Review article: Luminex technology for HLA antibody detection in organ transplantation

Since its inception in the early 1960s, the serologically based complement-dependent cytotoxicity (CDC) assay has been the cornerstone technique for the detection of human leucocyte antigen (HLA) antibodies, not only in pre-transplant renal patients, but also in other forms of organ transplantation. Recently, solid phase assays have been developed and introduced for this purpose, and in particular the Flow-based bead assays such as the Luminex system. This latter assay has proved to be far more sensitive than the CDC assay and has revealed pre-sensitization in potential transplant recipients not detected by other methods of HLA antibody detection. However, the clinical implications of this increased sensitivity have not been convincingly demonstrated until recently. This technology for HLA antibody detection permits the evaluation of the clinical importance of antibodies directed at, for example, HLA-DPB1 and HLA-DQA1, which has not been possible to date. There are Luminex issues, however, requiring resolution such as the ability to distinguish between complement fixing and non-complement fixing antibodies and determination of their relative clinical significance. Luminex technology will permit a re-evaluation of the role of HLA antibodies in both early and late antibody-mediated rejection.     

Effect of implementing anti-HLA antibody detection by Luminex in the kidney transplant program in Chile

The development of new highly sensitive, specific technologies to detect HLA antibodies has allowed a better definition of the profile of non-permitted antigens for patients awaiting kidney transplantation. The use of calculated or virtual panel reactive antibodies (CPRA or vPRA) seeks to improve the prediction of positive crossmatches (XM), but increases the proportion of sensitized patients on the waiting list. In 2008-2009, we implemented detection of antibodies using Luminex technology and applied vPRA since 2009. The objective of this study was to evaluate the impact of these innovations in defecting patient sensitization on kidney transplant waiting lists for deceased donors and among transplanted patients. We analyzed the waiting list for 2007 through 2009 and the first semester of 2010, including the patients transplanted in these periods and the XM with deceased donors. We observed an increase in the mean peak PRA of transplanted patients from 7.2% in 2007 to 17.1% in 2010 (P = .001), and in the proportion of patients transplanted with a peak PRA > 50% from 2.8% in 2007 to 15.7% in 2010 (P = .0001), with no increase in the proportion of this population on the waiting lists. There was a concurrent decrease in positive XM among patients with a peak PRA > 50%. The use of vPRA and Luminex permitted a greater number of transplants of patients with peak PRA > 50% and was a good predictor of a positive XM.     

肾移植受者群体反应性抗体监测的临床意义

目的 分析群体反应性抗体（PRA）监测对预测肾移植受者排斥反应发生的意义及探讨对高水平PRA受者的临床处理.方法 应用酶联免疫吸附分析法（ELISA法）动态监测肾移植受者的PRA水平,以PRA≥10%为阳性,10%≤PRA＜50%为低致敏、PRA≥50%为高致敏,并对37例术前高致敏患者行血浆置换.结果 1527例肾移植受者中,PRA阳性350例（22.9% ）,其中高致敏 94例（26.8% ）;PRA阳性组排斥反应发生率（21.1% ）高于PRA阴性组（3.8% , P〈0.01）, 术后PRA转为阳性组排斥反应发生率高于PRA无变化组（P〈0.01）,行血浆置换受者与未行血浆置换受者排斥反应发生率无差异（P〉0.05）,接受过移植、多次妊娠、多次输血受者易致敏,HLA-A、B、DR配型错配抗原〉3个受者急性排斥的发生率（16.9% ）明显高于错配抗原≤3个受者（1.7% , P〈0.01）.结论 动态监测PRA水平有助于预测排斥反应的发生.     

