Detection Of Donor-specific Antibodies Research Articles

The influence of donor specific antibody on renal function after renal transplantation

Objective To investigate the significance of donor specific antibody (DSA) on acute renal rejection and renal function.Methods DSA was detected with Luminex200 in 459 renal transplant patients who were operated in Yaitai Yuhuangding Hospital from June 2010 to April 2014.Penal reactive antibody ≥10％ was found in 46 patients,including 20 males and 26 females,the average age was 45 years,and DSA was positive in 18 patients.Results There was significant difference in acute renal rejection,delayed renal function and graft dysfunction between DSA-positive group and DSA-negative group,but there was no signaficent difference in patient survival between the two groups.Conclusion DSA played a great role in acute renal rejection and renal function.The detection of DSA in time was the effective method to predict acute rejection after renal transplantation. Key words: Donor specific antibody; Renal function; Renal transplantation

Antibody-mediated rejection: analyzing the risk, proposing solutions.

Antibody-mediated rejection: analyzing the risk, proposing solutions.

Calcineurin Inhibitor (CI) Use Reduces the Risk of Donor-Specific Antibody (DSA) Development After Kidney and Kidney/pancreas Transplant.

Background. The number of available drugs for use in maintenance immunosuppression regimens makes it possible to employ various combinations to avoid undesirable side effects or toxicities. This study was performed to compare overt evidence of allosensitization post-transplant with the use of various immunosuppression drugs within the first year post-transplant. Methods. Between 1/1/2002 and 12/31/2012 2455 adult, ABO compatible, XM negative kidney and combined kidney/pancreas transplants were performed and in 1757 transplants donor specific antibodies (DSA) were obtained post-transplant for surveillance or as a cause of organ dysfunction. Maintenance immunosuppression drugs consisted of microemulsion cyclosporine (CI), rapamune, and mycophenolic acid in various combinations without maintenance steroids. Exposure to each maintenance immunosuppression drug was determined at 1, 3, 6, and 12 months after transplant. Results. Of the 1756 transplants, 318 recipients (18.1%) developed at least 1 biopsy proven acute rejection (AR) episode. AR was associated with a high incidence of DSA detection, 49.7% (150/318) versus 12.4% (178/1439) without AR (HR = 6.6, CI 5.0 - 8.6, p<0.001). When analyzing maintenance immunosuppression drugs, only lack of CI exposure at 1, 3, 6 or 12 months post-transplant correlated with a significantly higher incidence of DSA development (p<0.001 for all time points). But lack of CI exposure also correlated with AR development (about 24% versus 14%, p<0.001 for all time points), obscuring the significance of CI exposure. However, when analyzing only transplants without AR, lack of CI exposure at 1, 3, 6 or 12 months post-transplant still correlated with a significantly higher incidence of DSA development (17-18% versus 10-11%, p<0.005 for all time points). When controlling for recipient age, African-American ethnicity, primary versus retransplantation, and living versus deceased donor in the 1438 transplants without AR, the increased risk of developing detectable DSA ranged from 59% to 77% when recipients were not exposed to a CI at 1, 3, 6 or 12 months after transplant. Conclusion. Use of a calcineurin inhibitor during the first post-transplant year reduces the risk of developing DSA after kidney or kidney/pancreas transplantation by decreasing the incidence of AR, and DSA in the absence of AR.

Acute and chronic antibody-mediated rejection in pediatric kidney transplantation.

Acute antibody-mediated rejection is a diagnostic challenge in renal transplantation medicine. However, it is an important diagnosis to make, since chronic antibody-mediated rejection (CAMR) is the main cause of long-term graft loss. Antibody-mediated rejection is diagnosed by detecting donor-specific antibodies (DSAs) in the blood in combination with observing typical histomorphological signs in kidney biopsy, as described in the Banff classification. Therapy is based on the removal of DSAs by administering intravenous immunoglobulins (IVIGs), plasmapheresis, or immunoadsorption. Reoccurrence of antibodies is diminished by the use of rituximab, increased immunosuppression, and in some cases additional experimental substances. A combination of these techniques has been shown to be successful in the majority of cases of acute and chronic antibody-mediated rejection. Routine DSA monitoring is warranted for early detection of antibody-mediated rejection.

