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     

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。     

胸腺注射供体脾细胞诱导移植心脏免疫耐受的实验研究

目的探讨诱导心脏移植免疫耐受的方法及其产生的可能机制. 方法采用大鼠腹部心脏移植模型,随机分成未处理(Ⅰ)组,胸腺注射供体脾细胞(Ⅱ)组,腹腔注射兔抗鼠淋巴细胞血清(Ⅲ)组,胸腺注射供体脾细胞联合应用兔抗鼠淋巴细胞血清(Ⅳ)组,每组6只大鼠.Ⅱ、Ⅳ组在移植前2 1 d将供体脾细胞2.5×107个注射到受体胸腺,Ⅲ、Ⅳ组受体腹腔注射兔抗鼠淋巴细胞血清(ALS)1 ml,然后行异位心脏移植.观察移植心脏存活时间,供心病理学改变及供、受体间的混合淋巴细胞反应(MLR). 结果Ⅳ组供心平均存活时间(MST)为(81.8±7.6)d,较Ⅰ组(7.3±1.0)d、Ⅱ组( 7.8±1.0)d、Ⅲ组(8.2±1.2)d显著延长,差异有显著性意义(P＜ 0.01 );供心仅见少量炎性细胞浸润;供、受体间MLR较正常对照组显著降低,差异有显著性意义(P＜0.01). 结论胸腺注射供体脾细胞联合应用ALS能成功诱导心脏移植的免疫耐受;胸腺内特异性T细胞克隆消除可能与免疫耐受的形成有关.     

门静脉注射供体脾细胞诱导大鼠移植肾长期存活

目的 :探讨门静脉内注射供体脾细胞诱导移植肾的免疫耐受情况。方法 :实验组 Wistar大鼠在肾移植同时将经过预处理的供体 SD大鼠脾细胞注入门静脉 ,对照组则注入生理盐水 ,然后用环孢素 A治疗 1周 ,并以大鼠平均存活时间为标准比较两组结果。结果 :对照组平均存活( 1 0 .5± 2 .1 ) d,实验组为 ( 72 .2± 32 .0 ) d( P <0 .0 1 )。实验组在肾移植 60 d后 ,再移植 SD大鼠和Lewis大鼠的皮肤 ,发现 SD大鼠的皮肤不被排异 ,Lewis大鼠的皮肤出现排异。结论 :门静脉内注射供体脾细胞可诱导肾移植免疫耐受 ,并且这种耐受具有特异性。     

协同信号途径阻断和供体脾细胞输注诱导预存同种记忆性T淋巴细胞大鼠心脏移植物的耐受

目的 联合阻断OX40/OX40L和CD28/B7双协同信号途径和供体特异性脾细胞输注,诱导预存同种反应性记忆T淋巴细胞大鼠对同种心脏移植物的耐受.方法 建立大鼠预存同种反应性记忆T淋巴细胞的移植模型,采用免疫磁珠法分选CD8+CD44-记忆性T细胞;对过继转移供体特异性CD8+记忆性T细胞3 d的Lewis大鼠分别/合并输注AdCTLA4Ig、AdOX40Ig、供体脾细胞(DST),同时移植来至DA大鼠的心脏;48 h后取出心脏进行组织学分析、细胞因子表达分析,同时观察不同处理移植心脏存活时间.结果 AdCTLA4Ig+AdOX40Ig+DST组分别与AdCT-LA4Ig,AdOX40Ig和DST比较,心脏组织病理级别较低,白细胞介素(IL)-2及干扰素(IFN)-γ的表达水平也明显比其他组低很多,而心脏存活时间显著延长.结论 联合阻断OX40/OX40L和CD28/B7和供体特异性脾细胞输注能较好地诱导大鼠心脏移植物耐受.     

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.     

供者脾细胞和环磷酰胺联合预处理对移植心脏存活的作用

目的　诱导同种异体心脏移植的免疫耐受 ,为心脏移植的抗排斥反应治疗提供依据。　方法　采用供者脾细胞和环磷酰胺联合预处理受者 ,诱导受者对移植心脏的免疫耐受 ,然后行大鼠颈部心脏移植术。将实验动物分成 5组。对照组 :受者不作任何预处理 ;组 1:预处理第 2天用环磷酰胺 5 0～ 80 mg/ kg预处理受者 ;组 2 :预处理当天用供者 5～ 10× 10 7个脾细胞预处理受者 ;组 3:受者不作任何预处理 ,手术当天开始用环孢菌素 A10 mg/ kg,每 2天 1次 ,共 8～ 10次 ,腹腔内注入 ;组 4:预处理当天用供者脾细胞 5～ 10× 10 7个和第 2天环磷酰胺 5 0～ 80 mg/ kg联合预处理受者。　结果　各组移植心脏的存活时间明显不同 ,5组移植心脏的存活时间差异有显著性 (P<0 .0 1)。供者脾细胞和环磷酰胺预处理受者的移植心脏存活时间明显延长。　结论　供者脾细胞和环磷酰胺联合预处理 ,可诱导受者对移植心脏的免疫耐受。     

