A monoclonal antibody to the interleukin-2 receptor enhances the survival of neural allografts: a time-course study.

A time-course study of the survival and immunological characteristics of rat neural allografts was undertaken in animals treated with a murine monoclonal antibody to the alpha-chain (p55) of the rat interleukin-2 receptor. This antibody, NDS 63, was administered for ten days following grafting beginning on the day of operation. Inbred rat strains differing at both major and minor histocompatibility loci were selected as donor and host. Furthermore, the recipient strain displayed a high responder major histocompatibility complex haplotype. All grafts were placed in the lateral ventricle. Comparison was drawn between NDS 63-treated recipients and two groups of controls; an untreated group and a second group treated with the monoclonal antibody NDS 66, directed at a second epitope on the alpha-chain of the interleukin-2 receptor, which has been shown to be ineffective in competing with interleukin-2 for binding. Immunocytochemical analysis of the transplants was performed at several time-points up to 150 days following grafting. Grafts of NDS 63-treated recipients exhibited 100% survival with minimal induction of major histocompatibility complex antigens (both class I and class II) and negligible leukocyte infiltration at all time-points studied. In contrast grafts from both groups of controls showed evidence of a chronic immune response with most grafts undergoing rejection as shown by markedly elevated major histocompatibility complex antigen expression accompanied by specific immune cell infiltration. This was a protracted process with several grafts undergoing complete rejection by 60 days and a majority, but not all, by 150 days after transplantation. It is concluded that NDS 63, a monoclonal antibody to the interleukin-2 receptor, may diminish the immune response to transplanted allogeneic neural tissue and thereby enhance its prospects for long-term survival.     

Immunologic Enhancement of Rat Renal Allografts: I. Comparative Morphology of Acutely Rejecting and Passively Enhanced Grafts

The acute unmodified rejection of (Lewis × Brown Norway) F₁ to Lewis renal allografts is characterized by an early and progressive lymphoid cell infiltrate, glomerular necrosis, necrotizing arteritis and ischemic cortical necrosis leading to graft destruction. A single low dose of enhancing antiserum given at the time of transplantation prolongs graft survival by abrogating the necrotizing lesions in glomeruli and arteries and the subsequent cortical necrosis. Passive enhancement in this model is interpreted as representing predominantly a block in the humoral antibody-mediated rejection response. It is suggested that the block is effected mainly, peripherally, ie, at the level of the transplanted kidney itself.     

The immunology of experimental liver transplantation in the rat.

In many species, the rejection of liver allografts is milder than that of other organs. This is especially so in the rat where, without immunosuppressive treatment, liver grafts between certain strain combinations are accepted permanently, whereas skin, heart and renal allografts undergo acute rejection. Reliable surgical methods, together with the availability of inbred strains and a rapidly developing knowledge of its MHC and immune system in general, have made the rat a prime species in which to study the immunological events which follow liver grafting. In non-rejector combinations, liver allografts possess remarkable properties of tolerance induction and antigen-specific immunosuppression, leading to a state of donor-specific unresponsiveness in which grafts of other organs are also accepted. Moreover, liver transplantation can terminate ongoing rejection reactions in other organs and convert an existing state of sensitization against donor antigens into one of unresponsiveness. This review describes recent progress in understanding the immunological mechanisms behind these phenomena. The topics discussed include the rat MHC (RT1) antigens and their distribution in the liver; the genetic control of rejection and non-rejection, including the role of MHC-linked immune response genes; and cellular and humoral mechanisms involved in tolerance and immunosuppression, such as clonal deletion of alloreactive lymphocytes and antibody-mediated enhancement.     

Immunogenetic aspects of intracerebral skin transplantation in inbred rats.

