Anti-CD25 mAb administration prevents spontaneous liver transplant tolerance

Liver allografts are accepted spontaneously in all mouse strain combinations without immunosuppressive therapy. The mechanisms underlying this phenomenon remain largely undefined. In this study, we examined the effect of CD4+ CD25+ T regulatory cells (Treg) on the induction of mouse liver transplant tolerance. Orthotopic liver transplantation was performed from B10 (H2b) to C3H (H2k) mice. Depleting rat anti-mouse CD25 mAb (PC61) was given to the donors or recipients (250 microg/d IP) pretransplant or to the recipients postoperatively. At day 5 posttransplantation, both effector T cells (mainly CD8) and CD4+ CD25+ Treg were increased in the liver allografts and host spleens compared to na?ve mice. Anti-CD25 mAb administration, either pretransplantation or posttransplantation, reduced the ratio of CD4+ CD25+ Treg to the CD3 T cells of liver grafts and recipient spleens and induced liver allograft acute rejection compared to IgG treatment. Anti-CD25 mAb administration elevated anti-donor T-cell proliferative responses and CTL and NK activities of graft infiltrates and host splenocytes; reduced CTLA4, Foxp3, and IDO mRNA levels; increased IL-10 and IFN-gamma; and decreased IL-4 mRNA levels in the livers or host spleens. The number of apoptotic T cells was reduced significantly in the liver grafts and treated host spleens. Therefore, anti-CD25 mAb administration changed the balance of CD4+ CD25+ Treg to activated T cells of liver graft recipients, preventing liver transplant tolerance. This was associated with enhanced anti-donor immune reactivity, downregulated Treg gene expression, and reduced T cell apoptosis in the grafts and host spleens.     

New Insights into Mechanisms of Spontaneous Liver Transplant Tolerance: The Role of Foxp3-Expressing CD25+CD4+ Regulatory T Cells

Liver allografts in mice are accepted across MHC barriers without requirement for immunosuppressive therapy. The mechanisms underlying this phenomenon remain largely undefined. In this study, we investigated the role of Foxp3-expressing CD25⁺CD4⁺ regulatory T cells (Treg) in the induction of murine liver transplant tolerance. Foxp3⁺CD25⁺CD4⁺ T cells were increased in liver grafts and recipient spleens from day 5 to day 100 posttransplantation, associated with enhanced CTLA4 and TGF-β expression and IL-4 production. Depletion of recipient CD25⁺CD4⁺ T cells using anti-CD25 mAb (250 μg/day) induced acute liver allograft rejection. This was associated with a decreased ratio of Foxp3⁺ Treg: T effector cells, decreased IL-4 and elevated IL-10 and IL-2 production by graft-infiltrating T cells, and reduced apoptotic activity of graft-infiltrating CD4⁺ and CD8⁺ T cells in anti-CD25-mAb-treated recipients. Thus, the data suggest that Foxp3⁺CD25⁺CD4⁺Treg are involved in spontaneous acceptance of liver allografts in mice. The ratio of Treg to T effector cells appears to determine liver transplant outcome. CTLA4, IL-4, TGF-β and apoptosis of graft-infiltrating T cells are also associated with liver transplant tolerance and may contribute, at least in part, to the mechanisms of Treg-mediated immune regulation in this model.     

外源性IL-2对小鼠CD4^＋CD25^＋调节性T细胞影响的实验研究

目的：探讨IL-2对CD4＋CD25＋调节性T细胞（Tregs）的增殖及功能的影响。方法：提取B6小鼠脾脏细胞,流式细胞仪分离CD4＋CD25＋Tregs,将新鲜分离的CD4＋CD25＋Tregs与抗CD3单克隆抗体、同种同系抗原递呈细胞（APCs）及外源性IL-2共同培养,测定其增殖活性;并检测体外扩增后的CD4＋CD25＋Tregs的免疫抑制活性及其Foxp3的表达。结果：与外源性IL-2共同培养的CD4＋CD25＋Tregs增殖程度强烈,与对照组比较,差异有统计学意义（P〈0.05）;体外扩增的CD4＋CD25＋Tregs抑制CD4＋CD25-T细胞增殖活性的能力与新鲜分离的CD4＋CD25＋Tregs相似（P〉0.05）。体外扩增的CD4＋CD25＋Tregs的Foxp3表达与新鲜分离的CD4＋CD25＋Tregs亦相似（P〉0.05）。结论：外源性IL-2能够消除CD4＋CD25＋Tregs的无反应状态,且体外扩增的CD4＋CD25＋Tregs保持了其抑制活性。     