T细胞疫苗诱导大鼠同种异体肢体移植免疫耐受的实验研究

目的 探讨T细胞疫苗（TCV）诱导大鼠同种异体肢体移植特异性免疫耐受的作用。方法 制备受者Lewis大鼠针对供者DA大鼠的TCV，应用TCV，免疫正常Lewis大鼠共3次，每周1次。设TCV组和TCV未接种组，在接种前及接种后5d进行混合淋巴细胞培养（MLR）；设TCV组、CsA组和空白对照组，于接种后7d进行DA大鼠针对Lewis大鼠的同种异体肢体移植，在术后7d进行淋巴细胞毒检测，术后21d进行嵌合分析。结果 MLR显示，Lewis大鼠的脾细胞反应程度接种组显著低于未接种组（P〈0．01）；微量细胞毒测定显示，死亡细胞百分率在TCV组、CsA组、空白对照组3组比较性差异有统计学意义（P〈0．01）；嵌合分析显示经处理的Lewis大鼠脾脏，胸腺中检测出了DA大鼠源性的骨髓嵌合体。结论 T细胞疫苗可以抑制受者对供者的免疫应答；作为骨髓移植前预处理手段，T细胞疫苗接种后行吻合血管的骨髓移植成功地诱导出同种异体肢体移植嵌合耐受。     

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.     

脾切除对心脏移植大鼠外周血淋巴细胞凋亡及调节性T淋巴细胞的影响

目的 探讨脾切除对同种异体心脏移植大鼠外周血淋巴细胞凋亡及调节性T淋巴细胞的影响.方法 以Wistar大鼠为供者、SD大鼠为受者,进行腹部异位心脏移植,同时切除受者的脾脏(心脏移植切脾组),并以不切脾者为对照(心脏移植对照组),另设不行任何处理的对照组和单纯切脾的单纯切脾组.术后第1、3、5、7天.取各组受者的移植心脏和外周血,观察移植心脏的组织学变化和细胞超微结构改变情况,以流式细胞仪检测外周血淋巴细胞的凋亡率及CD4+ CD25+ T淋巴细胞的变化,逆转录聚合酶链反应检测CD4+ CD25+ T淋巴细胞上Foxp3 mRNA的表达情况,记录移植心脏的存活时间.结果 心脏移植对照组移植心脏存活时间为(7.47±2.24)d,心脏移植切脾组移植心脏存活时间为(17.63±4.54)d,二者间的差异有统计学意义(P<0.05).心脏移植对照组的移植心脏肿胀,质硬,色暗,间质水肿、出血,弥漫性炎症细胞浸润,大量心肌细胞坏死、溶解,横纹不清;心脏移植切脾组的移植心脏质软,色红,局部灰白,外膜下以及细胞间局灶性水肿,炎症细胞浸润,心肌细胞结构完整,横纹清晰;心脏移植切脾组的细胞超微结构改变轻于心脏移植对照组.心脏移植切脾组术后第5天和第7天的淋巴细胞凋亡率分别为(7.62±2.15)%和(9.41±3.82)%,明显高于心脏移植对照组(P<0.05,P<0.05).心脏移植切脾组术后第3、5、7天时的CD4+ CD25+ T淋巴细胞明显多于心脏移植对照组(P<0.01,P<0.01,P<0.01),其Foxp3 mRNA的表达也较心脏移植对照组明显上调.结论 脾切除使心脏移植大鼠外周血淋巴细胞凋亡率增加,调节性T淋巴细胞增多,其Foxp3 mRNA表达上调,这些变化与移植心脏病理改变呈负相关.     

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.     

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.     

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.     

