IL15-mediated crosstalk between LSECs and CD8⁺ tissue-resident memory T cells drives alcohol-associated hepatitis.

BACKGROUND

Alcohol-associated hepatitis (AH) is a severe inflammatory liver condition driven by dysregulated immune responses. CD8 T cells accumulate in the liver during AH, yet their functional role remains poorly defined.

METHODS

A murine NIAAA chronic-binge model with lipopolysaccharide (LPS) challenge was used. Single-cell RNA sequencing of liver and blood immune cells defined CD8 T cell subsets, followed by pathway analysis and reanalysis of human AH datasets. Spatial relationships were validated by immunohistochemistry of human AH liver tissue with CD8 TRM and liver sinusoidal endothelial cell (LSEC) co-staining. LSEC-CD8 T cell interactions were examined using in vitro co-culture, and signaling pathways were assessed by bulk RNA sequencing and phospho-protein analyses. IL15 function was evaluated by in vivo neutralization.

RESULTS

Single-cell RNA sequencing in the murine AH model revealed a distinct population of CD8 tissue-resident memory T cells (TRM) with heightened activation and proinflammatory cytokine production. Analysis of human AH liver single-cell RNA sequencing data, along with immunohistochemistry validation, supported CD8 TRM enrichment in diseased tissue. IL15 emerged as a prominent pathway linked to TRM activation, and IL15 blockade reduced TRM abundance and attenuated EtOH/ lipopolysaccharide-induced liver injury. Mechanistically, LSECs not only provided a structural niche for TRM retention but also amplified IL15 signalling. In vitro, coculture experiments demonstrated that LSECs intensified activation in pre-stimulated CD8 T cells in a stimulus-dependent manner: under IL15 stimulation, LSECs boosted effector function without inducing cell death, whereas under T-cell receptor stimulation, LSECs drove hyperactivation and activation-induced cell death. Bulk RNA-seq and phospho-protein analysis identified the PI3K-AKT pathway as a shared pathway enhanced by LSEC coculture in activated CD8 T cells. These findings define a context-dependent mechanism in which LSECs promote IL15-driven signaling through AKT pathway amplification, promoting TRM persistence and inflammatory activity in AH.

CONCLUSIONS

IL15-associated signaling within the hepatic microenvironment, shaped by LSEC-CD8 T-cell interactions, promotes activation and persistence of CD8 TRM cells in AH. Targeting the IL15-LSEC-AKT axis may disrupt pathogenic TRM niches and represent a promising therapeutic strategy for severe AH.