Reduction of Foxp3-expressing regulatory T cell infiltrates during the progression of renal allograft rejection in a mouse model

BACKGROUND: Regulatory T (Treg) cells are the immune suppressors in the maintenance of immune homeostasis and tolerance to self and non-self antigens, and may have therapeutic potential in the treatment of transplant rejection in patients. However, Treg cell development and action are poorly understood in transplantation. In this study, the association of CD4(+)Foxp3(+) infiltrates within renal allograft tissue with graft survival was investigated in a mouse model. METHODS: Kidney donors from C57BL/6J mice (H-2(b)) were transplanted to bilaterally nephrectomized Balb/c recipient mice (H-2(d)). Treg cells were examined with FACS and immunohistochemical staining. RESULTS: Here we showed that without any immunosuppressive regimen, kidney allografts were mostly rejected from 20 to 60 days after transplantation. During the progression of allograft rejection Foxp3(+) Treg phenotype infiltrates were significantly diminished, while intragraft expression of TGF-beta1, IL-6, IL-17 and IL-23 was up-regulated. The regulatory function of CD4(+)CD25(+) infiltrates was confirmed by their suppressive activity in mixed lymphocyte reaction. Further in vitro studies indicated that primary renal tubular epithelial cell (TEC) cultures produced high levels of IL-6 in response to allogeneic lymphocyte or IL-17 stimulation, and neutralization of IL-6 increased CD4(+)CD25(+)Foxp3(+) cells in co-cultures with TEC. CONCLUSION: Diminution of Foxp3(+) Treg infiltrates associates with renal allograft rejection, and neutralization of IL-6 activity enhances Foxp3(+) Treg cell differentiation. Our findings suggest that increase in intragraft IL-6 may down-regulate infiltrating Foxp3(+) Treg cells.     

Costimulation blockade-induced cardiac allograft tolerance: inhibition of T cell expansion and accumulation of intragraft cD4(+)Foxp3(+) T cells

BACKGROUND: Previous studies have demonstrated that anti-CD40L or anti-B7 requires the presence of CD4(+)CD25(+) regulatory T cells (Treg) to induce antigen specific hyporesponsiveness. Other tolerance strategies involving Treg have shown a dependency on interleukin (IL)-10. The objective of this study was to investigate the role of CD4(+)CD25(+) Treg and IL-10 when treating transplant recipients with cytotoxic T lymphocyte-associated antigen (CTLA)-4 immunoglobulin (Ig), anti-CD40L, and anti-lymphocyte function-associated antigen (LFA)-1. METHODS: Recombinase activating gene-deficient (Rag1(-/-) mice were transplanted with BALB/c hearts and adoptively transferred with IL-10(-/-) CD4(+) T cells, CD4(+)CD25(-) T cells or CD4(+)CD25(-)CD103(-) T cells and treated with costimulation blockade. Intragraft T cells from C57BL/6 recipients were analyzed for the expression of the Foxp3 protein after tolerance induction. RESULTS: Mice reconstituted with IL-10(-/-) CD4(+) T cells, CD4(+)CD25(-) T cells or CD4(+)CD25(-) CD103(-) T cells and treated with costimulation blockade accepted allografts permanently. Analysis of cells from recipient mice adoptively transferred with CD4(+)CD25(-) T cells contained a population of CD4(low)CD25(+) T cells 100 days after transplantation. Costimulation blockade partially prevented the homeostatic proliferation of CD4(+)CD25(-)CD103(-) T cells in Rag-1(-/-) recipients. Accepted allografts contained an elevated number of CD4(+)Foxp3(+) T cells. CONCLUSIONS: These results indicate that T-cell derived IL-10 is not essential for induction of graft acceptance in mice treated with costimulation blockade, but that treatment limits T-cell expansion in the recipients. The results further indicate that tolerance is maintained by intragraft CD4(+)Foxp3(+) T cells.     

