The Importance of Anti-HLA-Specific Antibody Strength in Monitoring Kidney Transplant Patients

Approximately 25% of patients who undergo kidney transplantation develop HLA-specific antibodies, the strength of which has not been previously correlated with graft failure. The strength of these de novo antibodies is investigated in this study. Serial dilution of strong HLA-specific allo-antibodies (up to 1:25,600) and testing with HLA-antigen-coated beads showed that the titer of the reaction to different HLA antigens is directly correlated to maximum fluorescence values and the molecules of equivalent soluble fluorochrome (MESF) values obtained by Luminex machines. Thus, the strength of antibodies can be measured utilizing maximum fluorescence and MESF. The strength of antibodies in the sera from 39 patients who subsequently had graft failure were markedly higher than those in the sera of 26 patients who continued to have good graft function (p = 0.0084). A clear increase in the strength of antibodies was identified in nine patients with a subsequent increase in serum creatinine levels. If analyzed for donor specificity, a strong association was noted for donor-specific MESF and failure (p = 0.00000027). Our results suggest that it is important to monitor the strength of antibodies when evaluating patient sera posttransplant.     

Predictive value of HLA antibodies and serum creatinine in chronic rejection: results of a 2-year prospective trial

In this large collaborative study, 2,231 transplanted patients with functioning kidneys were tested for HLA antibodies, then examined 2 years later for graft survival. Among 478 patients with antibodies, 15.1% failed in 2 years, compared to 6.8% failure in 1,753 patients without antibodies (P=0.00000002). Cytotoxicity testing correlated better with outcome than flow cytometry or ELISA testing on HLA coated beads, possibly because it detected non-HLA antigens. When the patients were further broken down into those with serum creatinine at the time of testing of 0.5-1.9, 4.4% of antibody patients failed at 2 years, compared to 4.3% of patients without antibodies. This 0.1% difference increased among patients with serum creatinine values of 2.0-2.9 to 17.9%, and among those with 3.0-3.9 to 16.3%. We conclude that HLA antibodies posttransplantation is predictive of subsequent graft failure, and its predictive value can be enhanced among patients with higher serum creatinine values.     

Lack of Effect of MICA Antibodies on Graft Survival Following Heart Transplantation

Little is known about the effect of MICA antibodies (Abs) on cardiac allograft function and survival. Pretransplant and posttransplant serum from 491 and 196 adult cardiac allograft recipients, respectively, has been investigated for MICA Abs, donor specificity and the effect of MICA Abs on graft survival, acute rejection episodes (AR) and cardiac allograft vasculopathy (CAV). Patients with HLA Abs (11.6%) were excluded from the analysis. A total of 11.8% of patients had MICA Abs, without HLA Abs, before their transplant. Actuarial graft survival demonstrated slightly better survival of patients with donor-specific MICA Abs at 1 and 5 years (88.9% and 83.3%) than patients negative for MICA Abs (72% and 63.7%, p = 0.051). After transplantation, 15.8% of patients produced MICA Abs, and in 17 patients these were produced de novo . There was no effect of pretransplant or posttransplant production of MICA Abs on numbers of AR episodes in year 1, or CAV assessed at years 3 and 5. Immunocytochemistry of cardiac biopsies from 11 patients did not demonstrate a presence of MICA. Sera from only 4/69 patients with MICA Abs fixed complement prior to transplantation and from 7/38 patients following transplantation. In conclusion, this study suggests that MICA Abs do not adversely affect the outcome of cardiac transplantation.     

Monitoring of anti-HLA and anti-Major histocompatibility complex class I related chain A antibodies in living related renal donor transplantation

This study was undertaken with the aim to analyze the clinical relevance of posttransplant anti-HLA and anti-major histocompatibility complex class I related chain A (MICA) antibodies in response to living related donor renal transplantation. A total of 185 consecutive post-renal transplant recipient serum samples were analyzed for the detection of anti-HLA and MICA antibodies using enzyme-linked immunosolvent assay techniques. Patients carrying both anti-HLA as well as anti-MICA antibodies (MICA(+)/HLA(+)) were the worst affected, showing significantly poorer graft survival compared with the MICA-/HLA-negative group (17% vs 89%, chi(2) = 19.63, P = .000). Similarly, patients with only MICA antibodies or those with only HLA antibodies also had significantly lower graft survival (P = .035 and P = .001, respectively) as compared to the nonsensitized group. The study illustrated that posttransplant monitoring antibodies to both MICA as well as HLA could be good predictors of renal allograft failure.     