1021-LBP: The significance of donor-specific hla antibodies detected by C1Q-SAB or flow cytometry crossmatches in liver transplantation

Aim Unlike in other solid organ transplantations, the role of pre-existing antibodies to HLA in liver transplant is not well defined. The presence of alloantibody in liver transplantation has been thought to have no severe deleterious impact on grafts survival, therefore crossmatchings is not routinely performed prior to liver transplantations. Recent reports suggest a correlation between positive donor specific antibody (DSA) and adverse graft outcome leading to reassessment of these views. Detection of DSA by current solid phase immunoassays is highly sensitive and specific. The correlation between DSA detected by immunoassays and their relevance in flow cytometric crossmatch (FCXM), C1q testing and subsequent liver transplantation has not been analyzed. Methods We retrospectively examined the predictive value of detection of DSA by FCXM or C1q binding ability of the DSA from 175 liver transplant recipients. LABScreen Single Antigen (SAB) immunoassay revealed anti-HLA in 44 of 175 patients. These positive serum were tested by FCXM and C1q assays. Results In SAB positive patients, the sensitivity of FCXM in detecting DSA is 67% and the negative predictive value is 90.5%, whereas C1q tests revealed all DSAs identified by SAB were complement fixing. Two of the four patients with positive DSA detected by all three tests developed biopsy proven acute/subacute immune mediated (plasma cell) rejection. Two patients with positive DSA by C1q but negative by FCXM did not develop rejection over 8-month follow up period. Conclusions These data suggest DSA resulting in FCXM positivity can lead to liver allograft dysfunction, however clinical relevance of C1q assay liver transplantation is still uncertain given none of patients with positive C1q DSA and negative FCXM have developed rejection.

Detection of donor-specific antibodies in kidney transplantation.

Precise and timely detection of human leukocyte antigen (HLA) donor-specific antibodies (DSAs) is vital for evaluating humoral immune status of patients pre- and post-transplantation. Clinically relevant articles on theory, development, methodology and application of HLA-DSA testing in kidney transplantation. The availability of solid phase HLA-antibody testing revolutionized our ability to detect HLA-DSA and to appreciate their significance in kidney transplant outcome. The best approach to determine the strength, immunogenicity and pathogenicity of HLA antibodies still remains controversial. Assays to identify complement-binding antibodies were developed. Their clinical utilization, pre- and post-transplantation, is currently under investigation. Appreciation of the complexity of HLA-DQ antibodies should lead to better assignment of unacceptable antibodies and cPRA calculation. Characterization of HLA-antibody epitopes, and utilization of epitope matching to better define compatible donors could contribute to better transplant outcomes.

Excellent Results of Immunocomplex Capture Fluorescence Analysis-I for Cross-Match Test in Renal Transplantation

