FasL嵌合蛋白修饰的供者脾脏细胞输注诱导移植免疫耐受的动物研究

目的 探讨FasL嵌合蛋白修饰的供者脾脏细胞输注诱导移植免疫耐受的可行性.方法 采用ProtEx~(TM)源蛋白修饰技术,将FasL嵌合蛋白修饰供者WF大鼠的脾脏细胞,在围手术期分次输注给受者ACI大鼠.施行大鼠异位心脏移植术,按注射细胞的不同处理将实验动物随机分为3组:(1)SA-FasL修饰的供者脾脏细胞组(SA-FasL组,n=23);(2)链霉亲和素蛋白(SA)修饰的供者脾脏细胞对照组(n=20);(3)未修饰的供者脾脏细胞对照组(n=8).围手术期未作任何细胞治疗为空白对照组(n=10).将耐受大鼠脾脏细胞输注给未处理ACI大鼠再行心脏移植.进行混合淋巴细胞反应;将第三方F344大鼠心脏移植给耐受大鼠,观察排斥反应.结果 SA-FasL组移植心脏长期存活率为70%,显著高于其他组(P<0.05).耐受大鼠的脾脏细胞输注能够过继转移免疫耐受;混合淋巴细胞反应与第三方移植后的排斥反应表明形成了供者特异性免疫耐受.结论 FasL嵌合蛋白修饰的供者脾脏细胞输注能够诱导供者特异的免疫耐受,这一简便高效的方法具有潜在的临床应用价值.     

Bone marrow chimerism and tolerance induced by single-dose cyclophosphamide

BACKGROUND: Establishment of hematopoietic chimerism is the most stable strategy for donor-specific tolerance. Safer pretreatment regimens are needed for clinical application. We evaluated the efficacy of a simple protocol using cyclophosphamide (CYP) on induction of chimerism and organ transplant tolerance across major histocompatibility complex (MHC) barriers in the rat. MATERIALS AND METHODS: Bone marrow cells from BN (RT1(n)) donors were infused to LEW (RT1(l)) recipients on day 0 after a single injection of CYP at various doses on day -1. Donor-derived hematopoietic chimerism was evaluated by flowcytometry. The recipients received BN or third party (BUF) heart allografts on day 100. RESULTS: While pretreatment with 200 mg/kg of CYP induced high levels of hematopoietic chimerism, six of eight recipients died of severe graft-versus-host-disease (GVHD). CYP at dose of 150 mg/kg induced 36.5 +/- 24.1% of donor-derived chimerism on day 10, and sustained macrochimerism was seen until day 100 without GVHD. Pretreatment with 100 mg/kg of CYP resulted in only transient chimerism (4.8 +/- 5.2%) which disappeared by day 20. In the recipients with 50 mg/kg of CYP, donor bone marrow cells were rapidly rejected and no chimerism was observed. The recipients with 150 mg/kg of CYP accepted BN heart allografts (>100 days x 5), while rejecting BUF allografts by day 12 (n = 4). BN heart allografts were rejected in the recipients with 100 (MST: 57 days, n = 5) and 50 mg/kg (MST: 7 days, n = 5) of CYP. CONCLUSIONS: A single dose of CYP can induce hematopoietic chimerism across MHC-barriers. The dose of 150 mg/kg seems to be optimal to induce organ transplant tolerance without developing GVHD.     

免疫毒素及可溶性抗原诱导胰岛移植耐受

目的　通过静脉注入抗ＣＤ４ 、ＣＤ８ 免疫毒素及供体可溶性抗原诱导胰岛移植物免疫耐受。方法　供、受体分别为Ｗｉｓｔａｒ 大鼠和ＳＤ大鼠， 移植前１４ 天、７ 天分别将免疫毒素各２００ μｇ， 供体可溶性抗原５００ μｇ 经静脉注入受体， 然后将供体５００ 个胰岛移植于受体（ 糖尿病大鼠）左侧肾包膜下。结果　用免疫毒素及供体可溶性抗原联合处理组胰岛移植物存活时间显著延长（ Ｐ＜ ０ ．０１） ， 而单独应用抗ＣＤ４ 、ＣＤ８ 免疫毒素或供体可溶性抗原组仅能获得胰岛移植物存活时间轻度延长。结论　抗ＣＤ４、ＣＤ８ 免疫毒素及供体可溶性抗原联合应用可以诱导供体特异性免疫耐受     

Allograft tolerance by intrathymic donor splenocyte transfer: an age-dependent, species-specific phenomenon?

