Prevention of antibody-mediated kidney transplant rejection

There is increasing evidence that antibody-mediated rejection is the major cause of late kidney graft failure. Prevention of antibody-mediated allograft damage has therefore become an important issue in kidney transplantation. Such prevention starts already before transplantation with the avoidance of sensitizing events. When a patient is already sensitized, precise characterization of alloantibodies and exact HLA typing of the donor at the time of transplantation are mandatory. To ensure timely and successful transplantation of highly sensitized patients, desensitization, and inclusion in special programs such as the Eurotransplant Acceptable Mismatch Program should be considered. After transplantation, close monitoring of kidney function, testing for the de novo development or changing characteristics of alloantibodies, and attention to non-adherence to immunosuppression is obligatory. In the current overview, we discuss the currently available measures for the prevention of antibody-mediated kidney graft rejection.     

Tolerance induced by bone marrow chimerism prevents transplant vascular sclerosis in a rat model of small bowel transplant chronic rejection

BACKGROUND: The major impediment to success in solid organ transplantation is chronic rejection (CR). The characteristic lesion of CR is transplant vascular sclerosis (TVS). Although the mechanism of TVS is thought to have an immunologic basis, in humans immunosuppression does not prevent or reverse it. One possible therapy to prevent TVS is induction of donor-specific tolerance. Bone marrow chimerism has been successful in inducing tolerance in acute and chronic rejection heart and kidney transplant models. The highly immunogenic small bowel (SB) allograft provides a rigorous test of the efficacy of this tolerance regimen. We examined whether induction of tolerance by bone marrow chimerism could prevent TVS in a model of Fisher 344 (F344) to Lewis (LEW) rat SB transplantation. METHODS: Bone marrow chimeras (BMC) were created by transplantation of T-cell-depleted F344 bone marrow into irradiated LEW rats. Chimerism was assessed by flow cytometric method. F344 SB, heterotopically transplanted into the chimeras, was clinically and histologically assessed for CR. F344 SB grafts, transplanted into cyclosporine-A-treated LEW recipients, served as control grafts for CR. RESULTS: Cyclosporine-A-treated LEW rats chronically rejected F344 SB grafts. By contrast, the BMC group demonstrated tolerance and had long-term SB graft survival (>120 days) without TVS. The BMC demonstrated immunocompetence by prompt rejection of third party ACI (RT1av1) SB allografts. CONCLUSIONS: Bone marrow chimerism prevents chronic graft failure secondary to TVS in a model of chronic SB rejection. TVS fails to develop when tolerance is established, suggesting that the mechanisms involved in TVS are, in part, immunologically mediated.     

Progression of kidney disease in chronic renal transplant rejection

The rate of progression of renal insufficiency was quantitated from reciprocal of serum creatinine versus time plots in patients with clinical and histologic evidence of chronic renal transplant rejection. The plots were evaluated by the breakpoint test. This method identifies breakpoints in a linear plot and compares the statistical significance of the fit provided by two intersecting lines with that of a single straight line. The breakpoint test when applied to the 22 patients with a significant linear correlation between the reciprocal of serum creatinine versus time detected a change in the slope in 20 cases (90.9%) indicating the presence of a breakpoint. The average diastolic, systolic, and mean arterial pressures before the breakpoint were significantly correlated with the value of the serum creatinine at the time of the change of the slope (r = 0.45, P less than 0.05; r = 0.58, P less than 0.01; r = 0.56, P less than 0.05, respectively) demonstrating more severe hypertension in those patients with the more severe renal dysfunction. The slope after the breakpoint was significantly correlated with the mean diastolic blood pressure values after the breakpoint (r = 0.48, P less than 0.05) with higher pressures being found in those patients with faster rates of decline in renal function. Both before and after the breakpoint occurred, the rate of progression of the renal disease, as estimated by the reciprocal of serum creatinine versus time plot, was greater when the mean diastolic blood pressure was higher than 90 mmHg. In conclusion, the vast majority of patients with proven chronic rejection progress linearly although a change in the rate of progression was frequent. Higher levels of blood pressure correlate with greater rates of progression of renal insufficiency, and a faster progression associates with a diastolic blood pressure greater than 90 mmHg.     