A flow cytometry cross-match (FCXM) test is the gold standard for detection of human leukocyte antigen (HLA) antibodies in renal transplantation because of its high sensitivity. However, this technique can produce false-positive results when non-HLA antibodies or low-titer donor-specific antibodies (DSA) are detected. To determine the clinical relevance of the recently introduced novel cross-match test termed immunocomplex capture fluorescence analysis (ICFA), we retrospectively compared the results of ICFA and FCXM, including a single-antigen bead test for detection of DSA in renal transplant recipients. We found a correlation of 71.4% (235/329) between the results of ICFA-I and FCXM-T, whereas that between ICFA-II and FCXM-B was 41.1% (134/326). Ninety-four patients were ICFA-I negative and FCXM-T positive, and 188 were ICFA-II negative and FCXM-B positive, whereas 46.8% (44/94) and 61.7% (116/188) were found to be DSA-I and DSA-II negative, respectively, which classified them into the non-HLA antibody and low-titer DSA groups, respectively. The mean value of molecules of equivalent soluble fluorochrome for DSA-I was 22,994 in the ICFA-I–positive group, which was significantly higher than 2117 in the negative group (P < .0001), whereas there was no significant difference for DSA-II between the ICFA-II–positive and ICFA-II–negative groups. Graft survival in the ICFA-I–negative group was significantly higher than that in the ICFA-I–positive group (P = .0058). Our results indicate that ICFA-I does not respond to non-HLA antibodies or low-titer DSA, which have influence on graft survival. Therefore, this novel hybrid test, which combines cross-match testing and HLA antibody detection functions, may be useful for clinical pretransplantation evaluation of renal transplantation patients.

Time Course of Pathologic Changes in Kidney Allografts of Positive Crossmatch HLA-Incompatible Transplant Recipients

Recipients of incompatible allografts are at increased risk of graft loss. We hypothesized that analysis of sequential biopsies from these grafts could define progression of graft lesions and identify features predictive of progression. We studied the time course of histologic injury in 745 kidney graft biopsies from 129 patients transplanted with a positive crossmatch human leukocyte antigen-incompatible kidney between 2000 and 2010 (follow-up of 1-9 years). Graft survival was 98% at 1 year and 80% at 5 years after transplantation. Throughout follow-up, 70% of patients experienced rejection, with 52% showing subclinical rejection in the first year. Cell-mediated rejection was more frequent than antibody-mediated rejection throughout follow-up. Transplant glomerulopathy (TxGN; cg≥1) developed in 47% of patients over the period of the study, as early as 3 months in a few patients. TxGN was preceded by glomerulitis in more than 90% of cases, with a median time interval of 12 months. Glomerulitis and detectable posttransplantation donor-specific antibodies were risk factors for TxGN (P<0.0001 and P<0.05). C4d-negative antibody-mediated rejection manifesting as capillaritis (g≥1 and ptc≥1) with detectable donor-specific antibodies was observed in some recipients (<20%). There was progressively higher average tubulointerstitial scarring (ci+ct) from 3 to 6 to 12 months (P<0.001). Despite good graft survival, a significant incidence of biopsy-proven rejection occurred in this subset of closely monitored human leukocyte antigen-incompatible recipients throughout follow-up. Microcirculation inflammation, particularly glomerulitis, irrespective of C4d, is associated with a high risk of development of TxGN at 1 year.

Kidney Intragraft Donor-Specific Antibodies as Determinant of Antibody-Mediated Lesions and Poor Graft Outcome

Allograft pathology, antibody–tissue interaction as demonstrated by C4d deposition and serological evidence of donor-specific antibodies (DSA) are the cardinal diagnostic features of antibody-mediated lesions (AML) in kidney transplantation. However, discrepancy between histological and serological findings is common, and more reliable diagnostic tools are called for. Here, we asked whether the in situ detection of DSA could serve as marker for AML. To that end, we applied the anti-HLA single antigen flow bead assay to eluates from 51 needle core graft biopsies performed for cause. Intragraft antibody profiles were correlated to serum DSA (sDSA), histological data and transplant outcome. The prevalence and the mean number of intragraft DSA (gDSA) were lower than that of sDSA (15/51 gDSA+ vs. 37/51 sDSA+ patients; 1.64 gDSA vs. 2.24 sDSA per patient). DSA were detected in all anti-HLA antibody-positive biopsies (15/15). The presence of gDSA was significantly associated with (1) microcirculation lesions taken individually (g, cg) and analyzed in functional clusters (ptc + g + cg > 0, cg + mm > 0), (2) C4d positivity and (3) a worse short-term transplant outcome (p = 0.05). These associations were not found for patients presenting only sDSA. Taken together, these results indicate that gDSA is a severity marker of antibody-mediated pathogenic process.

