猪到猕猴异种心脏移植超急性排斥反应的免疫学及病理学变化

目的观察猪到猕猴异种心脏移植超急性排斥反应时的免疫学及病理学变化。方法采用猪到猕猴腹腔内异位心脏移植模型,检测发生超急性排斥反应者的血液中补体、天然抗体及T淋巴细胞亚群的变化,并对移植心脏进行免疫组化(测定C3、C4、C5b9、IgG及IgM的沉积)及病理学分析。结果发生超急性排斥反应时,血清补体C3、C4的含量、总补体活性及抗猪内皮细胞天然抗体均有一定程度的下降;CD4 /CD8 T淋巴细胞的比率也有所下降;移植心脏中均有补体C3、C4、C5b9的沉积,IgG及IgM也均有沉积,但IgG和IgM沉积强度的差异无统计学意义;病理学改变主要为心肌间质弥漫性出血、水肿,毛细血管内普遍淤血。结论补体通过经典途径激活参与猪到猕猴异种心脏移植超急性排斥反应;超急性排斥反应时受者血中天然抗体水平明显下降;CD4 T淋巴细胞可能参与异种移植超急性排斥反应过程并有所消耗;发生超急性排斥反应的移植物突出病理表现为间质出血。     

补体在猪到猴异种心脏移植中的作用及机理

目的 探讨补体在异种大动物猪到猴心脏移植排斥反应中的作用及机理.方法 以梅山猪为供者,中国猕猴为受者,行异种腹腔异位心脏移植.随机将受者分为3组.A组(5只):为空白对照组,受者心脏移植后不作任何处理.B组(5只):为照射预处理组,受者于心脏移植前28 d、即1.5个月龄时接受60Coγ3 Gy全身剂量照射,其余同A组.C组(8只):为照射+胸腺注射预处理组,心脏移植前21 d,将供者的脾细胞(按照5×107个/只的数量)注入受者的两侧胸腺内,其余同B组.观察心脏移植术后各组移植心的存活时间;猪对猴单向混合淋巴细胞培养的刺激效应;采用双抗体夹心法检测补体C3和CD46的血清浓度;通过流式细胞术检测受者外周血细胞表面IgM、IgG阳性细胞百分比水平.结果 A、B、C三组移植心的存活时间分别为:(36.6±5.8)h、(65.6±6.5)h和(91.1±22.8)h,C组移植心的存活时间明显延长,与A组比较,P＜0.01,与B组比较,P＜0.05.C组在猪对猴单向混合淋巴细胞反应中的刺激效应较A、B组明显下降(P＜0.01).B、C组移植前补体水平(C3)无明显变化,但随着IgM、IgG水平的上升,发生排斥反应时C3和CD46水平显著降低.C组猕猴特异性抗猪抗体IgM及IgG的上升速度均较A、B组明显延缓.结论 对受者进行异种胸腺注射联合全身照射预处理在抑制T淋巴细胞免疫及体液免疫方面有重要作用,但无法抑制异种排斥反应中补体的激活,补体通过经典途径参与了延迟性异种排斥反应的发生.     

异种移植排斥机理的探讨

补体的激活是超急性排斥的中心环节,为了研究经典及旁路途径在这种排斥中的作用,本研究建立了体外超急性排斥模型.选择猪血管内皮细胞为靶,人血清为天然抗体和补体源,用四唑盐法(methyl thagolyl tetragoliam,MTT)行补体依赖的细胞毒反应(complement-dependent cytotoxicity,CDC).人血清能溶解58±5%的猪血管内皮细胞.加入EGTA阻断经典途径后人血清的溶细胞率降为51±3%(P<0.01).同样Clq缺乏的人血清仅溶解37±7%猪血管内皮细胞(P<0.001).人血清50℃加热20min,阻断旁路途径后,其溶细胞率降为42±5%(P<0.001).B因子缺乏的人血清(阻断旁路途径)仅溶42±10%的猪血管内皮细胞(P<0.001)同种猪血清及加热灭活补体的人血清不溶猪血管内皮细胞.将经典途径及旁路途径缺陷的人血清等体积混合,血清的细胞毒作用恢复正常.同样,Clq缺乏人血清和B因子缺乏人血清分别加入Clq和B因子后,血清细胞毒作用亦恢复正常.在这一体外异种超急性排斥模型中,补体经典和旁路两条途径均参与超急性排斥反应.提示抑制猪/人之间的超急性排斥应考虑补体两条途径均激活的问题.     

