# CXCR5 identifies stem-like resident memory CD8⁺ T cells enriched for latent EBV specificity in tonsils

## TL;DR

CXCR5+ CD8+ T cells in tonsils have stem-like features and are especially good at targeting EBV, a common virus.

## Contribution

Identifies a CXCR5+ tissue-resident memory CD8+ T cell subset in tonsils with EBV-specific immune surveillance potential.

## Key findings

- Tonsils have the highest frequency of CXCR5+ CD8+ T cells compared to other tissues.
- CXCR5+ CD8+ T cells in tonsils show a PD-1+ resident stem-like phenotype and target EBV latent antigens.
- CXCR5 expression is more common in tonsil CD8+ T cells than in circulating cells, regardless of clonal identity.

## Abstract

CXCR5+ CD8+ T cells emerged as key mediators of antiviral immunity in the context of chronic infection. However, their functional attributes and tissue distribution remain incompletely defined, especially in relation to antigen specificity. Here, we investigated the anatomical localization and antiviral properties of CXCR5+ CD8+ T cells across multiple sites throughout the human body, with an emphasis on oropharyngeal lymphoid tissues. Tonsils harbored the highest frequencies of CXCR5+ CD8+ T cells compared to other tissues, many of which expressed Granzyme K and concurrently displayed tissue residency features, as demonstrated by single cell profiling. Irrespective of clonal identity and virus specificity, CD8+ T cells expressed CXCR5 more commonly in tonsils compared to vascular circulation. CXCR5 expression was particularly prominent among tonsil-localized CD8+ T cells targeting Epstein-Barr virus (EBV) latent antigens and associated with a PD-1+ resident stem-like phenotype. These data identify a CXCR5+ tissue-resident memory CD8+ T cell subset in human tonsils with a potential role in immune surveillance of EBV.

CXCR5+ memory CD8+ T cells in tonsils show stem-like resident traits and enrich for latent EBV antigen specificity.