Transcriptomic Analysis Identifies Tfrchi Acinar Population As Possible Driver of Terminal Exhaustion via CEACAM1-TIM-3 axis 2309656

Abstract Introduction Ocular graft-versus-host disease severity correlates with inflammation and fibrotic damage in the lacrimal gland (LG). Long-living stem-like progenitor exhausted TCF1+ PD-1+ T cells (Tpex) have been reported to maintain and replenish the reservoir of exhausted-like effector T cells (Texef). In chronic settings, the cumulative cytotoxicity of CD8+ Texef mediates tissue damage. A comprehensive characterization of the phenotypic and transcriptomic profiles of these pathogenic exhausted populations has not yet been reported. Methods To this end, we used an established minor MHC-mismatched murine model of sclerodermatous cGVHD (B10.D2 (H-2d) into BALB/c (H-2d), allogeneic (allo) cGVHD) using syngeneic (syn) controls (Balb/c into Balb/c) assessed at 14-, 21-, and 42-days post-transplant. Here, we longitudinally investigated transcriptional changes in exocrine tissue immune population. Results Microscopy identified increased lymphocyte infiltration in the lacrimal gland and conjunctiva. Single cell sequencing was performed on lacrimal gland. Datasets were processed using a robust integrative approach based on scVI deep learning architecture. We identified four distinct exhausted T cell subpopulations expanded in allo LG. Exhaustion, cytotoxic and residency scores were highest for these four subsets. Proportional distribution analysis revealed a substantial early increase in Tcf7+, Sell+, Il7r+, Slamf6+, Pdcd1+ CD8+ Tpex cells in the allo group. Importantly, allo lacrimal glands were marked by the expansion of Tcf7− CD8+ Texef cells that were not present in the syn group. Cell-cell communication analyses inferred an interaction between Tfrchi acinar cells and exhausted T cells through Ceacam1-Havcr2, signaling shown to drive terminal exhaustion of Texef. Conclusion Overall, scRNAseq results evince a major shift in T-cell fate towards a pathogenic exhausted-like phenotype possibly stemming from an early Tcf7+ expressing precursor exhausted population in cGVHD-affected LG. Funding Source Intramural program of the NIDCR, NIH Topic Categories Transplantation Immunology (TRAN)