大鼠T细胞疫苗的制备及其抗移植皮肤排斥作用的实验研究

目的 探讨T细胞疫苗(TCV)的制备方法及其抗移植皮肤排斥反应的作用.方法 制备针对特定SD大鼠的供体特异性T细胞疫苗,将其免疫受体Wistar大鼠;然后取免疫前和每次免疫后第五天的受体Wistar的淋巴细胞(反应细胞)与供体SD的淋巴细胞(刺激)进行体外单向混合淋巴细胞反应(MLR),以MTT法检测细胞免疫增值反应情况,比较疫苗接种后诱导淋巴细胞反应受抑制的情况:再将SD大鼠皮肤移植到TCV免疫后的Wistar大鼠,观察皮肤移植反应并统计移植物存活的时间.排斥反应的移植物行病理检查.结果 TCV组受体淋巴细胞反应程度比接种前显著减弱(P＜0.05);特异性TCV组皮肤移植物存活时间较非特异性TCV组及对照组延长(P＜0.05).移植皮肤排斥反应病理表现更轻.结论 TCV经腹腔接种可以诱导出针对同种抗原特异性免疫耐受,TCV能够延长同种异体移植皮肤的存活时间,有一定抗移植排斥反应作用.     

大鼠胸腺内注射同种抗原对甲状旁腺移植物存活的影响

目的　改善甲状旁腺移植物的存活时间。方法　用SDLewis及DA大鼠进行甲状旁腺移植实验。由供体Lewis大鼠的脾细胞提取抗原。按照不同的抗原注射途径（尾静脉、门静脉及胸腺内）,是否合用抗淋巴细胞血清及第3品系大鼠的甲状旁腺移植共分为9组。结果　胸腺内注射抗原结合抗淋巴细胞血清的应用，使甲状旁腺移植物的平均存活期达到（196.00±3.96）d，与其他各组相比差异有非常显著性（P＜0.01）。结论　大鼠胸腺内注射抗原结合抗淋巴细胞血清的应用成功地诱导受体产生了供体特异性免疫耐受。     

靶向CD40的shRNA干扰抗大鼠异体肢体移植急性排斥反应的实验研究

目的 探讨靶向CD40的RNA干扰对大鼠异体肢体移植急性排斥反应的影响. 方法以纯系SD大鼠为供体,纯系Wistar大鼠为受体,行同种异体右后肢移植.27只大鼠肢体移植后随机分为三组,A组:注射入梭华.Sofast.siCD40-2/pSilencer载体复合物600 μL;B组:注射Sofast-pSilencer4.1-CMV neo空载体复合物600 μL;C组:注射生理盐水600μL,以上均通过阴茎背静脉注射.观察移植物排斥反应征象及存活情况,并于第7天对产生免疫耐受大鼠进行混合淋巴细胞反应,同时进行组织学检查. 结果与B、C组相比,A组移植物发生排斥反应的时间及存活时间均显著延长,差异有统计学意义(P＜0.01)(＞13 d),未见排斥反应征象;B、C组均于术后近期发牛排斥反应.A组大鼠对供体的淋巴细胞呈现低反应性,移植的供体同系大鼠的肢体得以存活. 结论术后不应用免疫抑制剂的情况下,靶向CD40的shRNA干扰可以抗大鼠异体肢体移植急性排斥反应.     

胸腺内注射可溶性异基因主要组织相容性复合物抗原诱导皮肤移植特异性耐受

用３ｍｏｌ／ＬＫＣｌ从Ｃ５７ＢＬ／６小鼠脾细胞提取可溶性主要组织相容性复合物（ＭＨＣ）抗原，注射到ＢＡＬＢ／Ｃ受体鼠胸腺内，诱导了成年小鼠对该异基因小鼠皮肤移植物的耐受。除在胸腺注射当天及第３天给予抗Ｔ细胞单克隆抗体外，不使用免疫抑制剂。实验组移植皮肤平均存活时间（ＭＳＴ）为８３天，对照组ＭＳＴ为１１天。诱导耐受的小鼠对第３供体的移植皮肤仍正常排斥（ＭＳＴ为１２天）。单向混合淋巴细胞反应，耐受小鼠脾脏淋巴细胞对特异供体的脾细胞无反应，对第３供体的脾细胞反应正常，对丝裂原刺激的增殖反应正常。显示诱导的耐受是供体特异性的，无非特异性免疫抑制。     

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.     

