小剂量环孢素A对大鼠同种异体肢体移植的免疫抑制作用

目的通过大鼠同种异体肢体移植模型,分析小剂量环孢素A(cyvlosporinA ,CsA)对大鼠同种异体肢体移植急性排斥反应的免疫抑制作用。方法采用雄性Wistar和SD大鼠为供、受体,以CsA为免疫抑制剂。对照组14只,将Wistar大鼠肢体移植至SD大鼠,术后不用药。实验组术后按用药剂量的不同分为2组( 2mg/kg组17只大鼠和CsA 6mg/kg组18只大鼠)。2组术后用药时间均为4周(每日1次共2周,然后每周2次共2周)。术后观察大鼠一般情况、移植肢体排斥反应及存活时间;用免疫荧光染色流式细胞仪检测各组手术前后T细胞亚群的变化。结果对照组移植肢体平均存活时间为[( 7.0 0±0 .78)d , x±s ,下同] ;CsA 2mg/kg组为( 3 7.18±0 .5 1)d ,CsA 6mg/kg组为( 3 3 .2 0±1.0 5 )d。术后第3天,对照组的CD4/CD8比值显著增高,移植肢体开始出现肿胀、皮肤红斑等表现。实验组的CD4/CD8较术前无明显变化。结论小剂量CsA能抑制大鼠同种异体肢体移植术后急性排斥反应的发生,并能延长移植肢体的存活时间。     

FK506与来氟米特预防异种胰岛移植排斥反应的效果

目的　探讨FK5 0 6、来氟米特 (Lef)应用预防大鼠对小鼠异种胰岛移植排斥反应的效果。方法　将 10 0 0～ 12 0 0个大鼠胰岛移植于化学诱导的糖尿病小鼠肾被膜下 ,实验分为对照组、FK 5 0 6组、Lef组和FK5 0 6+Lef组 ,研究胰岛有功能存活情况 ,并在移植后第 5天行病理组织学观察排斥反应。结果　FK5 0 6( 2和 4mg·kg-1·d-1)、Lef( 5、10、2 0mg·kg-1·d-1)术后用药 10d ,胰岛存活时间分别为 ( 8.9± 2 .1)、( 12 .5± 0 .7)、( 10 .8± 1.9)、( 15 .8± 2 .4)、( 18.8± 2 .2 )d ,较对照组( 5 .9± 1.2 )d明显延长 (P <0 .0 1)。FK5 0 6+Lef组移植物存活时间 ( 2 1.8± 1.2 )d ,较单纯用药组效果更好 (P <0 .0 1)。病理组织学显示Lef组与FK5 0 6+Lef组细胞浸润明显减少 ,有更多的完整胰岛存留。结论　FK5 0 6与Lef对异种胰岛移植有抗排斥作用 ,且两药联合应用有协同作用。     

大鼠同种异体肢体移植急性排斥反应的实验研究

目的通过大鼠同种异体肢体移植模型,旨在分析大鼠同种异体肢体移植中各种不同组织的急性排斥反应特点,确定反映肢体移植排斥反应最具有代表性的组织类型.方法将29只Sprague-Dawley成年大鼠随机分成2组,对照组15只为自体肢体再植组,实验组14只为Wistar→SD同种异体肢体移植组,术后不用免疫抑制剂,观察急性排斥反应出现的时间及表现,并对移植肢体中各组织进行组织病理学检查.结果异体肢体移植术后第(3.36±1.15)d开始出现皮下水肿和皮肤红斑,这是最早的急性排斥反应表表现;移植肢体的平均存活时间为(7±0.78)d;移植肢体中皮肤组织的排斥反应程度最强.结论Wistar→SD同种异体肢体移植中皮肤是最具有代表性的、最易于观察排斥反应的组织类型.     