猕猴预致敏后肾移植加速性排斥反应的免疫学及病理学特点

目的 观察猕猴预致敏后肾移植加速性排斥反应的免疫学及病理学变化特点.方法 建立猕猴皮肤预致敏后肾移植加速性排斥反应模型(供、受者各3只).检测3只受者皮肤移植预致敏前、后及肾移植后血清内供者特异性抗体的变化.并在发生排斥反应时对移植肾进行免疫组织化学(测定补体、抗体的沉积及各类型淋巴细胞浸润情况)及病理学分析.结果 3只受者均发生了加速性排斥反应.其中2只受者在预致敏后血清中供者特异性抗体明显增加,对供者的淋巴毒反应明显升高;肾移植后受者血清中供者特异性抗体及针对供者的淋巴毒进一步升高.苏木精-伊红染色显示排斥反应的移植肾内有明显的动脉坏死、血栓形成、间质出血、中性粒细胞浸润;免疫组织化学及荧光染色显示移植肾内有大量的补体、抗体沉积(主要为IgG),而各种类型的淋巴细胞浸润少见.另1只受者体内的供者特异性抗体及对供者淋巴毒反应的升高程度不如前2只明显,病理学变化以肾小管损伤为主.结论 皮肤移植预致敏可以诱导受者产生程度不等的预存抗体,导致大多数移植肾在术后早期发牛主要南抗体和补体介导的严重的急性体液性排斥反应.     

输注供者CD8+CD28-调节性T淋巴细胞抑制大鼠肝移植急性排斥反应的作用

目的 评价具有免疫抑制作用的CD8+CD28-调节性T淋巴细胞(Treg)体内输注在抑制大鼠肝移植急性排斥反应中的作用.方法 建立近交系大鼠肝移植自发耐受及急性排斥反应模型.从肝移植自发耐受模型受者脾脏中分离CD8+CD28-Treg,于急性排斥反应模型建立前1 d输注给受者,比较不同的输注组间受者的存活时间和移植肝病理学表现.结果 来自自发耐受模型(LEW大鼠为供者,DA大鼠为受者)的CD8+CD28-Treg输注可以延长急性排斥反应模型(LEW大鼠为供者,BN大鼠为受者)受者的存活时间,由(14.0±2.2)d延长至(24.0±3.0)d(P＜0.01),移植肝病理学显示排斥反应程度减轻.结论 大鼠肝移植自发耐受模型受者体内诱导的CD8+CD28-Treg具有抑制急性排斥反应的作用,该免疫抑制作用具有抗原特异性.     