含丝裂霉素C的灌注液对大鼠移植心脏存活时间的影响

目的研究含丝裂霉素C灌注液对心脏移植物存活的影响以及作用机理。方法BN大鼠做供体，Lewis大鼠做受体。用含丝裂霉素c的溶液灌注及保存Brown—Norway大鼠供体心脏．移植到Lewis大鼠受体。为分析丝裂霉素C的体内效应，受体于术后注射丝裂霉素C或用丝裂霉素C孵化的供体外周血单核细胞进行预处理。结果含丝裂霉素C的灌注液能够显著延长移植物存活．丝裂霉素C预处理受体不能延长移植物存活，但注射丝裂霉素C预处理供体的外周血单核细胞致受体能够延长移植物存活。结论对供体心脏用含丝裂霉素C溶液灌注可减轻移植物的排斥反应，显著延长移植心脏的存活时间。     

FK506预处理下骨髓移植诱导同种异体小鼠皮肤移植耐受的实验研究

目的探讨短期大剂量FK506作为宏嵌合诱导供体特异性耐受中,骨髓移植前对受体预处理方法的可行性及临床实用性. 方法 100只雄性C57BL/6和60只雌性BALB/C小鼠分别作为皮肤移植的供体和受体,雄性ICR小鼠15只作为无关第三品系用以检测移植耐受状态的特异性.将60只受体小鼠随机分为5组,即无处理对照组、单纯FK506组、单纯骨髓细胞移植(BMT)组、实验组(FK506 BMT)和无关供体对照组,每组12只.FK506诱导及维持方案是皮肤移植前对受体小鼠先给予大剂量FK506腹腔注射(3 mg/kg×2 d),移植当天尾静脉输注2×107个骨髓细胞,再以小剂量FK506(0.5 mg/kg×7 d)短期维持治疗.观察皮肤移植存活时间、对第三方皮肤的排斥反应及对供体鼠的单向混合淋巴细胞反应,并用多聚酶链式反应(PCR)检测嵌合体的形成. 结果常规剂量的骨髓输注或短期FK506治疗并不能延长移植物的存活时间,也没有宏嵌合形成.实验组皮肤移植物存活时间(24.0±1.5)d比无处理对照组(9.6±1.1)d、单纯FK506组(10.5±1.6)d、单纯骨髓细胞移植组(10.3±1.5)d、无关供体对照组(9.8±1.1)d明显延长(P<0.05).混合淋巴细胞反应实验组供者特异性抑制率80.55%±14.10%明显高于单纯FK506组38.65%±12.43%及单纯骨髓细胞移植组35.41%±8.99%(P<0.05),实验组宏嵌合呈阳性. 结论采用短期大剂量FK506这一温和的非照射预处理方法,可获得一定程度的免疫耐受,延长移植物存活.移植前输注供体骨髓细胞能够促进宏嵌合的形成及移植物的存活.     

CD80mAb协同imDC诱导同种异体大鼠胰十二指肠移植免疫耐受

目的 观察共刺激分子阻断剂CD80单克隆抗体（CD80mAb）在协同未成熟树突细胞（imDC）诱导同种异体大鼠胰十二指肠移植免疫耐受中的作用。方法 建立糖尿病大鼠胰十二指肠移植动物模型；4E5杂交瘤细胞株BABIMC小鼠腹腔注射，抽取腹水，分离纯化后获得CD80mAb；分离供体大鼠骨髓来源DC细胞前体，经GM—CSF、IL-4体外刺激后。再加入IL-10共培养，鉴定为imDC；移植前7d，将2×10^6imDC经静脉途径注射至受体体内，同时分别给予生理盐水1ml、CD80mAb5mg连续14d。结果 四组受体大鼠移植后中位生存时间分别为12．7d、32．4d、50．2d、92．0d，实验组存活时间明显延长；组织学观察发现移植后7dCD80mAb＋imDC组移植物形态尚完整，淋巴细胞浸润减少；混合淋巴细胞反应证实移植后7dCD80mAb＋imDC组供受体间呈低反应性。结论 共刺激分子阻断剂CD80mAb能够协同imDC诱导受体T细胞对移植物的免疫耐受，降低宿主对移植物的急、慢性排斥反应，延长移植物的存活时间。     