Luminex技术监测抗HLA抗体对肾移植受者预后的影响

目的  探讨Luminex技术检测受者体内抗人类白细胞抗原(HLA)抗体水平在预测肾移植受者预后的价值。方法  选取2013年6月至2015年11月在解放军第181医院拟行肾移植患者1 105例(其中354例成功接受肾移植手术),收集肾移植术前、术后血清标本共1 923例次。采用Luminex技术检测术前和术后的抗HLA抗体的阳性率和抗体荧光强度,同时并对移植受者进行移植肾功能检测。结果  术前抗HLA抗体阳性血清样本占总数的51.0%(546/1 071),其中抗HLA Ⅰ类抗体阳性占26.0%(279/1 071),抗HLA Ⅱ类抗体阳性占24.9%(267/1 071),其中抗HLA抗体Ⅰ、Ⅱ类均为阳性占11.4%(122/1 071)。354例肾移植患者中,术后出现抗HLA抗体者占17%(59/354),其中单独抗HLA Ⅰ类抗体阳性者25例(术后新发阳性4例),单独抗HLA Ⅱ类抗体阳性者占15例(术后新发阳性1例),两者皆阳性者19例(术后新发阳性4例)。随访期间,术后抗HLA Ⅰ类、Ⅱ类及两种抗体均阳性者出现移植肾功能异常者分别为13例、5例和11例,其中术后抗体新发阳性者均出现移植肾功能异常。结论  Luminex技术可动态监测肾移植术后受者抗HLA抗体水平,而抗HLA抗体阳性对预测肾移植受者预后有重要的价值。     

HLA antibody screening in kidney transplantation: current guidelines

Background

In organ transplantation, the introduction of the solid phase immunoassay technology radically changed the practice of antibody monitoring against human leukocyte antigens (HLA).

Purpose

Precise identification of antibody specificities in complex sera of sensitized patients and monitoring of low levels of donor-specific HLA antibodies in the posttransplant phase became possible. However, at the same time, new technical problems and great variation emerged in the interpretation of test results, indicating a need for standardization.

Conclusion

In May 2012, The Transplantation Society (TTS) recruited a panel of laboratory and clinical experts to discuss emerging testing and clinical management issues that are associated with antibody testing in organ transplantation. In this article, we provide a summary of the TTS recommendations formulated in this international effort on the standardization of antibody monitoring in kidney transplantation.     

Flow-PRA evaluation for antibody screening in patients awaiting kidney transplantation

Flow-PRA is a flow cytometric method for both anti-HLA class I and class II antibody (Ab) detection. We evaluated this technique for Ab screening in patients awaiting kidney transplantation. After having established a rigorous threshold for positivity, a three-dilution difference in sensitivity between Flow-PRA and complement-dependent cytotoxicity (CDC) persisted. The sensitivity of the method was satisfactory since all CDC-positive sera were also found to be positive with the Flow-PRA method. Discrimination between anti-HLA class I and class II Abs was excellent. Furthermore, all sera responsible for a positive flow cytometry crossmatch (FCXM) and a negative CDC-crossmatch (CDCXM) at the time of a putative transplant were found to be positive with Flow-PRA beads. The specificity was excellent for anti-class I Ab detection since no false positive serum was found. On the other hand, the specificity was lower for anti-class II detection, since 8.3% (2/24) false positive results were detected among all the negative sera tested. Overall, our results suggested that Flow-PRA should be of value for anti-HLA Ab screening prior to kidney transplantation.     

肾移植术前透析患者抗体水平的检测

对４５９份肾移植前透析患者随机血清进行了抗体水平，对其中的７２份淋巴细胞毒高敏感患者血清做了抗体检测。结果表明，首次移植前血清抗体阳性率为２０．６％，再次移植前血清抗体阳性率７５％。７２份高敏感患者血清无论在４℃或在３７℃均对Ｂ淋巴细胞反应，而对Ｔ淋巴细胞反应则少。因排斥而切除移植肾的透析患者其抗Ｂ淋巴细胞毒抗体高于输血和妊娠所致的淋巴细胞毒抗体。认为系统地了解肾移植受者的抗体水平，对移植肾的存活     

非HLA抗体相关肾移植排斥反应的研究进展

人类白细胞抗原（HLA）是由HLA基因复合体所编码的产物,定位于6号染色体短臂上,是异体免疫的主要靶点,但HLA抗体阳性并不能解释所有的肾移植排斥反应。非HLA抗体是同种异体肾移植中供者基因表达的产物,术中缺血-再灌注损伤、异体和自身免疫相互作用、细胞外囊泡的介导作用等都可以触发免疫系统反应,促使非HLA抗体产生。多项研究表明非HLA抗体是诱发排斥反应、影响肾移植结局的重要因素。因此,本文就肾移植非HLA抗体类型及形成机制进行综述,总结非HLA抗体相关肾移植排斥反应的研究进展,以期为肾移植术后非HLA抗体相关排斥反应的研究提供参考。     

T细胞多克隆抗体在公民逝世后器官捐献供肾移植中有效性及安全性的研究

目的 观察T细胞多克隆抗体在公民逝世后器官捐献(deceased donation,DD)供肾移植患者中的有效性和安全性.方法 回顾性分析昆明市第一人民医院甘美医院自2015年8月20日至2020年2月28日符合研究标准的共324例肾移植受者资料,将其分为使用兔抗人胸腺细胞免疫球蛋白(rabbit anti human...     

