CD8+ T cells contribute to the development of transplant arteriosclerosis despite CD154 blockade

BACKGROUND: The CD40-CD154 receptor-ligand pair plays a critical role in allograft rejection by mediating the activation of endothelial cells, antigen-presenting cells, and T cells. Blockade of this interaction prevents acute allograft rejection and leads to prolonged allograft survival in numerous experimental models, but in most cases indefinite graft survival is not achieved due to evolving transplant arteriosclerosis. In this study, we have used a model of transplant arteriosclerosis to investigate whether CD4+ and CD8+ T cells are differentially affected by CD154 blockade. METHODS: BALB/c (H2d) aortic grafts were transplanted into C57BL/6 (H2b) recipients treated with anti-CD154 monoclonal antibody in the presence or absence of CD8+ T-cell depletion. Histology and morphometric measurements were performed on day 30 after transplantation. RESULTS: Only combined treatment with anti-CD154 and anti-CD8 monoclonal antibodies resulted in a significant reduction of intimal proliferation (33 +/-10% vs. 67+/-14%; untreated control). Administration of either antibody alone did not produce this effect. Thymectomy did not alter the degree of intimal proliferation observed in any of the treatment groups. CONCLUSIONS: Our data provide direct evidence that CD8+ T cells are not targeted effectively by CD154 blockade and that the transplant arteriosclerosis seen after CD154 blockade is not due to recent thymic emigrant T cells.     

Regulation of transplant arteriosclerosis by CD25+CD4+ T cells generated to alloantigen in vivo

BACKGROUND: CD25+CD4+ regulatory T cells have been shown to suppress alloimmunity in various experimental settings. Here, we hypothesized that alloantigen-reactive regulatory T cells would reduce the severity of transplant arteriosclerosis. METHODS: CD25+CD4+ T cells from CBA mice that were pretreated with C57BL/6 (B.6) blood (donor-specific transfusion, DST) and nondepleting anti-CD4 Ab (YTS 177) were cotransferred with na?ve CBA CD25-CD4+"effector" T cells into CBA-rag-/- mice. These animals received aorta transplants from B.6 CD31-/- donors. CBA wild-type recipients of B.6 aorta grafts were pretreated with 177/DST directly. Some animals received 6x10(5) CD25+CD4+ T cells from pretreated mice to augment regulation on day -1. Grafts were harvested on day 30. RESULTS: Luminal occlusion of the graft caused by neointima formation was 29.3+/-19.4% (n=5) after transfer of effector T cells only. Co-transfer of CD25+CD4+ regulators reduced occlusion significantly (2.4+/-3.3%, n=3; P=0.009). This effect was partially abrogated in the presence of a CTLA4 blocking Ab (11.1+/-4.7%, n=4; P=0.008). Pretreating immunocompetent CBA recipients of B.6 aortic allografts with 177/DST did not reduce transplant arteriosclerosis significantly (43.0+/-15.7%, n=5 vs. 56.6+/-16.8%, n=5; 177/DST vs. controls; P=0.22). However, when pretreated primary CBA recipients received an additional transfer of 6 x 10(5) CD25+CD4+ T cells procured from other mice pretreated with 177/DST before transplantation, luminal occlusion of the graft was markedly reduced (33.0+/-7.6%, n=5; P=0.002). CONCLUSION: Regulatory T cells generated in vivo to alloantigen can prevent CD25-CD4+ T-cell-mediated transplant arteriosclerosis. In immunocompetent recipients, these cells have potential to be used as cellular immunotherapy to control transplant arteriosclerosis.     

