734 research outputs found
Continuous Acquisition of MHC:Peptide Complexes by Recipient Cells Contributes to the Generation of Anti-Graft CD8+ T Cell Immunity
Understanding the evolution of the direct and indirect pathways of allorecognition following tissue transplantation is essential in the design of toleranceâpromoting protocols. On the basis that donor bone marrowâderived antigenâpresenting cells are eliminated within days of transplantation, it has been argued that the indirect response represents the major threat to longâterm transplant survival, and is consequently the key target for regulation. However, the detection of MHC transfer between cells, and particularly the capture of MHC:peptide complexes by dendritic cells (DCs), led us to propose a third, semidirect, pathway of MHC allorecognition. Persistence of this pathway would lead to sustained activation of directâpathway T cells, arguably persisting for the life of the transplant. In this study, we focused on the contribution of acquired MHCâclass I on recipient DCs during the life span of a skin graft. We observed that MHCâclass I acquisition by recipient DCs occurs for at least 1 month following transplantation and may be the main source of alloantigen that drives CD8(+) cytotoxic T cell responses. In addition, acquired MHCâclass I:peptide complexes stimulate T cell responses in vivo, further emphasizing the need to regulate both pathways to induce indefinite survival of the graft
Paleoelevation estimates for the northern and central protoâBasin and Range from carbonate clumped isotope thermometry
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99057/1/tect20016.pd
Inhibition of thrombin on endothelium enhances recruitment of regulatory T cells during IRI and when combined with adoptive Treg transfer, significantly protects against acute tissue injury and prolongs allograft survival
Ischemia-reperfusion injury (IRI) amplifies T cell alloimmune responses after transplantation with thrombin playing a key pro-inflammatory role. To explore the influence of thrombin on regulatory T cell recruitment and efficacy we used a well-established model of IRI in the native murine kidney. Administration of the cytotopic thrombin inhibitor PTL060 inhibited IRI, and by skewing expression of chemokines (reducing CCL2 and CCL3 but increasing CCL17 and CCL22) increased the infiltration of M2 macrophages and Tregs. When PTL060 was combined with infusion of additional Tregs, these effects were further amplified. To test the benefits of thrombin inhibition in a transplant model, BALB/c hearts were transplanted into B6 mice with or without perfusion with PTL060 in combination with Tregs. Thrombin inhibition or Treg infusion alone led to small increments in allograft survival. However, the combined therapy led to modest graft prolongation by the same mechanisms as in renal IRI; graft survival was accompanied by increased numbers of Tregs and anti inflammatory macrophages, and reduced expression of pro-inflammatory cytokines.
While the grafts succumbed to rejection associated with the emergence of alloantibody, these data suggest that thrombin inhibition within the transplant vasculature enhances the efficacy of Treg infusion, a therapy that is currently entering the clinic to promote transplant tolerance
Diversity of gut microflora is required for the generation of B cell with regulatory properties in a skin graft model
B cells have been reported to promote graft rejection through alloantibody production. However, there is growing evidence that B cells can contribute to the maintenance of tolerance. Here, we used a mouse model of MHC-class I mismatched skin transplantation to investigate the contribution of B cells to graft survival. We demonstrate that adoptive transfer of B cells prolongs skin graft survival but only when the B cells were isolated from mice housed in low sterility "conventional" (CV) facilities and not from mice housed in pathogen free facilities (SPF). However, prolongation of skin graft survival was lost when B cells were isolated from IL-10 deficient mice housed in CV facilities. The suppressive function of B cells isolated from mice housed in CV facilities correlated with an anti-inflammatory environment and with the presence of a different gut microflora compared to mice maintained in SPF facilities. Treatment of mice in the CV facility with antibiotics abrogated the regulatory capacity of B cells. Finally, we identified transitional B cells isolated from CV facilities as possessing the regulatory function. These findings demonstrate that B cells, and in particular transitional B cells, can promote prolongation of graft survival, a function dependent on licensing by gut microflora
Immunogenicity of retransplanted rat kidney allografts. Effect of inducing chimerism in the first recipient and quantitative studies on immunosuppression of the second recipient.
