# Circulating ex-Trm CD8 + T cells with skin-homing/chemoattraction phenotype are associated with disease severity in atopic dermatitis

## TL;DR

This study finds that a specific type of immune cell, CD8+ ex-Trm cells, is linked to more severe atopic dermatitis and may help track disease progression.

## Contribution

The study identifies CD8+ ex-Trm cells as a novel biomarker for disease severity in atopic dermatitis.

## Key findings

- CD8+ ex-Trm cells with skin-homing markers are increased in moderate-to-severe atopic dermatitis.
- These CD8+ cells correlate with clinical severity and may sustain inflammation by reseeding skin sites.
- CD4+ ex-Trm cells do not show similar expansion and may stay in inflamed skin.

## Abstract

Atopic dermatitis (AD) is a chronic inflammatory skin disease driven by skin-homing memory T cells. Recent evidence suggests that a subset of tissue-resident memory T (Trm) cells can exit tissues and recirculate as ex-Trm cells.

Peripheral blood memory T cell subpopulations were analyzed in adults with AD, stratified by disease severity, using multiparametric flow cytometry. CD4+ and CD8+ memory subsets and the skin-homing markers CLA, CCR4, and CCR10 were evaluated.

Overall CD4+ and CD8+ memory T cell distributions were preserved. AD patients showed expansion of CD4+ central memory T cells expressing CLA, CCR4, and CCR10. Most notably, a circulating population of CD8+ ex-Trm cells co-expressing CLA, CCR4, and CCR10 was increased in moderate-to-severe disease and correlated positively with clinical severity. No comparable expansion was observed for CD4+ ex-Trm cells.

Circulating CD8+ ex-Trm cells with skin-homing properties may contribute to AD progression by reseeding distant skin sites and sustaining inflammation, whereas CD4+ ex-Trm cells may remain preferentially retained within inflamed skin. These findings identify circulating CD8+ ex-Trm cells as potential biomarkers of disease severity and disease dissemination.