他克莫司和来氟米特合用抑制大鼠心脏移植排斥反应及T淋巴细胞增殖

目的　评价他克莫司 (FK5 0 6 )和来氟米特联合应用对大鼠心脏移植排斥反应的抑制作用。方法　将实验动物随机分为对照组、FK5 0 6组、来氟米特组以及FK5 0 6与来氟米特合用组 ,观察移植心存活时间 ,于术后 7d切取部分移植心做病理检查 ,并测定各组受者外周血T淋巴细胞亚群及肝、肾功能。结果　不用免疫抑制剂的对照组移植心存活时间为 ( 7.14± 1.0 7)d ,单用FK5 0 6的组为( 11.14± 1.73)d ,单用来氟米特的组为 ( 11.2 9± 1.80 )d ,两药合用组为 ( 14 .0 0± 2 .4 9)d ,合用组的病理切片提示排斥反应明显轻于两药单用组。术后 7d ,合用组外周血T淋巴细胞亚群中 ,CD4 +细胞明显低于两药单用组 (P <0 .0 5 ) ,而CD8+细胞各组间的差异无显著性 ;各组间肝、肾功能的差异也无显著性。结论　FK5 0 6和来氟米特联合应用对大鼠心脏移植的免疫抑制作用优于相同剂量的单一用药     

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。     

FK506对大鼠心脏移植细胞凋亡的作用

目的　观察大鼠心脏移植急性排斥反应中的细胞凋亡现象及FK5 0 6对它的影响。方法　进行 48次SD→Wistar的大鼠颈部心脏移植 ,用苏木素 伊红 (HE)染色和原位末端标记(TUNEL)技术检测移植心切片 ,进行排斥反应的病理分级并计算凋亡指数 (AI)。结果　移植心的细胞凋亡主要发生于心肌细胞 ;FK5 0 6能明显减少心肌细胞的凋亡 ,减轻移植心的组织损伤。移植后第 3、5、7天AI对照组分别为 3.73± 2 .32、8.30± 2 .97、10 .2 2± 5 .5 2 ;FK5 0 6治疗组为 1.2 7± 1.2 0、2 .89± 2 .18、3.11± 1.6 8;两组比较差异有非常显著性 (P <0 .0 1)。结论　细胞凋亡是心脏移植急性排斥中组织损伤的重要机制 ;FK5 0 6能明显抑制心肌细胞凋亡 ,这可能是FK5 0 6发挥免疫抑制作用的重要方面。     

大鼠同种异体肢体移植中T淋巴细胞亚群的变化及其意义

目的 建立大鼠同种异体肢体移植模型，研究肢体移植中T细胞亚群的变化及其与急性排斥反应的关系。方法 将31只SD雄性大鼠随机分成两组，其中对照组14只为Wista→SD肢体移植术后不用药组，实验组17只为FK506(4mg／kg体重) RS-61443(30mg／kg体重)联合免疫抑制治疗组，观察各组移植术后排斥反应；用免疫荧光染色流式细胞仪检测各组手术前后T细胞亚群。结果 术后第3天，CD4／CDs比值显著增高，移植肢体开始出现肿胀、皮肤红斑等表现；CD4／CD8比值增高与排斥反应程度呈正相关，而用药组术后，CD4／CD8较术前无明显变化，未出现排斥反应。结论 T细胞亚群中CD4／CD8比值的变化与肢体移植急性排斥反应的发生、强烈程度有密切关系，可作为监测异体肢体移植急性排斥反应的免疫学指标。     

骨化三醇在抑制大鼠同种肢体移植排斥反应中的作用

目的 探讨应用骨化三醇(1,25-二羟维生素D;简称:VD5)在抑制肢体移植排斥反应中的作用.方法 以Wistar大鼠为供者,SD大鼠为受者,建立同种肢体移植模型.随机将受者分为4组,每组12只.(1)对照组:术后不用免疫抑制剂,仅以15 ml·kg-1·d-1.生理盐水灌服.(2)他克莫司(FK506)组:将FK506用生理盐水稀释为0.5 mg/ml,术后前2周的用量为1.0 mg·kg-1·d-1,术后第3周起,每周灌服2次.(3)VD3组:将骨化三醇用生理盐水稀释为0.125 μg/ml,术后用量为2.5μg·kg-1·d-1,连续灌服4周.(4)VD3+FK506组:术后联合应用骨化三醇及FK506,用药方法和用量与FK506组和VD3组相同.术后观察各组受者移植肢体排斥反应发生的时间和存活时间;流式细胞仪检测T淋巴细胞亚群CD4+、CD8+细胞的百分率.结果 对照组、FK506组、VD3组以及VD3+FK506组肢体移植后排斥反应发生的时间分别为:(3.50±0.50)d、(13.13±1.50)d、(10.63±0.38)d和(29.25±0.63)d;移植肢体的存活时间分别为:(8.50±0.50)d、(26.25±1.50)d、(17.25±0.38)d和(62.00±0.63)d;与对照组比较,VD3组排斥反应发生的时间和移植肢体的存活时间均明显延长,差异有统计学意义(P＜0.01);VD3+FK506组抗排斥反应效果更佳,与FK506组和VD3组比较,差异有统计学意义(P＜0.01).VD3组T淋巴细胞亚群CD4+/CD8+细胞的比值明显低于对照组,VD3+FK506组又明显低于VD3组和FK506组(P＜0.01).结论 骨化三醇能明显减轻同种肢体移植排斥反应,延长移植肢体的存活时间;骨化三醇与FK506联合应用效果更佳,二者具有协同作用.     