吲哚胺2,3-双加氧酶在间充质干细胞诱导肾移植免疫耐受中的作用

目的研究探讨骨髓间充质干细胞(MSC)是否能够诱导肾脏移植物免疫耐受的产生以及吲哚胺2,3-双加氧酶(IDO)在MSC介导免疫调节反应中的作用。方法在BALB/c小鼠接受C57BL/6小鼠移植肾脏后24小时,C57BL/6小鼠来源的正常(wt)或IDO基因敲除(IDO-/-)的MSC(1×106)经静脉注入到移植受体中,分别作为wt-MSC治疗组和IDO-/--MSC治疗组,每组6只。以6只未注射的BALB/c移植小鼠受体为未治疗组。以移植物排斥反应所致小鼠死亡或术后100天设定为研究终点。长期存活的BALB/c肾移植受体在移植术后100天,接受来自C57BL/6供体或第三方移植物供体C3H(H-2k)小鼠的皮肤移植,监测移植皮肤情况。对3组小鼠进行移植物组织病理学观察,免疫组化评估肾脏组织Foxp3+细胞水平。用流式细胞技术进行抗原特异性抗体和细胞表型检测,用混合淋巴细胞反应(MLR)评估树突细胞(DC)和T细胞功能。结果本研究发现wt-MSC治疗可诱导受体产生同种异体移植物免疫耐受,表现为移植物病理检查结果正常、未发现抗原特异性抗体水平升高、免疫耐受受体中耐受性树突细胞(Tol-DC)数量显著增多等。同时,在免疫耐受的受体脾脏和肾移植物中均可发现大量CD4+CD25+Foxp3+调节性T细胞(Treg)。这些结果均提示Treg在MSC诱导免疫耐受中的重要作用。值得关注的是,经IDO-/--MSC处理的移植受体中,MSC丧失了其诱导同种异体移植物的免疫耐受的能力,肾移植物很快被排斥,同时机体移植物的排斥反应变化与未治疗组相同。结论由MSC分泌的IDO通过促进Treg的生成,在诱导肾脏移植免疫耐受中起着关键性的作用。本研究将为MSC在器官移植中的临床应用提供理论及临床转化依据。     

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     

供者基因转染受者细胞诱导特异性免疫耐受的实验研究

目的　探讨供体特异性基因片段MHCClassI类抗原分子RT1.AacDNA在诱导免疫耐受中的作用和可能机制。方法　采用大鼠同种异体心脏异位移植模型,通过供体MHCClassI类抗原的RT1.AacDNA基因片段转染受体成肌细胞（MB）并接种自体胸腺,观察移植物存活时间,判断受体免疫耐受产生和维持的状态。结果　经胸腺接种转染供体基因的自体成肌细胞并同时服用CsA,移植物平均存活时间高达(96.13±12.91)d,明显高于其它实验组（P＜0.05）;动态混合淋巴细胞反应（MLR）,无论外周输注或胸腺接种其对照组cpm值均高于各自实验组;CD4     

Prevention of bronchiolitis obliterans in rat lung allografts by type V collagen-induced oral tolerance