A short course of methylprednisolone immunosuppression inhibits both rejection and spontaneous acceptance of rat liver allografts

BACKGROUND: The effects of immunosuppressive drugs on transplant tolerance have not been extensively studied, although their effect on rejection is well established. METHODS: We examined the effects of a short course of treatment with the immunosuppressive drug methylprednisolone (MP) on the survival of PVG liver allografts in Dark Agouti (DA) recipients that accepted the livers and in Lewis recipients that rejected the livers. Infiltration of liver allografts was examined by immunohistochemical staining of liver sections, and apoptosis was measured by terminal deoxynucleotide transferase-mediated dUTP nick end labeling. RESULTS: A 5-day course of MP (days 0 to 4) led to rejection of four of six livers (mean survival time [MST] 99 days) in DA recipients compared with long-term survival (MST >100 days) in untreated animals. Delayed administration of MP (days 3 to 7) exacerbated rejection in DA recipients, and all eight animals rejected the graft (MST 68.5 days). Treatment of Lewis recipients with MP did not significantly prolong survival when administered from days 0 to 4 (MST 13 days), although delay of administration improved the outcome. Treatment from days 3 to 7 resulted in an MST of 21 days, whereas treatment from days 7 to 11 resulted in an MST of 41.5 days. MP treatment from day 3 to day 7 reduced T cells and interleukin 2 receptor-expressing cells but increased the numbers of apoptotic cells infiltrating both DA and Lewis strain allografts. CONCLUSIONS: These results show that immunosuppression with MP inhibits both spontaneous tolerance and rejection of liver allografts in a rat model and question the efficacy of administering MP to all liver allograft recipients from the time of transplantation.     

Cyclophosphamide-induced tolerance in rat orthotopic liver transplantation

BACKGROUND: We previously established a cyclophosphamide (CP)-induced tolerance system in rodent skin graft models. In this study, we applied this system to rat liver transplantation. METHODS: Lewis recipients were inoculated on day -2 with spleen and bone marrow cells (SC+BMC) from Dark Agouti (DA) donors, followed by 100 mg/kg CP on day 0. On day 25, DA livers were orthotopically grafted. We assessed the alloresponses to the donors of the long-term surviving recipients, using the second skin grafting and in vitro assay. RESULTS: The recipients that had been treated with SC+BMC and CP survived for more than 165 days. None of control group that received SC+BMC alone (mean survival times [MST]=13.8 days), CP alone (MST=40.0), SC+BMC from third-party PVG rats and CP (MST=45.0), or no treatment (MST=13.8) survived over 50 days. The donor-specific tolerance was confirmed by second skin grafts onto recipients with permanent DA liver grafts, which accepted DA skins (MST>75) but not PVG (MST=8.3). However, the lymphocytes from the tolerant recipients showed alloresponse to DA in vitro. To investigate whether the T helper type 2 deviation contributed to this "split tolerance," we assessed the production of cytokines in mixed lymphocyte reaction. Interleukin 2 and interferon-gamma were detected but interleukin 4 was not. CONCLUSIONS: These data showed that this protocol induced split tolerance in rat liver transplantation and, furthermore, the mechanism of split tolerance was not due to T helper 2 deviation.     

Prolongation of survival of fully allogeneic cardiac grafts and generation of regulatory cells by a histamine receptor 2 antagonist

BACKGROUND: The effects of histamine on immunologic responses via the histamine receptor 2 (HR2) have been studied, but few investigations explored the immunomodulatory role of histamine in vivo. We examined whether the HR2 antagonist ranitidine affects the alloimmune response in a murine model of cardiac transplantation. METHODS: CBA (H-2k) recipients were given no treatment or one intravenous injection of ranitidine on the day of transplantation of a heart from C57BL/10 (H-2b) donors. Survival of the allografts was recorded. The effect of the ranitidine treatment on cell proliferation and cytokine production was assessed by mixed leukocyte culture and enzyme-linked immunosorbent assays. An adoptive transfer study was conducted to determine whether regulatory cells were generated. The effect on graft survival of adding FK506 to the ranitidine treatment was also examined. RESULTS: CBA recipients given ranitidine (60 mg/kg) had prolonged graft survival (median survival time [MST], 87 days). Ranitidine treatment also suppressed the proliferation of splenocytes and production of interleukin (IL)-2 and up-regulated IL-10 production. Adoptive transfer of splenocytes and CD4 cells from ranitidine-treated allograft recipients induced significant prolongation of allograft survival in naive secondary recipients (MST, 71 and >100 days, respectively). CBA recipients given both ranitidine and FK506 (0.1 mg/kg/day for 14 days) had indefinite survival of cardiac allografts (MST, >100 days). CBA recipients treated with FK506 alone rejected the allografts (MST, 27 days). CONCLUSION: In our model, ranitidine treatment induced significantly prolonged survival of fully allogeneic cardiac grafts, generated CD4 regulatory cells, and indefinite survival when combined with FK506 (0.1 mg/kg/day).     