Radiolabelling of Polyclonally Expanded Human Regulatory T Cells (Treg) with âžâčZr-oxine for Medium-Term In Vivo Cell Tracking
Regulatory T cells (Tregs) are a promising candidate cell therapy to treat autoimmune diseases and aid the longevity of transplanted solid organs. Despite increasing numbers of clinical trials using human Treg therapy, important questions pertaining to their in vivo fate, distribution, and function remain unanswered. Treg accumulation in relevant tissues was found to be crucial for Treg therapy efficacy, but existing blood-borne biomarkers are unlikely to accurately reflect the tissue state. Non-invasive Treg tracking by whole-body imaging is a promising alternative and can be achieved by direct radiolabelling of Tregs and following the radiolabelled cells with positron emission tomography (PET). Our goal was to evaluate the radiolabelling of polyclonal Tregs with âžâčZr to permit their in vivo tracking by PET/CT for longer than one week with current preclinical PET instrumentation. We used [âžâčZr]Zr(oxinate)â as the cell-labelling agent and achieved successful radiolabelling efficiency of human Tregs spanning 0.1â11.1 Bq âžâčZr/Treg cell, which would be compatible with PET tracking beyond one week. We characterized the âžâčZr-Tregs, assessing their phenotypes, and found that they were not tolerating these intracellular âžâčZr amounts, as they failed to survive or expand in a âžâčZr-dose-dependent manner. Even at 0.1 Bq âžâčZr per Treg cell, while âžâčZr-Tregs remained functional as determined by a five-day-long effector T cell suppression assay, they failed to expand beyond day 3 in vitro. Moreover, PET imaging revealed signs of âžâčZr-Treg death after adoptive transfer in vivo. In summary, âžâčZr labelling of Tregs at intracellular radioisotope amounts compatible with cell tracking over several weeks did not achieve the desired outcomes, as âžâčZr-Tregs failed to expand and survive. Consequently, we conclude that indirect Treg labelling is likely to be the most effective alternative method to satisfy the requirements of this cell tracking scenario
Nox2-deficient Tregs improve heart transplant outcomes via their increased graft recruitment and enhanced potency
Nox2 is a ROS-generating enzyme, deficiency of which increases suppression by Tregs in vitro and in an in vivo model of cardiac remodelling. Since Tregs have emerged as a candidate therapy in autoimmunity and transplantation, we hypothesised that Nox2 deficiency in Tregs in recipient mice may improve outcomes in a heart transplant model. A novel B6129 mouse model with Treg-targeted Nox2 deletion (Nox2ᶠ˥/ᶠ˥FoxP3Creâș) was generated and transplanted with hearts from CB6F1 donors. As compared to littermate controls, Nox2ᶠ˥/ᶠ˥FoxP3Creâș mice had lower plasma levels of alloantibodies and troponin-I, reduced levels of IFN-Îł in heart allograft homogenates and diminished cardiomyocyte necrosis and allograft fibrosis. Single cell analyses of allografts revealed higher absolute numbers of Tregs and lower CD8âș T cell infiltration in Nox2-deficient recipients compared to Nox2-replete mice. Mechanistically, in addition to a greater suppression of CD8âșCD25â» T effector cell proliferation and IFN-Îł production, Nox2-deficient Tregs expressed higher levels of CCR4 and CCR8, driving cell migration to allografts; this was associated with increased expression of miR214-3p. These data indicate that Nox2 deletion in Tregs enhances their suppressive ability and migration to heart allografts. Therefore, Nox2 inhibition in Tregs may be a useful approach to improve their therapeutic efficacy
Spatiotemporal in vivo tracking of polyclonal human regulatory T cells reveals a role for innate immune cells in Treg transplant recruitment
Regulatory T cells (Tregs) are emerging as a new cell-based therapy in solid organ transplantation. Adoptive transfer of Tregs was shown preclinically to protect from graft rejection, and the safety of Treg therapy has been demonstrated in clinical trials. Despite these successes, the in vivo distribution and persistence of adoptively transferred Tregs remained elusive which hampers clinical translation. Here, we isolated human Tregs using a GMP-compatible protocol and lentivirally transduced them with the human sodium iodide symporter to render them traceable in vivo by radionuclide imaging. Engineered human Tregs were characterized for phenotype, survival, suppressive capacity, and reporter function. To study their trafficking behaviour, they were subsequently administered to humanized mice with human skin transplants. Traceable Tregs were quantified in skin grafts by non-invasive nanoSPECT/CT for up to 40 days and results validated ex vivo. Using this approach, we demonstrated that Treg trafficking to skin grafts was regulated by the presence of recipient Gr-1âș innate immune cells. We demonstrated the utility of radionuclide reporter gene afforded quantitative Treg in vivo tracking thereby addressing a fundamental need in Treg therapy development and offering clinically compatible methodology for future Treg therapy imaging in humans
Aging Impairs Recipient T Cell Intrinsic and Extrinsic Factors in Response to Transplantation
As increasing numbers of older people are listed for solid organ transplantation, there is an urgent need to better understand how aging modifies alloimmune responses. Here, we investigated whether aging impairs the ability of donor dendritic cells or recipient immunity to prime alloimmune responses to organ transplantation.Using murine experimental models, we found that aging impaired the host environment to expand and activate antigen specific CD8(+) T cells. Additionally, aging impaired the ability of polyclonal T cells to induce acute allograft rejection. However, the alloimmune priming capability of donor dendritic cells was preserved with aging.Aging impairs recipient responses, both T cell intrinsic and extrinsic, in response to organ transplantation
B lymphocytes contribute to indirect pathway T cell sensitisation via acquisition of extracellular vesicles
B cells have been implicated in transplant rejection via antibodyâmediated mechanisms and more recently by presenting donorâantigens to T cells. We have shown in patients with chronic antibodyâmediated rejection that B cells control the indirect T cell alloresponses. To understand more about the role of B cells as antigen presenting cells for CD4âș T cell with indirect allospecificity, B cells were depleted in C57BL/6 mice, using an antiâCD20 antibody, prior to receiving MHCâclass Iâmismatched (Ká”) skin. The absence of B cells at the time of transplantation prolonged skin graft survival. To study the mechanisms behind this observation, T cells with indirect allospecificity were transferred in mice receiving a Ká” skin transplant. T cell proliferation was markedly inhibited in the absence of recipient B cells, suggesting that B cells contribute to indirect pathway sensitisation. Furthermore, we have shown that a possible way in which B cells present alloantigens is via acquisition of MHCâpeptide complexes. Finally, we demonstrate that the addition of B cell depletion to the transfer of Tregs with indirect alloresponse further prolonged skin graft survival. This study supports an important role for B cells in indirect T cell priming and further emphasises the advantage of combination therapies in prolonging transplant survival
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