Resident memory T cells form during persistent antigen exposure leading to allograft rejection
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ABSTRACT: Tissue resident memory T cells (TRM) contained at sites of previous infection provide local protection against re-infection. Whether they form and function in organ transplants where cognate antigen persists is unclear. This is a key question in transplantation as T cells are detected long-term in allografts, but it is not known whether they are exhausted or are functional memory T cells. Using a mouse model of kidney transplantation, we showed that antigen-specific and polyclonal effector T cells differentiated in the graft into TRM and subqeuntly caused allograft rejection. TRM identity was established by surface phenotype, transcriptional profile, and inability to recirculate in parabiosis and re-transplantation experiments. Graft TRM proliferated locally, produced IFNγ upon re-stimulation, and their in vivo depletion attenuated rejection. Importantly, the vast majority of antigen-specific and polyclonal TRM lacked phenotypic and transcriptional exhaustion markers. Single cell analysis of graft T cells early and late after transplantation identified a transcriptional program associated with transition to the tissue resident state that could serve as a platform for the discovery of therapeutic targets. Thus, recipient effector T cells differentiate into functional graft TRM that maintain rejection locally. Targeting these TRM could improve renal transplant outcomes.
Project description:The site of transition between tissue resident memory (TRM) and circulating phenotypes of T cells is unknown. We integrated clonotype, alloreactivity and gene expression profiles of graft-repopulating recipient T cells in the intestinal mucosa at the single cell level after human intestinal transplantation. Host-versus-graft (HvG)-reactive T cells mainly distributed to TRM, Teff/TRM and T follicular helper compartments. RNA velocity analysis demonstrated a trajectory from TRM to effector T (Teff)/TRM clusters in association with rejection. By integrating pre- and post-Tx mixed lymphocyte reaction-determined alloreactive repertoires, we observed that pre-existing HvG-reactive T cells that demonstrated tolerance in the circulation were dominated by TRM profiles in quiescent allografts. Putative de novo HvG-reactive clones showed a transcriptional profile skewed to cytotoxic effectors in rejecting grafts. Inferred protein regulon network analysis revealed upstream regulators that accounted for the effector and tolerant T cell states. We demonstrate Teff/TRM interchangeability for individual T cell clones with known (allo)recognition in human gut, providing novel insight into TRM biology.
Project description:The extent to which tissue-resident memory T (TRM) cells in transplanted organs possess alloreactivity is uncertain. This study investigates the alloreactive potential of TRM cells in kidney explants from four patients who experienced severe acute rejection leading to graft loss. Alloreactive T-cell receptors (TCRs) clones were identified in pre-transplant blood samples through mixed lymphocyte reactions, followed by single-cell RNA and TCR sequencing of the proliferated recipient T cells. Subsequently, these TCR clones were traced in the TRM cells of kidney explants, which were also subjected to single-cell RNA and TCR sequencing. The proportion of TRM cells expressing an alloreactive TCR in the four kidney explants varied from 0% to 9%. Notably, these alloreactive TCRs were predominantly found among CD4+ and CD8+ TRM cells with an effector phenotype. Intriguingly, alloreactive clones were present not only in recipient-derived TRM cells but also in donor-derived TRM cells, constituting up to 4% of the donor population, suggesting the presence of self-reactive TRM cells. Overall, our study demonstrates that T cells with alloreactive potential present in the peripheral blood prior to transplantation can infiltrate the kidney transplant and adopt a TRM phenotype.
