Autoimmunity to type V collagen (col(V)) is a major risk factor for lung allograft rejection. Although col(V)-induced oral tolerance abrogates rejection of minor histoincompatible lung transplants, its ability to prevent rejection of fully MHC incompatible lung allografts is unknown. Rat lung allografts fully incompatible at MHC class I and II loci (Brown Norway (RT1n)) were transplanted into untreated Wistar Kyoto rat recipients (WKY, RT1l), or WKY rats were fed col(V) pretransplantation. To determine whether col(V) enhanced cyclosporine (CsA)-mediated immune suppression, WKY rats were treated with low-dose CsA (5 mg/kg), post-transplant, or oral col(V) plus CsA. The data showed that in contrast to col(V) or CsA, col(V) plus low-dose CsA significantly prevented rejection pathology, down-regulated alloantigen-induced production of IFN-γ and IL-17A, and suppressed chemotaxis for lung macrophages in allograft bronchoalveolar lavage fluid that was associated with lower local levels of MCP-1 (CCL2). Col(V) plus CsA was associated with alloantigen-induced expression of IL-10 in mediastinal lymph node or splenic T cells, intragraft expression of IL-10 and Foxp3 in perivascular and peribronchiolar mononuclear cells, and constitutive production of IL-10 from allograft alveolar macrophages. These data demonstrate that col(V) enhances low-dose CsA-mediated immune suppression, and suggest a role for oral col(V) in immune modulation in lung transplantation.
Chemokines provide signals for activation and recruitment of effector cells into sites of inflammation, acting via specific G protein–coupled receptors. However, in vitro data demonstrating the presence of multiple ligands for a given chemokine receptor, and often multiple receptors for a given chemokine, have led to concerns of biologic redundancy. Here we show that acute cardiac allograft rejection is accompanied by progressive intragraft production of the chemokines interferon (IFN)-γ–inducible protein of 10 kD (IP-10), monokine induced by IFN-γ (Mig), and IFN-inducible T cell α chemoattractant (I-TAC), and by infiltration of activated T cells bearing the corresponding chemokine receptor, CXCR3. We used three in vivo models to demonstrate a role for CXCR3 in the development of transplant rejection. First, CXCR3-deficient (CXCR3−/−) mice showed profound resistance to development of acute allograft rejection. Second, CXCR3−/− allograft recipients treated with a brief, subtherapeutic course of cyclosporin A maintained their allografts permanently and without evidence of chronic rejection. Third, CXCR+/+ mice treated with an anti-CXCR3 monoclonal antibody showed prolongation of allograft survival, even if begun after the onset of rejection. Taken in conjunction with our findings of CXCR3 expression in rejecting human cardiac allografts, we conclude that CXCR3 plays a key role in T cell activation, recruitment, and allograft destruction.
receptors; chemokine; transplantation; rejection; CXC chemokine receptor 3
Vascularized bone marrow transplantation (VBMT) is widely accepted as an efficient means of establishing chimerism and inducing tolerance. However, the mechanism underlying is poorly understood. Recently, regulatory T cells (Tregs) have been shown to play an important role in regulating immune responses to allogeneic antigens. In this study, we explored the role of Tregs in the induction of tolerance in an allogeneic hind limb transplantation model.
Forty-eight Lewis rats were divided into 6 groups. They received isografts and allografts from Brown-Norway hind limbs. Recipients in groups 1 and 2 received isografts and those in the other groups received allografts. The bone components of donor limbs were kept intact in groups 1, 3, and 5 but removed before transplantation into groups 2, 4, and 6. Tapered cyclosporin A (CsA) was administered to recipients in groups 5 and 6 after transplantation. During the 100-day observation period, all isografts survived, but the allografts in groups 3 and 4 were rejected within 8 to 12 days. CsA-treated intact allografts survived rejection-free for more than 100 days, and CsA-treated allografts lacking bone elements were rejected within 2 months. Stable peripheral chimerism and myeloid chimerism were observed in group 5. Declining peripheral chimerism and a lack of myeloid chimerism were observed in group 6. Donor-specific Tregs were exclusively detected in both peripheral blood and in the spleens of long-term recipient rats in group 5, with an increased FoxP3 mRNA expression in the allografts. This was further demonstrated to be responsible for donor-specific hyporeactivity by in vitro one-way mixed lymphocyte reaction (MLR).
Bone components in the allogeneic hind limbs can induce myeloid chimerism and donor-specific Tregs may be essential to tolerance induction. The bone-removal hind limb model may be a suitable counterpart to the induction of tolerance in the study of limb transplantation.
In this study, we investigated whether the infusion of bone marrow-derived mesenchymal stem cells (MSCs), combined with transient immunosuppressant treatment, could suppress allograft rejection and modulate T-cell regulation in a swine orthotopic hemi-facial composite tissue allotransplantation (CTA) model.