This study was undertaken to evaluate the ability of intracerebral skin grafts transplanted across different genetic disparities in the major histocompatibility complex (RT1) to elicit an immune response in inbred rats, as determined by histologic examination and by the ability of the grafts to sensitize the recipients to subsequent orthotopic skin grafts. The ability of intracerebral skin allografts to sensitize rats to transplantation antigens is related to the specific genetic disparity between the graft and the host: sensitization appears to occur more consistently across an A region barrier than across a B region barrier. Histologic changes of intracerebral graft rejection are more severe in rats with two intracerebral grafts than in those with one. The degree of histologic change attributable to intracerebral allograft rejection correlates with the ability of these grafts to sensitize the recipient. In certain strains intracerebral sensitization is accomplished with two grafts but not with one, indicating an antigenic dose requirement for intracerebral sensitization.     

Histological signs of immune reactions against allogeneic solid fetal neural grafts in the mouse cerebellum depend on the MHC locus

Summary Using an immunocytochemical method, we examined the immunological responses of adult mice to intracerebellar syngeneic and allogeneic fetal mouse brainstem transplants (embryonic days 12–14). Syngeneic grafts and major histocompatibility complex (MHC)-compatible and non-MHC-incompatible allogeneic grafts survived well, showing no histological signs of rejection even 6 months after transplantation, and with no expression of MHC antigens being observed in any of the grafts. However, most cases of both MHC- and non-MHC-incompatible allografts showed rejection responses, such as marked neovascularization, cellular infiltration and necrosis, two weeks to one month after transplantation. In animals showing rejection, Class I MHC antigens were found on grafted neuronal tissue. An increased number of reactive astrocytes was also observed in the grafts. High levels of Class I antigen expression and prominent gliosis correlated with vigorous cellular infiltration. A quantitative analysis of T cell subsets in the animals showing rejection revealed that the L3T4/Lyt-2 ratio was 1.02±0.21 (mean ± S.D.), indicating that helper/inducer and cytotoxic/suppressor T cells appeared equally in the rejection of MHC- and non-MHC-incompatible allografts. We consider that in these experiments, the brain was not completely an immunologically privileged site, and that MHC- and non-MHC-incompatible intraparenchymal neural transplants were not shielded from host immune surveillance.     

Antibody response against perlecan and collagen types IV and VI in chronic renal allograft rejection in the rat

Chronic rejection is the leading cause of late renal transplant failure. Various structural lesions are observed in grafts undergoing chronic rejection including glomerular basement membrane (GBM) duplications. The well-established Fisher (F344) to Lewis (LEW) rat renal transplant model for chronic rejection was used to assess the presence and role of the humoral immune response against graft antigens during chronic rejection. LEW recipients of F344 allografts develop transplant glomerulopathy and produce IgG1 antibodies directed against F344 GBM preparations that are detectable 3 weeks after transplantation. Glomerular IgG1 deposition was observed that in vitro co-localized with a rabbit anti-rat GBM antiserum in rejecting F344 grafts; elution experiments of isolated glomeruli yielded IgG1 antibodies reactive in vitro with F344 GBM, but not LEW GBM. Prevention of acute rejection by transient treatment of the recipients with cyclosporin A completely abrogated the production of anti-GBM antibodies. Using proteomic techniques we identified the antigens recognized by the LEW posttransplant sera as being the heparan sulfate proteoglycan perlecan and the alpha1 chain of collagen type VI in association with the alpha5 chain of collagen type IV. In conclusion, LEW recipients of F344 kidney grafts produce IgG1 antibodies against donor type perlecan and alpha1(VI)/alpha5(IV) collagen and develop transplant glomerulopathy. These data implicate an important role for the humoral immune response in the development of glomerulopathy during chronic rejection.     

The fate of allogeneic and xenogeneic neuronal tissue transplanted into the third ventricle of rodents