Project description:Tissue resident memory T cells (TRM) maintain immunity in diverse sites as determined in mouse models, while their establishment and role in human tissues has been difficult to assess. Here, we investigated human lung TRM generation, maintenance and function in airway samples obtained longitudinally from HLA-disparate lung transplant recipients, where donor and recipient T cells could be localized and tracked over time. Donor T cells persist specifically in the lungs (and not blood) of transplant recipients and express high levels of TRM signature markers including CD69, CD103, and CD49a, while lung-infiltrating recipient T cells gradually acquire TRM phenotypes over months in vivo. Single cell transcriptome profiling of airway T cells reveals that donor T cells comprise two TRM-like subsets with varying levels of expression of TRM-associated genes while recipient T cells comprised non-TRM and similar TRM-like subpopulations, suggesting de novo TRM generation. Transplant recipients exhibiting higher frequencies of persisting donor TRM experienced fewer adverse clinical events such as primary graft dysfunction and acute cellular rejection compared to recipients with low donor TRM persistence, suggesting that monitoring TRM dynamics could be clinically informative. Together, our results provide novel spatial and temporal insights into how human TRM develop, function, persist, and impact tissue integrity within the complexities of lung transplantation.
Project description:Tissue-resident memory (TRM) T cells are emerging as critical components of the immune response to cancer; yet, requirements for their ongoing function and maintenance remain unclear. Antigen presenting cells (APC) promote TRM cell differentiation and re-activation but have not been implicated in sustaining TRM cell responses. Here, we identified a novel role for dendritic cells in supporting tissue resident memory to melanoma. We showed that CD8 TRM cells remain in close proximity to dendritic cells in the skin. Depletion of CD11c+ cells results in rapid disaggregation and eventual loss of melanoma-specific TRM cells. Additionally, we determined that TRM migration and/or persistence requires chemotaxis and adhesion mediated by the CXCR6/CXCL16 axis. The interaction between CXCR6-expressing TRM cells and CXCL16-expressing APCs was found to be critical for sustaining TRM cell-mediated tumor protection. These findings substantially expand our knowledge of APC functions in tissue resident memory T cell homeostasis and longevity.
Project description:Tissue-resident memory CD8+ T cells (TRM) constitute a non-circulating memory T cell subset that provides early protection against re-infection. However, how TRM arise from antigen-triggered T cells has remained unclear. Exploiting the TRM-restricted expression of Hobit, we developed TRM reporter/deleter mice to study TRM differentiation. We found that Hobit was upregulated in a subset of LCMV-specific T cells located within peripheral tissues during the effector phase of the immune response. These Hobit+ effector T cells were identified as TRM precursors, given that their depletion substantially decreased TRM development, but not the formation of circulating memory T cells. Adoptive transfer experiments of Hobit+ effector T cells corroborated their biased contribution to the TRM lineage. Transcriptional profiling of Hobit+ effector T cells underlined the early establishment of TRM properties including downregulation of tissue exit receptors and upregulation of TRM-associated molecules. Importantly, we identified Eomes as a key factor instructing the early bifurcation of circulating and resident lineages. These findings establish that commitment of TRM occurs early in antigen-driven T cell differentiation and reveal the molecular mechanisms underlying this differentiation pathway.
Project description:Graft acceptance without the need for immunosuppressive drugs is the ultimate goal of transplantation therapy. In murine liver transplantation, allografts are accepted across major histocompatibility antigen complex barriers without the use of immunosuppressive drugs and constitute a suitable model for research on immunological rejection and tolerance. MicroRNA (miRNA) has been known to be involved in the immunological responses. In order to identify mRNAs in spontaneous liver allograft tolerance, miRNA expression in hepatic allografts was examined using this transplantation model. According to the graft pathological score and function, miR-146a, 15b, 223, 23a, 27a, 34a and 451 were upregulated compared with the expression observed in the syngeneic grafts. In contrast, miR-101a, 101b and 148a were downregulated. Our results demonstrated the alteration of miRNAs in the allografts and may indicate the role of miRNAs in the induction of tolerance after transplantation. Furthermore, our data suggest that monitoring the graft expression of novel miRNAs may allow clinicians to differentiate between rejection and tolerance. A better understanding of the tolerance inducing mechanism observed in murine hepatic allografts may provide a therapeutic strategy for attenuating allograft rejection. B10.BR mice were used as donors and B10.D2 mice were used as recipients. Liver allo-transplantation surgery on the mice was performed in this combination. Three mice from each group were sacrificed, and the liver grafts were removed on days 5, 8, 14 and 100 after transplantation. Total RNA, including miRNA was isolated. 100ng of total RNA was labeled by Cy3 and used as probe for hybridization to the microarray.