Outbred miniature swine underwent hemi-facial allotransplantation (day 0). Group-I (n = 5) consisted of untreated control animals. Group-II (n = 3) animals received MSCs alone (given on days −1, +1, +3, +7, +14, and +21). Group-III (n = 3) animals received CsA (days 0 to +28). Group-IV (n = 5) animals received CsA (days 0 to +28) and MSCs (days −1, +1, +3, +7, +14, and +21). The transplanted face tissue was observed daily for signs of rejection. Biopsies of donor tissues and recipient blood sample were obtained at specified predetermined times (per 2 weeks post-transplant) or at the time of clinically evident rejection. Our results indicated that the MSC-CsA group had significantly prolonged allograft survival compared to the other groups (P<0.001). Histological examination of the MSC-CsA group displayed the lowest degree of rejection in alloskin and lymphoid gland tissues. TNF-α expression in circulating blood revealed significant suppression in the MSC and MSC-CsA treatment groups, as compared to that in controls. IHC staining showed CD45 and IL-6 expression were significantly decreased in MSC-CsA treatment groups compared to controls. The number of CD4+/CD25+ regulatory T-cells and IL-10 expressions in the circulating blood significantly increased in the MSC-CsA group compared to the other groups. IHC staining of alloskin tissue biopsies revealed a significant increase in the numbers of foxp3+T-cells and TGF-β1 positive cells in the MSC-CsA group compared to the other groups.
These results demonstrate that MSCs significantly prolong hemifacial CTA survival. Our data indicate the MSCs did not only suppress inflammation and acute rejection of CTA, but also modulate T-cell regulation and related cytokines expression.
Although mononuclear cell infiltration is a hallmark of cellular rejection of a vascularized allograft, efforts to inhibit rejection by blocking leukocyte-endothelial cell adhesion have proved largely unsuccessful, perhaps in part because of persistent generation of chemokines within rejecting grafts. We now provide, to our knowledge, the first evidence that in vivo blockade of specific chemokine receptors is of therapeutic significance in organ transplantation. Inbred mice with a targeted deletion of the chemokine receptor CCR1 showed significant prolongation of allograft survival in 4 models. First, cardiac allografts across a class II mismatch were rejected by CCR1+/+ recipients but were accepted permanently by CCR1–/– recipients. Second, CCR1–/– mice rejected completely class I– and class II–mismatched BALB/c cardiac allografts more slowly than control mice. Third, levels of cyclosporin A that had marginal effects in CCR1+/+ mice resulted in permanent allograft acceptance in CCR1–/– recipients. These latter allografts showed no sign of chronic rejection 50–200 days after transplantation, and transfer of CD4+ splenic T cells from these mice to naive allograft recipients significantly prolonged allograft survival, whereas cells from CCR1+/+ mice conferred no such benefit. Finally, both CCR1+/+ and CCR1–/– allograft recipients, when treated with a mAb to CD4, showed permanent engraftment, but these allografts showed florid chronic rejection in the former strain and were normal in CCR1–/– mice. We conclude that therapies to block CCR1/ligand interactions may prove useful in preventing acute and chronic rejection clinically.
Blocking the CD28-B7 T cell costimulatory pathway with the fusion protein CTLA4Ig inhibits alloimmune responses in vitro and in vivo and induces tolerance to cardiac allografts in mice and rats, but the mechanisms mediating the tolerant state in vivo are unknown. Here, we report the effects and potential mechanisms of CTLA4Ig in the rat renal allograft model. LEW rats were nephrectomized and received renal allografts from major histocompatibility complex-incompatible WF rats. While all untreated and control immunoglobulin (Ig)-treated animals acutely rejected their allografts and died, 86% of rats that received a single injection of CTLA4Ig on day 2 after transplantation had prolonged survival (> 60-100 days) with preserved renal function. By contrast, only 29% of animals that received CTLA4Ig on the day of engraftment had prolonged survival. Long-term survivors (> 100 days) exhibited donor-specific tolerance, accepting donor-matched WF but acutely rejecting third-party BN cardiac allografts. Immunohistological analysis of grafts sampled at 1 week after transplantation showed that both control and CTLA4Ig-treated animals had mononuclear cell infiltrates, with a higher percentage of CD4+ cells in the CTLA4Ig- treated group. However, while this was associated with vasculitis and tubulitis in control grafts, there was no evidence of tissue injury in CTLA4Ig-treated animals. The immune response leading to graft rejection in control animals was characterized by expression of the T helper (Th) type 1 cytokines interleukin (IL)-2 and interferon-gamma. In contrast, the persistent CD4+ infiltrate without graft rejection in CTLA4Ig- treated animals was associated with increased staining for the Th2- related cytokines IL-4 and IL-10. Furthermore, grafts from CTLA4Ig- treated animals had marked upregulation of intragraft staining for IgG1, but not IgG2a or IgG2b. Administration of rIL-2 to CTLA4Ig- treated animals restored allograft rejection in 50% of animals tested. These results confirm that blockade of the CD28-B7 pathway after alloantigenic challenge induces donor-specific acceptance of vascularized organ allografts, and indicates in this model that CTLA4Ig inhibits Th1 but spares Th2 cytokines in vivo.