Sensitive Solid-Phase Detection of Donor-Specific Antibodies as an Aid Highly Relevant to Improving Allograft Outcomes

Transplant recipients who have had sensitizing events such as pregnancies, blood transfusions and previous transplants often develop antibodies directed against human leukocyte antigen (HLA)-molecules of the donor tissue. These pre-formed donor-specific antibodies (DSA) represent a high risk of organ failure as a consequence of antibody-mediated hyper-acute or acute allograft rejection. As a first assay to detect DSA, the complement-dependent lymphocytotoxicity assay (CDC) was established more than 40years ago. However, this assay is characterized by several drawbacks such as a low sensitivity and a high susceptibility to various artificial factors generally not leading to valid and reliable outcomes under several circumstances that are reviewed in this article. Furthermore, only those antibodies that exert complement-fixing activity are detected. As a consequence, novel procedures that act independently of the complement system and that do not represent functional assays were generated in the format of solid phase assays (SPAs) (bead- or ELISA-based). In this article, we review the pros and cons of these sensitive SPA in comparison with the detection of DSA through the use of the traditional methods such as CDC and flow cytometric analyses. Potential drawbacks of the alternative methodological approaches comprising high background reactivity, susceptibility to environmental factors and the possible influence of subjective operators' errors concerning the interpretation of the results are summarized and critically discussed for each method. We provide a forecast on the future role of SPAs reliably excluding highly deleterious DSA, thus leading to an improved graft survival.

34-P

To evaluate validate and analyse Luminex – X Map technology for detection of donor specific antibodies (DSA) and panel reactive antibody (PRA) screen in a standalone laboratory in India. Thirty –two samples and 22 controls were evaluated for presence of Class I and II DSA using of IgG isotype using Genprobe (USA) kits. B and T cell crossmatch had been performed on all samples by two stage basic NIH method on all samples. PRA screen was performed on 35 samples with inclusion of positive and negative controls in each of the three assays using commercial kits from the same vendor. Reproducibility in PRA screen testing was checked on eight samples of which three samples were tested in triplicate and five samples in duplicate. DSA was also carried out on five samples in duplicate. Data accrued from validation studies are shown in Table 1 . High background was observed in 20 and 10 percent of the samples for DSA and PRA respectively. The background was reduced by 35-60% on using Seraclean. The overall results were unaffected by high background. Results of PRA were concordant in 90 % of samples for class I DSA and PRA. DSA and PRA screen detected class II antibodies in far more cases than class I antibodies and both tests may be used for detection of antibodies which may be missed on serology.[ Table 1 ]

60-OR

Aim The C1qScreen™ assay detects complement binding HLA antibodies. Recent studies suggest that the presence of C1q positive donor specific antibodies (DSA) is associated with poor post-transplant outcomes. However, in some patients with documented episodes of antibody mediated rejection or graft failure, C1q binding DSA are not detected by the C1qScreen™ suggesting poor assay sensitivity. The goal of this study was to develop an enhanced C1q assay to improve the detection of complement binding HLA DSA. Methods Nine patient sera with well characterized (using IgG single antigen bead (SAB) assay) post-transplant DSA were tested for C1q binding using the standard C1qScreen™ and three modified protocols: 1) extended incubation (EI), 2) wash modified (WM) and 3) anti-human globulin (AHG) C1q enhanced (ACE) protocol. The number of class I/II DSA detected and DSA MFI values obtained with each protocol were compared. Results The C1qScreen™ was positive for only 30% of Class I (9/30) and 52% of Class II (15/29) IgG DSA specificities. The average MFI DSA values were markedly reduced compared with the IgG-SAB assay. The EI and WM protocols exhibited higher average DSA MFI values (2.25 and 3.4 fold higher respectively) compared to the standard protocol but only 2 additional DSA specificities were detected. In contrast, the ACE protocol identified 10 additional Class I (19/30; 63%) and 4 additional Class II (19/29; 66%) DSA specificities with an average increase in DSA MFI of 4.7 fold when compared with the standard C1qScreen™. Conclusions The C1qScreen™ exhibits poor assay sensitivity and fails to adequately identify many post-transplant complement fixing HLA DSA. The sensitivity of the C1qScreen™ to detect DSA can be improved with various protocol modifications. The ACE protocol was the most sensitive of the assays tested and detected the majority of post transplant HLA DSA. Future studies will investigate the clinical significance of HLA DSA detected by the ACE protocol.