负向免疫调节树突状细胞对心脏移植大鼠免疫状态的影响

目的 探讨经体外光化学法(PUVA)处理的供者脾淋巴细胞与受者树突状细胞(DC)共培养后,对移植受者体液免疫、细胞免疫及移植物排斥反应的影响.方法 以DA大鼠为供者,LEW大鼠为受者,建立大鼠腹部异位心脏移植模型.分离供者脾淋巴细胞(SP),制备经PUVA处理的供者脾淋巴细胞(PUVA-SP).在体外分别将供者PUVA-SP和SP与受者骨髓来源的未成熟DC共培养,得到PUVA-SP-DC及SP-DC,流式细胞仪检测上述DC表型.根据受者心脏移植术前1周静脉输注成分的不同,将受者随机分为3组:(1)对照组(n=7):单纯输注磷酸盐缓冲液(PBS);(2)SP-DC组(n=8):输注Sp-DC 5×106个;(3)PUVA-SP-DC组(n=8):输注PUVA-SP-DC 5×106个.每日观察各组移植心的存活状况.移植后第6天,检测受者血清中抗供者特异性IgG水平;通过混合淋巴细胞反应(MLR)检测受者脾脏T淋巴细胞对供者抗原刺激的增殖反应;比较各组受者脾脏体积的大小.结果 供者脾淋巴细胞经PUVA处理后细胞凋亡率为81.93%.正常LEW大鼠DC共刺激分子CD80和CD86阳性率分别为(3.5±0.27)%和(13.0±0.58)%,受者DC与供者SP混合培养后,其CD80和CD86的表达水平为(16.6±0.72)%和(36.5±0.87)%,后者明显高于前者(P<0.01);受者DC与供者PUVA-SP混合培养后,其CD86和CD80的表达率分别为(3.9±0.12)%和(13.4±0.59)%,与正常LEW大鼠DC相当(P>0.05).PUVA-SP-DC组的受者抗供者特异性IgG水平明显低于SP-DC组及对照组(P<0.01).PUVA-SP-DC组受者T淋巴细胞对供者抗原的刺激反应指数为1.66±0.29,明显低于SP-DC及对照组(7.28±0.38、4.19±0.16,P<0.01);而其对无关供者抗原的刺激反应指数为4.37±0.11,与SP-DC及对照组相当(4.51±0.40、4.36±0.14,P>0.05).PUVA-SP-DC组的移植心存活时间比其他两组明显延长(P<0.01),而且其脾脏体积最小.结论 PUVA-SP-DC能够特异性的下调移植受者对供者抗原的细胞免疫及体液免疫反应,从而明显延长移植物存活时间.     

异种移植超急性排斥机理的实验研究

为了研究补体经典和旁路途径在超急性排斥中的作用，选择猪血管内皮细胞为靶，人血清为天然抗体和补体源，用四唑盐法（MTT）行补体依赖的细胞毒反应（CDC）。人血清能溶解（58±5）％的猪血管内皮细胞；加入乙二醇四乙酸阻断经典途径后人血清的溶细胞率降为（51±3）％（P＜0．01）；入血清50℃加热20分钟，阻断旁路途径后，其落细胞率降为（42±5）％（P＜0．01）；将经典途径和旁路途径分别被阻断的人血清混合，血清的细胞毒作用恢复正常。在这一体外超急性排斥模型中，补体经典和旁路两条途径均参与超急性排斥。提示抑制猪-人之间的超急性排斥应考虑补体旁路途径激活的问题。     