Relevance of posttransplant flow cytometric T- and B-cell crossmatches in tacrolimus-treated renal transplant patients

BACKGROUND: De novo development of anti-human leukocyte antigen (HLA) antibodies after transplantation is associated with increased rejection and decreased graft survival. In this study, the effect of posttransplant HLA antibodies on clinical outcome was evaluated in patients treated with tacrolimus by means of flow cytometric crossmatches (FCXm). METHODS: T- and B-cell FCXm were performed retrospectively on posttransplant sera of patients who received a graft between 1997 and 1999. Ninety-four kidney-only recipients were tested and all FCXm positive sera were investigated for the presence of HLA class I and II antibodies by Flow panel reactive antibodies. RESULTS: From 94 patients with a negative pretransplant complement-dependent cytotoxicity crossmatch, seven (7%) showed a positive pretransplant FCXm. After transplantation the FCXm became positive in five patients (6%). The predictive value of a positive FCXm after transplantation, and the log-transformed relative change in fluorescence ratio between pretransplant and posttransplant serum, were not significant to rejection within six months, nor to graft survival censored for death. CONCLUSIONS: The presence of HLA antibodies before rejection or graft failure could only be shown in a minority of patients; most antibodies were detected after graft failure, especially after transplantectomy. Monitoring through antibody testing after transplantation on the basis of our results has no added value with tacrolimus-based immunosuppression.     

Development of posttransplant antidonor HLA antibodies is associated with acute humoral rejection and early graft dysfunction

BACKGROUND: The goal of this study was to determine whether the production of posttransplant antibodies directed against donor HLA mismatches (donor specific antibody; DSA) is associated with renal allograft rejection and early graft dysfunction. METHODS: Forty-nine adult renal allograft recipients with increased risk of rejection were enrolled during the period of October 2001 through May 2003 and were prospectively monitored for the development of anti-HLA antibodies. RESULTS: Of 49 patients, eight (16.3 %) patients were diagnosed with acute humoral rejection (AHR) and 11/49 (22.4%) patients were diagnosed with acute cellular rejection (ACR). A strong association between pretransplant HLA sensitization and AHR was found (P=0.005). Of the eight patients diagnosed with AHR, the majority developed DSA before or concomitant with episodes of rejection (P<0.001). Only 3 of 41 patients (7.3%) without AHR developed DSA. The pathogenic role of alloantibodies was further substantiated by analyzing their association with graft function as measured by serum creatinine levels. The average serum creatinine after the third month posttransplantation in DSA producers was 2.24+/-1.01 mg/dL, while in non-DSA patients the average serum creatinine was 1.41+/-0.37 mg/dL (P<0.01). CONCLUSION: This study reveals a strong association between the production of DSA, AHR, and early graft dysfunction. Our findings indicate that prospective monitoring for anti-HLA antibodies following transplantation is a useful test for the diagnosis and classification of AHR for identifying patients at risk of early graft dysfunction.     

Posttransplant De Novo Donor‐Specific HLA Antibodies Identify Pediatric Kidney Recipients at Risk for Late Antibody‐Mediated Rejection

The emerging role of humoral immunity in the pathogenesis of chronic allograft damage has prompted research aimed at assessing the role of anti‐HLA antibody (Ab) monitoring as a tool to predict allograft outcome. Data on the natural history of allografts in children developing de novo Ab after transplantation are limited. Utilizing sera collected pretransplant, and serially posttransplant, we retrospectively evaluated 82 consecutive primary pediatric kidney recipients, without pretransplant donor‐specific antibodies (DSA), for de novo Ab occurrence, and compared results with clinical–pathologic data. At 4.3‐year follow up, 19 patients (23%) developed de novo DSA whereas 24 had de novo non‐DSA (NDSA, 29%). DSA appeared at a median time of 24 months after transplantation and were mostly directed to HLA‐DQ antigens. Among the 82 patients, eight developed late/chronic active C4d+ antibody‐mediated rejection (AMR), and four C4d‐negative AMR. Late AMR correlated with DSA (p < 0.01), whose development preceded AMR by 1‐year median time. Patients with DSA had a median serum creatinine of 1.44 mg/dL at follow up, significantly higher than NDSA and Ab‐negative patients (p < 0.005). In our pediatric cohort, DSA identify patients at risk of renal dysfunction, AMR and graft loss; treatment started at Ab emergence might prevent AMR occurrence and/or progression to graft failure.     