Operational Tolerance in Kidney Transplantation—Improved Terminology May Enable More Precise Investigation

Operational Tolerance in Kidney Transplantation—Improved Terminology May Enable More Precise Investigation

Cryptic B Cell Response to Renal Transplantation

Transplantation reliably evokes allo-specific B cell and T cell responses in mice. Yet, human recipients of kidney transplants with normal function usually exhibit little or no antibody specific for the transplant donor during the early weeks and months after transplantation. Indeed, the absence of antidonor antibodies is taken to reflect effective immunosuppressive therapy and to predict a favorable outcome. Whether the absence of donor-specific antibodies reflects absence of a B cell response to the donor, tolerance to the donor or immunity masked by binding of donor-specific antibodies to the graft is not known. To distinguish between these possibilities, we devised a novel ELISPOT, using cultured donor, recipient and third-party fibroblasts as targets. We enumerated donor-specific antibody-secreting cells in the blood of nine renal allograft recipients with normal kidney function before and after transplantation. Although none of the nine subjects had detectable donor-specific antibodies before or after transplantation, all exhibited increases in the frequency of donor-specific antibody-secreting cells eight weeks after transplantation. The responses were directed against the donor HLA-class I antigens. The increase in frequency of donor-specific antibody-secreting cells after renal transplantation indicates that B cells respond specifically to the transplant donor more often than previously thought.

Frequent development of subclinical chronic antibody-mediated rejection within 1year after renal transplantation with pre-transplant positive donor-specific antibodies and negative CDC crossmatches

Although short-term graft survival has been improved by recent desensitization protocols including B cell depletion therapy, little is known about risk factors of chronic antibody-mediated rejection (CAMR) in HLA-incompatible (HLA-I) renal transplantation (RTx). Twenty-six HLA-I RTx with positive donor-specific antibodies (DSA) and negative T cell cytotoxic crossmatches were compared with 88 ABO-incompatible (ABO-I) and 207 ABO-identical/compatible (ABO-Id/C) RTx. The desensitization therapy consisted of mycophenolate mofetil, rituximab and double-filtration plasmapheresis. Protocol biopsies within 1 year revealed subclinical CAMR in 36% of HLA-I, 5% of ABO-I and 3% of ABO-Id/C, although clinical acute AMR was observed in 8%, 3% and 1%, respectively. The incidence of CAMR was not different between class I and class II DSA. Most of class I DSA (94%) changed to negative 1 year after RTx, whereas 77% of class II DSA remained positive. In addition, the remaining DRB ± DQB DSA caused CAMR in 80% of patients, while DQB DSA alone did not. The progress of subclinical CAMR within 1 year could not be circumvented by rituximab. Sustained class II (DRB ± DQB) DSA detection after RTx may pose a potential risk for developing CAMR, but negative change in class I DSA could also elicit CAMR.

Impact of sensitivity of human leucocyte antigen antibody detection by Luminex technology on graft loss at 1 year.