BACKGROUND: We have reported that feeding type V collagen (col(V)) to lung allograft recipients induces immune tolerance that prevents acute lung allograft rejection. Repeated acute rejection is a risk factor for or associated with chronic rejection, known as bronchiolitis obliterans (BO), the leading cause of death in lung allograft recipients. The current study examines if col(V)-induced oral tolerance prevents BO. METHODS: WKY rats (RT1l) were fed either col(V) or diluent before orthotopic transplantation of F344 (RT1lvl) lung allografts. No rats received any immunosuppression. At 10 weeks posttransplantation the time to onset of BO, delayed type hypersensitivity (DTH) responses to donor antigens, and col(V) were examined. In addition, proliferative responses of recipient T lymphocytes to donor antigens, and ability of recipient antigen presenting cells to present alloantigens in lung allografts were evaluated. RESULTS: The data show that recipient rats have sustained DTH responses to donor antigens and col(V). T lymphocytes from col(V)-fed lung allograft recipients were unable to proliferate in response to donor antigens, but feeding col(V) had no effect on the presentation of donor alloantigens by recipient antigen presenting cells. All diluent fed rats developed BO, but only mild acute rejection (grade 2) was present in all rats fed col(V). Transforming growth factor (TGF)-beta production was up-regulated systemically in col(V)-fed, but not diluent fed, lung allograft recipients, and neutralizing TGF-beta [corrected] recovered the DTH response to donor antigens in col(V)-fed rats. CONCLUSIONS: Collectively these data show that col(V)-induces oral tolerance that prevents BO, and that tolerance may be mediated by systemic production of TGF-beta [corrected].     

Thymus-mediated immune tolerance to renal allograft is donor but not tissue specific.

Studies were conducted in Lewis (RT1l) rats to determine whether the process of unresponsiveness to kidney graft induced by the intrathymic glomerular transplantation were donor-strain specific as suggested by previous studies (Remuzzi et al., Lancet 1991;337:750-752). When glomeruli from Sprague-Dawley rats were injected in the thymus of Lewis rats, the subsequent kidney graft from a "third party" Brown-Norway (RT1n) rejected within 9 to 14 days. Moreover, an alternative site for glomerular antigen inoculation, such as i.p. administration, failed to induce a state of unresponsiveness to renal allograft. Whether tolerance was tissue specific was investigated by intrathymic injection of a preparation of donor blood cells that only included white cells. Such a maneuver, followed 10 days later by a kidney transplant, allowed indefinite renal graft survival in all animals, whereas all rats injected intrathymically with blood cell medium alone rejected the kidney graft in 8 to 11 days. Shortening the time interval between intrathymic injection of blood cells and kidney transplantation still allowed the graft to survive indefinitely. Finally, Lewis (RT1l) rats with chronic renal failure injected intrathymically with blood cells from Brown-Norway (RT1n) rats tolerated indefinitely a subsequent kidney graft from the same donor. These findings indicate that (1) the induction of immune tolerance to renal allograft induced by intrathymic injection of antigens is donor but not tissue specific; (2) the time interval between intrathymic injection of donor cells and the subsequent kidney transplantation can be reduced to 24 h; and (3) uremia does not preclude the possibility of renal allograft tolerance after the thymus procedure.     

成年大鼠联体共生诱导肾移植耐受及其机制研究

目的：建立异基因大鼠联体共生的动物模型,探讨其诱导肾移耐受机理,方法对DA和LEW大鼠实施联体手术并诱导耐受,然后进行DA→LEW的肾移植。FACS检测术后脾脏、脾胸中嵌中状态态;检测体内、外过继转移耐受大鼠脾细胞对正常大鼠单向混合淋巴细胞反应（MLR）和迟发性过敏反应（DTH）的抑制作用,以及T细胞克隆不应答在耐受中的作用。结果：联体共生诱导耐受可使DA→LEW的肾移植存活明显延长。耐受组脾脏、胸腺中供体细胞的嵌合比例明显高于排斥组。耐受可通过体内,外过继转移给正常大鼠。外源性IL－2可部分逆转耐受状态。结论嵌合状态态与肾移植耐受存在明显相关性,克隆不应答、抑制细胞参与了耐受的形态。     

Successful allogeneic leg transplantation in rats in conjunction with intra-bone marrow injection of donor bone marrow cells