Peritransplant Immunoadsorption for Positive Crossmatch Deceased Donor Kidney Transplantation

Various desensitization protocols were shown to enable successful living donor kidney transplantation across a positive complement‐dependent cytotoxicity crossmatch (CDCXM). Positive crossmatch transplantation, however, is less well established for deceased donor transplantation. We report a cohort of 68 deceased donor renal allograft recipients who, on the basis of broad sensitization (lymphocytotoxic panel reactivity ≥40%), were subjected to a protocol of peritransplant immunoadsorption (IA). Treatment consisted of a single session of immediate pretransplant IA (protein A) followed by posttransplant IA and antilymphocyte antibody therapy. Twenty‐one patients had a positive CDCXM, which could be rendered negative by pretransplant apheresis. Solid phase HLA antibody detection revealed preformed donor‐specific antibodies (DSA) in all 21 CDCXM‐positive and in 30 CDCXM‐negative recipients. At 5 years, overall graft survival, death‐censored graft survival and patient survival were 63%, 76% and 87%, respectively, without any differences between CDCXM‐positive, CDCXM‐negative/DSA‐positive and CDCXM‐negative/DSA‐negative recipients. Furthermore, groups did not differ regarding rates of antibody‐mediated rejection (24% vs. 30% vs. 24%, p = 0.84), cellular rejection (14% vs. 23% vs. 18%, p = 0.7) or allograft function (median 5‐year serum creatinine: 1.3 vs. 1.8 vs. 1.7 mg/dL, p = 0.62). Our results suggest that peritransplant IA is an effective strategy for rapid desensitization in deceased donor transplantation.     

High Risk of Sensitization After Failed Islet Transplantation

Human Leukocyte Antigen (HLA) antibodies posttransplant have been associated with an increased risk of early graft failure in kidney transplants. Whether this also applies to islet transplantation is not clear. To achieve insulin independence after islet transplants multiple donor infusions may be required. Hence, islet transplant recipients are at risk of sensitization after transplantation. Islet transplant recipients were screened for HLA antibodies posttransplant by flow-based methods. A total of 98 patients were studied. Twenty-nine patients (31%) developed de novo donor specific antibodies (DSA) posttransplant. Twenty-three patients developed DSA while on immunosuppression (IS). Among recipients who have discontinued IS, 10/14 (71%) are broadly sensitized with panel reactive antibody (PRA) >or=50%. The risk of becoming broadly sensitized after transplant was 11/69 (16%) if the recipient was unsensitized prior to transplant. The majority of these antibodies have persisted over time. Appearance of HLA antibodies posttransplant is concerning, and the incidence rises abruptly in subjects weaned completely from IS. This may negatively impact the ability of these individuals to undergo further islet, pancreas or kidney transplantation and should be discussed upfront during evaluation of candidates for islet transplantation.     

Predicting Kidney Graft Failure by HLA Antibodies: a Prospective Trial

HLA antibodies have been shown to be associated with late graft loss of organ transplants in prior studies. Recently they were even shown to appear years BEFORE rejection. (1) An international cooperative study of 4763 patients from 36 centers was undertaken to determine the frequency of HLA antibodies in patients with functional transplants. The overall frequency of HLA antibodies among kidney transplant recipients was 20.9%; 19.3% in the liver, 22.8% in the heart, and 14.2% in the lung. Patients treated with CsA-MMF had significantly lower antibodies (9.8%) than those treated with CsA-Aza (18.1%) (0.00008). (2) Second, a prospective trial was performed in 23 kidney transplant centers to determine whether HLA antibodies could predict failures within 1 year. Among the 2278 patients followed up, 91 grafts failed and 34 patients died. Of 500 patients who had HLA antibodies, 6.6% failed compared with 3.3% among 1778 patients without antibodies (p = 0.0007). Among 244 patients who made de novo antibodies, 8.6% failed compared with 3.0% failures among 1421 patients who did not make antibodies (p = 0.00003). Death occurred in 1.5% of patients and was not associated with antibodies. Thus, after 1 year in this prospective trial, patients with HLA antibodies had graft failure at a significantly higher rate than those without antibodies.     