Abstract  Protocols that allow al lograft survival without immuno-suppression remain the ultimate goal in transplantation. Intrathymic injection of donor splenocytes into a transiently immunosuppressed recipient has induced tolerance to a variety of subsequently transplanted allografts in rats. The purpose of this study was to determine if recipient age is critical to intrathymic tolerance in light of age-dependent thy-mic changes, and if this protocol can be extended to an outbred, large animal model. Prepubertal and postpubertal Wistar-Furth rats underwent intrathymic injection of splenocytes from Lewis rats and an-tilymphocyte serum (ALS) intra-peritoneally. On day 21, a hetero-topic Lewis heart was transplanted, with graft survival evaluated by car diac palpation. Graft tolerance (> 100 days) occurred in four out of five (80%) of the prepubertal rats compared to two out of six (33%) postpubertal rats. Tolerance was not demonstrated in rats receiving in trathymic injection of buffer only. In puppies, groups 1 and 2 underwent splenectomy with intrathymic injection of allo splenocytes. Control puppies (group 3) received intrathymic auto splenocytes. Groups 1 and 3 were given antilymphocyte gamma globulin (ALG) on days 7 to 0 with respect to the intrathymic injection. Group 2 did not receive ALG, but instead received cyclosporin A (CSA) on days 0–2. On day 21, all puppies underwent bilateral ne-phrectomy and single renal trans plantation. No additional immuno-suppression was given. Tolerance (creatinine < 7 mg/dl for 100 days) was not obtained by any dog in all three groups. There was no difference in graft survival between control and experimental dogs, with the longest surviving graft seen in a control dog (26 days). Our results suggest that thymic change during maturation may alter the ability to induce tolerance by intrathymic injection of donor cells in rats, and that the protocol is not easily adapted to large animals.     

Allograft tolerance induced by intact active bone co-transplantation and anti-CD40L monoclonal antibody therapy

BACKGROUND: One of the most promising approaches to achieving allograft tolerance involves the transient inhibition of co-stimulatory signals in T cells. There is, however, increasing evidence that this approach alone cannot universally elicit allograft tolerance and that adjunct therapies capable of synergizing with co-stimulation blockade may be necessary. METHODS: We developed a novel tolerance strategy involving co-transplantation of intact allogeneic bone fragments containing active bone marrow (intact active bone [IAB]) with heart allograft and transient anti-CD40L monoclonal antibody therapy. RESULTS: Mice treated with IAB and anti-CD40L were tolerant to major histocompatibility complex and minor antigen-mismatched cardiac and skin allografts. Heart allografts had normal histology up to 270 days posttransplantation, and the production of graft-reactive antibodies was inhibited. Microchimerism, but no macrochimerism, of donor cells was detected in the peripheral blood or lymphoid organs of tolerant mice receiving IAB and anti-CD40L. Lymphocytes from tolerant mice retained normal proliferative responsiveness to donor cells in vitro but demonstrated a donor-specific loss in the priming of interferon-gamma responses. The ability to produce interleukin-2 or -4 when stimulated with donor cells was normal. CONCLUSIONS: Contrary to previous reports of the ability of bone marrow cells to induce central deletional tolerance, our data suggest that the regimen involving co-transplantation of IAB on the day of heart allograft transplantation and transient anti-CD40L therapy induces a robust donor-specific peripheral tolerance.     

