抑制性T淋巴细胞在大鼠同种心脏移植免疫耐受中的作用

目的　探讨抑制性T淋巴细胞在同种心脏移植免疫耐受中的作用。方法　将纯系DA(供体 )、纯系Lewis大鼠 (受体 )各 5 0只随机分为未处理组、脾细胞组、环磷酰胺组、脾细胞 环磷酰胺组、转移组 ,每组受、供体鼠各 10只 ,各组受体鼠分别采用不处理、门静脉注入供体脾细胞 ( 3× 10 8个 )、腹腔注入环磷酰胺 ( 80mg/kg)、供体脾细胞 环磷酰胺、脾细胞 环磷酰胺组心脏移植术后30d受体大鼠脾细胞进行免疫耐受诱导后行腹部心脏移植 ;观察各组供心存活时间、病理改变及供受体间的混合淋巴细胞反应 (MLR)。结果　脾细胞 环磷酰胺组产生了长期的免疫耐受 ,供心平均存活时间为 ( 71 5± 2 9 1)d ,较未处理组、脾细胞组、环磷酰胺组均显著延长 (t=- 14 0 6 3,- 13 915 ,- 13 777,均P <0 0 1) ,供心仅有少量炎性细胞浸润 ,供受体间MLR特异性降低 (t =2 9 90 2 ,P <0 0 1)。转移组供心平均存活时间为 ( 5 2 3± 7 5 )d ,供心仅有少量炎性细胞浸润 ,供受体间MLR特异性降低 (t=2 3 0 4 7,P <0 0 1)。结论　脾细胞 环磷酰胺可成功诱导同种大鼠心脏移植的免疫耐受 ,其免疫耐受状态可过继转移给正常的同系受体 ,抑制性T淋巴细胞在这种免疫耐受状态中起重要作用     

多次输注供体脾细胞诱导心脏移植免疫耐受的实验研究

目的　探讨供体脾细胞诱导心脏移植免疫耐受的作用。方法　将 5 0只行腹部心脏移植的纯系雄性Lewis大鼠 ,随机分为未处理组、一次脾细胞组、环磷酰胺组、一次脾细胞 环磷酰胺组、多次脾细胞 环磷酰胺组 ,每组 10只大鼠 ,以 5 0只纯系雄性DA大鼠为供体。观察移植心脏平均存活时间 (MST) ,移植后第 6天观察供体心脏病理学改变 ,供受体间的混合淋巴细胞反应 (MLR)、外源性白细胞介素 2 (IL 2 )对MLR的影响及体外过继转移实验。结果　多次脾细胞 环磷酰胺组供体心脏MST为 (85 3± 7 5 )d ,较未处理组 (7 3± 1 0 )d、一次脾细胞组 (7 9± 0 9)d、环磷酰胺组(8 1± 1 2 )d、一次脾细胞 环磷酰胺组 (2 5 8± 3 5 )d显著延长 (t=0 ,P <0 0 1) ;供体心脏仅见少量炎性细胞浸润 ;供受体间MLR较DA Lewis对照组显著降低 ,差异有显著意义 (P <0 0 1) ;外源性IL 2可以部分逆转DA Lewis耐受组MLR的低反应性 ;其免疫耐受状态可过继转移给正常的同系大鼠。结论　多次输注供体脾细胞联合应用环磷酰胺 ,可成功诱导同种大鼠心脏移植的免疫耐受。     

嵌合体在同种心脏移植免疫耐受中的作用

目的探讨嵌合体在同种心脏移植免疫耐受中的作用.方法采用大鼠腹部心脏移植模型,将30只Lewis大鼠随机分成正常对照组(Ⅰ组)、排斥反应组(Ⅱ组)、免疫耐受组(Ⅲ组),每组10只.观察移植心存活时间,供心病理学改变,供、受者间的混合淋巴细胞反应(MLR)和脾、胸腺嵌合体.结果Ⅲ组供心平均存活时间(85.28±7.48天)较Ⅱ组(7.33±1.03天)显著长(P＜0.01);Ⅱ组供心见大量炎性细胞浸润,Ⅲ组供心仅见少量炎性细胞浸润;Ⅲ组供、受者间MLR较Ⅰ组显著低(P＜0.01);Ⅲ组受者的脾、胸腺形成了稳定的供者细胞嵌合体.结论移植免疫耐受的受者形成了稳定的中枢和外周嵌合体,嵌合体的形成对移植耐受起重要的作用.     