Four-year Follow-up of a Prospective Trial of HLA and MICA Antibodies on Kidney Graft Survival

In 2002, 1329 patients with functioning transplants were prospectively tested for HLA antibodies in the 13th International Histocompatibility Workshop. Four years after testing, deceased donor graft survival among 806 patients not having antibodies in 2002 was 81% compared to 58% for 158 patients with HLA antibodies (p < 0.0001) and 72% for 69 patients with MICA antibodies (p = 0.02). Hazard ratio (HR) using death-censored graft survival from multivariate analysis of HLA antibodies was 3.3 (p < 0.00001) and 2.04 for MICA (p = 0.01). In the 14th Workshop, at 1 year follow-up, survival for 1319 patients receiving deceased donor grafts and no HLA antibodies was 96% compared to 94% for 344 patients with HLA antibodies (p = 0.0004) and 83% survival for 33 patients with MICA (p = 0.0005). HR from multivariate analysis: HLA antibodies was 3.6 (p < 0.00001) and 6.1 for MICA (p = 0.006). Twelve patients with donor specific antibodies tested by single antigen beads had a 1 year survival of 64% (p = 0.008), and 27 patients with non-donor specific 'strong' antibodies had a 66% survival (p = 0.0003) compared to 92% survival in those with no antibodies. In conclusion, these two prospective trials, after 1 and 4 years, provided strong evidence that HLA and MICA antibodies are associated with graft failure.     

HLA class I sensitization in islet transplant recipients: report from the Collaborative Islet Transplant Registry

Pancreatic islet transplantation is a promising treatment option for patients severely affected with type 1 diabetes. This report from CITR presents pre- and posttransplant human leukocyte antigen (HLA) class I sensitization rates in islet-alone transplantation. Data came from 303 recipients transplanted with islet-alone between January 1999 and December 2008. HLA class I sensitization was determined by the presence of anti-HLA class I antibodies. Panel-reactive antibodies (PRA) from prior to islet infusion and at 6 months, and yearly posttransplant was correlated to measures of islet graft failure. The cumulative number of mismatched HLA alleles increased with each additional islet infusion from a median of 3 for one infusion to 9 for three infusions. Pretransplant PRA was not predictive of islet graft failure. However, development of PRA >20% posttransplant was associated with 3.6-fold (p < 0.001) increased hazard ratio for graft failure. Patients with complete graft loss who had discontinued immunosuppression had significantly higher rate of PRA ≥ 20% compared to those with functioning grafts who remained on immunosuppression. Exposure to repeat HLA class I mismatch at second or third islet infusions resulted in less frequent development of de novo HLA class I antibodies when compared to increased class I mismatch. The development of HLA class I antibodies while on immunosuppression is associated with subsequent islet graft failure. The risk of sensitization may be reduced by minimizing the number of islet donors used per recipient, and in the absence of donor-specific anti-HLA antibodies, repeating HLA class I mismatches with subsequent islet infusions.     

Impact of donor-specific antibodies on chronic rejection occurrence and graft loss in renal transplantation: posttransplant analysis using flow cytometric techniques

BACKGROUND: Improvements in immunosuppressive therapy have greatly reduced acute rejection (ARj) episodes, ensuring better short-term graft outcome, but have not modified long-term survival in renal transplantation. It is now well accepted that chronic rejection (CRj) can be determined by both immune and/or nonimmune mechanisms. The aim of this study was to evaluate the importance of the posttransplant humoral immune response towards mismatched HLA graft antigens in CRj occurrence and graft outcome. METHODS: Serum samples from 120 nonpresensitized renal transplant recipients were prospectively screened for 1 year after surgery by means of flow cytometry cross-match (FCXM) and FlowPRA beads (microbeads coated with purified HLA class I and class II antigens) assays. All transplants were followed-up for 2 years or until graft removal. RESULTS: FCXM monitoring identified donor-specific antibodies (DS-Abs) in 29 (24.2%) of 120 transplanted patients. Correlation with clinical data highlighted a higher incidence of ARj in DS-Abs-positive patients compared to negative patients (62% vs. 13%, P<0.00001). Furthermore, graft failure occurred more frequently among FCXM-positive patients than among negative patients (34% vs. 1%, P<0.00001). The deleterious effect of DS-Abs on graft function was confirmed by serum creatinine levels 2 years after transplantation. These were in fact higher in subjects producing DS-Abs than in subjects with only ARj (mean creatinine: 2.5+/-1.3 mg/dL vs.1.7+/-0.5 mg/dL, P=0.04). FlowPRA analysis of DS-Ab HLA specificity highlighted the presence of anti-HLA class I antibodies in 85% of FCXM-positive patients, who also presented with a higher incidence of HLA-B mismatches than FCXM-negative patients (1.23+/-0.66 vs. 0.92+/-0.59, P=0.02). CONCLUSIONS: Flow cytometric techniques are precious tools for investigating the activation of the humoral response against HLA antigens of the graft in renal transplantation. DS-Abs production has a worse impact on organ function and survival than ARj episodes. These findings represent further proof of the threat posed by DS-Abs on long-term graft function and draw attention to the need for a specific immunosuppressive therapy aimed at counteracting the different kinds of immune activation toward graft.     