Cytokines and chronic rejection: a study in kidney transplant long-term survivors

BACKGROUND: In part, the long-term survival of kidney transplants depends on the efforts to perform grafts with good human leukocyte antigen (HLA) compatibility, but there are other mechanisms that must induce some sort of tolerance and impair the anti-graft immune reaction. Because cytokines are one of the main components of immune response, we evaluated single nucleotide polymorphisms (SNPs) of several cytokine genes that may influence the production of a given cytokine and therefore the features of immune reactions. METHODS: A total of 416 first cadaveric kidney transplants were monitored for HLA matching. After 10 years, the graft was still functional in 171 of 416 patients; 102 of 171 patients were also typed for cytokine polymorphisms. RESULTS: The mismatch distributions in patients who underwent transplantation were not statistically different from the entire group of patients who underwent transplantation during the same time period. Moreover, it seems that almost all of the HLA class I incompatible long-term survivors are homozygous for GG at the -1082 interleukin (IL)-10 or CC at the -33IL4. CONCLUSIONS: We observed that a match for class I and class II HLA antigens apparently does not favor the long-term survival of transplanted kidneys. In fact, matched grafts are lost before 10 years in the same proportion as the mismatched grafts. We also demonstrated (1) that patients who are homozygous for GG at the SNP -1082IL10 (high IL-10 producers) and HLA class I mismatched (but matched for class II) are protected from chronic rejection, and (2) that patients who are homozygous for CC at the SNP -33IL4 (low IL-4 producers) and HLA class I mismatched (regardless of matching for class II) are protected from chronic rejection.     

Development of a mouse aortic transplant model of chronic rejection

Chronic rejection is the most common cause of late graft failure after solid organ transplantation. A model of chronic rejection, the rat aortic allograft, has histologic features that parallel those in the vessels of human transplanted organs. However, the molecular tools required to dissect the immunology of chronic rejection are unavailable in the rat. We developed aortic transplantation in the mouse as a new model of chronic rejection. This will allow the use of the diversity of recombinant cytokines and monoclonal antibodies available for the mouse and its well-defined genetics to investigate chronic rejection in greater detail. We describe the perioperative care and surgical technique for the model in which a 1 cm segment of donor thoracic aorta was used to replace a section of recipient abdominal aorta below the renal arteries and above the aortic bifurcation. Mortality rates were initially high (70%) due to thrombosis and shock. Changes in technique and operator facility resulted in a high rate of success (75%). After 192 operations, the current success rate is >80%. Mice free from complications at 12 hrs postop had indefinite survival, and after 2 months the typical vascular lesion of chronic rejection was present. This new model of chronic rejection will be a valuable tool to study the molecular immunology and genetics of chronic rejection. © 1995 Wiley-Liss, Inc.     

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。     

A rat small bowel transplant model of chronic rejection: histopathologic characteristics.

BACKGROUND: The major impediment to long-term success in solid organ transplantation is the development of chronic rejection (CR). The vascular lesion of CR, transplant vascular sclerosis (TVS) is characterized by neointimal smooth muscle cell proliferation, and is driven by both immune- and nonimmune-mediated mechanisms. Although the features of chronic heart and kidney allograft rejection have been well characterized, the more immunogenic small bowel allograft has not received similar study. METHODS: F344 small bowel (SB) was transplanted heterotopically into Lewis recipients that were treated with low-dose Cyclosporine A for 15 days. Lewis recipients of F344 or Lewis SB grafts without immunosuppression, served as controls. Grafts were assessed histologically when recipients showed clinical signs of rejection or at predetermined time points. The immunological components involved in the chronic rejection process were evaluated by immunohistochemical staining. RESULTS: All SB allografts (100%) developed histologic evidence of CR Cyclosporine A. TVS was seen in 36 of the 46 (78%) of these allografts. The median time to develop TVS was 45 days. Immunohistochemical staining of chronically rejected grafts showed infiltration predominantly by CD4+ cells and macrophages, uniform up-regulation of class II MHC molecule expression, moderate to intense ICAM-1 staining in grafts harvested at postoperative day 45, and uniform neointimal cell staining for smooth muscle cell alpha-actin in the TVS lesions. CONCLUSIONS: This F344 to Lewis SB transplant model is a useful model that reproduces significant features of CR. The highly immunogenic nature of the SB allografts allows this model to serve as a stringent test for protocols designed to prevent CR.     