Neural grafts from day 17-19 fetal rats or mice survived well when transplanted into syngeneic, or immunodeficient hosts, thus demonstrating that there are no non-immunological barriers to cross-species transplantation of neuronal tissue in rats and mice. However, intraventricular grafts from rat to mouse, or vice versa, in immunocompetent animals were rejected in less than 30 days. By this time all graft tissue had been destroyed and scavenged, presumably by the macrophages seen infiltrating the grafts within 10 days of grafting. Rat allografts from major histocompatibility complex disparate donors disparate donors survived well as did grafts between rats differing only at minor histocompatibility loci. However, allografts from donors that differed from recipients at both major and minor histocompatibility complex loci had a variable survival time. When neural tissue was grafted into immunologically primed recipients, it was rejected as was similar tissue grafted beneath the kidney capsule of an allogeneic host. Concomitant grafting of allogeneic tissue under the kidney capsule and into the third ventricle was followed by rejection in both sites. A striking observation in these studies was the induction of Class I major histocompatibility complex antigens on grafted neuronal tissue. High levels of antigen expression were correlated with a vigorous host response and poor graft survival but lower levels were not indicative of impending graft destruction. Whilst the brain can be regarded as an immunologically privileged site, the privilege is not absolute and caution needs to be exercised in the interpretation of results from allogeneic or xenogeneic grafts.     

慢性排斥肾移植大鼠继发对自身组织蛋白vimentin的细胞和体液免疫反应

目的:研究慢性排斥肾移植受体对自身组织抗原--波形蛋白（vimentin）的细胞和体液免疫反应.方法:近交系Lewis大鼠接受F344大鼠供肾行左侧原位肾移植,7天后对侧肾切除,建立肾移植慢性排斥反应模型.术后每2周检测受体蛋白尿水平,术后第49天与98天取供肾作病理检查,观察慢性移植肾肾病（CAN）进程.术后第14、49、98天收获受体脾细胞,以酶联免疫斑点法（ELISPOT）检测vimentin特异性IFNγ分泌T细胞的数量;收获受体血清以酶联免疫吸附法（ELISA）检测vimentin特异性抗体水平.自体肾移植Lewis大鼠持续行肾功能检测,第98天收获肾脏、脾脏、血清作病理及免疫检测.结果:同种肾移植受体蛋白尿水平在6周后逐渐升高,49天时病理检查发现肾间质纤维化、肾小管萎缩等典型CAN病变,CAN病情逐渐加重.而自体肾移植大鼠术后98天蛋白尿水平无改变,无CAN病变.经体外vimentin特异性刺激,同种肾移植大鼠IFNγ分泌T细胞的数量在肾移植后49天明显增多（28.3±2.0 vs.10.1±2.1）,98天时其数量显著上升（126.0±10.4 vs.26.3±4.1,P＜0.01）.而自体肾移植大鼠vimentin特异性IFNγ分泌T细胞数量无明显变化.同种肾移植大鼠vimentin特异性抗体水平术后14天即显著升高（0.230±0.018 vs.0.063±0.008,P＜0.05）,并维持在较高水平.而自体肾移植大鼠vimentin特异性抗体水平无明显改变.结论:慢性排斥肾移植受体继发针对自身抗原vimentin的细胞与体液免疫反应,继发自身免疫可能参与CAN的发展.     

Mechanisms in passive enhancement of cardiac and renal allografts by serum from liver-grafted rats.

The ability of serum from PVG (haplotype RT1c) rats carrying long-term surviving orthotopic DA (RT1a) liver grafts (OLT serum) to enhance cardiac allografts has been confirmed and extended to renal allografts. One millilitre of OLT serum given at the time of allografting was sufficient to cause permanent acceptance of PVG.RT1a heart or kidney grafts in PVG recipients ('enhanced recipients'); the PVG.RT1a being congenic with respect to PVG, and sharing the RT1a haplotype with DA. Adoptive transfer of thoracic duct lymphocytes (TDL) from rats carrying enhanced liver grafts into irradiated recipients indicated that specific alloreactive clones had been functionally inactivated or deleted; this was accompanied by active suppression in which specific alloreactivity of normal TDL was partially inhibited. In vitro, splenic T cells from rats with enhanced grafts mediated allospecific suppression in mixed lymphocyte reaction (MLR). The serum of rats carrying enhanced grafts was able to specifically suppress MLR of the same donor/recipient combination. Thus enhancement by orthotopic liver transplantation (OLT) serum leads to cellular and serological changes in the recipient associated with maintenance of unresponsiveness. Such changes are similar to those seen in liver graft recipients themselves.     