Lymphocyte activation is regulated by costimulatory and inhibitory receptors of which both B and T lymphocyte attenuator (BTLA) and CD160 engage Herpesvirus entry mediator (HVEM). Notably, it remains unclear how HVEM functions with each of its ligands during immune responses. Here, we show that HVEM specifically activates CD160 on effector NK cells challenged with virus-infected cells. Human CD56dim NK cells were costimulated specifically by HVEM, but not by other receptors that share the HVEM ligands LIGHT, Lymphotoxin-α, or BTLA. HVEM enhanced human NK cell activation by type I IFN and IL-2, resulting in increased IFN-γ and TNF-α secretion, and tumor cell-expressed HVEM activated CD160 in a human NK cell line causing rapid hyper-phosphorylation of serine kinases ERK1/2 and AKT, and enhanced cytolysis of target cells. In contrast, HVEM activation of BTLA reduced cytolysis of target cells. Together, our results demonstrate that HVEM functions as a regulator of immune function that activates NK cells via CD160, and limits lymphocyte-induced inflammation via association with BTLA.
The interaction between the tumor necrosis factor (TNF) family member LIGHT and the TNF family receptor herpes virus entry mediator (HVEM) co-stimulates T cells and promotes inflammation. However, HVEM also triggers inhibitory signals by acting as a ligand that binds to B and T lymphocyte attenuator (BTLA), an immunoglobulin super family member. The contribution of HVEM interacting with these two binding partners in inflammatory processes remains unknown. In this study, we investigated the role of HVEM in the development of colitis induced by the transfer of CD4+CD45RBhigh T cells into recombination activating gene (Rag)−/− mice. Although the absence of HVEM on the donor T cells led to a slight decrease in pathogenesis, surprisingly, the absence of HVEM in the Rag−/− recipients led to the opposite effect, a dramatic acceleration of intestinal inflammation. Furthermore, the critical role of HVEM in preventing colitis acceleration mainly involved HVEM expression by radioresistant cells in the Rag−/− recipients interacting with BTLA. Our experiments emphasize the antiinflammatory role of HVEM and the importance of HVEM expression by innate immune cells in preventing runaway inflammation in the intestine.
The inhibitory cosignaling pathway formed between the TNF receptor herpesvirus entry mediator (HVEM, TNFRSF14) and the Ig superfamily members, B and T lymphocyte attenuator (BTLA) and CD160, limits the activation of T cells. However, BTLA and CD160 can also serve as activating ligands for HVEM when presented in trans by adjacent cells, thus forming a bidirectional signaling pathway. BTLA and CD160 can directly activate the HVEM-dependent NF-κB RelA transcriptional complex raising the question of how NF-κB activation is repressed in naive T cells. In this study, we show BTLA interacts with HVEM in cis, forming a heterodimeric complex in naive T cells that inhibits HVEM-dependent NF-κB activation. The cis-interaction between HVEM and BTLA is the predominant form expressed on the surface of naive human and mouse T cells. The BTLA ectodomain acts as a competitive inhibitor blocking BTLA and CD160 from binding in trans to HVEM and initiating NF-κB activation. The TNF-related ligand, LIGHT (homologous to lymphotoxins, exhibits inducible expression, and competes with HSV glycoprotein D for HVEM, a receptor expressed by T lymphocytes, or TNFSF14) binds HVEM in the cis-complex, but NF-κB activation was attenuated, suggesting BTLA prevents oligomerization of HVEM in the cis-complex. Genetic deletion of BTLA or pharmacologic disruption of the HVEM-BTLA cis-complex in T cells promoted HVEM activation in trans. Interestingly, herpes simplex virus envelope glycoprotein D formed a cis-complex with HVEM, yet surprisingly, promoted the activation NF-κB RelA. We suggest that the HVEM-BTLA cis-complex competitively inhibits HVEM activation by ligands expressed in the surrounding microenvironment, thus helping maintain T cells in the naive state.
To investigate the effects of topical FTY720 and cyclosporin A (CsA) on allogeneic corneal transplantation in mice.
A total of 75 BALB/c mice received corneal grafts from C57BL/6 donors. Recipients were treated with 0.1%, 0.3%, or 0.5% FTY720 ophthalmic gel or 1% CsA eye-drops after the graft (controls received no treatment). The number of cluster of differentiation (CD)4+ T cells and CD4+CD25+forkhead box P3 (Foxp3)+ regulatory (Treg) cell phenotypes were measured by flow cytometry. Cytokine mRNA expression in corneal grafts was analyzed by real-time quantitative PCR. CD4 + T cells and cytokines in corneal samples were identified by immunohistochemical staining.
Corneal graft survival was prolonged by treatment with topical 0.5% FTY720 (mean survival time [MST], 24.1±1.6 days) or 1% CsA eye-drops (MST 25.0±1.9 days) compared with controls (MST, 13.4±0.5 days; n=9, both p<0.01). Topical 0.5% FTY720 treatment significantly increased the percentages of CD4 + T (p<0.05) and Treg cells (p<0.01; n=5) in the cervical lymph nodes compared with controls. Transforming growth factor-β1 (TGF-β1) mRNA transcription in corneal grafts after topical 0.5% FTY720 increased (p<0.05, n=3), while interleukin-2 (IL-2) and interferon-γ (IFN-γ) mRNA expression in corneal grafts treated with 1% CsA decreased (p<0.01, p<0.05, respectively). These cytokine results were paralleled by similar immunohistochemical staining. Topical 0.5% FTY720 and 1% CsA treatment reduced the infiltration of CD4+ Tcells in the grafts.