抗γ公共链单克隆抗体诱导治疗延长小鼠移植心脏存活时间及其机理

目的 探讨以抗γ公共链(γc链)单克隆抗体特异性阻断同种反应性T淋巴细胞的信号通路对心脏移植物存活的影响,并探讨相关机制.方法 分离Balb/c小鼠和C57BL/6小鼠的脾细胞,荧光染色后进行混合培养,分别于培养时(实验Ⅰ组)和培养第3天时(实验Ⅱ组)在培养体系中加入抗γc链单克隆抗体,以单一细胞培养为阴性对照,混合细胞培养但不加抗γc链单克隆抗体为阳性对照,观察培养不同时间的细胞增殖和凋亡情况.另以刀豆蛋白刺激C57BL/6小鼠脾细胞,然后加入抗γc单克隆抗体作用14 h,进行膜联蛋白5染色,观察细胞凋亡情况.制作移植物抗宿主反应(GVHR)模型,静脉给予抗γc链单克隆抗体,观察肝脏内T淋巴细胞凋亡情况.以Balb/c小鼠为供者,C57BL/6小鼠为受者,进行颈部异位心脏移植,致敏组术前静脉输注供者脾细胞悬液;干预组术前静脉输注供者脾细胞悬液,并于心脏移植前7、5、3、1 d经尾静脉注射抗γc链单克隆抗体,观察各组术后移植心脏的存活情况.结果 混合淋巴细胞培养中,实验Ⅰ组、实验Ⅱ组及阴性对照组细胞的荧光强度未见明显减弱;培养第3天后,实验Ⅰ组、实验Ⅱ组的前G1期细胞数均较阴性、阳性对照组有所增加,其中实验Ⅰ组前G1期细胞数与阳性对照组的差异最为明显(P<0.01).经抗7c链单克隆抗体作用后,膜联蛋白5阳性细胞数增多,且为cD3阳性细胞.GVHR小鼠接受抗γc链单克隆抗体输注后,门静脉周围聚集的淋巴细胞出现凋亡.对照组和致敏组的移植心脏分别在术后(8.7±0.5)d和(4.3±0.5)d停跳,干预组的移植心脏存活时间达到(50.2±33.9)d,明显长于致敏组和对照组(P<0.01),其中1只受者的移植心脏存活时间达到114 d.结论 抗γc链单克隆抗体可以显著延长小鼠移植心脏存活时间,其机理与特异性清除供者反应性T淋巴细胞有关.     

供犬脾灌注对特异性致敏犬移植肾功能的影响

目的探讨供犬脾灌注对特异性致敏犬移植肾的免疫保护作用。方法雄性家犬作为肾移植的供、受者。首先采用供者淋巴细胞多次输注诱导18只受者致敏后，随机平均将致敏受者分为3组。特异性脾灌注组：用加工过的人用血液透析穿刺管将同一供者的离体脾动、静脉与受者的腹主动脉及下腔静脉连通后开放血流（血流量约18-25ml／min），充盈后轻揉脾脏，灌注40min，然后用同一供肾行肾移植术；非特异性脾灌注组：离体脾灌注以及肾移植的方法与特异性脾灌注组相同，不同的是供脾和供肾均来自于无关供者；对照组：开腹旷置40min后，同法行肾移植。监测脾灌注前、后各组受者微量淋巴细胞毒（CDC）试验和混合淋巴细胞培养（MLC）的变化；观察供者脾灌注对受者移植肾排斥反应发生和肾功能的影响。结果各组受者均在输注淋巴细胞3～4次后诱导致敏成功。特异性脾灌注可以显著降低受者CDC配型水平和MLC淋巴细胞增殖水平，使受者外周血白细胞计数一过性减少，总补体溶血活性（CH50）下降。肾移植术后特异性脾灌注组移植肾肾小球滤过率下降较非特异性脾灌注组和对照组缓慢；病理检查提示术后特异性脾灌注组移植肾排斥反应较非特异性脾灌注组和对照组为轻。结论供者脾灌注可以特异性吸附毒性抗体，使外周血激活淋巴细胞归巢，耗竭血小板，从而延缓特异性致敏受者肾移植后排斥反应的发生，改善移植肾功能。     

转染人补体调节基因对猪血管内皮细胞的保护作用

供者血管内皮细胞(EC)是猪到人异种移植时引发超急性排斥反应的靶抗原的主要分布部位。利用转基因技术让猪的内皮细胞表达人补体调节基因(hDAF)，可能会增强其血管内皮细胞的防御能力，借以克服超急性排斥反应的发生，联合转染一种以上人补体调节蛋白基因可能效果更好。为此，我们进行了如下实验。     

猪血管内皮细胞与人血清反应早期PGI2和TXA2的变化

目的 探讨在猪与人异种移植超急性排斥反应中血管内皮细胞的作用。方法 用体外培养的猪血管内皮细胞和不同人的血清共同反应,建立猪与人异种移植超急性排斥反应的体外实验模型。用放射免疫法检测上清液中前列环素（ＰＧＩ２）和血栓素Ａ２（ＴＸＡ２）的稳定代谢产物（ＰＧＦ１α和ＴＸＢ２）含量,将其作为评定血管内皮细胞激活和损伤的标志。结果 各组血清与猪血管骨皮细胞反应０．５ｈ后,正常人血清组ＰＧＦ１α／ＴＸＢ２比     