Project description:Measurement of specific gene expression in clinical samples is a promising approach for monitoring the recipient immune status to the graft in organ transplantation. Identification of biomarker genes closely associated with tolerance or rejection is critical for this monitoring protocol. Unlike previous studies, our microarray analysis focused on donor antigen-reactive T cells, which were prepared by collecting CD69+ T cells from cocultures of recipient peripheral T cells and donor antigen-presenting cells. A comparison of different recipient groups enabled us to identify several tolerance- and rejection-correlated biomarker genes, including previously unknown genes. By measuring biomarker gene expression in the CD69+ T cell fraction using quantitative reverse-transcription polymerase chain reaction, we were able to precisely detect the immune status of recipients relative to their graft.
Project description:Measurement of specific gene expression in clinical samples is a promising approach for monitoring the recipient immune status to the graft in organ transplantation. Identification of biomarker genes closely associated with tolerance or rejection is critical for this monitoring protocol. Unlike previous studies, our microarray analysis focused on donor antigen-reactive T cells, which were prepared by collecting CD69+ T cells from cocultures of recipient peripheral T cells and donor antigen-presenting cells. A comparison of different recipient groups enabled us to identify several tolerance- and rejection-correlated biomarker genes, including previously unknown genes. By measuring biomarker gene expression in the CD69+ T cell fraction using quantitative reverse-transcription polymerase chain reaction, we were able to precisely detect the immune status of recipients relative to their graft.
Project description:Tissue-resident memory T cells (TRM) persist locally in non-lymphoid tissues where they provide front-line defense against recurring insults. TRM at barrier surfaces express the markers CD103 and/or CD69 which function to retain them in epithelial tissues. In humans, neither the long-term migratory behavior of TRM nor their ability to re-enter the circulation and potentially migrate to distant tissue sites have been investigated. Using tissue explant cultures, we found that CD4+CD69+CD103+ TRM in human skin can downregulate CD69 and exit the tissue. Additionally, we identified a skin-tropic CD4+CD69-CD103+ population in human lymph and blood that is transcriptionally, functionally and clonally related to the CD4+CD69+CD103+ TRM population in the skin. Using a skin xenograft model, we confirmed that a fraction of the human cutaneous CD4+CD103+ TRM population can re-enter circulation, and migrate to secondary human skin sites where they re-assume a TRM phenotype. Thus, our data challenge current concepts regarding the strict tissue compartmentalization of CD4+ T cell memory in humans.
Project description:Graft acceptance without the need for immunosuppressive drugs is the ultimate goal of transplantation therapy. In murine liver transplantation, allografts are accepted across major histocompatibility antigen complex barriers without the use of immunosuppressive drugs and constitute a suitable model for research on immunological rejection and tolerance. MicroRNA (miRNA) has been known to be involved in the immunological responses. In order to identify mRNAs in spontaneous liver allograft tolerance, miRNA expression in hepatic allografts was examined using this transplantation model. According to the graft pathological score and function, miR-146a, 15b, 223, 23a, 27a, 34a and 451 were upregulated compared with the expression observed in the syngeneic grafts. In contrast, miR-101a, 101b and 148a were downregulated. Our results demonstrated the alteration of miRNAs in the allografts and may indicate the role of miRNAs in the induction of tolerance after transplantation. Furthermore, our data suggest that monitoring the graft expression of novel miRNAs may allow clinicians to differentiate between rejection and tolerance. A better understanding of the tolerance inducing mechanism observed in murine hepatic allografts may provide a therapeutic strategy for attenuating allograft rejection.