Topical 0.5% FTY720 and 1% CsA can effectively prolong allogeneic corneal graft survival in mice. Treatment with topical 0.5% FTY720 increases the percentage of CD4+ T cells and the percentage of Treg cells in cervical lymph nodes. The 0.5% FTY720 increased TGF-β1 mRNA expression and decreases infiltration of CD4+ T cells in corneal grafts, while topical 1% CsA down-regulated the expression of IL-2 and IFN-γ.
Blocking HVEM–LIGHT interactions on T cells reduces the persistence of antigen-specific memory T cell populations after secondary expansion through decreased Akt activity and loss of Bcl-2 expression.
Memory T helper cells (Th cells) play an important role in host defense against pathogens but also contribute to the pathogenesis of inflammatory disorders. We found that a soluble decoy lymphotoxin β receptor (LT-βR)–Fc, which can block tumor necrosis factor (TNF)–related ligands LIGHT (TNFSF14) and LT-αβ binding to the herpesvirus entry mediator (HVEM) and the LT-βR, inhibited the accumulation of memory Th2 cells after antigen encounter and correspondingly reduced inflammatory responses in vivo. Showing that this was a function of the receptor for LIGHT, antigen-specific memory CD4 T cells deficient in HVEM were also unable to persist, despite having a normal immediate response to recall antigen. HVEM−/− memory Th2 cells displayed reduced activity of PKB (protein kinase B; Akt), and constitutively active Akt rescued their survival and restored strong inflammation after antigen rechallenge. This was not restricted to Th2 memory cells as HVEM-deficient Th1 memory cells were also impaired in surviving after encounter with recall antigen. Furthermore, the absence of LIGHT on T cells recapitulated the defect seen with the absence of HVEM, suggesting that activated T cells communicate through LIGHT–HVEM interactions. Collectively, our results demonstrate a critical role of HVEM signals in the persistence of large pools of memory CD4 T cells.
Female donors and recipients have increased risk of acute rejection and subsequent chronic allograft nephropathy (CAN), especially when cyclosporine A (CsA) is used. Decreased renal nitric oxide (NO) production is associated with chronic kidney disease. In the present study, we investigated the impact of gender, CsA dose and renal NO synthase (NOS) on CAN.Kidneys from male and female F344 rats were transplanted into same-sex Lewis allograft or F344 isograft recipients and recipient rats were treated with 1.5 or 3 mg/kg per day CsA for 10 days. Grafts were removed at 22 weeks post-transplantation. Normal two-kidney F344 rats were investigated as age-matched controls.Low-dose CsA was associated with accelerated CAN in female rats compared with male rats; however, with high-dose CsA, allograft females had similar pathology/function to allograft males. Isograft females (similar to isograft males) had no graft failure and only slightly, albeit significantly, greater injury than age-matched controls. Isograft females had higher renal cortical neuronal (n) NOS but lower medullary endothelial (e) NOS than isograft males. There was no difference in renal eNOS and nNOS between allograft groups.In conclusion, 1.5 mg/kg per day CsA is not sufficient to prevent early graft loss in females. When the dose of CsA is doubled, allograft females and males have similar post-transplant survival. Renal NOS expression was unremarkable in any transplant group.
cyclosporine; immunosuppression; kidney transplantation; sex difference
Costimulation blockade protocols are effective in prolonging allograft survival in animal models and are entering clinical trials, but how environmental perturbants affect graft survival remains largely unstudied. We used a costimulation blockade protocol consisting of a donor-specific transfusion and anti-CD154 mAb to address this question. We observed that lymphocytic choriomeningitis virus infection at the time of donor-specific transfusion and anti-CD154 mAb shortens allograft survival. Lymphocytic choriomeningitis virus 1) activates innate immunity, 2) induces allo-cross-reactive T cells, and 3) generates virus-specific responses, all of which may adversely affect allograft survival. To investigate the role of innate immunity, mice given costimulation blockade and skin allografts were coinjected with TLR2 (Pam3Cys), TLR3 (polyinosinic:polycytidylic acid), TLR4 (LPS), or TLR9 (CpG) agonists. Costimulation blockade prolonged skin allograft survival that was shortened after coinjection by TLR agonists. To investigate underlying mechanisms, we used “synchimeric” mice which circulate trace populations of anti-H2b transgenic alloreactive CD8+ T cells. In synchimeric mice treated with costimulation blockade, coadministration of all four TLR agonists prevented deletion of alloreactive CD8+ T cells and shortened skin allograft survival. These alloreactive CD8+ T cells 1) expressed the proliferation marker Ki-67, 2) up-regulated CD44, and 3) failed to undergo apoptosis. B6.TNFR2−/− and B6.IL-12R−/− mice treated with costimulation blockade plus LPS also exhibited short skin allograft survival whereas similarly treated B6.CD8α−/− and TLR4−/− mice exhibited prolonged allograft survival. We conclude that TLR signaling abrogates the effects of costimulation blockade by preventing alloreactive CD8+ T cell apoptosis through a mechanism not dependent on TNFR2 or IL-12R signaling.