Prevention and treatment of alloantibody‐mediated kidney transplant rejection

Summary Antibody‐mediated rejection (AMR), which is commonly caused by preformed and/or de novo HLA alloantibodies, has evolved as a leading cause of early and late kidney allograft injury. In recent years, effective treatment strategies have been established to counteract the deleterious effects of humoral alloreactivity. One major therapeutic challenge is the barrier of a positive pretransplant lymphocytotoxic crossmatch. Several apheresis‐ and/or IVIG‐based protocols have been shown to enable successful crossmatch conversion, including a strategy of peritransplant immunoadsorption for rapid crossmatch conversion immediately before deceased donor transplantation. While such protocols may increase transplant rates and allow for acceptable graft survival, at least in the short‐term, it has become evident that, despite intense treatment, many patients still experience clinical or subclinical AMR. This reinforces the need for innovative strategies, such as complementary allocation programs to improve transplant outcomes. For acute AMR, various studies have suggested efficiency of plasmapheresis‐ or immunoadsorption‐based protocols. There is, however, no established treatment for chronic AMR and the development of strategies to reverse or at least halt chronic active rejection remains a big challenge. Major improvements can be expected from studies evaluating innovative therapeutic concepts, such as proteasome inhibition or complement blocking agents.     

Prolonged cold ischemia accelerates cellular and humoral chronic rejection in a rat model of kidney allotransplantation

One of the leading causes of long-term kidney graft loss is chronic allograft injury (CAI), a pathological process triggered by alloantigen-dependent and alloantigen-independent factors. Alloantigen-independent factors, such as cold ischemia (CI) may amplify the recipient immune response against the graft. We investigated the impact of prolonged cold ischemia and the subsequent delayed graft function on CAI in a fully MHC-mismatched rat model of kidney allotransplantation. Prolonged CI was associated with anticipation of proteinuria onset and graft function deterioration (ischemia: 90d; no ischemia: 150d), more severe tubular atrophy, interstitial fibrosis, and glomerulosclerosis, and increased mortality rate (180d survival, ischemia: 0%; no ischemia: 67%). In ischemic allografts, T and B cells were detected very early and were organized in inflammatory clusters. Higher expression of BAFF-R and TACI within the ischemic allografts indicates that B cells are mature and activated. As a consequence of B cell activity, anti-donor antibodies, glomerular C4d and IgG deposition, important features of chronic humoral rejection, appeared earlier in ischemic than in non-ischemic allograft recipients. Thus, prolonged CI time plays a main role in CAI development by triggering acceleration of cellular and humoral reactions of chronic rejection. Limiting CI time should be considered as a main target in kidney transplantation.     

Association between cytomegalovirus disease and chronic rejection in kidney transplant recipients

BACKGROUND: It has long been suggested that cytomegalovirus (CMV) disease plays a role in the pathogenesis of chronic rejection (CR). However, its role has been difficult to prove, given the strong association between acute rejection and CMV, and the even stronger association between acute rejection and CR. To try to isolate the relative contribution of CMV infection in the pathogenesis of CR, we used multivariate techniques to examine risk factors for CR, including CMV disease. METHODS: Our study population consisted of adult recipients of a first kidney graft who underwent transplantation at a single center between 1/1/85 and 6/30/97 (n = 1339). RESULTS: Multivariate analysis using time to CR as the dependent variable demonstrated acute rejection to be the strongest risk factor (relative risk [RR] = 17.8, P = 0.0001), followed by older donor age (RR = 1.46, P = 0.01). The presence of CMV disease showed a trend toward increased risk for CR (RR = 1.30, P = 0.10), although the association was not as strong as with the other two variables. Comparing only those recipients with acute rejection and CMV disease versus those with acute rejection but no CMV disease, the relative risk of developing CR was 1.37 times higher in the former group. Recipients with acute rejection and CMV developed CR sooner and with a higher incidence versus those with acute rejection but no CMV (P = 0.002). It is interesting, however, that CMV disease was only a risk factor for CR in the presence of acute rejection. Recipients with no acute rejection and CMV disease did not have a higher incidence of CR versus those with no acute rejection and no CMV (P = NS). CONCLUSION: CMV disease seems to play some role in the pathogenesis of CR but only in the presence of acute rejection. Reasons may include (i) the inability to adequately treat acute rejection due to the presence of CMV disease or (ii) the increased virulence of latent CMV virus in recipients being treated for acute rejection. Our data may suggest a role for more aggressive prophylaxis against CMV disease, especially at the time of treatment for acute rejection.     

