Pathogenic Tissue-Resident Memory T Cells in Exocrine Gland Chronic Graft-Versus-Host Disease

Abstract

Abstract Salivary glands are frequently affected in chronic graft-versus-host disease (cGVHD), an autoimmune-like disease that occurs after allogeneic hematopoietic stem cell transplant resulting in tissue sclerosis and gland dysfunction. Alloreactive T cells have been identified as disease drivers, yet the function/pathogenicity of tissue-resident memory cells (Trm) in target organs remain unclear. In this study, we examined glandular Trm populations and tissue-specific signals that regulate Trm differentiation and functionality. scRNAseq analysis of human labial minor salivary glands (MSG) revealed enrichment of immune cell clusters in MSG of oral cGVHD patients. Focusing on T CD8 cells, we identified 4 clusters, one of them unique to affected patients which had low expression of CD69, but expressed other markers of Trm, including CD103, BLIMP1 and PD1. Additionally, this cluster was enriched for genes associated with cytotoxicity (IFNG, PRF1 and GZMB) and exhaustion (TIM3, LAG3 and TIGIT). Interestingly, this population showed high expression of CXCR6 and ligand-receptor analysis predicted CXCL16 an important signaling ligand that targets T CD8 cells. Further analysis implicates macrophages as the main source of CXCL16, suggesting their role in local accumulation of CXCR6+ Trm in the gland. Flow cytometry confirmed increased number of CD69+CD103±CD8+ Trm cells in cGVHD patients. Lymphocytic infiltration in MSG using IHC, spatially related the elevated frequency of CD8+IFNg+ T cells within interacinar stroma and damaged acini. The importance of Trm in site-specific cGVHD still needs further investigation. Based on current data, site-specific Trm cells may represent a druggable target in the therapy of refractory local cGVHD. Supported by NIDCR (1ZIADE000747-05)