CD154 on the surface of CD4+CD25+ regulatory T cells contributes to skin transplant tolerance

BACKGROUND: It is known that the infusion of whole blood from donors (donor-specific transfusion) into recipients combined with anti-CD154 therapy can prolong allograft survival. It has generally been agreed that the effectiveness of anti-CD154 therapy is caused by the inactivation of alloreactive CD4+ and CD8+ effector T cells. The recent literature has implicated CD4+CD25+ regulatory T cells in the suppression of autoimmunity and graft rejection, and we therefore examined whether CD154 blockade is effective because of its blockade of inflammatory T-cell activation or because of a direct impact on the regulatory T cells. METHODS: RAG(-/-) mice were adoptively transfused with CD4+ T cells or a subset of the population (CD4+CD25+ or CD4+CD25- T cells) alone or in combination with donor-specific transfusion and anti-CD154 and given an allo-skin transplant. The longevity of the transplant was determined over time. CD154(-/-)CD4+ T cells were used to assess the importance of CD154 in graft rejection and acceptance. RESULTS: CD154 blockade (or loss of CD154) on CD4+CD25+ regulatory T cells enhanced their immunosuppressive activities and was a contributing factor to anti-CD154-induced immune suppression in vivo. In a model of allograft tolerance, suppression was elicited by antigen and anti-CD154 or antigen alone if the CD4+CD25+ regulatory T cells were deficient in CD154 expression. CONCLUSIONS: Neutralizing the function of CD154 on regulatory T cells upon antigen exposure induces heightened levels of suppressive activities and is likely a contributing factor to the long-lived therapeutic effects of anti-CD154 treatment.     

Islet xenograft rejection in absence of CD8+ T cells does not require either interferon-gamma or interleukin-5

We recently demonstrated that interleukin-5 and eosinophils mediate rejection of skin allografts when CD8+ T cell-dependent and Th1-type CD4+ T cell-dependent pathways are not functional. The purpose of this study was to determine whether a similar mechanism might be operative during rejection of rat islet xenografts in mice. First, we observed that eosinophils indeed infiltrate rejected islet grafts together with CD4+ and CD8+ T cells. CD8+ T cell depletion significantly enhanced graft survival and a further prolongation of islet function was obtained in combination with interferon-gamma neutralization. However, islet rejection characterized by prominent eosinophil and macrophage infiltration still occurred in this setting. Although eosinophil infiltrates were dramatically reduced in interleukin-5 deficient mice, the ability of these animals to reject islet xenografts under CD8+ T cell depletion and interferon-gamma neutralization was similar to that of wild-type mice. We conclude that in absence of CD8+ T cells and interferon-gamma, macrophages, but not eosinophils, mediate rejection of rat-to-mouse islet xenografts.     

Apoptosis and allograft rejection in the absence of CD8+ T cells.

BACKGROUND: The requirement for cytotoxic T lymphocytes during allograft rejection is controversial. We previously demonstrated that CD8+ T cells are not necessary for allograft rejection or for the induction of apoptosis in rat small intestinal transplantation. In this study, we examined the mechanisms of apoptosis and rejection after liver transplantation in the absence of CD8+ T cells. METHODS: Either Lewis or dark agouti rat liver grafts were transplanted into Lewis recipients to create syngeneic and allogeneic combinations. CD8+ T cells were depleted in an additional allogeneic group by treatment with OX-8 mAb on day -1 and day 1 after liver transplant. RESULTS: Apoptosis and rejection were observed in both the CD8+ T cell-depleted allogeneic and allogeneic grafts by hematoxylin and eosin staining, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining, and radiolabeled-annexin V in vivo imaging. Granzyme B and FasL were expressed in all allogeneic transplants, including those depleted of CD8+ T cells, indicating that a mononuclear cell other than a CD8+ T cell can be the source of these molecules during allograft rejection. Activation of the caspase cascade was detected in all rejecting allografts. Caspases 3, 8, and 9 were activated at similar significantly elevated levels in both allogeneic and CD8+ T cell-depleted liver grafts. CONCLUSION: These data indicate that in the absence of CD8+ T cells an alternative pathway, associated with granzyme B and FasL expression and activation of the caspase cascade, can mediate apoptosis and graft rejection.     