Synthetic peptides which inhibit the interaction between C1q and immunoglobulin and prolong xenograft survival

BACKGROUND: Acute vascular xenograft rejection (AVXR), also termed delayed xenograft rejection (DXR), occurs when hyperacute rejection (HAR) is prevented by strategies directed at xenoreactive natural antibodies and/or complement activation. We have hypothesized that AVXR/DXR is initiated in part by early components of the complement cascade, notably C1q. We have developed synthetic peptides (termed CBP2 and WY) that interfere with the interaction between C1q and antibody. METHODS: CBP2 and the WY-conjugates were used as inhibitors of immunoglobulin aggregate binding to solid phase C1q. Inhibition of complement activation by the peptides of the classical system was determined using lysis assays with sensitized sheep red blood cells or porcine aortic endothelial cells as targets and of the alternate complement pathway using guinea pig red blood cells as targets. Two transplant models were used to study the effects of administering peptides to recipients: rat heart transplant to presensitized mouse, and guinea heart transplant to PVG C6-deficient rats. RESULTS: CBP2 and WY-conjugates inhibited immunoglobulin aggregate binding to C1q. The peptides also inhibited human complement-mediated lysis of sensitized sheep red blood cells and porcine aortic endothelial cells in a dose-dependent manner and the WY-conjugates prevented activation of the alternate complement pathway as shown by inhibition of guinea pig red blood cells lysis with human serum. In addition, the use of the peptides and conjugates resulted in significant prolongation of xenograft survival. CONCLUSIONS: The CBP2 and WY peptides exhibit the functional activity of inhibition of complement activation. These peptides also prolong xenograft survival and thus provide reagents for the study of the importance of C1q and other complement components in transplant rejection mechanisms.     

The association of antivascular endothelial cell antibody with hyperacute rejection: a case report

Early graft loss almost always occurs when recipients of a renal allograft develop antibody directed against antigens specific for donor vascular endothelial cells (VECs) and peripheral blood monocytes. In studies involving recipients of human leukocyte antigen identical, living-related grafts exhibiting preformed antibody to the VEC antigens of their donors, the median onset of rejection was 3 days after transplantation. Although preformed antibody to VEC antigens has been related in numerous articles to early graft loss, there has never been a published report of anti-VEC antibody leading to hyperacute rejection. We report a patient who hyperacutely rejected a renal allograft after undergoing a donor-specific transfusion protocol with her mother in which the kidney was removed in less than 24 hours. Nine months later the patient had a retransplantation with an allograft from a cadaveric donor. The cadaveric graft was again hyperacutely rejected, and this kidney was removed immediately. Anti-VEC/monocyte antibody directed against both donors was detected in the patient's pretransplant sera. With the exception of a positive B-lymphocyte crossmatch with her mother, all the standard crossmatches were negative.     

Humoral Human Xenoreactivity Against Isolated Pig Pancreatic Islets

It is widely believed that the hyperacute rejection of vascularized xenografts in the pig-to-human combination is triggered by the binding of human preformed natural antibodies (PNAbs) to the Galα.(1,3)Gal epitope in pig endothelium and the subsequent activation of complement. However, it remains poorly defined whether xenogeneic pig pancreatic islets are damaged by antibody and complement-mediated mechanisms. We examined the expression of Galα(1,3)Gal on isolated adult pig islets and the presence of PNAbs in normal human sera directed against islets, using immunofluorescence staining and confocal laser scanning microscopy. The pig islets were not stained with Galα(1,3)Gal-specific lectin GSIB4; however, the exocrine cells reacted strongly with GSIB4, indicating that the Galα(1,3)Gal epitope was highly expressed on exocrine cells, but not on islets. Human sera showed weak reactivity of IgM and IgG class PNAbs to the islets, but strong reactivity to the exocrine cells. Furthermore, we investigated the cytotoxic effect of human serum on pig islets using an in vitro model of pig-to-human islet transplantation. The incubation of pig islets with normal human sera for 45 min resulted in less than 10% specific lysis despite the binding of PNAbs, whereas exposure of porcine aortic endothelial cells to the same human sera caused 56% complement-mediated lysis, determined using a MTT cytotoxic assay. These results support the view that pig islets might not undergo early antibody and complement-mediated rejection in humans. Received: July 8, 1999 / Accepted: May 30, 2000     