Targeting acute allograft rejection by immunotherapy with ex vivo-expanded natural CD4+ CD25+ regulatory T cells

BACKGROUND: Natural CD4CD25 regulatory T (Treg) cells have been implicated in suppressing alloreactivity in vitro and in vivo. We hypothesized that immunotherapy using ex vivo-expanded natural Treg could prevent acute allograft rejection in mice. METHODS: Natural CD4+ CD25+ Treg were freshly purified from naive mice via automated magnetic cell sorter and expanded ex vivo by anti-CD3/CD28 monoclonal antibody (mAb)-coated Dynabeads. Suppression was assayed in vitro by mixed lymphocyte reaction and in vivo by targeting cardiac allograft rejection. Survival of Treg or effector T (Teff) cells after adoptive transfer in vivo was tracked by flow cytometry and all allografts were examined by histology and immunohistochemistry. RESULTS: By day nine in culture, 26.6+/-5.3-fold of expansion was achieved by co-culture of fresh natural Treg with anti-CD3/CD28 mAb-coated Dynabeads and interleukin-2. Ex vivo-expanded Treg exerted stronger suppression than fresh ones towards alloantigens in vitro and prevented CD4 Teff-mediated but only delayed CD4+/CD8+ Teff-mediated heart allograft rejection in Rag-/- mice. Long-term surviving allografts showed no signs of acute or chronic rejection with graft-infiltrating Treg expressing CD25 and FoxP3. Infused Treg persisted and expanded long-term in vivo and trafficked through the peripheral lymphoid tissues. CD25 expression was dynamic in vivo: maintained CD25 expression on Treg was indicative for the preservation of allosuppression, while significantly enhanced CD25 expression on CD4+ effector T cells was most likely associated with T-cell expansion and graft rejection. CONCLUSIONS: Therapeutic use of ex vivo-expanded natural CD4+ CD25+ Treg may be a feasible and nontoxic modality for controlling allograft rejection or perhaps inducing allograft tolerance.     

Observational support for an immunoregulatory role of CD3+CD4+CD25+IFN-gamma+ blood lymphocytes in kidney transplant recipients with good long-term graft outcome.

There is evidence that interferon-gamma (IFN-gamma)-dependent interactions of dendritic cell (DC), T regulatory (Treg), and T suppressor (Ts) subpopulations contribute to allograft acceptance. We measured DC subsets, CD3+CD4+CD25+ (Treg phenotype) and CD3+CD8+CD28(-) (Ts phenotype) peripheral blood lymphocytes (PBL) expressing Foxp3, Th1 or Th2 cytokines, peripheral T- and B-cell counts, and plasma cytokines in 33 kidney transplant recipients with a serum creatinine of < or =1.8 mg/dl and 32 recipients with a serum creatinine of > or =2.0 mg/dl more than 100 days post-transplant. Cell subsets were measured in whole blood using four-color flow cytometry. Patients with increased creatinine had less frequently detectable CD3+CD4+CD25+IFN-gamma+ PBL than patients with good graft function (P = 0.017). In patients with good graft function, CD3+CD4+CD25+IFN-gamma+ PBL were associated with high Foxp3+, IL-2+, IL-12+, IL-4+, and IL-10+ CD3+CD4+CD25+ T PBL (P < 0.001), low CD3+CD8+CD28(-)Foxp3+ (P = 0.002), CD3+CD4+DR+ (P = 0.002), CD3+CD8+DR+ T (P = 0.005) and CD19+ B PBL (P = 0.005), and low lineage(-)HLA-DR+CD11c+CD123(-) DC1 (P = 0.006). Patients with impaired graft function did not show these associations. Additional flow cytometric analysis confirmed strong co-expression of IFN-gamma and Foxp3 by CD4+CD25+ PBL particularly in patients with good graft function. Our data support an immunoregulatory role of CD3+CD4+CD25+Foxp3+IFN-gamma+ cells in a subgroup of transplant recipients with good graft acceptance.     