Differential impact of CD154 costimulation blockade on alloreactive effector and regulatory T cells in murine renal transplant recipients

BACKGROUND: Although CD154 costimulation blockade prolongs allograft survival in multiple transplantation models, the underlying immunological mechanisms remain to be elucidated. METHODS AND RESULTS: We used a murine orthotopic kidney allograft (KTx) model to analyze the impact of CD154 blockade on trafficking and function of alloreactive T effector versus T regulatory cells. A single dose of MR1 Ab treatment at the time of KTx significantly improved the survival of Balb/c KTx in na?ve C57BL/6 recipients (mean survival time >100 days vs. 52 days in controls; P<0.005), and improved graft histology, as evidenced by decreased lymphocyte infiltration and preservation of tissue architecture (days 6-8). In the early posttransplant phase, fluorescence-activated cell sorting analysis revealed preferential depression of T effector (CD8+CD25+) and relative enrichment of T-regulatory (CD4+ CD25+ CD152+) cells selectively in KTx. This pattern was further supported by intragraft gene expression analysis, which showed increased FoxP3/Tbet ratio and simultaneously decreased granzyme B/IFN-gamma levels in Ab-treated recipients. Additionally, MR1 Ab selectively up-regulated intragraft CCL17, but suppressed CXCL9/CCL5, in parallel with increased CCR4/CCR8 but unaltered CXCR3 expression. CONCLUSION: These results provide evidence, at both cellular and molecular levels, that CD154 blockade in murine KTx recipients differentially targeted T-effector and T-regulatory cell subsets by regulating intragraft induction of chemokines targeting distinct T-cell subsets.     

Detection of vimentin-specific autoreactive CD8+ T cells in cardiac transplant patients

BACKGROUND: Evidence is emerging that autoimmunity can play a role in allograft rejection. Reports have described the presence of autoantibodies in transplant patients and CD4+ autoreactive T cells in rodent models of allograft rejection. The objective of this study was to seek evidence of CD8+ T-cell-mediated autoimmunity in the transplant setting. The author have previously observed autoimmunity to the non-polymorphic cytoskeletal protein vimentin in cardia transplant patients. In this study, vimentin antibody positive patients were screened for the presence of vimentin-specific self-major histocompatibility complex class I-restricted CD8+ T cells. METHODS: Two peptide sequences from vimentin that bound HLA-A*0201 were identified and fluorochrome-labeled A*0201 tetramers with each peptide were constructed to screen for vimentin-specific T cells. RESULTS: Tetramer-binding CD8+ T cells were detected in peripheral blood lymphocytes from two of six patients after expansion by in vitro stimulation with peptide. Tetramer-binding T cells produced interferon-gamma in an antigen-specific fashion. No autoreactive T cells specific for vimentin were detected after peptide stimulation of T cells from eight healthy A*0201-positive volunteers. CONCLUSIONS: This finding is the first evidence of CD8+ T-cell-mediated autoimmunity in human transplant patients.     

Differentiation of human alloreactive CD4+ and CD8+ T cells in vitro

BACKGROUND: Recent studies have revealed that, during viral infection, ordered phenotypic and functional changes occur in human antigen-specific T cells. We analyzed whether a similar differentiation program is induced after alloantigen stimulation in vitro. METHODS: Peripheral blood mononuclear cells and purified CD4(+)CD45RA+, CD4(+)CD45RO+, and CD8+ T cells from healthy individuals were labeled with 5-(and-6)-carboxyfluorescein diacetate succinimidyl ester (CFSE). Cells were co-cultured with allogeneic irradiated cells. Flow cytometric analysis was performed on days 3, 5, and 7 of culture using surface CD45RA, CD27, CD28, CCR7, and intracellular perforin and granzyme B markers in relation to CFSE dilution. RESULTS: Based on the decrease in CFSE fluorescence, both CD4+ and CD8+ T cells showed an early and vigorous response to allogeneic stimulation. Loss of CD45RA expression and up-regulation of CD27 and CD28 costimulatory molecules was an early event occurring in the first generations of dividing cells. Differentiation at later stages of proliferation was characterized by loss of CCR7 homing receptor expression, more pronounced in CD4+ than in CD8+ T cells, indicating the decreased ability of these cells to traffic to secondary lymphoid organs. Production of the cytotoxic effector molecules perforin and granzyme B increased with the number of cell divisions. CONCLUSIONS: Our data thus show that short-term phenotypic and functional changes of alloreactive T cells follow the differentiation pattern seen in the early stages of an antiviral immune response.     