Role of the antibody to vascular endothelial cells in hyperacute rejection in patients undergoing cardiac transplantation

Traditionally, the human lymphocyte antigens have been considered to be the major barrier to successful transplantation, and lymphocytes have been used as the target cell in evaluating histocompatibility. The presence in the serum of recipients of preformed antibodies, cytotoxic to donors lymphocytes, is associated with a high probability of hyperacute rejection. We identified 11 patients in whom, despite a compatible direct lymphocytotoxic cross-match, acute failure of the cardiac homograft was associated with histologic and immunologic findings consistent with hyperacute rejection. Direct immunofluorescence and immunohistochemical staining showed the presence of antibodies on the surface of vascular endothelial cells in each of these 11 patients. The serum of these recipients was found to contain antibodies against a panel of endothelial cells. In contrast, cytotoxic antibodies to vascular endothelial cells were not present in a control group of 18 heart transplant recipients who did not experience hyperacute rejection. Thus the presence of antibodies against vascular endothelial cells seems to be related to hyperacute rejection of the cardiac allograft.     

Hyperacute rejection of living related kidney grafts caused by endothelial cell-specific antibodies: case reports

We describe two cases of hyperacute humoral rejection of living related kidney grafts despite negative pretransplantation T- and B-lymphocyte flow cytometric crossmatches and blood group identity. Retrospectively, antiendothelial IgG antibodies were detected on a panel of umbilical cord cells in the first case, and IgM antibodies against donor endothelial precursor cells were detected using a new endothelial cell crossmatch kit in the second case. Standard crossmatch methods using donor lymphocytes failed to detect these pathogenic antibodies and did not predict the danger of hyperacute rejection.     

Transplant Accommodation in Highly Sensitized Patients: A Potential Role for Bcl-xL and Alloantibody

Transplantation of renal allografts into recipients with circulating anti-HLA antibodies results in hyperacute rejection. In some cases, however, antibodies return without causing harm; this phenomenon has been termed 'accommodation'. We have investigated this process in human allotransplantation. We removed anti-HLA antibodies by immunoadsorption in seven highly sensitized dialysis patients who subsequently underwent renal transplantation. Immunohistochemistry of renal biopsies for IgG and antiapoptotic proteins was performed. We also developed a model of 'accommodation' using anti-HLA antibodies eluted from sensitized patients and incubated with human umbilical vein endothelial cells (HUVECs) at different concentrations. Their effect on HUVEC phenotype was then analysed. Anti-donor antibody returned in 4/7 patients, without evidence of hyperacute rejection. Three out of four of these 'accommodated' grafts showed specific endothelial up-regulation of Bcl-xL and 2/2 tested positive for endothelial IgG deposition. HUVECs incubated with subsaturating concentrations of anti-HLA antibody showed increased expression of Bcl-xL, were rendered refractory to endothelial cell activation and became resistant to complement-mediated lysis. In contrast, HUVECs incubated with saturating concentrations underwent activation and expressed low levels of Bcl-xL. In conclusion, endothelial Bcl-xL expression defines the accommodation process in human allografts and this phenotype may be initiated by exposure of endothelium to low concentrations of anti-donor HLA antibodies.     