Mesenchymal stem cells (MSCs) are suggested to be immune modulators because of their therapeutic potential in transplantation. In the present study, we evaluated the therapeutic potential of autologous MSCs for preventing graft rejection after allogeneic rat islet transplantation. We assessed the ability of MSCs to elicit an antiproliferative response in alloreactive lymphocytes and tested the immunosuppressive effect of MSCs in allogeneic islet transplantation. In islet allotransplantation, injection of autologous MSCs or a subtherapeutic dose of cyclosporine A (CsA; 5 mg/kg) alone did not prolong allograft survival. However, graft survival was attained for >100 d in 33% of autologous MSC-plus-CsA–treated recipients, indicating that graft acceptance was achieved in a subgroup of allograft recipients. Splenocytes from autologous MSC-plus-CsA–treated rats exhibited a reduced mixed lymphocyte reaction (MLR)-proliferative response to donor stimulators and increased interleukin (IL)-10 release. Interestingly, after excluding host CD11b+ cells, splenic T cells from autologous MSC-plus-CsA–treated rats did not produce IL-10 or did not inhibit proliferative responses under the same conditions. The use of autologous MSC-plus-CsA downregulated immune responses, inducing donor-specific T-cell hyporesponsiveness by reducing the production of proinflammatory cytokines and inducing antiinflammatory cytokine production, especially that of IL-10, during the early posttransplantation period. T-regulatory cells made a contribution at a later phase. In conclusion, the combined use of autologous MSCs and low-dose CsA exerted a synergistic immunosuppressive effect in an islet allograft model, suggesting a role for autologous MSCs as an immune modulator.
Introduction. Allograft survival can be prolonged by overexpression of cytoprotective genes such as heme oxygenase-1 (HO-1). Modifications in vector design and delivery have provided new opportunities to safely and effectively administer HO-1 into the heart prior to transplantation to improve long-term graft outcome. Methods. HO-1 was delivered to the donor heart using an adeno-associated virus vector (AAV) with a pseudotype 6 capsid and vascular endothelial growth factor (VEGF) to enhance myocardial tropism and microvascular permeability. Survival of mouse cardiac allografts, fully or partially mismatched at the MHC, was determined with and without cyclosporine A. Intragraft cytokine gene expression was examined by PCR.
Results. The use of AAV6 to deliver HO-1 to the donor heart, combined with immunosuppression, prolonged allograft survival by 55.3% when donor and recipient were completely mismatched at the MHC and by 94.6% if partially mismatched. The combination of gene therapy and immunosuppression was more beneficial than treatment with either AAV6-HO-1 or CsA alone. IL-17a, b, e and f were induced in the heart at rejection.
Conclusions. Pretreatment of cardiac allografts with AAV6-HO-1 plus cyclosporine A prolonged graft survival. HO-1 gene therapy represents a beneficial adjunct to immunosuppressive therapy in cardiac transplantation.
The calcium-binding proteins myeloid-related protein (MRP)-8 (S100A8) and MRP-14 (S100A9) form MRP-8/14 heterodimers (S100A8/A9, calprotectin) that regulate myeloid cell function and inflammatory responses, and serve as early serum markers for monitoring acute allograft rejection. Despite functioning as a pro-inflammatory mediator, the pathophysiological role of MRP-8/14 complexes in cardiovascular disease is incompletely defined. This study investigated the role of MRP-8/14 in cardiac allograft rejection using MRP-14-deficient mice (MRP14-/-) that lack MRP-8/14 complexes.
Methods and Results
We examined parenchymal rejection (PR) after major histocompatibility complex (MHC) class II allomismatched cardiac transplantation (bm12 donor heart and B6 recipients) in wild-type (WT) and MRP14-/- recipients. Allograft survival averaged 5.9 ± 2.9 weeks (n=10) in MRP14-/- recipients, compared to > 12 weeks (n = 15, p < 0.0001) in WT recipients. Two weeks after transplantation, allografts in MRP14-/- recipients had significantly higher PR scores (2.8 ± 0.8, n=8) than did WT recipients (0.8 ± 0.8, n=12, p<0.0001). Compared to WT recipients, allografts in MRP14-/- recipients had significantly increased T-cell and macrophage infiltration, as well as increased mRNA levels of IFN-γ and IFN-γ–associated chemokines (CXCL9, CXCL10, and CXCL11), IL-6, and IL-17, with significantly higher levels of Th17 cells. MRP14-/- recipients also had significantly more lymphocytes in the adjacent paraaortic lymph nodes than did WT recipients (cell number per lymph node: 23.7 ± 0.7 × 105 for MRP14-/- vs. 6.0 ± 0.2 × 105 for WT, p < 0.0001). The dendritic cells (DCs) of the MRP14-/- recipients of bm12 hearts expressed significantly higher levels of the co-stimulatory molecules CD80 and CD86 than did those of WT recipients 2 weeks after transplantation. Mixed leukocyte reactions using allo-EC-primed MRP14-/- DCs resulted in significantly higher antigen-presenting function than reactions using WT DCs. Ovalbumin-primed MRP14-/- DCs augmented proliferation of OT-II CD4+ T cells with increased IL-2 and IFN-γ production. Cardiac allografts of B6 MHC class II-/- hosts and of B6 WT hosts receiving MRP14-/- DCs had significantly augmented inflammatory cell infiltration and accelerated allograft rejection, compared to WT DCs from transferred recipient allografts. Bone marrow–derived MRP14-/- DCs infected with MRP-8 and MRP-14 retroviral vectors showed significantly decreased CD80 and CD86 expression compared to controls, indicating that MRP-8/14 regulates B7-costimulatory molecule expression.