不同免疫抑制剂对肝移植受者外周血中调节性T淋巴细胞比例的影响

目的 探讨西罗莫司(SRL)和钙调磷酸酶抑制剂(CNI)对肝移植受者外周血中CD4+CD25high T淋巴细胞水平的影响.方法 排除肝移植远期移植肝功能异常的受者,将移植肝功能长期(超过2年)稳定的受者47例纳入研究,其中免疫抑制方案使用SRL者15例(SRL组),使用CNI(均为他克莫司)者32例(CNI组).以同期38名健康成人志愿者作为正常对照.使用流式细胞仪检测各组受试者外周血中单个核细胞CD4、CD25及Foxp3的表达水平,比较各组间外周血中CD4+CD25high调节性T淋巴细胞(Treg细胞)的差异.结果 与正常对照组相比,CNI组外周血淋巴细胞中CD4+ CD25high T淋巴细胞的比例显著减少(P<0.05),SRL组CD4+ CD25high T淋巴细胞的比例显著升高(P<0.05).SRL组、正常对照组和CNI组受试者外周血中CD4+ CD25high Foxp3+ Treg 细胞占CD4+ T淋巴细胞的比例依次降低,分别为1.88%(1.56%～2.60%)、1.15%(0.57%～1.48%)和0.84%(0.46%～1.45%),3组间两两比较,差异均有统计学意义(P<0.01或P<0.05).CD4+ CD25 high T淋巴细胞表达Foxp3的阳性率超过95%,CD4+ CD25 low T淋巴细胞表达Foxp3的阳性率低于20%,CD4+ CD25-T淋巴细胞不表达Foxp3.结论 SRL可促进肝移植受者外周血中Treg细胞水平的升高,而CNI可降低Treg细胞的水平.     

Regulatory CD4+CD25+ T cells in the peripheral blood of lung transplant recipients: correlation with transplant outcome

BACKGROUND: The subset of CD4+CD25+ regulatory T cells, recently identified in humans, may play a central role in the regulation of immune tolerance to graft survival. METHODS: This study assesses the frequency and functional profile of CD4+CD25+CD69- cells in the peripheral blood of lung transplant recipients (>3 years from transplantation), 10 of whom were in a stable clinical condition and 11 of whom demonstrated chronic rejection (bronchiolitis obliterans syndrome). We also studied a group of seven healthy subjects. RESULTS: The frequency of CD4+ T cells expressing CD25 (CD4+CD25+) and the highest levels (CD25) were lower in patients with bronchiolitis obliterans syndrome compared with healthy subjects and subjects in a stable clinical condition (P < or = 0.01). Purified CD4+CD25+ cells exhibited a regulatory functional profile in vitro: they were hyporesponsive, suppressed the proliferation of CD4+CD25- cells, and produced interleukin-10. CONCLUSION: These results provide in vivo evidence that peripheral CD4+CD25+ T cells may represent an important regulatory subset in lung transplantation.     

The influence of immuosuppressive therapy on the development of CD4+CD25+ T cells after renal transplantation

A growing number of studies suggest that CD4(+)CD25(+) T regulatory (Treg) cells play a significant role to downregulate the immune response to alloantigens. In this study, we investigated the possible influence of immunosuppressive therapy, including cyclosporine (CsA) or rapamycin (sirolimus), on the level of CD4(+)CD25(+), CD4(+)CD25(+)FOXP3(+), and CD4(+)CD25(+)CTLA-4(+) T cells in the peripheral blood of renal allograft recipients. The study was performed on renal allograft recipients who displayed uneventful stable courses (RAR-S; n = 15) versus biopsy-proven chronic rejection (RAR-CH; n = 12). The patients were divided based on the immunosuppressive protocol: group 1 (prednisone+CsA+Aza) and group II (prednisone+sirolimus). The control group consisted of 10 healthy blood donors. We examined the expression of CD4, CD25, CTLA-4, and Foxp3 in peripheral blood T cells. Flow cytometry was performed with a FACSCalibur (BD Biosciences) instrument with data analyzed using Cell Quest software. The percentage of CD4(+)CD25(+)Foxp3(+) T cells in rapamycin (sirolimus) treated patients did not differ from that observed in healthy individuals, but was significantly higher compared with CsA-treated patients. CsA therapy resulted in a reduction in the percentage of CD4(+)CD25(+)CTLA-4(+) and CD4(+)CD25(+)Foxp3(+) regulatory T cells after renal transplantation in both groups (RAR-S and RAR-CH) compared with patients treated with rapamycin or to healthy donors. The type of immunosuppressive therapy (with or without calcineurin inhibitors) may have an important role in tolerance induction and graft function.     