CD4^＋CD25^＋调节性T细胞在维持小鼠肝脏移植自发性免疫耐受状态中的作用

目的 探讨CD4^＋CD25^＋调节性T细胞在维持小鼠肝脏移植免疫耐受状态中的作用。方法 进行小鼠原位肝脏移植,诱导出移植免疫耐受后,向受体注射抗CD25抗体（PC61）以去除CD4^＋CD25^＋T细胞,检测受体内CD4^＋CD25^＋T细胞数量及叉状头／翅膀状螺旋转录因子（Foxp3）的表达以确定CD4^＋CD25^＋T细胞完全被清除,同时观察受体生存时间。结果与同种同系小鼠肝脏移植结果相似,同种异系肝脏移植小鼠的生存时间亦均超过70d。移植免疫耐受诱导后,PC61不同注射方案均能完全去除受体小鼠肝脏、脾脏及血液中的CD4^＋CD25^＋T细胞,且移植肝脏中Foxp3mRNA的表达也明显降低,表明完全去除了CD4^＋CD25。调节性T细胞,但肝脏移植动物生存时间并未受到影响。结论CD4^＋CD25^＋调节性T细胞对于小鼠肝脏移植自发性免疫耐受的维持并非必需。     

Thymocyte/splenocyte-derived CD4+CD25+Treg stimulated by anti-CD200R2 derived dendritic cells suppress mixed leukocyte cultures and skin graft rejection

BACKGROUND: CD200 delivers immunoregulatory signals following engagement of its receptor, CD200R. A family of CD200Rs (CD200R1-4) has been described. Spleen expresses cell surface CD200R1, while bone marrow shows predominantly expression of cell surface CD200R2/R3. We showed that dendritic cell precursors (DCp) cultured with anti-CD200R2/3 develop the capacity to induce CD4(+)CD25(+) regulatory T cells (Treg) from peripheral lymphocytes. We now characterize DCs involved in induction of antigen-specific Treg from thymocytes or peripheral T cells, and the properties of Treg cells maintained in long-term culture. METHODS: Bone marrow DCp (C3H or BL/6 origin) were cultured for 8 days with GMCSF, IL-4 and anti-CD200R2, or with CD200Fc and a previously described peptide inhibitor of CD200R1 to allow preferential engagement of non-CD200R1 receptors by CD200. Mixed leukocyte cultures (MLCs) were initiated with allogeneic responder lymphocytes/thymocytes (BL/6 or C3H) and mitomycin-c treated DCs to induce Treg. Treg cells were maintained by reculture with DCs derived in the same manner and IL-2, cloned at limiting dilution, and tested for their ability to suppress MLCs and skin graft rejection in vivo. RESULTS: Foxp3(+) CD4(+)CD25(+) Treg were derived from 60-hr thymocyte and splenocyte T cell cultures using both DC populations. Cloned C3H Treg (Foxp3(+)) suppressed both C3H anti-BL/6 reactivity in a fresh MLC and rejection of BL/6 skin allografts in C3H recipients; the converse was true for BL/6 Treg. CONCLUSIONS: We conclude that CD200 triggering of bone-marrow DCs in the absence of CD200R1 engagement induces CD4(+)CD25(+) Treg, and these cloned antigen-specific Treg may have clinical utility.     