Our results indicate that MRP-14 regulates B7 molecule expression and reduces antigen presentation by DCs, and subsequent T-cell priming. The absence of MRP-14 markedly increased T-cell activation and exacerbated allograft rejection, indicating a previously unrecognized role for MRP-14 in immune cell biology.
MRP-8 (S100A8); MRP-14 (S100A9); T-lymphocytes; macrophages; dendritic cells; antigen-presenting cells; cytokine; heart transplantation; pathogenesis
KRP203, a structural FTY720 analog, has 5-fold greater selectivity for binding to sphingosine-1-phosphate receptor 1 (S1PR1) versus S1PR3 and 100-fold greater selectivity over S1PR2 and S1PR5. Although the immune regulatory effects of FTY720 have been tested in clinical and experimental research, the therapeutic efficacy of KRP203 in allograft models remains elusive. In this study, we investigated the potential of KRP203 alone and in combination with intra-graft injection of CD4+CD25+FoxP3+ regulatory T cells (Tregs) to induce islet allograft tolerance.
Balb/c (H-2d) mice received transplants of fresh C57BL/10 (H-2b) islet allografts under the kidney capsule and were treated for 7 days with 0.3, 1.0 or 3.0 mg/kg KRP203 alone or in combination with intragraft-infused Tregs.
Untreated Balb/c mice acutely rejected C57BL/10 islet allografts at a mean survival time (MST) of 13.8 ± 2.7 days (n=5). A 7-day dosing of 0.3 or 1.0 mg/kg KRP203 produced long-term islet allograft survival (>200 days) in 1 out of 5 and 2 out of 7 recipients, respectively. A 3 mg/kg KRP203 dose resulted in islet graft survival for greater than 200 days in 5 out of 12 recipients. While recipients that received 500 allogeneic islets admixed with 5–7 × 105 Tregs survived 83.6 ± 67.2 days, addition of transient 3 mg/kg KRP203 therapy induced prolonged drug-free graft survival (>200 days) in all recipients.
A brief treatment with KRP203 significantly prolonged islet allograft survival, while additional intragraft delivery of Tregs induced tolerogenic effects selective to islet allo-antigens.
Pancreatic islets; regulatory T-cells; tolerance; S1P-1
Reduced appetite and body weight loss are typical symptoms of inflammatory diseases. A number of inflammatory stimuli are responsible for the imbalance in energy homeostasis, leading to metabolic disorders. The herpes virus entry mediator (HVEM) protein plays an important role in the development of various inflammatory diseases, such as intestinal inflammation and diet-induced obesity. However, the role of HVEM in the brain is largely unknown. This study aims to investigate whether HVEM signaling in the brain is involved in inflammation-induced anorexia and body weight loss.
Food intake and body weight were measured at 24 hours after intraperitoneal injection of lipopolysaccharide (LPS) or intracerebroventricular injection of recombinant mouse LIGHT (also called tumor necrosis factor receptor superfamily 14, TNFSF14), an HVEM ligand, into 8- to 10-week-old male C57BL/6 mice and mice lacking HVEM expression (HVEM-/-). We also assessed LPS-induced change in hypothalamic expression of HVEM using immunohistochemistry.
Administration of LPS significantly reduced food intake and body weight, and moreover, increased expression of HVEM in the hypothalamic arcuate nucleus. However, LPS induced only minor decreases in food intake and body weight in HVEM-/- mice. Administration of LIGHT into the brain was very effective at decreasing food intake and body weight in wild-type mice, but was less effective in HVEM-/- mice.
Activation of brain HVEM signaling is responsible for inflammation-induced anorexia and body weight loss.
Brain; Inflammation; Receptors, tumor necrosis factor; Anorexia
We have previously shown that tolerance of kidney allografts across a full major histocompatibility complex (MHC) barrier can be induced in miniature swine by a 12-day course of high-dose tacrolimus. However, that treatment did not prolong survival of heart allografts across the same barrier. We have now tested the effect of cotransplanting an allogeneic heart and kidney from the same MHC-mismatched donor using the same treatment regimen. Heart allografts (n = 3) or heart plus kidney allografts (n = 5) were transplanted into MHC-mismatched recipients treated with high-dose tacrolimus for 12 days. As expected, all isolated heart allografts rejected by postoperative day 40. In contrast, heart and kidney allografts survived for >200 days with no evidence of rejection on serial cardiac biopsies. Heart/kidney recipients lost donor-specific responsiveness in cell-mediated lympholysis and mixed-lymphocyte reaction assays, were free of alloantibody and exhibited prolonged survival of donor, but not third-party skin grafts. Late (>100 days) removal of the kidney allografts did not cause acute rejection of the heart allografts (n = 2) and did not abrogate donor-specific unresponsiveness in vitro. While kidney-induced cardiac allograft tolerance (KI-CAT) has previously been demonstrated across a Class I disparity, these data demonstrate that this phenomenon can also be observed across the more clinically relevant full MHC mismatch. Elucidating the renal element(s) responsible for KICAT could provide mechanistic information relevant to the induction of tolerance in recipients of isolated heart allografts as well as other tolerance-resistant organs.