肿瘤坏死因子-α诱导蛋白-8样分子2在调节性T细胞中的表达

目的:观察肿瘤坏死因子-α诱导蛋白-8样分子2(TIPE2)在CD4<'+>CD25<'+>调节性T细胞(CD4<'+>CD25<'+>Treg)中的表达.方法:免疫磁珠法分离正常BALB/C小鼠脾脏CD4<'+>CD25<'+>Tregs,流式细胞术鉴定CD4<'+>CD25<'+>Treg的纯度.激光共聚焦荧光法检...     

Roles of CD4+ and CD8+ T cells in discordant skin xenograft rejection

An essential role of murine CD4+ T cells in immune reactivity and skin graft rejection in discordant xenogeneic combinations have been reported. Our study was conducted to further clarify the roles of CD4+ and CD8+ T cells in discordant skin xenograft rejection, by using CD4 and CD8 knockout [C57BL/6 Cr Slc (B6; H-2b) background] mice. When human skins were grafted on CD8 knockout mice or B6 mice, both hosts rejected human skin grafts within 12 days after grafting. By contrast, survival of human skin grafts was significantly prolonged in CD4 knockout mice (mean survival times=19.3+/-(SD) 1.6 days; median 19 days). Fully allogeneic C3H/He Slc (H-2k) skin grafts were rejected within 14 days in CD4 knockout mice, suggesting that non-CD4+ T cells in CD4 knockout mice were immunocompetent for allograft rejection. In spleens of these recipient mice, CD8+ T cells seemed to be activated 10 days after human skin grafting. Immunohistological analysis revealed the infiltration of CD8+ T cells at the site of transplanted human skin on CD4 knockout mice. To further examine the role of CD8+ T cells in CD4 knockout mice, human skin grafting was performed on day 0 followed by administration of anti-CD8 monoclonal antibody on days 0, 5, and 14. The administration of anti-CD8 monoclonal antibodies caused the significant prolongation of human skin graft survival. These results indicate the following two conclusions: (1) CD4+ T cells have an essential role in rejecting discordant human skin xenografts rapidly and (2) however, CD8+ T cells also are capable of rejecting discordant human skin xenografts.     

Acceleration of apoptosis in CD4+CD8+ thymocytes by rapamycin accompanied by increased CD4+CD25+ T cells in the periphery

BACKGROUND: Rapamycin (Rapa) is an immunosuppressant that is used in patients and animal models to control allograft rejection. Its mechanisms of action are not fully understood. In this article, the authors have investigated the effects of therapeutic doses of Rapa on both thymic and peripheral T-cell populations in the adult rat. METHODS: The therapeutic dosage of Rapa was optimized using cardiac transplantation between LEW and DA rats. Thymic morphology was assessed by hematoxylin-eosin staining. Flow cytometric analysis was performed to analyze T-cell phenotype and apoptosis. T-cell receptor (TCR)-mediated T-cell responsiveness was evaluated by 3[H]-thymidine deoxyribose incorporation. RESULTS: Rapa induced atrophy in the thymus but not in peripheral lymphoid organs. Moreover, fibrosis occurred in thymus that was long-lasting after Rapa withdrawal. In animals treated with Rapa, there was a significant reduction in CD4+CD8+ thymocytes caused by accelerated apoptosis, whereas CD4-CD8-, CD4+CD8-, and CD8+CD4- populations remained unaffected. In contrast, the cellularity of the periphery lymphoid organs was not altered. Within the CD4+ thymocyte population, CD4+CD25+ thymocytes were resistant to Rapa-accelerated apoptosis, and in the periphery, the ratio of CD4+CD25+ to CD4+CD25- T cells was increased. Notably, the peripheral CD4+CD25+ T cells were hyporesponsive to TCR-mediated activation. CONCLUSIONS: The resistance of the peripheral CD4+CD25+ T cells to Rapa treatment might contribute to its immunosuppressive action. The long-term effects of Rapa on thymus atrophy and thymocyte development requires consideration with respect to its clinical application.     