The humoral immune response to allografts of foetal small intestine in mice.

The influence of the presence of "passenger leucocytes" on the production of anti-H2 antibodies has been studied in mice receiving allografts of foetal small intestine, adult skin or intradermally injected spleen cells. It was found that the humoral immune response to foetal intestine (a tissue without passenger leucocytes) was identical temporarily to that elicited by skin allografts and these responses differed from that following injection of allogeneic spleen cells in that antibodies to solid grafts took longer to appear. The humoral immune response to small intestine grafts was not evident until several days after the onset of graft rejection as assessed morphologicallymanti H2 antibody production was not observed in thymus deprived recipients of foetal small intestine allografts or allogeneic spleen cells, and this suggests that the humoral immune response to transplantation antigens is thymus dependent.     

口服供体脾细胞对大鼠移植肾的影响

背景：口服供体抗原诱导免疫耐受已被证实有显著效果,而脾脏为人体最大淋巴器官,富含T淋巴细胞,可提供丰富抗原。 目的：观察口服供体脾细胞对大鼠肾移植移植肾功能影响。 方法：肾移植前脾细胞组Lewis (RT11)大鼠采取口服灌胃5×105个BN (RT1n)大鼠供体脾细胞,1次/d,持续7 d;肾移植组Lewis (RT11)大鼠口服灌胃1 mL PBS为对照。 结果与结论：移植后第5天肾移植组出现移植肾排斥症状,脾细胞组平均存活时间长于肾移植组,移植后脾细胞组血肌酐、尿素氮水平升高明显慢于肾移植组;苏木精-伊红染色显示肾移植组移植肾发生急性排斥变化早于脾细胞组。说明口服供体脾细胞能诱导免疫耐受,延长移植肾存活时间。     

Humoral transplantation antibodies play a role in protracted rejection of murine renal allografts.

Murine renal allografts were studied using (C57BL/6J x A/J)F1 mice as recipients and DBA/2 mice as donors. In this strain combination, protracted rejection was noted in that the circulation was maintained in the graft for over 10 weeks. In all grafts examined after 3 weeks, mononuclear cell infiltrates were noted; in addition, all grafts had immune deposits, apparently containing transplantation antibodies, in glomeruli, tubuli and vessels. These results stressed the role of humoral immunity in protracted renal allograft rejection.     

Up-regulation of macrophage migration inhibitory factor in acute renal allograft rejection in the rat.

Recent studies have identified a key role for macrophage migration inhibitory factor (MIF) in a number of immune cell-mediated diseases. The current study investigated the potential role of MIF in acute allograft rejection. Lewis rats underwent bilateral nephrectomy and then received an orthotopic DA renal allograft or an orthotopic Lewis renal isograft. Groups of six animals were killed at day 1 or 5 after transplantation. No immunosuppression was used. Animals receiving a renal allograft exhibited severe rejection on day 5, as shown by high levels of serum creatinine, very low rates of creatinine clearance, and severe tubulitis with a dense macrophage and T cell infiltrate. In contrast, isografts had normal renal function on day 5 with no histological evidence of rejection. Northern blotting showed that renal MIF mRNA expression was unchanged at day 1, but was increased 3.5-fold on day 5. In situ hybridization showed a marked increase in MIF mRNA expression by tubular cells and MIF mRNA expression by many infiltrating mononuclear cells in day 5 allografts. Immunostaining confirmed an increase in tubular MIF protein expression, particularly in areas of severe tubular damage with prominent leucocytic infiltration. Double staining showed that many infiltrating macrophages and T cells expressed the MIF protein in day 5 allografts. There was only a minor increase in MIF expression in day 5 isografts, demonstrating that neither surgical injury nor stress cause significant up-regulation of MIF expression in allograft rejection. In conclusion, this study has demonstrated that local MIF production is specifically increased in acute renal allograft rejection. These results suggest that MIF may play an important role in the cellular immune response mediating acute allograft rejection.     