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.     

供体脾细胞胸腺注射对大鼠肢体移植存活的研究

目的 :通过大鼠肢体移植模型 ,旨在分析供体脾细胞注射对大鼠肢体移植中免疫耐受的诱导作用。方法 :选择雄性Wistar和SD大鼠为供、受体 ,对照组为胸腺注射脾细胞培养液 ,实验组为供体脾细胞注射 ,进行了 1 6例异体肢体移植动物实验。观察大鼠移植肢体排斥反应时间及存活时间。结果 :对照组肢体平均存活时间为 ( 9.38± 1 .92 )d ;实验组移植肢体存活时间为 ( 1 5.38± 2 .97)d。结论 :供体脾细胞胸腺注射大鼠肢体移植术后能够明显延长移植肢体的存活时间。     

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。     

联体共生诱导大鼠心脏移植免疫耐受的实验研究

目的　通过联体共生模型 ,建立供、受者嵌合体 ,探讨嵌合体与免疫耐受的关系。方法　纯系雄性DA(RT1a)大鼠为供者 ,Lewis(RT11)大鼠为受者 ,随机分成 3组 ,每组供、受者各 15只。Ⅰ组 (未处理组 ) :仅行DA到Lewis大鼠的腹部心脏移植 ,手术前后不作任何处理。Ⅱ组 (环磷酰胺组 ) :DA到Lewis大鼠的心脏移植前后分别经腹腔注射环磷酰胺 80mg/kg。Ⅲ组 (联体组 ) :0d :供、受者大鼠腹腔注射环磷酰胺 80mg/kg ;第6d :供、受者联体 ;第 16d :联体大鼠腹腔注射环磷酰胺80mg/kg ;第2 1d :分开联体 ,行DA到Lewis大鼠的心脏移植。观察各组移植心存活时间 ,供心病理学改变 ,供、受者间的混合淋巴细胞反应 (MLR)。结果　Ⅲ组形成了稳定的供、受者嵌合体 ,供心平均存活时间为 :(76 .33± 10 .71)d ,较Ⅰ组 (7.17± 1.17)d、Ⅱ组 (8.5 0± 1.87)d显著延长 ,差异有显著性 (P <0 .0 1) ;Ⅲ组的供心仅见少量炎性细胞浸润 ;供、受者间MLR较正常对照组显著降低 ,差异有显著性 (P <0 .0 1)。结论　联体共生可形成稳定的外周和中枢嵌合体 ,嵌合体在同种心脏移植的免疫耐受中起重要作用。     

新生大鼠胸腺内脾细胞注射对同种移植心存活的影响

目的探讨诱导新生大鼠免疫耐受的方法.方法分别给新生SD大鼠胸腺或腹腔内注射2.5×107个Wistar大鼠脾淋巴细胞,8～10周龄时行Wistar及第三品系大鼠供心移植.结果胸腺或腹腔注射Wistar大鼠脾淋巴细胞者移植Wistar大鼠心脏后移植物的存活时间显著延长,胸腺注射者平均存活时间超过60.4*!d(P＜0.001),腹腔注射者平均存活时间为15.8*!d(P＜0.02),而第三品系大鼠的心脏移植后平均存活9.2*!d(P＞0.05).结论单一胸腺或腹腔内注射同种脾细胞可以诱导新生大鼠的特异性免疫耐受.     