Short-term anti-CD25 monoclonal antibody treatment and neogenetic CD4(+)CD25(high) regulatory T cells in kidney transplantation

CD4(+)CD25(high) T cells named regulatory T (Treg) cells are generated and play a key role in the induction and maintenance of transplant tolerance in organ recipients. Interleukin-2 (IL-2) enhance the development of effector cells and is essential for generation of Treg cells. The effect of the anti-CD25 monoclonal antibody (anti-CD25mAb) induction therapy on the neogenetic CD4(+)CD25(high)Treg cells is important for therapeutic strategies in kidney transplant. To clarify the question, a prospective study was conducted in 21 living donor kidney transplant recipients who randomly divided into the anti-CD25mAb group (Daclizumab) with 11 patients and the control group with 10 patients. The frequency of CD4(+)CD25(high)Treg cells in total CD4(+) T cells was analyzed by flow cytometry and FoxP3 expression by RT-PCR in peripheral blood, and results were compared at day 0, 3, 13, 17, 27 posttransplantation. There was no significant difference in patient characteristics and allograft survival. The present study showed that in vivo antigen-specific Treg cells population were generated and expanded after transplant. Both groups showed a significant increase in the frequency of CD4(+)CD25(high)Treg cells and higher level of FoxP3 mRNA after transplantation while the serum creatinine declined. Compared with the control group, recipients with anti-CD25mAb injection had significantly lower percentage of CD4(+)CD25(high) in total CD4(+) cells (1.13%+/-0.13% vs 1.94%+/-0.22%, P=0.00; 3.75%+/-0.28% vs 7.11%+/-0.51%, P=0.00) on day 3, 17 after transplantation. While, the percentage was not significantly different on day 10, 27 (3.72%+/-0.19% vs 4.36%+/-0.28%, P=0.08; 7.84%+/-0.35% vs 8.56%+/-0.36%, P=0.16). However, there was not obvious difference in Foxp3 expression level associated with the source of the CD4(+)CD25(high)Treg cells at the different time point after transplant. Our data indicated that CD4(+)CD25(high)Treg cells were transiently affected by anti-CD25mAb, without depletion. In conclusion, the short-term treatment with anti-CD25mAb might not prevent the production, proliferation of neogenetic Treg cells in organ transplant.     

Studies on the participation of different T cell subsets in rat liver allograft rejection

In this study, we investigated which subsets of rat T cells (CD8 + vs. CD4 + ) are involved in the rejection of liver allografts by the in vivo administration of monoclonal antibody (OX-8 or OX-38, and W3/25 MAb) into thymectomized recipient Lewis (RTI¹) rats prior to DA (RTI^a) liver transplantation. We also compared the results of allograft survival of liver and heart transplants under the same experimental conditions. In order to deplete either CD8 + T cells or CD4 + T cells from recipient animals, 0.4 ml of OX-8 (ascitic form) or a 0.8 ml cocktail of MAb W3/25 and OX-38 (0.4 ml each) was injected into thymectomized recipient rats, respectively. Untreated Lewis rats consistently rejected donor DA liver grafts between 9 and 11 days (n = 7, 9.8 days ± 1.1 days). In contrast, anti-CD8 MAb pretreatment extended the survival times of DA liver grafts for up to 40 days (n = 5, 26.8 days ± 8.4 days). Furthermore, survival of DA liver grafts was significantly prolonged in Lewis rats that had been pretreated with anti-CD4 MAb (n = 7,35.6 days ± 17.9 days). Two out of seven recipient animals survived for more than 60 days. For heart transplantation, untreated Lewis rats rejected DA heart grafts between 6 and 8 days after operation (n = 6, 6.5 days ± 1.2 days). Anti-CD4 MAb treatment prolonged heart graft survival for more than 60 days in all cases (n = 3, > 60 days). However, there was virtually no effect of anti-CD8 MAb treatment on heart graft survival (n = 4, 7.0 days ± 0.9 days). These results suggested that when whole MHC disparity prevailed between donor and recipient, both subsets of T cells were required for the rejection of liver allografts and that class II reactive T cells predominantly mediated liver graft rejection. Furthermore, CD8 + T cells played a differential role in the rejection of rat liver and heart allograft.     