BACKGROUND: We have recently established a new method for bone marrow transplantation (BMT) in mice: bone marrow cells are directly injected into the intra-bone marrow (IBM) cavity. IBM-BMT induces persistent donor-specific tolerance and enhances the rapid recovery or reconstitution of the hematolymphoid system of donor origin without any signs of graft-versus-host disease (GVHD) or graft failure. Furthermore, the prior injection of fludarabine can reduce the irradiation dose to the sublethal level (4.5 Gy x 2). Therefore, we hypothesize that IBM-BMT plus fludarabine is applicable to allogeneic leg transplantation in rats. METHODS: Brown Norway (BN; RT1An) rats were injected intravenously with 50 mg/kg of fludarabine phosphate, followed by sublethal fractionated irradiation (4.5 Gy x 2) 1 day before IBM-BMT. The hind limbs from Fischer 344 (F344; RT1Al) rats were transplanted on day 0, and bone marrow cells (3 x 10(7) cells/50 microL) obtained from the donor F344 rats were injected into the bone marrow cavity of the left tibias of the recipient BN rats. RESULTS: The hematolymphoid cells in the recipient BN rats were completely reconstituted by the cells of the donor F344 rats. The limbs transplanted from the donor F344 rats were accepted for >1 year without any clinical signs of rejection (10 of 10). The lymphocytes of the BN rats showed tolerance to both donor-type and recipient-type major histocompatibility complex determinants in mixed lymphocyte reaction, but showed a significant response to the third-party major histocompatibility complex determinants. CONCLUSIONS: Using a combination of the injection of fludarabine, low-dose irradiation, and IBM-BMT, we have succeeded in allogeneic limb transplantation without using any immunosuppressants after the operation. This strategy would be applicable to the transplantation of other vascularized organs in humans.     

High-dose tacrolimus and lengthy survival of the combined rat pancreas/spleen graft in a high-responder combination.

Pancreas grafts do not survive for lengthy periods, especially in a high-responder rat combination. Recent data indicated that a combined spleen/pancreas graft protects against acute graft rejection and induces donor-specific tolerance. In this study, we performed a combination spleen/pancreas transplantation using high-dose tacrolimus in a high-responder rat combination of DA (RT1a) to LEW (RT1) and induced permanent survival in the few recipient rats. In these recipients, there was no difference in the mixed lymphocyte reaction (MLR) of the recipients when compared with that of the naive LEW splenic cells, but MLR inhibition by the serum from the recipients was significantly decreased. We also performed immunoblotting and detected a protein that has an affinity for the anti-DA class antibody. This protein may be an anti-idiotypic antibody and contribute to donor- and tissue-specific tolerance.     

Initiation of rejection of established islet allografts by third-party thyroid allografts and splenic dendritic cells

Due to concerns of cross-reactivity between renal and islet allografts in initiation of rejection, we determined the ability of donor-specific and third-party splenic dendritic cells (DCs) and thyroids (whole-organ transplant) to initiate rejection of established islet allografts. Purified islets from neonatal F-344 (RT1Lv1) rats were transplanted bilaterally under the kidney capsule of Wistar-Furth (W/F, RT1u) rats without immunosuppression. The islet allografts were not rejected by 21 days posttransplantation. On day 22, freshly isolated or cultured DCs were injected intraperitoneally into the host. Both freshly isolated and cultured donor-specific (F-344) and some third-party (Buffalo, RT1b; ACI, RT1a) DCs initiated rejection of the islets as indicated by lymphocyte infiltration and destruction of the allograft. DCs, whether freshly isolated or cultured for 8 days from the recipient strain (W/F) and one third-party rat (Brown Norway, RT1n), did not initiate rejection. Splenic DCs from the Lewis (RT1l) rat, which has the same class I and II antigen haplotype as F-344 islet donor rats, also initiated rejection. Only 10(3)-10(4) DCs isolated from the spleen of donor rats were required to initiate rejection of the allograft. In a parallel series of W/F rats with islet allografts, a thyroid (half lobe) from the islet donor strain (F-344), recipient strain (W/F), or third-party rat (Buffalo, Brown Norway, or ACI) was inserted under the kidney capsule at 22 days post-islet transplantation. At 35 days, all thyroids and most islet allografts exhibited active or complete rejection after thyroid transplant from Buffalo, F-344, or ACI rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Induction of donor-specific hyporesponsiveness and prolongation of cardiac allograft survival by jejunal administration of donor splenocytes