Successful living related kidney transplantation across an anti-donor HLA antibody

In preconditioning highly sensitized kidney transplant candidates, renal allograft outcomes have been better when the serum titer for class I anti-HLA donor-specific antibody (DSA) is low in the recipient at the time of transplantation. However, the ideal level to which the titer should be lowered is still controversial. We report a primary living related kidney transplant in a 34-year-old highly sensitized woman (pretransplant panel-reactive antibody=70%) with end-stage renal disease secondary to chronic glomerulonephritis. We sought to desensitize by lowering the DSA titer specifically to 1:4 pretransplant. A standard complement-dependent cytotoxicity cross-match with her donor (sister) was repeatedly negative, although she was positive for class I antibody against her mismatched HLA antigen (A*2402) at a titer up to 1:16 by the single-antigen flowbead assay. The target DSA titer of 1:4 before transplant was achieved by 12 sessions of plasmapheresis (PP) over 7 weeks, plus two intravenous immune globulin infusions (IVIG) (500 mg/kg/infusion). The patient outcome was excellent. Neither IVIG nor PP was needed posttransplant. The serum creatinine ranged between 0.5 mg/dL and 1.2 mg/dL, and no rejection episode was documented at 28 weeks posttransplant. Therefore, we encourage the use of IVIG and PP to lower the DSA titer to at least 1:4 before kidney transplantation in highly sensitized patients. Large prospective trials are needed to establish a consensus for pretransplant risk assignment and to evaluate the need for desensitization.     

The clinical significance of human leukocyte antigen antibody development in kidney transplantation

Background

This retrospective study uses the LAT-M (One Lambda Inc., Calif) screen assay to reexamine the impacts (a), of pretransplant human leukocyte antigen (HLA) antibody on long-term graft survival; (b) posttransplant HLA antibody on long-term graft survival and (c) immunosuppressive regimen on posttransplant HLA antibody development.

Patients and methods

Pretransplant sera from 222 renal transplant recipients and posttransplant sera from 216 renal transplant recipients were studied for the impact of HLA antibody on long-term graft survival.

Results

Among the patients who did not display pretransplant HLA antibodies, 85% enjoyed 5-year and 59% 10-year graft survival, whereas the patients who tested positive were 83% and 83% (P = .5596). Among the patients who did not show posttransplant HLA antibodies, 99% enjoyed 5-, 91% 10-, and 65% 15-year graft survival, whereas for the 44 patients who tested positive they were 59%, 44%, and 30%, respectively (P < .0001). Patients prescribed cyclosporine + myfortic (odds ratio 0.17, P = .05) or FK + Cellcept (odds ratio 0.36, P = .04) showed the lowest posttransplant HLA antibody development.

Conclusion

Both regimens improve graft survival.     

Comprehensive assessment of sensitizing events and anti-HLA antibody development in women awaiting kidney transplantation