Identification of the rat NKG2D ligands,RAE1L and RRLT,and their role in allograft rejection

NKG2D is a receptor expressed by NK cells and subsets of T lymphocytes. On NK cells, NKG2D functions as a stimulatory receptor that induces effector functions. We cloned and expressed two rat NKG2D ligands, both members of the RAE1 family, RAE1L and RRLT, and demonstrate that these ligands can induce IFN‐γ secretion and cytotoxicity by rat NK cells. To examine changes in expression of NKG2D and the NKG2D ligands RAE1L and RRLT after transplantation, we used a Dark Agouti (DA)→Lewis rat model of liver transplantation. NKG2D expression was significantly increased in allogeneic liver grafts by day 7 post‐transplant. Ligands of NKG2D, absent in normal liver, were readily detected in both syngeneic and allogeneic liver grafts by day 1 post‐transplant. By day 7 post‐transplant, hepatocyte RAE1L and RRLT expression was significantly and specifically increased in liver allografts. In contrast to acute rejection that develops in the DA→Lewis model, transplantation of Lewis livers into DA recipients (Lewis→DA) results in spontaneous tolerance. Interestingly, expression of RAE1L and RRLT is low in Lewis→DA liver allografts, but significantly increased in DA→Lewis liver allografts undergoing rejection. In conclusion, our results suggest that expression of NKG2D ligands may be important in allograft rejection.     

Humoral rejection of human organ transplants

Although T-cell mediated rejection has remained the most common form of acute rejection, humoral rejection now accounts for a substantial fraction in patients with kidney or heart allografts, and probably causes the majority of acute graft losses. The frequency, variously estimated at 20–30%, is attributed to improved methods of detection, including staining for C4d in tissues, which is more sensitive and specific than histological features. Detection of circulating anti-donor reactive antibody (usually to donor HLA antigens) confirms the diagnosis. The clinico-pathological entity of acute humoral rejection is well accepted in kidney and increasingly in heart transplantation. Recent evidence points to a new category of chronic humoral rejection, which accounts for about 60% of chronic rejection of kidneys. Importantly, the hallmark of humoral rejection, C4d, can be detected in the grafts before development of histological evidence of chronic rejection. Humoral rejection is generally not responsive to the usual anti-T cell immunosuppressive agents, but small, non-controlled trials suggest humoral rejection can be reversed with plasmapheresis, intravenous immunoglobulin, anti-CD20 and other treatments, all of which deserve formal clinical evaluation. Prophylaxis for chronic rejection is expected to require donor-specific serological monitoring and protocol biopsies.     

The generation and maintenance of serum alloantibody

Donor-specific alloantibodies (DSA) mediate hyperacute and acute antibody-mediated rejection (AMR), which can lead to early graft damage and loss, and are also associated with chronic AMR and reduced long-term graft survival. Such alloantibodies can be generated by previous exposure to major histocompatibility (MHC) antigens (usually via blood transfusions, previous allografts or pregnancy) or can occur de novo after transplantation. Recent studies also suggest that non-MHC antibodies, including those recognising major histocompatibility complex class I-related chain A (MICA), MICB, vimentin, angiotensin II type I receptor may also have an adverse impact on allograft outcomes. In this review, we consider how the dose, route and context of antigen exposure influences DSA induction and describe factors which control the generation, maintenance and survival of alloantibody-producing plasma cells. Finally, we discuss the implications of these variables on therapeutic approaches to DSA.     

Analysis of chronic rejection and obliterative arteriopathy. Possible contributions of donor antigen-presenting cells and lymphatic disruption.