BackgroundThe clinical relevance of the detection of human leucocyte antigen (HLA) antibodies in sera of renal transplant recipients by highly sensitive methods such as Luminex alone is uncertain and a matter of debate. The choice of output thresholds affects antibody detection and thus organ allocation, yet there are no internationally agreed threshold levels. This study aims at evaluating our current practice of using an MFI threshold of 1000 in antibody detection.MethodsWe carried out a case–control study by looking at 761 renal transplant recipients at one unit between 2000 and 2010. Of these, there were 93 cases of graft loss within 1 year and stored serum samples of 40 cases were available for testing. Controls were selected (graft function >2 years) and individually matched according to age, sex, number of transplants and date of transplant. All 40 cases and 40 controls had negative crossmatch by complement-dependent cytotoxicity (CDC) at the time of transplant, and pre-transplant sera were re-analysed for the presence of detectable HLA and donor-specific antibodies (DSAs) using Luminex screen and single-antigen beads and MFI threshold values of 1000, 2000 and 4000.ResultsIn nearly 48% of cases with graft loss within a year, HLA antibodies were detectable by Luminex when using a 1000 MFI threshold. This was 25% greater than in controls (P = 0.017). There was also a 15% increase in detected DSAs; however, statistical significance depends on the inclusion or exclusion of one specific case. Using MFI thresholds of 2000 and 4000, no DSAs were found in any long-term surviving grafts.ConclusionsSelection of appropriate MFI cut-off values influences the detection of DSAs and, thus, organ allocation. Using a threshold of 1000 led to the detection of DSAs in 5% of long-term graft survivors in our population and should be considered too sensitive. Using a detection threshold of 2000 is sufficiently sensitive and leads to clinically relevant detection of DSA.

Virtual Crossmatch Predicts Compatibility for Heart Transplantation with Favorable Outcomes in Sensitized Patients

Purpose Alloantibodies to human leukocyte antigens (HLA) in patients awaiting orthotopic heart transplantation (OHT) are associated with prolonged wait time to transplant, and increased risk of rejection. Virtual crossmatch (VC) allows comparison of recipient HLA antibodies to prospective donor HLA antigens to safely transplant a patient without prospective crossmatch. We have evaluated the performance at our center, correlating VC results with post-transplant outcomes. Methods and Materials From 2010 to 2012, VC performance was evaluated. HLA antibody testing was performed using Luminex single antigen bead multi-array platforms. Crossmatching was done using 3-color Flow cytometric analysis on a 1024 channel scale. We compared VC with actual crossmatch results, and examined 1-year acute rejection episodes and survival. Results Eighty-four patients were transplanted with a concordance rate of 96.5% between virtual and actual crossmatch results: 79/84 crossmatches were both predicted and confirmed flow crossmatch negative, while 2/84 were predicted and confirmed flow crossmatch positive. One patient with a negative crossmatch demonstrated weak, recently evolved anti-A2 (donor-specific) reactivity by Luminex analysis (MFI=1984) in day of transplant serum. Two patients were predicted to be negative, but positive crossmatches were observed in the absence of detectable donor specific antibodies (possible non-HLA / non-specific fluorescence). A significant number of recipients (28.6%; n=24) were sensitized prior to transplant (3 patients > 80% PRA; 10 between 20-79% PRA; and 11 patients Conclusions Virtual crossmatch accurately predicts actual flow crossmatch results in patients undergoing OHT. This technique can be reliably used in sensitized patients without compromising patient safety or clinical outcome.

Solid phase detection of C4d-fixing HLA antibodies to predict rejection in high immunological risk kidney transplant recipients

Protocols for recipient desensitization may allow for successful kidney transplantation across major immunological barriers. Desensitized recipients, however, still face a considerable risk of antibody-mediated rejection (AMR), which underscores the need for risk stratification tools to individually tailor treatment. Here, we investigated whether solid phase detection of complement-fixing donor-specific antibodies (DSA) has the potential to improve AMR prediction in high-risk transplants. The study included 68 sensitized recipients of deceased donor kidney allografts who underwent peritransplant immunoadsorption for alloantibody depletion (median cytotoxic panel reactivity: 73%; crossmatch conversion: n=21). Pre and post-transplant sera were subjected to detection of DSA-triggered C4d deposition ([C4d]DSA) applying single-antigen bead (SAB) technology. While standard crossmatch and [IgG]SAB testing failed to predict outcomes in our desensitized patients, detection of preformed [C4d]DSA (n=44) was tightly associated with C4d-positive AMR [36% vs. 8%, P=0.01; binary logistic regression: odds ratio: 10.1 (95% confidence interval: 1.6-64.2), P=0.01]. Moreover, long-term death-censored graft survival tended to be worse among [C4d]DSA-positive recipients (P=0.07). There were no associations with C4d-negative AMR or cellular rejection. [C4d]DSA detected 6months post-transplantation were not related to clinical outcomes. Our data suggest that pretransplant SAB-based detection of complement-fixing DSA may be a valuable tool for risk stratification.