肾移植术后监测受者抗HLA抗体的临床意义

目的 监测肾移植受者术后抗HLA抗体水平,探讨新生的抗HLA抗体对移植肾功能的影响.方法 共有384例肾移植受者术后进行了抗HLA抗体的监测,监测时间3～96个月,所有受者术前的抗HLA抗体水平均为阴性.使用莱姆德抗原板,采用酶联免疫吸附法(ELISA)检测抗HLA抗体,抗HLA抗体水平＞10%为阳性.对术后抗HLA抗体阳性者与阴性者间移植肾功能进行比较,观察新生抗HLA抗体对移植肾功能的影响.结果 术后抗HLA抗体阴性者318例(82.8%);阳性者66例(17.2%),其中抗HLA Ⅰ类抗体阳性者3例,抗HLAⅡ类抗体阳性者61例,抗HLA Ⅰ类和Ⅱ类抗体均为阳性者2例.HLA-DR位点0个抗原错配者92例受者中有7例新生抗HLA抗体,1～2个抗原错配者292例中有59例新生抗HLA抗体,二者比较,差异有统计学意义(P＜0.01).术后抗HLA抗体阴性者中移植肾功能良好者占87.4%(278/318),抗HLA抗体阳性者中移植肾功能良好者占65.2%(43/66),二者比较,差异有统计学意义(P＜0.05).结论 HLADR位点的抗原错配与肾移植后抗HLA抗体的产生密切相关,而新生抗HLA抗体会造成移植肾功能下降,从而降低移植存活率,肾移植术后监测抗HLA抗体有一定的临床意义.

Abstract：

Objective To detect de novo development of anti-HLA antibodies after renal transplantation, and to investigate their influence on graft function. Methods 384 kidney recipients,who were negative for anti-HLA antibody before transplantation, were monitored for anti-HLA antibodies over a period of 3-96 months, and a sensitive enzyme-linked immunosorbent assay (ELISA) was used to detect anti-HLA antibodies. HLA antibody ＞10 % was defined as positive levels. Results Among 384 recipients tested, 318 recipients (82. 8 %) were negative for anti-HLA antibody after transplantation; 66 recipients (17. 2 %) developed de novo HLA antibodies, 3 recipients with HLA class Ⅰ, 61 with HLA class Ⅱ, 2 with both HLA class Ⅰ and Ⅱ. According to amino acid residue matching, 7 cases developed de novo antibodies among 92 recipients with 0 HLA-DR mismatches,compared with 59 cases among 292 recipients with 1-2 mismatches, which showed significant difference between two groups (P＜0. 01 ). 87. 4 % (278/318) recipients negative for HLA antibodies after transplantation achieved good graft function, in comparison with 65. 2 % (43/66) recipients positive for HLA antibodies (P＜0. 05). Conclusion De novo production of HLA antibodies posttransplantation may be closely associated with HLA-DR mismatch. De novo HLA antibodies posttransplantation might damage graft function and reduce graft survival rate. The detection of de novo development of anti-HLA antibodies after renal transplantation has clinical significance for assessing renal allograft function.     