大鼠同种异体肢体移植急性排斥反应动物模型的制作

目的　建立同种异体肢体移植的动物模式。　方法　Wistar大鼠的肢体移植给SD大鼠 ,术后抗炎 ,显微外科常规护理 ,观察移植后宿主及移植物的变化。　结果　大鼠的异体肢体移植 8例 ,成功 6例 ;移植物的排斥反应再现稳定 ,生存时间为 (14± 2 )d。　结论　Wistar→SD大鼠的同种异体肢体移植模型的建立 ,为基础研究提供了动物模型     

大鼠异体肢体移植中淋巴细胞亚群的动态观察

目的 探讨大鼠后肢异体移植中排斥反应与T淋巴细胞亚群和活化T细胞的关系。方法 将24只（8只Wistar，16只SD）大鼠随机分成两组，实验组8只为Wistar-→SD后肢移植未作免疫抑制组，对照组8只为FK506（2mg／kg体重）和霉酚酸（20mg／kg体重）免疫抑制组，观察术后排斥反应及病理检查；流式细胞仪检测T细胞亚群和活化T细胞。结果 术后6～8d，实验组移植肢体出现排斥反应，活化T细胞（CD3／CD69、CD3／CD25、CD3／HLA-DR）已于排斥反应发生（6．88±0．83）d前2—4d显著升高，CIM／CD8比值中度升高；活化T细胞增高与排斥反应程度呈正相关（相关系数r为0．874、0．854、0．879，P〈0．05）；CIM／CD8比值与排斥反应程度无明显相关（相关系数r=0．544，P〉0．05）；对照组，活化T细胞较术前无明显变化，未出现排斥反应。结论 动态监测活化T细胞将有助于异体肢体移植急性排斥反应的早期诊断。     

Limb allografts in rats immunosuppressed with FK506. I. Reversal of rejection and indefinite survival

We have tested the effects of FK506 (FK), a new immunosuppressive agent, on a rat limb allograft model. Histoincompatible BN limb allografts were rejected in untreated F344 hosts within 11 +/- 1 days (mean +/- SD) after operation. A single injection of 2 mg/kg, 10 mg/kg, or 50 mg/kg of FK on the day of limb transplantation (day 0) significantly prolonged graft survival in a dose-dependent manner--i.e., mean limb survival times (MST) based on gross signs of skin rejection were 16 +/- 3 days, 51 +/- 6 days, or 104 +/- 17 days, respectively (P less than 0.01). Delayed treatment with a single injection of 10 mg/kg of FK at when early signs of rejection were visible (day 7 or day 10) reversed the ongoing rejection. The MSTs in these groups were comparable to that of those treated with the same dosage of FK on day 0. The FK-induced unresponsiveness toward limb allografts was donor-specific because limb-allografted. FK-protected rats could not accept the skin grafts from a third-party donor. In the next set of experiments, rats were given a single administration of 10 mg/kg of FK on the day of limb allograft, followed by intermittent injections of 3 mg/kg of FK once a week. This regimen produced complete graft survival for more than 200 days, though Pneumocystis carinii pneumonia occurred in most of the recipients. These results represent the unique effects of FK in preventing or reversing the graft rejection and in inducing indefinite survival in this animal model of composite tissue allografts.     

The role of cyclophosphamide and granulocyte colony-stimulation factor in achieving high-level chimerism in allotransplanted limbs.