Prevalence of Circulating Donor Specific Anti-HLA Antibodies and C4d Deposition in Live Renal Transplant Recipients with Chronic Allograft Dysfunction

Introduction and aims: The detection of donor specific antibodies (DSA) and C4d staining of renal allograft biopsies has emerged as an important tool for the diagnosis of alloantibody dependent allograft injury. The present study was undertaken to determine the prevalence of circulating donor reactive anti-HLA class I and II antibodies and peritubular capillary C4d deposition in biopsies of patients with chronic allograft dysfunction. Methods: Thirty six live donor renal allograft recipients with graft dysfunction at more than one year post transplant based on serum creatinine of more than 2 mg% or proteinuria more than 600 mg were evaluated by graft biopsy and ELISA for presence of circulating IgG DSA. Biopsies were assessed by 3 independent pathologists based on light microscopy, immunofluorescence and C4d staining. Results: Of the 36 biopsies 10 had evidence of antibody mediated rejection (AMR), 11 showed evidence of transplant glomerulopathy (TG) and 12 were C4d positive (11 diffuse and 1 focal). All C4d positive biopsies had evidence of AMR (n=4), TG (n=3) or both (n=5). Of the 10 biopsies with AMR, 9 were C4d positive while 8 out of 11 biopsies showing TG also showed C4d positivity. Three patients had circulating donor specific anti-HLA class II antibodies alone. Of these one patient had membranous glomerulonephritis progressing to graft loss, another had acute cellular rejection (ACR) and the last had arterionephrosclerosis. Conclusions: There was good correlation between C4d and antibody mediated changes (AMR or TG). The presence of C4d positivity was significantly associated with graft loss or persistent graft dysfunction (P< 0.001). There was no correlation between DSA and AMR, TG or C4d staining.

Antibody Monitoring System to Support the Single-Antigen Luminex Assay in Donor-Specific Antibody Detection

The antibody monitoring system (AMS) is a crossmatch test using enzyme-linked immunoassay to detect donor-specific anti-HLA antibodies (DSA). The aim of this study was to determine whether the AMS assay is useful for supporting DSA results measured with single-antigen Luminex assay (Luminex-DSA) in renal transplant recipients. Thirty sera from 12 sensitized recipients and 71 sera from 60 non-sensitized recipients were screened by complement-dependent cytotoxic crossmatch (CDC-XM), flow cytometric crossmatch (FCXM), AMS, and the Luminex assays. Twenty-two (73.3%) sera from sensitized patients were positive for Luminex-DSA and the AMS assay revealed the great specificity and positive predictive value for detecting Luminex-DSA in sera from sensitized patients. Positivity in the AMS assay was observed most frequently in Luminex-DSA-positive sera with ≥ 10000 MFI levels (66.7%). Of the 101 sera, the results of the AMS assay were compatible with CDC-XM results in 73 (91.3%) sera and with FCXM results in 72 (90.0%) sera; these rates were significantly higher for the AMS assay than for the Luminex assay (p = 0.008 for CDC-XM and p = 0.001 for FCXM). In conclusion, the AMS assay is useful as a supportive solid-phase method for predicting actual crossmatch and high level of Luminex-DSA in sensitized patients.