Project description:Acute and chronic rejection continue to represent serious challenges in transplant medicine. Current medical regimens focus on suppressing T-cell responses, lack effectiveness for some patients and impose significant risks of infection and malignancy. Recent studies have suggested that inhibition of co-stimulation pathways between antigen presenting cells (dendritic cells, macrophages, B-cells) and T-cells may serve as an effective strategy to prevent rejection by promoting allograft tolerance as opposed to simply suppressing immune responses. This concept has garnered excitement across the transplant community and demonstrated promising results in human renal transplant studies. A commonly used approach is inhibition of B7-CD28 and CD40-CD40L costimulatory pathways. Blocking these pathways leads to prolonged allograft survival in fully HLA-mismatched mouse heart transplantation models and non-human primates. There are important gaps in knowledge pertaining to mechanisms by which co-stimulation blockade modulates the recipient immune responses and confers donor organ tolerance. The precise immune cell populations and mechanisms responsible for induction and maintenance of donor organ tolerance remain incompletely understood. We have leveraged single cell RNA sequencing to dissect how traditional immunosuppression (cyclosporine) and co-stimulation blockade (CTLA-4 Ig, anti-CD40L neutralizing antibodies) differentially impact the immune landscape of the transplanted heart using a fully HLA-mismatched mouse model (Balb/c donor heart à B6 recipient). Analysis of these datasets demonstrated striking differences between these treatment regimens. Mice that received co-stimulation blockade displayed a marked increase in the abundance of classical dendritic cells (cDC1s and cDC2s). Compared to the cyclosporine treated group, these cells expressed negative regulators of T-cell stimulation including PDL1. Using recipient mice that lack either cDC1s or cDC2s, we found that cDC1s are absolutely required for co-stimulation blockade to confer long-term allograft survival and prevent recipient immune responses against the transplanted donor heart.
Project description:Allograft rejection has been an obstacle for the long-term survival of patients. CD70, a tumor necrosis factor (TNF) family member critically expressed on antigen-presenting cells and strongly but transiently up-regulated during lymphocyte activation, represents an important co-stimulatory molecule that induces effective T cell responses. We used a mouse heterotopic cardiac transplantation model to evaluate the effects of monotherapy with the antibody targeting mouse CD70 (FR70) on transplantation tolerance and its immunoregulatory activity. FR70-treated C3H recipient mice permanently accepted B6 fully mismatched cardiac allografts. Consistent with the graft survival, the infiltration of CD8+ T cells in the graft was reduced, dendritic cells were differentiated into a tolerogenic status, and the number of regulatory T cells was elevated both in the graft and the recipient's spleen. In addition, naïve C3H given an adoptive transfer of spleen cells from the primary recipients with FR70 treatment accepted a heart graft from a matching B6 donor but not third-party BALB/c mice. Our findings show that treatment with FR70 induced regulatory cells and inhibited cytotoxic T cell proliferation, which led to long-term acceptance of mouse cardiac allografts. These findings highlight the potential role of anti-CD70 antibodies as a clinically effective treatment for allograft rejection.
Project description:Classical dendritic cells may be found in mouse bone marrow and spleen. Due to the differences in their local environment, two populations may express different genes and potentially carry different functions We used microarrays to compare the gene expression profiles between myeloid dendritic cells and classical dendritic cells in spleen. Our data supported the hypothesis that bone marrow myeloid dendritic cells are enriched for the expression of certain sets of genes that may play specific functions in the bone marrow microenvironment
Project description:The mechanisms by which innate immune signals regulate alloimmune responses remain poorly understood. In the present study, we show by intravital 2-photon microscopy direct interactions between graft-infiltrating neutrophils and donor CD11c(+) dendritic cells (DCs) within orthotopic lung allografts immediately after reperfusion. Neutrophils isolated from the airways of lung transplantation recipients stimulate donor DCs in a contact-dependent fashion to augment their production of IL-12 and expand alloantigen-specific IFN-γ(+) T cells. DC IL-12 expression is largely regulated by degranulation and induced by TNF-α associated with the neutrophil plasma membrane. Extended cold ischemic graft storage enhances G-CSF-mediated granulopoiesis and neutrophil graft infiltration, resulting in exacerbation of ischemia-reperfusion injury after lung transplantation. Ischemia reperfusion injury prevents immunosuppression-mediated acceptance of mouse lung allografts unless G-CSF-mediated granulopoiesis is inhibited. Our findings identify granulopoiesis-mediated augmentation of alloimmunity as a novel link between innate and adaptive immune responses after organ transplantation.
Project description:The Australian Chronic Allograft Dysfunction (AUSCAD) study is an ongoing single centre cohort study at Westmead hospital in Australia. In this section of the study, we aimed to identify biomarkers for chronic allograft dysfunction in kidney transplant recipients. Our study recruited 136 patients, each having protocol renal allograft biopsies taken pre transplantation.