Vitamin D3 combined with antibody agents suppresses alloreactive memory T-cell responses to induce heart allograft long-term survival

BackgroundThe pre-stored memory T cells in organ transplant patient carry a high risk of allograft rejection. The current study aimed to determine whether the allogenic response of adoptively transferred memory T cells in mice was suppressed by vitamin D3 monotherapy alone or in combination with monoclonal antibody treatment.MethodsPrior to vascularized heterotopic heart transplantation, naïve C57BL/6 mice were primed with memory T cells. Recipient mice were administered vitamin D3 alone or in combination with monoclonal antibodies (anti-CD40L/ anti-LFA-1). Memory T cells and CD4⁺ forkhead box P3⁺ T cells in recipient spleens were measured using flow cytometry. Additionally, the expression of cytokines was measured by ELISA and quantitative PCR. Inflammatory factors in the grafts were identified by hematoxylin and eosin staining.ResultsVitamin D3 in conjunction with anti-CD40L/ anti-LFA-1 antibodies were administered according to the median survival time from 6.5 to 80 days. The results revealed that grafts were protected through the prevention of inflammatory cell infiltration. Combined treatment decreased the mRNA levels of IL-2, IFN-γ and IL-10 and increased the mRNA levels of IL-4, Foxp3 and TGF-β in the allograft. Rejection was suppressed by a reduction of CD4⁺CD44^high CD62L⁺ and CD8⁺ CD44^high CD62L⁺ memory T cells, the induction of regulatory T cells in the recipient spleen and a reduction of serum IL-2, IFN-γ and IL-10 levels.ConclusionVitamin D3 efficiently protected allografts from memory T-cell allo-responses when combined with anti-CD40L/anti-LFA-1 antibodies therapy.     

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.     

Role of IFNγ in Allograft Tolerance Mediated by CD4+CD25+ Regulatory T Cells by Induction of IDO in Endothelial Cells

Regulatory T cells have been described to specifically accumulate at the site of regulation together with effector T cells and antigen-presenting cells, establishing a state of local immune privilege. However the mechanisms of this interplay remain to be defined. We previously demonstrated, in a fully MHC mismatched rat cardiac allograft combination, that a short-term treatment with a deoxyspergualine analogue, LF15-0195, induces long-term allograft tolerance with a specific expansion of regulatory CD4+CD25+T cells that accumulate within the graft. In this study, we show that following transfer of regulatory CD4+T cells to a secondary irradiated recipient, regulatory CD25+Foxp3+ and CD25+Foxp3(-) CD4+T cells accumulate at the graft site and induce graft endothelial cell expression of Indoleamine 2, 3-dioxygenase (IDO) by an IFNgamma-dependent mechanism. Moreover, in vivo transfer of tolerance can be abrogated by blocking IFNgamma or IDO, and anti-IFNgamma reduces the survival/expansion of alloantigen-induced regulatory Foxp3+CD4+T cells. Together, our results demonstrate interrelated mechanisms between regulatory CD4+CD25+T cells and the graft endothelial cells in this local immune privilege, and a key role for IFNgamma and IDO in this process.     

Infusion of Lin- bone marrow cells results in multilineage macrochimerism and skin allograft tolerance in minimally conditioned recipient mice

Donor-specific immunological tolerance using high doses of donor bone marrow cells (BMC) has been demonstrated in mixed chimerism-based tolerance induction protocols; however, the development of graft versus host disease (GVHD) remains a risk. In the present study, we demonstrate that the infusion of low numbers of donor Lin(-) bone marrow cells (Lin(-) BMC) 7 days post allograft transplantation facilitates high level macrochimerism induction and graft tolerance. Full-thickness BALB/c skin allografts were transplanted onto C57BL/6 mice. Mice were treated with anti-CD4 and anti-CD8 mAbs on day 0, +2, +5, +7 and +14 along with low dose busulfan on day +5. A low dose of highly purified Lin(-) BMC from BALB/c donor mice was infused on day +7. Chimerism and clonal cell deletion were evaluated using flow cytometry. Donor-specific tolerance was tested by donor and third-party skin grafting and mixed leukocyte reaction (MLR). Lin(-) BMC infusion with minimal immunosuppression led to stable, mixed, multilineage macrochimerism and long-term allograft survival (>300 days). Mixed donor-recipient macrochimerism was observed. Donor-reactive T cells were clonally deleted and a 130% increase in CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) was observed in the spleen. Tolerant mice subsequently accepted second donor, but not third-party (C3H), skin grafts and recipient splenocytes failed to react with allogeneic donor cells indicating donor-specific immunological tolerance was achieved. We conclude that the infusion of donor Lin(-) BMC without cytoreductive recipient conditioning can induce indefinite survival of skin allografts via mechanisms involving the establishment of a multilineage macrochimeric state principally through clonal deletion of alloreactive T cells and peripherally induced CD4(+)Foxp3(+) Tregs.     