简单条件下大鼠肾移植模型的建立

目的探讨在简单条件下,稳定的、用于移植后早期免疫功能等实验研究的大鼠肾移植模型的建立方法。方法以Wistar大鼠为供体,Sprague Dawley大鼠为受体。取供体大鼠左肾,移植物包括与肾静脉相连的下腔静脉段,与肾动脉相连的腹主动脉段,以及与输尿管相连的供体膀胱瓣,经腹主动脉原位低温灌注6～8mL4℃肝素生理盐水。受体手术于裸眼下完成,供体下腔静脉与受体下腔静脉、供体腹主动脉与受体腹主动脉行端侧吻合,供体输尿管带膀胱瓣与受体膀胱两定点连续缝合。结果共完成50例异体肾移植大鼠模型,存活41例,手术成功率82%,存活时间（6.3±1.6）d。供体手术时间（44.8±7.4）min、受体手术时间（59.0±6.6）min、动脉吻合时间（15.9±2.3）min、静脉吻合时间（14.2±2.7）min、尿路重建时间（5.3±0.8）min、热缺血时间（55.7±4.5）s和冷缺血时间（55.1±5.9）min。结论建立此模型所需要的实验条件简单,术者容易掌握,移植成功率高。     

Prediction of early kidney transplant rejection by a crossmatch with donor skin

Immunofluorescence staining of donor skin with recipient serum was performed in 25 patients undergoing kidney transplantation. Transplants were performed when cytotoxicity T cell crossmatches with long incubation and with antiglobulin enhancement were negative. In 20 patients the skin crossmatch was negative and all had an uneventful course. In 5 other recipients, the crossmatch with skin was positive and all developed severe rejection 1-8 days after transplantation. The correlation between skin crossmatch and early rejection was statistically highly significant (P less than 0.00001). Rejection in the skin-crossmatch-positive group led to graft loss in 3, and chronic rejection with poor residual function in the other 2 patients. Serum creatinine at one month was in the 2.6-5.0 mg/dl range in these two patients, while in the group with negative skin crossmatches 15 had serum creatinine levels of less than 1.6, and 5 were in the 1.6-2.5 mg/dl range. Although the nature of the skin antigen is unknown, it appears that this crossmatch procedure was highly accurate in predicting early kidney transplant rejection.     

Acute antibody-mediated rejection in kidney transplant recipients

Antibody-mediated rejection has now been recognized as one of the most important causes of graft loss. Transplantation across HLA barriers and nonadherence can result in acute antibody-mediated rejection, which is associated with particularly worse graft outcomes. New technologies, including genomic studies and assays to detect and define donor-specific antibodies, have provided important insights into the pathophysiology and diagnosis of acute antibody-mediated rejection but have engendered many questions about the clinical application of these tests in the prognosis and prevention of this protean disease process. In this article, we review the pathophysiology of acute antibody-mediated rejection, the evolving diagnostic criteria, and specific challenges related to its prognosis, treatment, and prevention.     

大鼠肾移植模型建立研究进展

大鼠肾移植实验模型建立显微外科以及分析移植相关方面的研究有着其重要的意义.随着临床肾移植的不断发展,以及对于器官移植排斥反应研究的重视,大鼠肾移植模型愈来愈受到人们的关注,本文对于大鼠肾移植模型建立研究进展综述如下.