Functional clonal deletion versus active suppression in transplantation tolerance induced by total-lymphoid irradiation

Transplantation tolerance and stable chimerism were established in adult mice conditioned with a short course of total-lymphoid irradiation (TLI) followed by infusion of 30 X 10(6) allogeneic bone marrow cells. Spleen cells of tolerant mice could not exert a proliferative or cytotoxic response against host-type cells in vitro and were unable to induce graft-versus-host reaction in secondary host-type recipients. The degree of suppression assessed by coculturing tolerant splenocytes in vitro in the one-way mixed lymphocyte reaction was quite variable--and, in some cases, was not at all demonstrable, although tolerance was clearly maintained. Suppression, when apparent, could not be ascribed to T lymphocytes. Suppressor cells were found to bind soybean agglutinin and could be separated from the nonsuppressive cells by means of this lectin. Dissociation of the suppressive population (SBA+ cells) from that which is normally alloreactive (SBA- cells) resulted in a suppressor cell-depleted fraction that was still unable to respond to host-type cells but regained reactivity to unrelated cells. Limiting dilution analysis of chimeric splenocytes revealed markedly reduced frequencies of cytotoxic T lymphocyte precursors (CTL-P) directed against host-type cells, as compared with normal splenocytes reacting against the same target cells. This difference was accentuated when these cells were sensitized to host-type target cells prior to plating in limiting dilution cultures. In 1:1 mixing experiments of normal and chimeric splenocytes, there was no evidence of any in vitro suppressive activity to account for hyporeactivity of chimeric cells against host-type cells. Thus, maintenance of TLI-induced tolerance seemed not to be mediated primarily through an active suppressor cell mechanism.     

Attempts to break perimetamorphically induced skin graft tolerance by treatment of Xenopus with cyclophosphamide and interleukin-2

The maintenance of skin allotolerance induced by perimetamorphic application of MHC-disparate skin to isogeneic Xenopus is investigated. Removal of the perimetamorphically applied first-set graft after 4 weeks did not, in general, completely break allotolerance; however, many second-set semi-allogeneic grafts, applied up to 14 weeks after first-set removal, were no longer maintained in perfect condition. Skin allografts tolerated for up to 42 weeks continued to express donor histocompatibility antigens, as indicated by their survival times when transplanted back to the original donor or recipient strain. Treatment with human recombinant IL-2 (rIL-2), shown elsewhere to be an effective immunoregulatory lymphokine for Xenopus in vivo, failed to cause long-term-tolerated 1st-set allografts, or newly-applied 2nd-set grafts, to be rejected. In contrast, cyclophosphamide (CyP) treatment led to acute (less than 4 weeks) destruction of both 1st- and 2nd-set allografts; breaking of tolerance was regularly seen when donor and host differed by two MHC haplotypes, but occurred infrequently in semiallogeneic combinations. The experiments suggest that skin-induced allotolerance is maintained by an immunosuppressive mechanism, that is CyP-sensitive but resistant to rIL-2 treatment.     

Dominant tolerance and linked suppression induced by therapeutic antibodies do not depend on Fas-FasL interactions

BACKGROUND: Nonlytic anti-CD4 monoclonal antibody therapy can be used to induce transplantation tolerance in rodent models. Such tolerance is often associated with dominant regulation, mediated by CD4+ cells, and characterized by infectious tolerance and linked suppression. Understanding the mechanisms by which CD4+ regulatory cells function may improve the manner in which current immunosuppressants are applied and may lead to the development of new tolerance-inducing therapeutics. Fas-mediated apoptosis has been characterized as an important mechanism of peripheral self-tolerance and we here examine whether it has any role in anti-CD4 monoclonal antibody-induced dominant tolerance. METHODS: Tolerance to transplanted skin and bone marrow, mismatched for multiple minor histocompatibility antigens, was induced in Fas mutant and control mice using anti-CD4 and anti-CD8 monoclonal antibodies. To test for linked suppression, animals were transplanted with a second graft-bearing tolerated and third party antigens. The ability of splenocytes from tolerant animals to suppress graft rejection was assessed by transfer into partially immunocompromised recipients. RESULTS: Monoclonal antibody therapy rendered Fas mutant mice tolerant of minor disparate skin and bone marrow. Splenocytes from these and control tolerant animals when transferred into partially immunocompromised Fas mutant or control recipients, induced antigen-specific suppression of graft rejection. Additionally, tolerant Fas mutant mice accepted grafts bearing tolerated and third party antigens. CONCLUSIONS: Signal transduction through the Fas receptor plays no essential role in the induction of tolerance using anti-CD4 and anti-CD8 monoclonal antibodies or its maintenance by active regulation.     