基因重组融合蛋白B7-CD28共刺激阻断剂对大鼠移植肾存活的影响

目的观察基因重组融合蛋白B7-CD28共刺激阻断剂CTLA-4Ig对大鼠移植肾存活的影响.方法肾移植术后第2天每只用药组大鼠腹腔内注射CTLA-4Ig0.5mg,观察移植肾存活时间;术后第20天,测定受体对供体及无关大鼠的单向混合淋巴细胞反应(MLR),并观察移植肾病理改变.结果与对照组相比,用药组移植肾存活时间显著延长[(42.6±6.4)d,(8.2±1.2)d,P＜0.001)].术后第20天,用药组移植肾仅有散在淋巴细胞浸润;受体对供体的MLR明显低于正常对照[(5832±674)cpm、(13486±2166)cpm,P＜0.001)],而受体对无关大鼠的MLR与正常对照相比无显著差异(P＞0.05).结论CTLA-4Ig通过诱导受体对供体抗原特异性的免疫反应低下状态明显延长了大鼠移植肾存活时间.     

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     

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.     

MHC class II presenting cells are necessary for the induction of intrathymic tolerance.

OBJECTIVE: This study determined the form of cellular donor MHC alloantigen necessary for the induction of intrathymic tolerance. BACKGROUND: The authors have achieved indefinite donor-specific tolerance, to a fully MHC-disparate rat heterotopic cardiac allograft, after the pretransplant intrathymic injection of unfractionated donor splenocytes and a single injection of rabbit anti-rat lymphocyte serum (ALS), without subsequent immunosuppression. METHODS: Male 4-12-week-old Buffalo (RT1b) rats underwent an intrathymic injection of either fractionated Lewis (RT1(1)) red blood cells (purified by Ficoll gradient) or T lymphocytes (purified by nylon wool column and plastic adherence), both of which express only MHC class I alloantigens, or B lymphocytes, macrophages, and dendritic cells (purified by plastic adherence) which express both MHC class I and class II alloantigens. At the completion of alloantigen injection the Buffalo recipient rats were given 1 ml of ALS intraperitoneally. Twenty-one days later a heterotopic Lewis heart was transplanted. RESULTS: The intrathymic injection of the fractions of Lewis MHC class I and class II expressing B lymphocytes, macrophages, and dendritic cells induced a donor-specific tolerance that resulted in indefinite Lewis cardiac allograft survival (MST > 125 days) in all recipients without further immunosuppression, whereas groups receiving MHC class I expressing red blood cell or T lymphocyte injections plus ALS rejected Lewis cardiac allografts with a MST of 7.3 and 16.5 days, respectively, thus indicating that the MHC class II expressing cell is necessary for the induction of intrathymic tolerance. Buffalo recipients with a long-term surviving Lewis cardiac allograft, after Lewis MHC class II expressing cells were still able to reject a third-party heterotopic ACI (RT1a) cardiac allograft in normal time (MST = 7.0 days), but did not reject a second Lewis cardiac allograft (MST > 100 days). Additionally, the intrathymic injection of MHC class II expressing cells resulted in decreased interleukin-2 (IL-2) production and an 80% decrease in in vitro donor-specific cell mediated cytotoxicity, whereas the cytolytic response to a third party was unaltered. CONCLUSION: Donor MHC class II, and not class I, expressing cells are the cells in donor splenocytes, injected intrathymically, responsible for the development of donor-specific allograft tolerance.     

Infectious tolerance develops after intrathymic alloantigen-induced acceptance of rat heart allografts can be adoptively transferred

BACKGROUND: We have shown that intrathymic (IT) injection of alloantigen with antirat lymphocyte serum (ALS) treatment can induce donor-specific allograft acceptance. The purpose of this study was to investigate whether T-regulatory (T-reg) cells play a role in the maintenance of donor-specific heart graft tolerance that develops after IT injection of Lewis (LEW, RT1(l)) alloantigen into a Dark Agouti (DA, RT1(a)). METHODS: Na?ve DA rats were injected IT with 2.5 x10(7) LEW donor splenocytes and injected intraperitoneally with 1 mL ALS. Twenty-one days after pretreatment, a LEW or Brown Norway (BN, RT1(n)) heart was transplanted into a treated DA recipient. Splenocytes (1 x 10(8) or 5 x 10(7)) from a LEW heart-tolerant long-term survivor (LTS; >60 days) DA recipient were harvested and adoptively transferred (AT) into an irradiated (450 rad) na?ve DA rat 24 hours before transplanting a LEW heart. RESULTS: All LEW heart allografts were rejected by untreated DA rats in a mean survival time (MST) of 7.4 +/- 1.7 days (n=7). In contrast, 66.7% of LEW heart grafts into IT+ALS-pretreated DA recipients were accepted indefinitely (n=24). When either 1 x 10(8) (n=5) or 5 x 10(7) (n=5) splenocytes from a LEW heart graft-tolerant LTS (>60 days) DA recipient were AT into a new na?ve DA rat, all new LEW heart grafts were accepted indefinitely. CONCLUSIONS: The donor-specific tolerance that develops after IT+ALS-induced LEW heart acceptance by DA recipients can be transferred adoptively to new na?ve DA recipients, thus indicating that it is infectious tolerance.     