The establishment of a high-level of chimerism may be the most stable strategy for donor-specific tolerance. The purpose of this study was to evaluate the efficacy of a new protocol using cyclophosphamide (CYP) and granulocyte colony-stimulation factor (G-CSF) to induce high-level chimerism following rat whole-limb allotransplantation. Seventy-three whole-limb allotransplants from LacZ transgenic rats to LEW rats were performed. CYP was injected at day 2, and G-CSF was given from day 0 to 3. Nontreated limb allografts were rejected after 4.2 days. In FK506-treated group for 28 days, the survival time was prolonged to 64 days. In the group treated with CYP/G-CSF, limb allografts were rejected after 5.4 days and 5 of 15 recipients showed acute lethal graft-versus-host disease (GVHD). Polymerase chain reaction (PCR) study showed a high level of chimerism even within 1 week after transplantation. Fourteen of 30 recipients given CYP/G-CSF/FK506 died within 2 weeks. The limb survival was significantly prolonged, however, with three grafts surviving more than 300 days. Seven recipients (24%) showed chronic GVHD. A high-level of chimerism was maintained when limb allografts were not rejected by recipients. Limb allografting could function as a vascularized carrier for bone marrow transplantation, provide a continuous source of donor cells and contribute to a high level of chimerism in the recipient. Pretransplant CYP followed by G-CSF and FK506 treatment significantly prolonged the survival of limb allografts but frequently caused chronic GVHD in the recipients.     

Prolonged survival of rat whole-limb allografts treated with cyclophosphamide, granulocyte colony-stimulation factor and FK506

We evaluated the efficacy of a new protocol using cyclophosphamide (CYP), granulocyte colony-stimulation factor (G-CSF) and FK506 to induce high level chimerism following rat whole-limb allotransplantation. The present study investigated the dose requirement and toxicity of CYP monotherapy in inducing stable bone marrow chimerism. Fifty-six whole-limb allotransplants from LacZ transgenic rats to LEW rats were performed. CYP at a dose of 100 mg to 200 mg/kg was injected 2 days before transplantation and G-CSF of 25 microg/kg/day was given for 4 days. FK506 was used for 28 days at 1 mg/kg/day. The level of chimerism was evaluated by semi-quantitative polymerase chain reaction. The survival of limb allografts in recipients treated with CYP of 150 mg/kg was significantly prolonged to 107 days. The onset of rejection was more prolonged to 158 days in recipients with CYP of 200 mg/kg, with two of eight grafts surviving >1 year and three recipients (38%) showed chronic, nonlethal GVHD with a high level of bone marrow chimerism. Limb allografting could contribute to chimerism in the recipient. Pretreatment with CYP had the dose-dependent effects of prolonging the survival of limb allografts. A CYP dose of 200 mg/kg appears to significantly prolong limb graft survival but frequently causes chronic nonlethal GVHD in the longer surviving recipients.     

Prolonged survival of rat hindlimb allografts following short-course FK506 and mycophenolate mofetil combination therapy

The immunosuppressive effect of combined therapy using FK506 and mycophenolate mofetil (MMF) was studied in rat limb allotransplantation. Dark Agouti rat donor hindlimbs were orthotopically transplanted into Lewis rat recipients. In total, 38 models of transplantation were performed and divided into 8 groups that were treated individually or in combination with FK506 + MMF therapy. Animals were immunosuppressed for 28 days and then observed for up to 140 days. Graft rejection was evaluated both macroscopically and histologically. Survival times for rat limb allotransplants receiving combination FK506 + MMF therapy were significantly longer than with FK506 or MMF monotherapy, and this was achieved without serious side effects. A histopathological study demonstrated a significantly lower level of rejection with FK506 + MMF combination treatment compared to groups receiving FK506 or MMF monotherapy. Combined FK506 + MMF treatment can prolong the survival of rat limb allografts.     