短期运用环孢素A对供者骨髓移植所诱导的混合嵌合体和免疫耐受的抑制作用

目的探讨临床常用免疫抑制剂对供者骨髓移植和T淋巴细胞协同刺激信号阻滞联合诱导的混合嵌合体和免疫耐受的影响。方法将BALB/c小鼠的皮肤移植于C57BL/6小鼠背部,术后经尾静脉注射BALB/c小鼠骨髓细胞5×10~7个和AdCTLA4-FasL 5×10~9 PFU(标准方案组),部分小鼠在此基础上还接受环孢素A(CsA组)、霉酚酸酯(MMF组)和环孢素A、霉酚酸酯联合(CsA+ MMF组)皮下或腹腔注射,共用药28 d,同时设移植后不给任何处理的对照组。观察移植皮肤存活情况,流式细胞仪测定受者外周血Vβ11~+T淋巴细胞的水平和供者来源细胞的嵌合水平,行单向混合淋巴细胞反应(MLR)了解受者对供者抗原的反应。结果除对照组外,其它几个组在短期内(21 d)均诱导了高水平的混合嵌合体(＞30%),但在停药后的140 d,仅标准方案组和MMF组仍保持稳定的嵌合水平。对照组移植皮片的存活时间为(9．8±1．2)d,CsA组和CsA+MMF组皮片存活时间均不超过50 d,标准方案组和MMF组皮片存活时间均超过150 d,明显长于CsA组和CsA+MMF组(P＜0．05)。术后150 d,标准方案组和MMF组的MLR受到显著抑制,刺激指数均＜1,而CsA组和CsA+MMF组的MLR未受抑制(刺激指数均＞1)。术后21d时,各组小鼠外周血中Vβ11~+T淋巴细胞的水平均低于对照组,但标准方案组和MMF组的Vβ11~+ T淋巴细胞较CsA组和CsA+ MMF组更低(P＜0．05),至术后140 d时,标准方案组和MMF组的Vβ11~+ T淋巴细胞比例降至更低水平。结论CsA或含CsA的免疫抑制方案对供者骨髓移植和输注CTLA4-FasL联合诱导的混合嵌合体和免疫耐受具有抑制作用,其机理可能与早期外周供者反应性T淋巴细胞删除减少有关。     

供体骨髓细胞输注诱导大鼠肢体移植免疫耐受

目的 探讨环磷酰胺(CP)加供体脾细胞输注联合供体骨髓细胞(DBMC)输注诱导大鼠肢体移植免疫耐受的效果及机制.方法选择25只雄性Wistar大鼠、25只雌性SD大鼠分别作为肢体移植的供体和受体.实验分为五组:A组:无处理对照组,B组:受体在肢体移植前给予供体脾细胞输注预处理;C组:受体在肢体移植前给予CP预处理,D组:受体在肢体移植前给予供体脾细胞输注加CP预处理,E组:受体在肢体移植前给予供体脾细胞输注联合DBMC输注加CP预处理,每组5只.建立肢体移植动物模型,诱导耐受后观察大鼠一般情况,移植肢体排斥反应出现时间及存活时间,通过混合淋巴细胞培养确定耐受状态,采用PCR检测嵌合体的形成.结果 E组肢体移植物的存活时间[(27.6±1.1)d]较A组[(6.8±0.4)d]、B组[(7.2±0.8)d]、C组[(7.8±1.3)d]、D组[(17.8±0.8)d]显著延长,差异均有统计学意义(P＜0.01).混合淋巴细胞反应E组特异性抑制率[(88.00±1.06)%]显著高于B组[(36.90±1.08)%]、C组[(37.90±0.95)%]和D组[(67.20±1.12)%],差异均有统计学意义(P＜0.01).E组嵌合体呈阳性.结论联合CP加供体脾细胞输注及DBMC输注可一定程度诱导大鼠同种异体肢体移植的免疫耐受,延长移植物存活时间.嵌合体的形成可能与免疫耐受的形成及维持有关.     