Heart transplantation; kidney transplantation; miniature swine; tolerance
In cardiac transplantation, chronic rejection takes the form of an occlusive vasculopathy. The mechanism underlying this disorder remains unclear. The purpose of this study was to investigate the role nitric oxide (NO) may play in the development of allograft arteriosclerosis. Rat aortic allografts from ACI donors to Wistar Furth recipients with a strong genetic disparity in both major and minor histocompatibility antigens were used for transplantation. Allografts collected at 28 d were found to have significant increases in both inducible NO synthase (iNOS) mRNA and protein as well as in intimal thickness when compared with isografts. Inhibiting NO production with an iNOS inhibitor increased the intimal thickening by 57.2%, indicating that NO suppresses the development of allograft arteriosclerosis. Next, we evaluated the effect of cyclosporine (CsA) on iNOS expression and allograft arteriosclerosis. CsA (10 mg/kg/d) suppressed the expression of iNOS in response to balloon-induced aortic injury. Similarly, CsA inhibited iNOS expression in the aortic allografts, associated with a 65% increase in intimal thickening. Finally, we investigated the effect of adenoviral-mediated iNOS gene transfer on allograft arteriosclerosis. Transduction with iNOS using an adenoviral vector suppressed completely the development of allograft arteriosclerosis in both untreated recipients and recipients treated with CsA. These results suggest that the early immune-mediated upregulation in iNOS expression partially protects aortic allografts from the development of allograft arteriosclerosis, and that iNOS gene transfer strategies may prove useful in preventing the development of this otherwise untreatable disease process.
Cytomegalovirus (CMV) reactivation is a well described complication of solid organ transplantation. These studies were performed to 1.) determine if cardiac allograft transplantation of latently infected recipients results in reactivation of CMV, and 2.) determine what impact CMV might have on development of graft acceptance/tolerance. BALB/c cardiac allografts were transplanted into C57BL/6 mice with/without latent murine CMV (MCMV). Recipients were treated with gallium nitrate induction and monitored for graft survival, viral immunity, and donor reactive DTH responses. Latently infected allograft recipients had ∼80% graft loss by 100 days after transplant, compared with ∼8% graft loss in naïve recipients. PCR evaluation demonstrated that MCMV was transmitted to cardiac grafts in all latently infected recipients, and 4/8 allografts had active viral transcription compared to 0/6 isografts. Latently infected allograft recipients showed intragraft IFN-α expression consistent with MCMV reactivation, but MCMV did not appear to negatively influence regulatory gene expression. Infected allograft recipients had disruption of splenocyte DTH regulation, but recipient splenocytes remained unresponsive to donor antigen even after allograft losses. These data suggest that transplantation in an environment of latent CMV infection may reactivate virus, and that intragraft responses disrupt development of allograft acceptance.
The recently described tumor necrosis factor (TNF) family member LIGHT (herpes virus entry mediator [HVEM]-L/TNFSF14), a ligand for the lymphotoxin (LT)β receptor, HVEM, and DcR3, was inactivated in the mouse. In contrast to mice deficient in any other member of the LT core family, LIGHT−/− mice develop intact lymphoid organs. Interestingly, a lower percentage of LIGHT−/−LTβ−/− animals contain mesenteric lymph nodes as compared with LTβ−/− mice, whereas the splenic microarchitecture of LIGHT−/−LTβ−/− and LTβ−/− mice shows a comparable state of disruption. This suggests the existance of an additional undiscovered ligand for the LTβ receptor (LTβR) or a weak LTα3–LTβR interaction in vivo involved in the formation of secondary lymphoid organs. LIGHT acts synergistically with CD28 in skin allograft rejection in vivo. The underlying mechanism was identified in in vitro allogeneic MLR studies, showing a reduced cytotoxic T lymphocyte activity and cytokine production. Detailed analyses revealed that proliferative responses specifically of CD8+ T cells are impaired and interleukin 2 secretion of CD4+ T cells is defective in the absence of LIGHT. Furthermore, a reduced 3[H]-thymidine incorporation after T cell receptor stimulation was observed. This for the first time provides in vivo evidence for a cooperative role for LIGHT and LTβ in lymphoid organogenesis and indicates important costimulatory functions for LIGHT in T cell activation.
TNF; lymphotoxin; HVEM; lymphoid organogenesis; transplantation
Islet allograft rejection in sensitized recipients is difficult to control by costimulation blockade using anti-CD154 and cytotoxic T-lymphocyte antigen-4 immunoglobulin (CTLA4Ig). Because leukocyte function antigen (LFA) 1 is highly expressed on memory T cells, adding an LFA-1 blockade may inhibit memory T-cell activities. We examined the effects on islet allograft survival of triple costimulation blockade in presensitized recipient mice.