Injection of donor-derived splenic dendritic cells plus a nondepleting anti-CD4 monoclonal antibody to prolong primary skin graft survival indefinitely and abrogate the production of donor-specific antibodies in the Fischer-to-Lewis rat combination

We have previously shown that injection of donor-derived Fischer rat OX62+ dendritic cells plus an anti-CD4 monoclonal antibody generates donor-specific CD4+CD25+FoxP3+ regulatory T cells in Lewis rats spleens. The regulatory T cells indefinitely prolonged the survival of skin graft from Fischer rat and abrogated the antidonor antibody response. We have now shown that an injection of 2 × 10(6) donor-derived OX62+ dendritic cells plus 2 mg nondepleting anti-CD4 monoclonal antibody (W3/25) at 28 days before grafting induced indefinite skin graft survival in this combination; whereas an injection on day -1 prolonged it only to 50 days. This effect is donor specific. In both cases, we suppressed the antidonor antibody response. It is likely that the efficacy of this protocol is, at least in part, dependent on induction of donor-specific regulatory T cells, as suggested by previous data. The 28 days necessary to obtain tolerance of allogenic skin grafts may be due to the time required for the host to induce proliferation of donor-specific regulatory T cells.     

小鼠补体调节蛋白对CD4+T淋巴细胞的调控作用及其机制

目的 研究小鼠补体调节蛋白Crry对CD4+T淋巴细胞的调控作用及诱导同种移植免疫低反应性的机制.方法 分离C57BL/6小鼠脾淋巴细胞,用免疫磁珠法分选出CD4+T淋巴细胞后,将CD4+T淋巴细胞分为A、B、C、D、E和F组,分别用抗小鼠CD3、CD28、Crry、CD3/CD28、CD3/Crry和CD3/CD28/Crry抗体共刺激通路与CD4+T淋巴细胞进行反应,采用噻唑蓝(MTT)法检测各组CD4+T淋巴细胞的增殖情况,并采用酶联免疫吸附试验检测CD4+T淋巴细胞培养上清中白细胞介素2(IL-2)、γ干扰素(γ-IFN)、IL-4和IL-10的水平;另外,以BALB/c小鼠和C57BL/6小鼠的脾细胞分别作为刺激细胞和反应细胞,建立同种混合淋巴细胞反应(MLR)体系并加入抗小鼠Crry抗体,通过岍法观察Crry对MLR的影响.结果 D、E、F组的CD4+T淋巴细胞均出现明显增殖,增殖活性显著高于A、B、C组(P<0.05),其中F组显著高于D组和E组(P<0.05),D组和E组间增殖活性的差异无统计学意义.D组CD4+T淋巴细胞经抗CD3/CD28抗体共刺激后,培养上清中γ-IFN和IL-2的水平显著升高,与A、B、C和E组比较,差异均有统计学意义(P<0.05),但与F组的差异无统计学意义;E组CD4+T淋巴细胞经抗CD3/Crry抗体共刺激后,IL-4的水平显著升高,与A、B、C、D组比较,差异均有统计学意义(P<0.05),但显著低于F组(P<0.05);各组间IL-10水平的差异无统计学意义.Crry可以明显抑制MLR中的细胞增殖(P<0.05).结论 补体调节蛋白Crry能刺激CD4+T淋巴细胞的增殖,并使其IL-4的表达升高及抑制IL-2和γ-IFN的表达,从而诱导同种移植免疫低反应性.