胸腺修饰诱导大鼠心脏移植耐受与白细胞介素-2,10的关系

目的在手术当天进行胸腺修饰,诱导大鼠同种心脏移植免疫耐受,并对其可能机制作初步分析.方法通过胸腺注射和围手术期短程使用FK506来诱导心脏移植耐受,观察供心存活天数、混合淋巴细胞反应及受体鼠血清中白细胞介素(IL)-2、IL-10水平的变化.结果无处理组、对照组、经典诱导组和实验组供心存活时间分别为(6.8±1.9)、(17.4±5.1)、(73.8±8.6)、(55.0±24.7)d,实验组与经典诱导组比较差异无统计学意义(P＞0.05).无处理组、经典诱导组和实验组的供受体脾细胞混合淋巴细胞培养刺激效应分别为198.72%、95.80%、67.94%,实验组和经典诱导组较无处理组增殖反应均明显降低(P＜0.05),而两者间增殖反应差异无统计学意义(P＞0.05).IL-10水平在无处理组移植心脏被排斥时为(48.10±5.14)ng/L较移植前(52.60±10.14)ng/L差异无统计学意义(P＞0.05);而在实验组早期呈低水平表达,为(36.10±2.30)ng/L,术后中期(281.80±65.44)ng/L晚期(80.90±12.39)ng/L较移植前水平高得多,差异有统计学意义(P＜0.05).受体IL-2水平在无处理组发生排斥时为(159.80±59.19)ng/L较移植前(54.80±8.42)ng/L明显升高,差异有统计学意义(P＜0.05).结论心脏移植手术当日胸腺内注射供体同种抗原,与术前21 d胸腺注射的经典诱导组同样能诱导宿主对移植物的低反应状态;IL-2的水平与排斥反应的发生有关,而IL-10可能是免疫耐受的特异性指标,IL-10更可能与免疫耐受的维持有关.     

胸腺注射转染供者主要组织相容性复合物基因的T淋巴细胞诱导免疫耐受的实验

目的 探讨受者胸腺内注射可表达供者主要组织相容性复合物（MHC）基因的受者T淋巴细胞诱导的免疫耐受的效果。方法 将携带供鼠（C57BL／6，H－2^b）k位点基因cDNA的逆转录病毒载体质粒PXN（N2－B19－H－2K^b）经包装细胞PA317细胞包装为重组病毒后，感染体外培养的受鼠（Balb/c,H-2^d）T淋巴细胞，再将此可表达供者MHC抗原的受者T淋巴细胞（H－2K^db）回输受鼠胸腺内，然后将供鼠（H－2^b）的皮肤移植给受鼠（H－2^d），观察免疫耐受的诱导情况。结果 外源性MHC基因（H－2K^b）整合到靶细胞（H－2^d）染色体DNA，并有效地转录，在细胞膜上有H－2K^b分子表达；对照组移植皮肤平均存活时间（MST）为9d；注射单克隆抗体对照组MST为11d；第三供者组MST为11.5d；实验组（胸腺回输H－2K^db嵌合体T淋巴细胞）MST为35d；实验组脾细胞对刀豆素A（ConA）的增殖反应在正常范围，单向混合淋巴细胞反应对第三供者的脾细胞反应正常，但对特异供者的脾细胞无反应。结论 自身T淋巴细胞在胸腺内表达供者MHC抗原可在成年动物诱导出对供者移植的特异性免疫耐受，无非特异性免疫抑制。     

Intrathymic injection of donor alloantigens induces donor-specific vascularized allograft tolerance without immunosuppression.