C57BL/6 mice were sensitized by transplantation under the kidney capsule or intraperitoneal injection of Balb/c islets. Four weeks after transplantation, sensitization was confirmed by flow-cytometric detection of alloreactive antibodies. Diabetes was induced by a single intravenous injection of streptozotocin. Recipients were transplanted with 200 Balb/c islets under the right kidney capsule. Graft function was assessed by daily blood glucose and body weight records. Transplanted animals were divided into 3 treatment groups: group 1, control antibody; group 2, anti-CD154 and CTLA-4 Ig double therapy; group 3, anti-CD154, CTLA4Ig, and anti–LFA-1 triple therapy. Injections were administered every second day from day – 2 to day 8.
Naïve mice rejected islet allografts between days 7 and 29 (mean 16 ± 6 d; n = 5), sensitized mice in group 1 between days 0 and 14 (mean 7 ± 5 d; n = 8), in group 2 between days 4 and 16 (mean 8 ± 4 d; n = 7), and in group 3 between days 4 and 26 (mean 11 ± 7 d; n = 10).
Triple costimulation blockade with anti-CD154, CTLA4Ig, and anti–LFA-1 was not sufficient to improve islet allograft survival in sensitized recipients.
Allograft fibrosis still remains a critical problem in transplantation, including heart transplantation. The IL-13/TGF-β1 interaction has previously been identified as a key pathway orchestrating fibrosis in different inflammatory immune disorders. Here we investigate if this pathway is also responsible for allograft fibrosis and if interference with the IL-13/TGF-β1 interaction prevents allograft fibrosis.
FVB or control DBA/1 donor hearts were transplanted heterotopically into DBA/1 recipient mice and hearts were explanted at day 60 and 100 post-transplantation. Cardiac tissue was examined by Masson’s trichrome staining and immunohistochemistry for CD4, CD8, CD11b, IL-13, Fas ligand, matrix metalloproteinase (MMP)-1, MMP-13, β2-microglobulin, and Gremlin-1. Graft-infiltrating cells were isolated and analyzed by flow cytometry. IL-13 and TGF-β1 levels were determined by enzyme-linked immunosorbent assay (ELISA) and the amount of collagen was quantified using a Sircol assay; IL-13Rα2 expression was detected by Western blotting. In some experiments IL-13/ TGF-β1 signaling was blocked with specific IL-13Rα2 siRNA. Additionally, a PCR array of RNA isolated from the allografts was performed to analyze expression of multiple genes involved in fibrosis.
Both groups survived long-term (>100 days). The allogeneic grafts were infiltrated by significantly increased numbers of CD4+ (P <0.0001), CD8+ (P <0.0001), and CD11b+ cells (P = 0.0065) by day 100. Furthermore, elevated IL-13 levels (P = 0.0003) and numbers of infiltrating IL-13+ cells (P = 0.0037), together with an expression of IL-13Rα2, were detected only within allografts. The expression of IL-13 and IL-13Rα2 resulted in significantly increased TGF-β1 levels (P <0.0001), higher numbers of CD11bhighGr1intermediateTGF-β1+ cells, and elevated cardiac collagen deposition (P = 0.0094). The allograft fibrosis found in these experiments was accompanied by upregulation of multiple profibrotic genes, which was confirmed by immunohistochemical stainings of allograft tissue. Blockage of the IL-13/TGF-β1 interaction by IL-13Rα2 siRNA led to lower numbers of CD11bhighGr1intermediateTGF-β1+, CD4+, CD8+, and CD11b+ cells, and prevented collagen deposition (P = 0.0018) within these allografts.
IL-13 signaling via IL-13Rα2 induces TGF-β1 and causes allograft fibrosis in a murine model of chronic transplant rejection. Blockage of this IL-13/TGF-β1 interaction by IL-13Rα2 siRNA prevents cardiac allograft fibrosis. Thus, IL-13Rα2 may be exploitable as a future target to reduce allograft fibrosis in organ transplantation.
IL-13; IL-13Rα2; TGF-β1; Allograft fibrosis; Heart transplantation
Although certain chemokines and their receptors guide homeostatic recirculation of T cells and others promote recruitment of activated T cells to inflammatory sites, little is known of the mechanisms underlying a third function, migration of Foxp3+ regulatory T (T reg) cells to sites where they maintain unresponsiveness. We studied how T reg cells are recruited to cardiac allografts in recipients tolerized with CD154 monoclonal antibody (mAb) plus donor-specific transfusion (DST). Real-time polymerase chain reaction showed that intragraft Foxp3 levels in tolerized recipients were ∼100-fold higher than rejecting allografts or allografts associated with other therapies inducing prolonged survival but not tolerance. Foxp3+ cells were essential for tolerance because pretransplant thymectomy or peritransplant depletion of CD25+ cells prevented long-term survival, as did CD25 mAb therapy in well-functioning allografts after CD154/DST therapy. Analysis of multiple chemokine pathways showed that tolerance was accompanied by intragraft up-regulation of CCR4 and one of its ligands, macrophage-derived chemokine (CCL22), and that tolerance induction could not be achieved in CCR4−/− recipients. We conclude that Foxp3 expression is specifically up-regulated within allografts of mice displaying donor-specific tolerance, that recruitment of Foxp3-expressing T reg cells to an allograft tissue is dependent on the chemokine receptor, CCR4, and that, in the absence of such recruitment, tolerizing strategies such as CD154 mAb therapy are ineffectual.