Inhibition of host-versus-graft and graft-versus-host responses after small bowel transplantation in rats by rapamycin.

The effect of rapamycin (RAPA) on both host-versus-graft (HVG) and graft-versus-host (GVH) immune responses was examined in small bowel transplant models using strongly histoincompatible donor-recipient combinations. Normal Wistar Furth (WFu; RT-1u) recipients rejected Buffalo (BUF; RT-1b) small bowel allografts within a mean survival time (MST) of 10.5 +/- 0.5 days. Administration of RAPA (0.8 mg/kg) by continuous intravenous infusion for 14 days via an osmotic pump prolonged graft survival to 25.0 +/- 4.6 days (P = 0.01). In a second strain combination, the 12.5 +/- 2.2 day survival of Brown Norway (BN; RT-1n) small bowel allografts in Lewis (RT-1l) recipients was prolonged to 21.6 +/- 2.0 and 28.5 +/- 2.8 days by 14 days of i.v. RAPA at doses of 0.8 and 1.6 mg/kg, respectively. In this model RAPA is five times more effective than cyclosporine, which at 4.0 mg/kg prolongs BN small bowel allografts in Lewis recipients to 21.6 +/- 6.3. To isolate HVG and GVH immune responses, (BN x Lewis)F1 hybrid rats served as the graft donor or host, respectively. In the HVG model, (BN x Lewis)F1 small bowel allografts, which were rejected by normal Lewis recipients at 12.2 +/- 3.6 days, were prolonged to 40.8 +/- 5.8 days (P = 0.001) by RAPA (0.8 mg/kg x 14 days). In the GVH model, the ability of Lewis small bowel allografts to produce severe GVH disease in untreated (BN x Lewis)F1 recipients at 12.3 +/- 2.8 days was delayed to 21.3 +/- 5.2 days by 0.8 mg/kg RAPA (P = 0.025). Thus, RAPA protects small bowel allografts more effectively against HVG than GVH immune responses.     

"Infectious tolerance" develops after the spontaneous acceptance of Lewis-to-Dark Agouti rat liver transplants

BACKGROUND: After monoclonal antibody or donor-specific transfusion treatment, infectious tolerance to rat or mouse heart or skin transplants can be passed on to naive recipients by adoptive transfer of tolerant lymphocytes. We examined whether similar regulatory cells develop after the spontaneous acceptance of Lewis-to-Dark Agouti (DA) rat liver transplants without immunomodulating agents. METHODS: After Lewis-to-DA rat liver transplantation, 100 x 10(6) splenocytes were harvested and adoptively transferred into a 450 rad-irradiated naive DA rat 24 hours before Lewis heart transplantation. Adoptive transfer of CD4+ or CD8+ T cells was also examined. In some experiments, splenocytes from recipients with long-term accepted Lewis hearts induced by adoptive transfer were serially transferred to multiple generations of recipients before Lewis rat heart transplantation. In vitro mixed lymphocyte culture response and cytotoxic T lymphocyte generation were measured. RESULTS: When splenocytes from a DA rat recipient >60 days after Lewis rat liver acceptance were transferred into irradiated DA rat recipients, all Lewis rat hearts were accepted, whereas third-party Brown-Norway rat hearts were rejected. However, splenocytes from DA rat recipients 30 days after liver transplantation did not prolong Lewis rat heart survival. Adoptive transfer of 40 x 10(6) CD4+, 10 x 10(6) CD4+ or 10 x 10(6) CD8+ cells from a DA rat bearing Lewis rat liver >60 days resulted in acceptance of 88%, 80%, or 57% acceptance of Lewis rat hearts, respectively. Serial second and third adoptive transfer of long-term survivor splenocytes resulted in the acceptance of all Lewis rat hearts. In mixed lymphocyte culture, splenocytes from a naive DA rat and a DA rat accepting a Lewis rat liver transplant for >60 days showed similar proliferative responses to both Lewis and Brown-Norway rat stimulators. An equivalent level of indirect cytotoxic T lymphocyte activity was exhibited by splenocytes from both a naive DA and a DA rat accepting a Lewis rat liver transplant for >60 days. CONCLUSIONS: Regulatory cells developing after the spontaneous acceptance of a Lewis to DA liver transplant can serially adoptively transfer the acceptance of a Lewis rat cardiac graft in spite of the presence of in vitro antidonor reactivity. Both CD4+ and CD8+ populations have this regulatory activity, although the CD4+ population plays the dominant role.