BackgroundAlloimmunization remains a critical factor which affects the success of kidney transplantation. Patients awaiting solid organ transplantation may develop anti-HLA antibodies after pregnancies, transfusions and previous events of transplantations.AimWe evaluated the effects of different sensitizing events on the anti-HLA antibody production and the potential role of patient HLA alleles in the context of antibody development in both the overall and pregnancy sensitized groups.Material and methodsWe retrospectively stratified 411 women on waiting list for kidney transplantation by route of sensitization. The presence of anti-HLA antibodies was evaluated by Solid Phase Assay and HLA typing was performed by serological and molecular methods.ResultsIn our study population, 54% of women had anti-HLA antibodies. We found that the 51.6% of women with pregnancy only, 44% of women with transfusion only and 100% of women with a history of transplantation only developed anti-HLA antibodies. Pregnancy only resulted significantly associated with all anti-HLA antibody development such as anti-A, -B, -C, -DR, -DP as well as anti-DQB and -DQA antibodies. We investigated the influence of patient HLA alleles on the antibody development in the overall study population. Patients expressing HLA A*32 (p = 0.024, OR = 0.42), B*14 (p = 0.035, OR = 0.44), HLA-B*44 (p = 0.026, OR = 0.51) and DRB1*01 (p = 0.029, OR = 0.55) alleles produced anti-HLA antibodies less frequently compared to subjects with other alleles. In the pregnancy only group, B*14 (p = 0.010, OR = 0.12) and B*51 (p = 0.005, OR = 0.24) alleles were associated with a low risk of anti-HLA antibody development, while A*11 (p = 0.033, OR = 3.56) and DRB1*04 (p = 0.022, OR = 3.03) alleles seem to represent a higher risk.ConclusionsPregnancy still remains a strong sensitizing event in women awaiting kidney transplantation. The anti-HLA antibody development in pregnancy appears to be associated with the expression of particular HLA alleles.     

肾移植患者应用ELISA方法检测HLA抗体的价值

目的 探讨ELISA方法检测HLA抗体在临床肾移植中的应用价值。方法 在167例次肾移植受者中应用ELISA方法检测HILA抗体,比较不同抗体水平患者的移植效果及抗体水平在发生排斥反应前后的变化。结果 不同抗体水平组的移植效果有显著性差异(P<0.05)。术后抗体水平变化与急性排斥反应的发生及逆转呈现正则关。结论 ELISA方法检测HLA抗体对于预测移植风险、辅助诊断排斥反应都有较高的临床应用价值。     

Application of flow cytometry to monitor antibody levels in ABO incompatible kidney transplantation

Current methods of measuring ABO antibody levels based on the hemagglutination (HA) titers have the disadvantages of relatively poor reproducibility and do not offer fine discrimination of antibody concentration. We therefore developed a simple and rapid method of measuring ABO antibody levels using flow cytometry (FC). For validation, we analyzed plasma samples from 79 blood donors. Both IgM and IgG were detected and measured with IgG essentially restricted blood group O donors. Forty-two successive samples were collected from a patient with blood group O undergoing antibody removal and subsequent transplantation from a group A2 donor and tested by both HA and FC. Changes in IgG measured by FC (relative median fluorescence) correlated well with HA titers and importantly rejection episodes were preempted by a rising relative median fluorescence. The method allowed quantitative discrimination in the range of antibody levels relevant to ABO incompatible transplantation and has the advantages over HA of objective measurement and reproducibility.     

Role of anti-A/B antibody titers in results of ABO-incompatible kidney transplantation

BACKGROUND: Our previous studies showed that the incidence of humoral rejection was extremely high in ABO-incompatible living kidney transplantation. This result suggests that anti-A/B antibody titers directly influence the graft survival of ABO-incompatible kidney transplantation. In this study, we examined the impact of preoperative anti-A/B antibody titers on the results of ABO-incompatible living kidney transplantation. METHODS: Sixty-seven patients underwent ABO-incompatible living kidney transplantation at our institution between January 1989 and December 1995. The mean age was 34.9 years with 38 males and 29 females. Sixty-one of the 67 recipients were included in an analysis of the impact of anti-A/B antibody titer in long-term graft survival. The remaining six patients were excluded because of death with a functioning graft (three patients) and withdrawal of immunosuppression due to nonimmunological reasons (three patients) within 1 year after renal transplantation. RESULTS: The graft survival rate for the level of less than 1:16 in maximum IgG antibody before transplantation (n=21) at 1, 5, and 8 years was 81.0, 66.8, and 66.8%, respectively. The corresponding values for the level of 1:32-1:64 (n=33) and higher than 1:128 (n=7) were 93.9, 90.5, and 79.7%, and 42.9, 28.6, and 28.6%, respectively (log-rank test, P=0.0007). There was no significant association between maximum anti-A/B IgM titers, minimum anti-A/B IgM titers, minimum anti-A/B IgG titers, and graft survival. CONCLUSIONS: Preoperative maximum anti-A/B IgG titers correlated with the long-term graft survival in ABO-incompatible living kidney transplantation. Thus, preoperative maximum levels of anti-A/B IgG titers are one of the good predictors of the results of ABO-incompatible living kidney transplantation.