HLA class I donor-specific triplet antibodies detected after renal transplantation

The purpose of this study was to investigate whether IgG, non-donor-specific anti-HLA class I antibodies (HLAabI) detected after renal transplantation recognize immunogenic amino acid triplets expressed on the foreign graft. In addition, we sought to evaluate the effect of these antibodies as well as other posttransplant HLAabI on graft outcome. Posttransplant sera from 264 renal recipients were tested for the presence of IgG HLAabI and HLA class II-specific alloantibodies (HLAabII) by ELISA. The HLAMatchmaker computer algorithm was used to define the HLA class I non-donor-specific antibodies, which seem to recognize immunogenic amino acid triplets. Donor-specific triplet antibodies (DSTRab) were detected in 16 of 22 (72.7%) recipients based on at least one HLA-A or -B mismatched antigen with the donor. DSTRab were found either without (n = 7) or with (n = 9) HLA donor-specific antibodies (HLA-DSA). The presence of DSTRab alone in the periphery was associated with acute rejection, whereas the presence of both DSTRab and HLA-DSA was associated with chronic rejection and graft failure.     

主要组织相容性一类相关链A基因抗体与慢性移植肾功能减退的相关性研究

目的 探讨肾移植术后主要组织相容性一类相关链A基因(MICA)抗体对稳定期移植肾功能的影响.方法 采用免疫荧光液相芯片技术检测57例肾移植术后超过半年患者的MICA抗体水平及特异性.并同时检测SCr水平,分析MICA抗体对移植肾功能的影响. 结果 57例患者中HLA抗体和MICA抗体均为阴性者38例,HLA抗体阳性、MICA抗体阴性者11例,HLA抗体阴性、MICA抗体阳性者5例,HLA抗体和MICA抗体均阳性者3例.在MICA特异性抗体不同类型中,MICA019抗体5例、MICA027抗体3例、MICA018抗体2例、MICA004和017抗体各1例,MICA抗体阳性值≥6分者9例,占75%(9/12).MICA抗体阳性组8例与MICA抗体阴性组49例在术前输血史、淋巴毒试验、冷缺血时间、术后时间方面差异均无统计学意义(P＞0.05);而在术时年龄方面差异有统计学意义[(32.5±7.9)岁与(43.0±10.4)岁(P=0.008)3.MICA抗体阳性HLA抗体阴性组SCr水平[(117.20±12.30)μmol/L]及SCr异常比例(5/5)均高于HLA抗体和MICA抗体均阴性组[(89.40±28.95)μmol/L及23.7%(9/38),P＜0.05].结论 肾移植术后监测MICA抗体可作为肾移植HLA阴性患者预后重要的标志物,并且MICA抗体与慢性移植肾功能减退存在明显的相关性.     

Enzyme-linked immunosorbent assay for human leukocyte antigen antibody detection and urine protein test recommended for follow-up monitoring after renal transplantation

BACKGROUND: Although the usefulness of posttransplant human leukocyte antigen (HLA) antibody monitoring has been demonstrated, detailed recommendations have not been worked out in its frequency, the type of patients and methods to be used. Enzyme-linked immunosorbent assay is a simple and cost-efficient assay. The urine protein test that reflects renal dysfunction is performed everywhere. We assessed the clinical value of HLA antibody and urine protein monitoring after renal transplantation. METHODS: Serum samples were consecutively collected from outpatients (n=323) in 2004 and in 2006. Because 18 had graft failure and 8 died with functioning graft for 2 years, 297 paired sera were tested for HLA antibody using enzyme-linked immunosorbent assay. Urine protein was determined to be positive when the dipstick protein reaction was+/-or over (20 mg/dL). RESULTS: Total 297 patients were divided according to the change of HLA antibody status. Only patients with all of (i) de novo HLA antibody production, (ii) continuous detection from peripheral blood, and (iii) positive urine protein test had a significantly higher serum creatinine than the others and demonstrated rapid deterioration of Cr (DeltaCr 1.26 mg/dL during 2 years). Negative change of HLA antibody stopped the increase of serum creatinine. CONCLUSION: The status of HLA antibody and urine protein provides useful information on graft prognosis. Although the tempo of graft injury is relatively slow, a yearly routine HLA antibody test for all patients and the attempt to reduce HLA antibody to negative levels is recommended, when HLA antibody is newly detected and urine protein test is positive.     