The induction of donor-specific tolerance could prevent the side effects of immunosuppression while improving allograft survival. Male adult Buffalo (RT1b) rats underwent an intrathymic (IT), portal venous (PV), intrasplenic (IS), or subcutaneous (SQ) injection of 25 x 10(6) major histocompatibility complex (MHC) mismatched Lewis (RT1(1)), UV-B-irradiated Lewis (RT1(1)), ACI (RT1a), or syngeneic Buffalo (RT1b) splenocytes. At the completion of the donor alloantigen injection, 1 mL rabbit anti-rat lymphocyte serum (ALS) was administered intraperitoneally to the Buffalo recipients, and 21 days later a heterotopic Lewis or ACI heart was transplanted. Intrathymic injection of donor alloantigen induced a donor-specific tolerance that allowed the cardiac allograft to survive indefinitely (mean survival time [MST] > 140.7 days) in 84% of the recipients without further immunosuppression, whereas groups receiving antigen injections at other sites (PV, IS, and SQ) plus ALS rejected cardiac allografts in normal fashion (MST approximately 8.0 days). Buffalo recipient rats with long-term surviving Lewis cardiac allografts after Lewis IT injection and ALS subsequently rejected a heterotopic third-party ACI cardiac allograft in normal fashion (MST approximately 7 days), whereas a second Lewis cardiac allograft was not rejected (MST > 116 days). Microchimerism is unlikely because Lewis allograft survival was also prolonged (MST > 38.7 days) in rats receiving UV-B-irradiated splenocytes IT, which cannot proliferate. Survival of Lewis renal allografts was also prolonged, but not indefinitely, in Buffalo recipients possessing a long-term surviving Lewis cardiac allograft (MST approximately 17.6 days versus 7 days for control). This model emphasizes the potential role of exposure of immature thymocytes to foreign donor alloantigens during maturation in the thymic environment for the development of unresponsiveness to an MHC-mismatched donor-specific vascularized allograft.     

Operational tolerance induced by pretreatment with donor dendritic cells under blockade of CD40 pathway.

BACKGROUND: Dendritic cells can mount immune response as competent antigen presenting cells. Recently, it has been reported that immature dendritic cells induce prolongation of allograft survival. However, the ability of mature dendritic cells to induce operational tolerance is unclear. Therefore, in this study, we examined the ability of splenic mature dendritic cells to induce operational tolerance to fully allogeneic antigens using mouse heterotopic heart transplantation model. METHODS: CBA (H2k) mice received i.v. injections with donor splenic dendritic cells or B cells in the absence or presence of monoclonal antibody (mAb) specific for CD40 ligand or CD80/CD86 2 weeks before transplantation of a C57BL/10 (H2b) heart. RESULTS: When donor dendritic cells were injected i.v. 2 weeks before transplantation, rejection response was accelerated compared with that of naive mice [median survival time (MST) = 7 and 8 days, respectively]. However, when CD40 pathway was blocked by anti-CD40 ligand mAb, i.v. injection of donor dendritic cells but not B cells induced indefinite graft survival (MST >100 and 20 days, respectively). Mice treated with anti-CD40 ligand mAb alone rejected their grafts with a MST of 18 days. Intravenous injection of donor dendritic cells and B cells in combination with anti-CD80/CD86 mAbs was less effective to induce graft prolongation (MST = 9.5 and 13 days, respectively). CONCLUSIONS: Therefore, under blockade of CD40 pathway, mature dendritic cells were tolerogens in vivo independent of CD80/86 pathways.     

