A CD8+ CD27+ TIM-3+ T cell population expanded in chronically rejected human lung allografts 4126

Abstract Description Long-term survival in lung transplantation is limited by the eventual development of chronic lung allograft dysfunction (CLAD), resulting in the loss of the transplanted lung. We hypothesized that analysis of the pulmonary T cell transcriptome would reveal novel T cell populations that drive CLAD pathogenesis. Human lung tissue samples (9 CLAD, 5 donor as healthy control) were obtained and processed into single cell suspensions. T cells were enriched through magnetic selection of CD45+ leukocytes followed by fluorescence-activated cell sorting. Sorted cells then underwent 5’ single cell RNA sequencing (scRNAseq) using 10x Genomics. scRNAseq data was analyzed using Seurat. T cell clusters of interest were validated at the protein level using spectral flow cytometry Comparison between lung samples revealed a cluster that was only present in CLAD samples (6/9 CLAD lungs vs. 0/5 donor lungs, Fig A), characterized by RNA expression of CD8, CD27 and HAVCR2 (TIM-3, Fig B). Flow cytometry analysis of T cells from CLAD lungs (n = 3) and donor lungs (n = 4) similarly showed that CD8+ CD27+TIM-3+ T cells were uniquely present in CLAD lungs (Fig C). Utilizing pseudotime trajectroy analysis to examine cellular changes, this cluster appears to be terminally differentiated (Fig D). We conclude that a CD8+ T cell population expressing CD27 and TIM-3 is enriched in CLAD lung T cells. This phenotype is suggestive of a memory/exhaustion phenotype that could play an important role in CLAD. Funding Sources New Frontiers in Research Fund - Transformation Grant Topic Categories Transplantation Immunology (TRAN)