Role of CD4+ and CD8+ T cells in the rejection of concordant pancreas xenografts

BACKGROUND: We studied the ability of CD4 and CD8 T cells to induce rejection of pancreas xenografts in a concordant combination using rat pancreas xenografts as donors and chemically induced diabetic mice as recipients. METHODS: Lewis rat (2 to 3 weeks old) pancreas xenografts were transplanted into streptozotocin (STZ)-induced diabetic mice. Lymphocyte proliferation and cytokine production were analyzed in vitro. All pancreas xenografts were assessed by functional (blood glucose) and histopathologic examinations. RESULTS: Lewis rat pancreas grafts were rejected within 10 to 13 days, with mononuclear cell infiltrate and tissue necrosis in STZ-induced diabetic mice. A predominant T cell receptor alphabeta -CD4 cell (on day 4) and T cell receptor alphabeta -CD8 cell (on day 8) infiltrate and IgM deposition were found in the pancreas xenografts after transplantation. Anti-CD4 (GK1.5), but not anti-CD8 (YTS169.4), monoclonal antibodies resulted in a prolonged survival of Lewis rat pancreas xenografts. Lewis pancreas xenografts were permanently accepted by CD4 knockout mice but not by CD8 knockout mice. The pancreas xenografts were acutely rejected with a mean survival time of 15.3 days in B cell-deficient mice (microMT/microMT). Transfer of CD4 but not CD8 spleen cells from na?ve C57BL/6 mice into Rag2 mice led to acute rejection of transplanted pancreas xenografts. However, activated CD8 spleen cells elicited rejection of Lewis rat pancreas xenografts in SZT-induced diabetic mice. CONCLUSION: The current results show that CD4 T cells are necessary and sufficient for mediating the rejection of Lewis rat pancreas xenografts in STZ-induced diabetic mice. However, CD8 cells, when activated, can also induce acute rejection of concordant pancreas xenografts.     

CD4+CD25-T淋巴细胞转化为CD4-CD8-调节T细胞的体外实验研究

目的 探讨体外诱导和纯化CD4+ CD25-T淋巴细胞(effector T cell,Teff)转化为CD4-CD8-双阴性调节T细胞(double negative regulatory T cell,DN Treg)的最适条件.方法 采用免疫磁珠分选方法提取C57BL/6小鼠的CD4+ CD25-T淋巴细胞、DBA/2小鼠的成熟树突状细胞共培养,加入不同剂量的IL-2,通过流式细胞检测CD4-CD8-T细胞的转化比例并确定最适条件,免疫磁珠阴性选择分选提纯转化的CD3+ CI4-CD8-T细胞,流式细胞仪检测转化的CD4-CD8-调节T细胞对CD4+ CD25-效应T细胞增殖抑制情况.结果 CD4+ CD25-T淋巴细胞与DBA/2小鼠的树突状细胞共培养6d后检测CD4-CD8-调节T细胞的转化比率为6.21％ ±2.03％,实验组加入不同浓度IL-2的转化率:A组(25 ng/ml)为14.77％±2.15％,B组(50 ng/ml)为21.29％±2.68％,C组(75 ng/ml)为43.45％ ±4.45％,D组(100 ng/ml)为28.59％±3.05％,IL-2浓度在75 ng/ml时,转化获得率最高(C组与对照组、实验A、B、D组比较分别t=10.700,8.288,6.158,3.932,均P＜0.05);分离提纯CD4-CD8-双阴性调节细胞纯度达到98.10％,CD4-CD8-双阴性调节细胞与CFSE染色的CD4+ CD25-T淋巴细胞、小鼠树突状细胞共培养6d,实验组增殖指数为1.15明显低于对照组2.07.结论 小鼠CD4+ CW25-T淋巴细胞在体外,成熟树突状细胞刺激下可转化为CD4-CD8-双阴性调节T细胞,IL-2可显著提高其转化率.