Hydrocephalus induced by cyclophosphamide in chick embryos

Cyclophosphamide was injected into the yolk sac of chick embryos for 6 days (Days 0-5). Embryos collected on the 21st day of incubation had a 37% incidence of hydrocephalus. Agenesis or stenosis of the aqueduct, as well as hypertrophy of the choroid plexus, was observed in 20% of the embryos.     

Abortive alloantigen presentation by donor dendritic cells leads to donor-specific tolerance: a study with a preoperative CTLA4Ig inoculation

Donor dendritic cells (DCs) within allografts initiate the induction of an allospecific T cell response, while an abortive alloantigen presentation by DCs may induce allospecific unresponsiveness. We thus investigated the tolerogenic effect of donor DCs that were made incompetent in alloantigen presentation by treatment of CTLA4Ig. When we treated rats with donor DCs (2 × 10⁶/rat i.v.) on the preoperative day, nine rejected allografts in an accelerated manner (5.0 ± 2.2 vs. 8.2 ± 1.6 days in the control group). Preoperative inoculation of DCs pulsed with CTLA4Ig, a procedure which suppresses an allogeneic mixed lymphocyte reaction (MLR), also provoked an accelerated rejection (5.6 ± 1.7 days). When DCs and CTLA4Ig (500 μg/rat i.p. on days −9, −7 and −5) were concomitantly inoculated, allograft survival was significantly prolonged (>38.7 ± 40.0 days); a preoperative CTLA4Ig inoculation alone failed to do so (7.5 ± 1.2 days). Long-term graft survivors tolerated skin grafts from the donor but not from those from a third party. These results indicate that abortive alloantigen presentation by donor DCs, upon which an accessory signal pathway is suppressed by CTLA4Ig, leads to prolonged graft survival and donor-specific tolerance. Received: 12 June 1999 / Accepted: 1 October 1999     

Transforming growth factor beta1-modified donor cell transfusion induced allo-heart tolerance

The therapeutic value of the transforming growth factor beta 1 (TGF-beta1) in transplantation has been reported; however, cell-mediated gene therapy using TGF-beta1 is not a widespread application in organ transplantation. This study was performed to evaluate whether TGF-beta1-modified donor spleen cell-specific transfusion could induce tolerogenicity and prolong allograft survival in rat heterotopic heart transplantation. Stable TGF-beta1-transduced spleen cells were established. Wistar rat splenic T-cell responses to donor spleen cells that received TGF-beta1-transduced were severely impaired. Survival of Sprague-Dawley cardiac allografts in Wistar rats given TGF-beta1-modified donor spleen cells (5 x 10(6), 7 days before transplantation), was extended modestly but significantly. Liposome transduction of donor spleen cells to overexpress TGF-beta1 is associated with marked impairment of their T-cell allostimulatory activity but only modest prolongation of allo-heart survival.     

Liver sinusoidal endothelial cells contribute to alloreactive T-cell tolerance induced by portal venous injection of donor splenocytes

We demonstrated that an indirect pathway of alloantigen presentation via liver sinusoidal endothelial cells (LSEC) is involved in alloreactive T-cell tolerance induced by portal venous injection (PI) of donor cells. Thirty million C57BL/6 (B6) splenocytes that were either untreated or treated with 30-Gy irradiation were injected via the portal vein into Balb/c mice. Host LSEC expressing major histocompatibility complex class II actively endocytosed the allogeneic naive splenocytes as well as irradiated splenocytes after PI. Using a transendothelial migration assay, it was demonstrated that host-type Balb/c CD4(+) T cells that transmigrated across LSEC that had captured irradiated B6 splenocytes were rendered tolerant to subsequent alloantigen presentation by host professional antigen-presenting cells. Consistently, PI of irradiated donor-type splenocytes led to remarkable prolongation of the survival of subsequently transplanted heart allografts. These results indicate that indirect antigen presentation by LSEC significantly contributes to alloreactive T-cell tolerance induced by PI of irradiated donor splenocytes.