C4d Fixing, Luminex Binding Antibodies—A New Tool for Prediction of Graft Failure After Heart Transplantation

The standard method to detect pretransplant antibodies has been the complement dependent cytotoxicity (CDC) test of donor leukocytes. Solid phase assays to detect HLA antibodies in pretransplant serum reveal a greater number of sensitized patients, but their clinical impact is less certain. Here we have developed a method of detecting C4d fixing HLA antibodies on Luminex beads. Pretransplant serum from 565 cardiac transplant patients was retrospectively tested for the presence of HLA antibodies using CDC, HLA coated Luminex beads and C4d deposition on Luminex beads, and the results correlated with graft survival. Whereas 5/565 patients had CDC positive donor specific antibodies (DSA) before their transplant, this number was increased by 19 using Luminex beads. The 1-year survival of CDC -ve/Luminex +ve patients with DSA (n = 19) was 42% compared with 77% for CDC -ve/Luminex +ve without DSA (n = 39, p = 0.0039). Fixation of C4d (22/67 Luminex positive sera) had a negative effect on graft outcome; 1-year graft survival was, C4d +ve/DSA +ve (n = 11) 20%, C4d +ve/DSA -ve (n = 11) 91%, C4d -ve DSA +ve (n = 13) 54%, C4d -ve DSA -ve (n = 32) 75%, compared with 75% for antibody-negative patients (p = 0.0002). In conclusion, detection of Luminex +ve DSA in pretransplant serum provides a powerful negative predictor of graft survival, especially if they bind C4d.     

Anti-HLA antibodies in kidney transplanted patients

Anti-human leukocyte antibodies (HLA) play a central role in graft survival, particularly in kidney transplantation. The presence of preformed donor specific anti-HLA antibodies is always excluded before transplantation by performing crossmatches using current and historic recipient serum samples. Several recent studies have observed a correlation between HLA antibodies and graft rejection. It has been suggested that these antibodies should be monitored routinely after kidney transplant to predict graft failure. Here in report the results of a study of on serum samples from 111 kidney transplant recipients that were monitored for anti-HLA antibodies using flow cytometry. Anti-HLA antibodies were only detected in four pre-immunized patients and showed the same HLA specificity that was present before the transplantation (in two cases against previous graft antigens). Furthermore, only two patients with functioning grafts developed anti-HLA antibodies, at 1 month and 1 year after the transplantation. However, they were not donor specific, but probably related to posttransplant transfusions. In our study, none of the patients who suffered an adverse event during the first year (including two with histologically documented acute rejection) developed anti-HLA antibodies. These results are probably related to the use of mycophenolate mofetil, which may reduce the incidence of HLA antibodies. We cannot exclude the possibility that antibodies produced by some patients may not be detectable because they are attached to the graft.     

动态分析HLA和MICA特异性抗体对移植肾功能的影响

目的 探讨肾移植前后人类白细胞抗原(HLA)和主要组织相容性一类相关链A基因(MICA)抗体特异性对移植后排斥反应和移植肾功能的影响. 方法采用免疫荧光液相芯片技术检测27例肾移植(尸供22例,亲属活体供肾5例)受者手术前后抗HLA抗体和MICA抗体的特异性和阳性值变化,并结合供受者的基因分型,区分供体特异性抗体和非供体特异性抗体.取同期的临床资料和SCr水平进行分析. 结果 27例移植患者中带肾存活26例,移植肾失功1例.移植后1、3、6、12个月时动态随访24例,失访2例.27例患者移植前预存抗体7例(25.9%),其中HLA抗体阳性2例、MICA抗体阳性3例,HLA和MICA抗体均阳性2例.肾移植前HLA和MICA抗体均阴性者中移植后3～6个月产生新生抗体3例.1例新生HLA-Ⅱ类特异性抗体者,移植半年后出现慢性排斥反应,经治疗术后1年SCr>200 btmol/L.3例肾移植前MICA抗体阳性者,术后MICA抗体的特异性均无改变,但抗体的阳性分值呈现2～8分的变化,1年后均升高到移植前(4～8分)水平.移植前预存低阳性率HLA-Ⅱ类特异性抗体者1例,移植后2周有发热等排斥反应,巨细胞病毒检测阳性,移植后1个月时SCr为171μmol/L,3个月升高到236μmol/L.24例分为抗体阴性组(14例)和抗体阳性组(10例).移植后1个月和1年时SCr水平2组间比较差异有统计学意义(P=0.03,0.05). 结论 移植后3～6个月是新生抗体变化的重要随访时间,可根据HLA和MICA抗体的特异性和阳性分值变化,尽早采取有效方法预防排斥反应和减少移植肾功能减退的发生和发展.