Prolonged survival of experimental extremity allografts: A new protocol with total body irradiation,granulocyte‐colony stimulation factor,and FK506

The induction of a high‐level of chimerism (macrochimerism) may be the most reliable strategy for achieving donor‐specific tolerance. The purpose of this study was to evaluate the efficacy of a new protocol using total‐body irradiation (TBI) and granulocyte‐colony stimulation factor (G‐CSF) to induce high‐level chimerism following rat whole‐limb allotransplantation. In this study, we investigated whether the timing of TBI influenced the period of graft survival. In total, 50 whole‐limb allotransplants from LacZ transgenic rats to LEW rats were performed. TBI was performed at days 0 and 14, and G‐CSF was given for 4 days after TBI. FK506 was given for 28 days after transplant. Nontreated limb allografts were rejected after 4.2 days. The survival time was prolonged to 64 days in the FK506 monotherapy group. In the group receiving TBI at day 14, limb allograft survival was significantly prolonged to 81 days. In the group receiving TBI at day 0, 26% of recipients died but in the surviving recipients the grafts survived for longer than 1 year without lethal graft‐versus‐host disease (GVHD). Polymerase chain reaction (PCR) analysis revealed a high level of intrabone marrow chimerism in the recipient, thus demonstrating successful induction of macrochimerism. A new protocol of pretransplant TBI followed by treatment with G‐CSF and FK506 was found to induce a high level of chimerism and to significantly prolong the survival of limb allografts in recipients without lethal GVHD. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:457–461, 2010     

Mucosal glutamine utilization after small-bowel transplantation: an electrophysiologic study.

A short course of FK 506 after small bowel transplantation averts rejection in the rat and achieves indefinite survival of the recipient whose nutritional status is dependent on the function of the intestinal graft. Ex vivo electrophysiologic studies using the Ussing Cell were conducted to delineate functional competence of the graft by evaluating mucosal ion transport and glutamine utilization. Orthotopic small-bowel transplantation was performed in Lewis (LEW) rats as recipients of either Brown-Norway (BN) allografts or LEW syngeneic grafts. Allograft recipients received FK 506 either as a short course (2 mg/kg on Day 0-4 after transplantation) or continuously (2 mg/kg Day 0-4, then 0.5 mg/kg weekly). Ileal mucosa was harvested from small bowel grafts 9 and 60 days after transplantation and mounted in the Ussing Cell containing Hanks' balanced salt solution with/without L-glutamine (20 mM). Transmembrane potential difference (PD), which represents mucosal active ion transport, and mucosal resistance, an index of membrane integrity, were recorded. Nine days after transplantation, mucosal PD was the same in the ileum from syngeneic grafts, allografts treated with FK 506 and normal LEW and BN rats, and the addition of glutamine increased PD equally in all groups. In comparison, PD was markedly decreased in allografts undergoing rejection, and the glutamine response was blunted. Sixty days after transplantation, mucosal PD was reduced in allografts treated with a short course of FK 506, but normal in allografts receiving continuous immunosuppression with FK 506 and in syngeneic grafts. A decrease of mucosal resistance was not a feature of rejection nor a sequel of limited FK 506 therapy. Our data indicate that allograft rejection results in a significant decrease in mucosal PD and a poor response to glutamine. Control of rejection by FK 506 preserves normal electrophysiologic responses of the allograft mucosa.     

The necessity of differential immunosuppression for prevention of immune rejection by FK506 in rat islet allografts transplanted into the liver or beneath the kidney capsule.

The purpose of the present study was to achieve prevention of immune rejection in rat islet allografts by FK506. WKA/Qdj (RT1u) islets were transplanted either into the liver via the portal vein (p.v.) or beneath the kidney capsule (k.c.) of streptozotocin (60 mg/kg) induced diabetic Lewis (RT1(1)) rats. Fresh or cultured (24 degrees C, 1 week) islets were used as donors. A miniosmotic pump (0.2 ml, Alzet 2001) containing 5 mg FK was implanted s.c. at the time of transplantation for continuous delivery of FK506 for 7 days after transplantation. The mean survival time (MST) of the fresh p.v. grafts with a pump was offater than 61.4 +/- 37.2 days (mean +/- SD, n = 17) (control 5.5 +/- 0.6, n = 4). Ten out of 17 were normoglycemic for more than 90 days after transplantation. When low-temperature cultured islets were used and FK506 was delivered for 7 days, all the rats were normoglycemic for more than 90 days after transplantation. The MST of the fresh or cultured k.c. grafts with a pump was 22.0 +/- 14.2 or 24.7 +/- 5.0 days, respectively. Long-term administration of FK506 by repeated implantations (5 times; days 0, 7, 14, 21, and 28) of pumps containing 5 mg FK506 produced marked prolongation of the fresh or cultured k.c. graft survival with an MST of greater than 58.7 +/- 22.1 or greater than 56.9 +/- 18.0 days, respectively. These findings clearly demonstrate that the prevention of immune rejection in the islet allografts transplanted into the liver was achieved by short-term post-transplant administration of FK506 and low-temperature culture of donor islets, and also show that long-term continuous administration of FK506 was needed for the prolongation of the graft survival when the renal subcapsular space was the site for implantation of islets. Thus, the present study indicates that in different transplant sites different immunosuppressive regimes are needed for the control of rejection by FK506 in rat islet allografts.     

