Organ-specific microenvironments drive divergent T cell evolution in acute graft-versus-host disease

Tissue-specific T cell immune responses play a critical role in maintaining organ health but can also drive immune pathology during both autoimmunity and alloimmunity. The mechanisms controlling intratissue T cell programming remain unclear. Here, we leveraged a nonhuman primate model of acute graft-versus-host disease (aGVHD) after allogeneic hematopoietic stem cell transplantation to probe the biological underpinnings of tissue-specific alloimmune disease using a comprehensive systems immunology approach including multiparameter flow cytometry, population-based transcriptional profiling, and multiplexed single-cell RNA sequencing and TCR sequencing. Transcriptional profiling revealed substantial biological differences between T cells infiltrating the lung and liver during aGVHD. These included enrichment for transcriptional pathways controlling extracellular matrix remodeling and chemotaxis in the lung and enrichment for transcriptional pathways linked to nucleic acid metabolism and proliferation in the liver. Single-cell RNA sequencing and TCR sequencing substantiated divergent organ-specific transcriptional programing of tissue-infiltrating T cells, which was linked to clonal expansion, with expanded clones progressively enriched for <i>C-X3-C motif chemokine receptor 1</i> (<i>CX3CR1</i>)-expressing CD8 effector T cells in the lung and <i>eomesodermin</i> (<i>EOMES</i>)-expressing CD8 effector-memory T cells in the liver. This divergent evolution of T cells was maintained even for T cells sharing the same TCRs, indicating its independence from antigen specificity. Together, these results provide insights into the role that tissue microenvironment-derived signals play in local T cell transcriptional programming during alloimmune-mediated clonal expansion and suggest potential opportunities to develop tissue-specific therapeutics to curtail pathogenic immunity after transplant.