BACKGROUND: Donor-specific immunosuppression is important in transplantation surgery. We examined the immunosuppressive effects of donor splenocytes administered postoperatively into the jejunum and the effect of such treatment on the survival of heterotopic vascularized cardiac allograft in rats. METHODS: Lewis (LEW, RT-1l) recipient rats were treated with 5x10(7) Brown Norway (BN, RT-1n) donor splenocytes for 5 days orally, intrajejunally, or subcutaneously. The immune responses of LEW treated with either donor BN or irrelevant Wistar King A (WKA, RT-1k) were examined by mixed lymphocyte reaction (MLR) and delayed type hypersensitivity (DTH). The effect of postoperative enteral treatment for 6 days with suboptimal dose of cyclosporine (CsA) on heterotopic cardiac allotransplantation was investigated. We measured the production of cytokines (interleukin [IL]-2, IL-4, IL-10, and interferon-gamma [IFN-gamma]) in the supernatant of MLR by ELISA. The effect of intravenous dose of GdCls to block Kupffer cell function was also investigated before the administration of splenocytes. RESULTS: MLR and DTH responses were strongly inhibited in a BN-restricted manner after jejunal or oral feeding of donor BN splenocytes but not by subcutaneous injection or injections by any routs of WKA splenocytes. The effect was more prominent in jejunal than oral feeding. Immunosuppression was associated with a significant inhibition of IL-2 and IFN-gamma production and increased concentrations of IL-4 and IL-10 in MLR supernatants. Immunosuppression was abrogated by pretreatment with GdCl3. Postoperative intrajejunal feeding of donor splenocytes with CsA significantly prolonged cardiac allograft survival time (18.7+/-7.3 vs. 9.9+/-1.7 days for control animals). CONCLUSION: Jejunal administration of splenocytes produces donor-specific immunosuppression and prolongs cardiac allograft survival. Our results suggest the involvement of T helper (Th) 2 cytokines and Kupffer cells in the induction of immune hyporesponsiveness, and indicate that this method represents a unique approach for induction of donor-specific immunosuppression.     

Induction of indirect donor-specific hyporesponsiveness by transportal RT1-peptide pulse in rat skin transplantation

In the present study, we examined whether transportal pulse of class I major histocompatibility complex (MHC) allopeptides can induce indirect (non-chimeric) donor-specific hyporesponsiveness, using a high-responder rat skin transplantation model. Two donor-specific 8-amino acid peptides corresponding to residues 58-65 and 70-77 in the alpha(1) helical region of RT1.A(a) were synthesized. In order to test immunogenicity of these peptides, mixed lymphocyte reaction (MLR) was performed. Then, 100-microg portions of peptides were injected into recipient Lewis (LEW, RT1.A(l)) rats via the portal vein 14 days before skin transplantation. Skin allografts from August Copenhagen Irish (ACI, RT1(a)) or Wistar King A (WKA, RT1(k), third-party) donors were transplanted to LEW (RT1(l)) recipients. Transportal pulse of residues 58-65 and 70-77 prolonged graft survival significantly in ACI-to-LEW skin transplantation (17.6+/-0.40 and 18.0+/-0.45 days) compared with control (14.2+/-0.37 days). However, pulse of residues 106-113, a non-donor-specific control, did not prolong graft survival time (14.6+/-0.40 days) in the same combination. Regarding the third-party donor, residues 58-65 injected into LEW recipients had no effect on survival time of skin grafts (19.0+/-0.84 days) derived from WKA donors compared with the untreated WKA-to-LEW control (19.4+/-0.93 days). Transportal pulse of RT1.A(a) peptides induced donor-specific hyporesponsiveness even in a high-responder rat skin transplantation model. Our results suggest that graft enhancement by transportal exposure to donor cells may not be induced by a chimeric process but, instead, by an indirect mechanism not involving intervention of viable donor cells.