Brief cyclosporine treatment prevents intrathymic (IT) tolerance induction and precipitates acute rejection in an IT rat cardiac allograft model

BACKGROUND: Intrathymic (IT) alloantigen combined with administration of rabbit anti-rat anti-lymphocyte serum (ALS) intraperitoneally induces donor-specific tolerance to rat cardiac transplants. The purpose of this study was to examine the effect of a brief course (4 days) of cyclosporine (CsA) on the development of IT tolerance. METHODS: Buffalo (BUF) (RT1b) rats were given 25x10(6) fully MHC-mismatched Lewis (LEW) (RT1l) splenocytes by IT injection plus 1.0 ml of ALS intraperitoneally. Twenty-one days later, IT donor-specific LEW (group 1) or third-party (ACI, RT1a) (group 2) hearts were heterotopically transplanted to the abdominal aorta A third group of BUF (group 3) were given daily CsA (10 mg/kg) by oral gavage for 4 days before administration of IT LEW cells and ALS. Rejection as defined by the cessation of a palpable heartbeat was confirmed by histology. Cytokine profiles of allografts from all groups were then analyzed using a multi-probe RNase protection assay. RESULTS: Sixty-seven percent of IT/ALS-treated BUF recipients not pretreated with CsA accepted LEW heart grafts for greater than 90 days. However, 86% of animals treated with CsA for 4 days before IT injection and ALS rejected allografts at 10.7+/-3.2 days. Third-party allografts (ACI) were uniformly rejected (7.0+/-0.0 days). Histology confirmed cellular rejection in CsA-treated allografts and cytokine analysis detected increased interleukin (IL)-3, IL-5, and tumor necrosis factor-alpha when compared to increased IL-2 and interferon-gamma in rejecting untreated controls. CONCLUSIONS: CsA can prevent the induction of intrathymic alloantigen tolerance. These results support the development of a CsA-sensitive, but IL-2-independent, active regulatory mechanism after intrathymic exposure to donor-specific alloantigen and depletion of mature peripheral T cells.     

Skin allograft survival following intrathymic injection of donor bone marrow.

BACKGROUND: Success has been reported using intrathymic injection in the preconditioning regimen to induce allograft tolerance. Although long-term stable tolerance has been achieved in numerous rodent vascularized solid organ allograft models, tolerance to skin transplants has only been achieved across minor antigenic or concordant species disparities. This study sought to induce tolerance across an allogeneic barrier in a rat model with a major genetic disparity. MATERIALS AND METHODS: Lewis rats were injected intrathymically with 1 x 10(8) Brown-Norway (BN) bone marrow cells and intraperitoneally with 1.0 cc of rabbit anti-rat anti-lymphocyte serum (ALS). Twenty-one days later, BN skin grafts were placed on the injected animals. Control groups were included to isolate the effect of technique, thymic manipulation, strain specificity, and ALS. RESULTS: Animals receiving both intrathymic bone marrow cells and ALS had a skin graft median survival time of 24 days versus 8 days for the control group (P = 0.003). Groups receiving anti-lymphocyte serum alone or intrathymic bone marrow cell injection alone exhibited no skin graft survival prolongation. Mixed lymphocyte reactions revealed normal responsiveness of tolerant animal lymphocytes to donor strain lymphocytes. CONCLUSION: This protocol utilizing the intrathymic injection of donor bone marrow cells along with short-term immunosuppression with anti-lymphocyte serum produced markedly prolonged survival of skin allografts transplanted across a major histocompatibility barrier. Although tolerance was incomplete, significant prolongation has not previously been reported in genetic disparities of this degree. These results suggest that the application of this technique for central immune modulation may be beneficial for allograft tolerance induction and deserves further study in large animals models.     