Sequential analysis of changes that lead to chronic rejection was undertaken in an animal model of chronic rejection and obliterative arteriopathy. Brown Norway rats are pretreated with a Lewis bone marrow infusion or a Lewis orthotopic liver allograft and a short course of immunosuppression. They are challenged 100 days later with a Lewis heterotopic heart graft without immunosuppression. The heart grafts in both groups undergo a transient acute rejection, but all rats are operationally tolerant; the heart grafts are accepted and remain beating for more than 100 days. Early arterial remodeling, marked by arterial bromodeoxyuridine incorporation, occurred in both groups between 5 and 30 days during the transient acute rejection. It coincided with the presence of interstitial (but not arterial intimal) inflammation and lymphatic disruption and resulted in mild intimal thickening. Significant arterial narrowing occurred only in the bone-marrow-pretreated rats between 60 and 100 days. It was associated with T lymphocyte and macrophage inflammation of the heart graft that accumulated in the endocardium and arterial intima and adventitia near draining lymphatics. There also was loss of passenger leukocytes from the heart graft, up-regulation of cytokine mRNA and major histocompatibility class II on the endothelium, and focal disruption of lymphatics. In contrast, long-surviving heart grafts from the Lewis orthotopic liver allograft pretreated group are near normal and freedom from chronic rejection in this group was associated with persistence of donor major histocompatibility class-II-positive hematolymphoid cells, including OX62+ donor dendritic cells. This study offers insights into two different aspects of chronic rejection: 1) possible mechanisms underlying the persistent immunological injury and 2) the association between immunological injury and the development of obliterative arteriopathy. Based on the findings, it is not unreasonable to raise the testable hypothesis that direct presentation of alloantigen by donor antigen-presenting cells is required for long-term, chronic-rejection-free allograft acceptance. In addition, chronic intermittent lymphatic disruption is implicated as a possible mechanism for the association between chronic interstitial allograft inflammation and the development of obliterative arteriopathy.     

Intraparenchymal allografts in the mouse brain in relation to immunocytochemical identification of T lymphocyte subsets

In a study of intracerebellar allografts of mice brainstem anlagen (embryonic day 12-14), we examined immunocytochemically the expression of two different types of T lymphocytes in and around the grafts. Helper/inducer and cytotoxic/suppressor T cells were identified with anti-L3T4 and anti-Lyt-2 monoclonal antibodies, respectively. Allografts into major histocompatibility complex (MHC)-compatible recipients showed no histological signs of rejection such as marked neovascularization and cellular infiltrates even 6 months after transplantation, but those into MHC-incompatible recipients generally had rejection reactions within one month after transplantation. In the latter cases, the L3T4/Lyt-2 ratio for the T lymphocytes in the infiltrates of the grafts was 1.03 +/- 0.14 (mean +/- S.D.), suggesting that both helper/inducer and cytotoxic/suppressor T cells may play important roles in the mediation of intraparenchymal brain allograft rejection.     

Recent advances in the immunology of xenotransplantation

The transplantation of tissue and organs between individuals of different species, that is xenotransplantation, engenders a variety of severe immune responses. Xenogeneic immune responses mediated by naturally occurring antibodies and complement lead to hyperacute and acute vascular rejection of vascularized organ grafts and may also cause vascular rejection of cell and tissue grafts. Under some circumstances, however, a vascularized organ graft may evade humoral rejection despite the presence of antidonor antibodies in the circulation of the recipient; this condition is called accommodation. Xenogeneic immune responses mediated by T-lymphocytes and natural killer cells may cause acute cellular rejection. The extent to which cellular rejection of xenografts resembles cellular rejection of allografts remains to be determined. New insights into the molecular mechanisms underlying the immune responses to xenotransplantation have shed new light on the pathogenesis of immunological disease and have allowed the development of specific immunomodulatory strategies that may facilitate clinical application of xenotransplantation.     

Isolation of human minor histocompatibility peptides.

Incompatibility of human minor histocompatibility (hmH) antigens induces rejection of grafts in organ transplantation and graft versus host disease in bone marrow transplantation if donor and recipient are matched for human leukocyte antigen (HLA) genes. These antigens are recognized only by T cells. We describe here the isolation of hmH peptides recognized by a hmH antigen specific, HLA-B35 restricted CTL clone which was derived from a patient who rejected the kidneys from two HLA-identical sisters. Naturally occurring hmH peptides were isolated from a donor derived B cell line and an HLA-B35 transfected human B cell line by acid elution. Analysis of various HLA class I transfectant cells demonstrated that MHC class I molecules themselves determine the peptides which are naturally processed and presented to T cells.