Successful living donor renal transplantation despite ABO incompatibility and a positive crossmatch

Potential live kidney donors have been rejected when the prospective recipients are blood type or crossmatch incompatible. By utilizing plasmapheresis combined with intravenous immune globulin (PP/IVIg) prior to surgery, donor-specific antibodies against blood group or human leukocyte antigens (HLA) have been removed, thereby allowing successful renal transplantation. A 26-yr-old male with a panel reactive antibody level of 100% and repeated positive crossmatches against deceased donor kidney offers, including zero HLA mismatched donors, successfully underwent ABO-incompatible kidney transplantation from his HLA-identical but nevertheless crossmatch-incompatible sister. The initial anti-A blood group isoagglutinin titers were 128, 256, and 1024 at room temperature, 37 degrees C, and 37 degrees C anti-IgG enhanced, respectively. With an individualized PP/IVIg regimen based on donor-specific antibody titer, however, the relevant antibodies were adequately reduced and hyperacute rejection avoided. Subsequent antibody-mediated rejection, likely directed against a minor histocompatibility antigen, was diagnosed on postoperative day 7 and successfully treated. Neither ABO, or crossmatch incompatibility, or both in combination prohibit kidney transplantation.     

Role of porcine P-selectin in complement-dependent adhesion of human leukocytes to porcine endothelial cells

BACKGROUND: Rapid leukocyte adherence to donor organ vasculature is a hallmark of hyperacute xenograft rejection. However, the molecular interactions required for leukocyte binding to vascular endothelium have not been characterized. METHODS AND RESULTS: Binding assays performed between human neutrophils and porcine aortic endothelial cells (PAEC) after exposure to human complement demonstrated that adhesion was mediated by both surface-bound C3b and C5b-9 activity. C5b-9-dependent adhesion was blocked by neuraminidase treatment of the neutrophils, suggesting that this binding was mediated by porcine P-selectin. Porcine P-selectin was isolated from a PAEC cDNA library. The porcine P-selectin primary sequence contained an open reading frame encoding 646 amino acids with 82% identity to human P-selectin. Recombinant soluble porcine P-selectin specifically bound to human neutrophils and HL-60 cells. Transfection of COS cells with the full-length porcine P-selectin cDNA resulted in surface expression of the protein and markedly increased the binding of human neutrophils to these cells. The binding of both soluble and COS-expressed porcine P-selectin to human neutrophils was blocked by pretreatment of the neutrophils with neuraminidase or the addition of EDTA. Finally, treatment of PAEC with human thrombin or normal human serum but not purified human C5a- or C8-deficient human serum resulted in the rapid expression of porcine P-selectin on the cell surface. CONCLUSIONS: This report establishes that porcine P-selectin supports the binding of human neutrophils to PAEC in vitro. Further, these data suggest that sublytic deposition of C5b-9 during hyperacute rejection results in the expression of porcine P-selectin, which may contribute to the rapid adhesion of neutrophils to porcine xenografts.     

The prospects for renal xenotransplantation

Summary: Xenotransplantation of non-human organs into human recipients has long been proposed as a possible strategy to overcome the acute shortage of donor organs. However, vascular organ transplants to humans from phylogenetically disparate species such as the pig are not currently possible due to a rapid rejection process termed hyperacute rejection. This process is initiated by the binding of host pre-formed 'natural antibodies' to the donor vascular endothelium, activation of the host complement system and activation or injury of the donor endothelial cells, leading to intravascular coagulation and loss of the graft due to ischaemic necrosis within minutes to hours of engraftment. Prevention of natural antibody binding and complement activation is viewed as paramount to preventing hyperacute rejection. Even if hyperacute rejection can be prevented, further barriers to successful discordant xenografts such as delayed xenograft rejection and a donor-directed cell-mediated rejection process will still represent major obstacles. This review examines recent advances being made in the various areas of xenograft research and the potential clinical application of pig-to-human xenografts that these strategies may bring.