诱导免疫耐受预防大鼠肾脏移植排斥反应的研究

目的 探讨具有临床应用前景的移植耐受诱导方法。方法 以Lewis大鼠和DA大鼠分别作为肾脏移植的受体和供体,采用注射抗淋巴细胞血清（ALS）、输入供体骨髓细胞（BMT）和环磷酰胺（Cp）注射方法进行移植耐受诱导,观察肾脏移植物的存活情况及受体对供体细胞抗原免疫应答改变。结果 经耐受诱导的大鼠肾脏移植物存活时间明显延长,7只鼠中5只移植物存活73－90 d时仍无排斥反应迹象,混合淋巴细胞反应及诱导迟发型超敏反应表现为供体特异性降低。结论 诱导免疫耐受预防肾脏移植排斥反应具有重要的临床意义,此方法有一定的临床应用前景。     

Intrathymic inoculation of donor antigen: an ineffective strategy for prolonging xenograft survival

The aim of this study was to determine whether intrathymic inoculation of the recipient with donor antigen and short-term depletion of peripheral lymphocytes would lead to donor-specific unresponsiveness to rat pancreatic islet xenografts. The results were compared directly with an allograft model to determine whether there were substantial differences in the mechanisms of graft prolongation between allografts and xenografts using an identical conditioning regimen. Streptozotocin-induced diabetic C57B6 mice were injected with up to 0.3 ml of rat anti-mouse lymphocyte serum (ALS) 1 day before intrathymic injection of donor splenocytes. DA rat islet xenografts or Balb/c mouse islet allografts were transplanted 3 days later. ALS depleted CD3⁺ and CD4⁺ peripheral blood T lymphocytes to less than 5% of values in control mice by 24 h. Median islet xenograft survival (MGS) was 9 days in untreated mice, 28 days in mice receiving 0.2 ml of ALS and 32 days in mice receiving 0.3 ml of ALS alone. Intrathymic injection of 5 × 10⁶ DA splenocytes plus 0.2 ml of ALS did not improve islet xenograft survival beyond 28 days. Increasing the intrathymic inoculum to 10⁷ DA splenocytes with or without a higher dose of ALS (0.3 ml) did not increase MGS beyond 26 days, although 2 out of 18 animals survived beyond 100 days. These long-term surviving mice rejected a second DA rat islet graft in less than 22 days, indicating that tolerance was not achieved. To confirm the efficacy of this treatment regimen in allotransplantation, diabetic C57B6 mice received 10⁷ Balb/c splenocytes intrathymically and 0.3 ml of ALS. A Balb/c islet allograft was performed 3 days later. Allograft survival was similar to that of rat islet xenografts with 40% (4 out of 10) of grafts surviving beyond 100 days. In contrast to the xenograft recipients, a second Balb/c islet allograft survived indefinitely, indicating that tolerance was achieved. Histology of the long-surviving allografts showed intact islets with a sparse cellular infiltrate, whereas the long-surviving xenografts (> 100 days) showed a large cellular infiltrate and significant islet destruction. To investigate further the role of the thymus, adult thymectomized C57B6 mice were treated with 0.3 ml of ALS and received a DA rat islet xenograft. The median graft survival was 52 days and no graft survived beyond 80 days, suggesting that peripheral xenoreactive T cells remained after ALS treatment and greater T-cell depletion was necessary to obtain permanent engraftment. These results show that peripheral xenoreactive T cells which remain after profound T-cell depletion are capable of rejecting an islet xenograft despite intrathymic inoculation of donor antigen. The T-cell-mediated xenograft response appears to be stronger and more difficult to suppress than the allograft response using this strategy.     

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.