor immunosurveillance. Animal models have demonstrated that CXCR5+ CD8+ T cells have multiple roles, including cytotoxic, stem-like, and regulatory functions. Many of these functions might be disease-dependent, where human studies are lacking to understand if CXCR5+ CD8+ T cells show signs of significant heterogeneity. To this end, we performed simultaneous single-cell (sc) RNA−, TCR−, and CITE-seq on CXCR5+ and CXCR5− memory CD8+ T cells from matched tonsils and blood to unravel if CXCR5+ CD8+ T cells show potential differences between human lymphoid tissue and blood. Our analysis indicates that a high proportion of CXCR5+ CD8+ T cells in tonsils show tissue residency-like (TRM) features, including CD69 and CD103 expression. Instead, blood CXCR5+ CD8+ T cells showed increased signs of cytotoxic functions in blood compared to their counterparts in tonsils. GSEA analysis identified groups of genes differentially expressed, such as the p53 pathway enriched in tonsils compared to ribosome-related pathways in blood CXCR5+ memory CD8+ T cells. Additionally, with CITE-seq markers, we identified the protein landscape of sub-populations and found increased PD-1 and CD45RO expression in tonsils compared to blood CXCR5+ memory CD8+ T cells. Overall, these findings indicate that CXCR5+ CD8+ T cells are heterogeneous with potentially distinct functional subsets that patrol blood and lymphoid tissues.