RS-61443--a new, potent immunosuppressive agent

The immunosuppressive activity of RS-61443, a semisynthetic derivative of mycophenolic acid, was examined in 33 canine renal allografts. Initial studies established that triple therapy consisting of 20 mg/kg RS-61443 in combination with 5 mg/kg cyclosporine and 0.1 mg/kg methylprednisolone was the optimal combination to prevent graft rejection. The median survival time was 8.1 +/- 1.2 days in dogs without treatment (n = 5), 8.5 +/- 1.7 days in the treatment control group (CsA 5 mg/kg, MP 0.1 mg/kg; n = 6), 36.0 +/- 9.6 days with RS-61443 monotherapy (40 mg/kg; n = 6); and 122.4 +/- 38.75 days with triple therapy (n = 16). Graft prolongation was statistically significant when compared with controls (P less than 0.05 and 0.002, respectively). Six recipients in the triple therapy group survived over 150 days without major adverse effects. Long-term administration of RS-61443 (20 mg/kg/day) did not cause nephrotoxicity, hematotoxicity, or hepatotoxicity, with the exception of a slight elevation of the alkaline phosphatase levels. Gastrointestinal symptoms including gastritis, diarrhea, and anorexia were common, especially under 40 mg/kg RS-61443 monotherapy, and appeared to be dose-related. Despite its immunosuppressive activity, an increased susceptibility to bacterial or viral infections was not observed. Histological studies of the kidney grafts revealed slight interstitial cell infiltration without vascular or glomerular damage.     

FK506 as the sole immunosuppressive agent for prolongation of islet allograft survival in the rat.

The purpose of the present study was to determine immunosuppressive effects of a new immunosuppressive agent, FK506, on rat islet allografts and also whether FK is toxic to the islet grafts since the diabetogenic effects of FK is controversial. Hand-picked clean fresh islets (WKA/Qdj:RT1u) were transplanted either beneath the renal capsule or into the liver via the portal vein of the diabetic (STZ, 60 mg/kg) rats (Lewis:RT1(1)). FK506 was administered s.c. for 7 days after transplantation. The mean survival times (MST)* of the renal subcapsular grafts receiving 0 (control), 0.32 or 1.0 mg/kg FK were 7.2 +/- 1.1 (mean +/- SD, n = 5), 13.8 +/- 4.8 (n = 4), and 20.2 +/- 8.0 days (n = 5), respectively. The MST of the intrahepatic grafts receiving 0, 0.1, 0.32, or 1.0 mg/kg FK were 4.4 +/- 1.1 (n = 5), 7.2 +/- 0.8 (n = 5), greater than 45.3 +/- 23.1 (n = 6) or greater than 54.4 +/- 8.8 days (n = 5), respectively. Histologically, islets were found easily in the liver of normoglycemic recipients for more than 60 days after transplantation and appeared intact, with well-granulated beta cells. Foci of mononuclear cells were occasionally seen adjacent to the islet cells. The plasma glucose of the recipients with 1.0 mg/kg FK fluctuated between 150 and 350 mg/dl without rejection. In the recipients treated with 3.2 mg/kg FK the plasma glucose of all the recipients (n = 3) returned to pretransplant levels by 21 days after transplantation. However, islet cells were present in the liver of all these recipients without mononuclear cell infiltration. Immunohistochemically islet grafts stained weakly for insulin, but to the same extent as the controls for glucagon and somatostatin. These findings clearly demonstrate the immunosuppressive effect of FK506 on islet allografts and the importance of the transplant site for prolongation of graft survival by FK, and also suggest that FK has toxic effects on the islet grafts (B cells) when used in high dosages.