Analysis of preformed donor-specific anti-HLA antibodies characteristics for prediction of antibody-mediated rejection in kidney transplantation.

The relevance of preformed donor specific antibodies (DSA) detected by Luminex assays, with a negative complement-dependent cytotoxicity (CDC) crossmatch, remains unsettled in kidney transplantation (KT). We aimed to analyze the impact of preformed DSA characteristics on kidney graft outcomes. In 462 patients that received a kidney graft in our unit, between 2007 and 2012, pre-transplant sera were analyzed by Luminex screening assay to determine the presence of anti-human leukocyte antigen (HLA) antibodies and single-antigen bead assay [positive if mean fluorescence intensity (MFI) ≥ 1000] to assign anti-HLA specificities. Anti-HLA antibodies were present in 95 patients (20.6%), but only 40 (8.7%) had DSA. Antibody-mediated rejection (AMR) at 1-year was higher in patients with DSA (35.0%) than in those without them (0.9%) (P < 0.001). Only DSA with a MFI of >3000 were significantly associated with AMR occurrence. Receiver operator curves revealed that a MFI of >4900 in the highest DSA bead had a high sensitivity (85.7%) and that the sum of all DSA beads MFI > 11,000 had a high specificity (92.3%) for AMR prediction. Anti-thymocyte globulin versus basiliximab induction was more frequent in DSA+ AMR- (65.4%) versus DSA+ AMR+ (34.6%) patients (P = 0.072). Five-year censored graft survival was lower in DSA+ than in DSA- patients (respectively, 84.8% versus 94.9%, P = 0.006), although survival was only reduced in DSA+ AMR+ (68.8%) versus DSA+ AMR- (96.0%) patients (P = 0.038). Preformed DSA is associated with kidney graft loss, in relation with AMR occurrence. DSA strength may be used to improve immunological risk stratification of sensitized patients and their clinical management.

Malheiro J ，Tafulo S ，Dias L ，Martins LS ，Fonseca I ，Beirão I ，Castro-Henriques A ，Cabrita A ... -  《-》

Impact of alloantibody strength in crossmatch negative DSA positive kidney transplantation.

The clinical relevance of pre-transplant "low-level" donor specific anti-HLA antibodies (DSAs) in crossmatch negative kidney transplant recipients remains unclear. To determine what level of DSA associates with antibody mediated rejection (AMR) could be the way to measure the clinical relevance of pre-transplant "low-level" donor specific anti-HLA antibodies (DSAs) in crossmatch negative kidney transplant recipients. A retrospective analysis of 221 patients from October 2008 to December 2009 was included in this study. Sera were obtained pre-transplant and two weeks post-transplant and tested for DSA using LABScreen single antigen beads. Among the 221 patients, 11 experienced AMR within 200days after transplant (5%). Pre-transplant DSA was associated with AMR at multiple mean fluorescence intensity (MFI) cutoffs (500, 1000, 2000, 3000, 5000; p=0.003, 0.001, 0.007, 0.003, and 0.003, respectively). No correlation was seen between acute T-cell mediated rejection (CMR) and pre-transplant DSA at any of the same MFI cutoffs. There was an increased risk of AMR with higher levels of pre-transplant DSA. Finally, an increase in DSA MFI from pre- to two weeks post-transplant was indicative of a higher probability of AMR. Overall, this data supports using the single antigen bead to detect "low-level" DSA both pre- and post- as having a positive and persistent DSA may be predictive of higher AMR rates and poorer graft survival.

Wu P ，Jin J ，Everly MJ ，Lin C ，Terasaki PI ，Chen J ... -  《-》

Clinical relevance of pretransplant anti-HLA donor-specific antibodies: does C1q-fixation matter?

Anti-HLA donor-specific antibodies (DSA) identified by single antigen bead array (SAB) are questioned for their excess in sensitivity and lack of event prediction after transplantation. We retrospectively evaluated specific types of preformed DSA (class I, class II or C1q-fixing) and their impact on graft survival. Kidney transplantations performed across negative CDC-crossmatch were included (n=355). Anti-HLA antibodies were tested using SAB to identify DSA and their capacity to fix C1q. Twenty-eight patients with pretransplant DSA(+) with MFI>2000 were selected to assess C1q fixation. DSA were C1q+ in 15 patients and C1q- in 13, without significant differences in demographics, acute rejection, graft loss or renal function. The maximum MFI of DSA in patients with C1q-fixing DSA was significantly higher (p=0.008). Patients with DSA class-I suffered more antibody-mediated rejection (AMR) and had worse graft survival than class-II. The capacity of DSA I to fix C1q did not correlate with rejection, graft function or graft loss. C1q testing in pretransplant sera with DSA was unable to predict acute antibody-mediated rejection or early graft loss, but the presence of DSA class I compared to DSA only class II did. Despite non-fixing complement in vitro, pretransplant C1q-negative DSA I can mediate rejection and graft loss.

Crespo M ，Torio A ，Mas V ，Redondo D ，Pérez-Sáez MJ ，Mir M ，Faura A ，Guerra R ，Montes-Ares O ，Checa MD ，Pascual J ... -  《-》

Pre-transplant donor specific anti-HLA antibody is associated with antibody-mediated rejection, progressive graft dysfunction and patient death.

The long term effect of donor specific antibodies (DSA) detected by Luminex Single Antigen Bead (SAB) assay in the absence of a positive complement-dependant cytotoxicity (CDC) crossmatch is unclear. DSA at the time of transplant were determined retrospectively in 258 renal transplant recipients from 2003 to 2007 and their relationship with rejection and graft function prospectively evaluated. After a median of 5.6 years follow-up 9% of patients had antibody mediated rejection (AMR) (DSA 11/37 (30%), DSA-Neg 13/221 (6%), HR 6.6, p<0.001). Patients with anti-HLA class II (HR 6.1) or both class I+II (HR 10.1) DSA had the greatest risk for AMR. The Mean Fluorescent Intensity (MFI) of the DSA was significantly higher in patients with AMR than those with no rejection (p=0.006). Moreover, the strength of the antibody was shown to be important, with the risk of AMR significantly greater in those with DSA >8000 MFI than those with DSA <8000 MFI (HR 23, p<0.001). eGFR progressively declined in patients with DSA but was stable in those without DSA (35.7 ± 20.4 mls/min vs 48.5 ± 22.7) and composite patient and graft survival was significantly worse in those with class II (HR 2.9) or both class I+II (HR 3.7) but not class I DSA. Class II DSA alone, or in combination with class I DSA had the strongest association with graft loss and patient death. Patients with DSA not only have increased rates of acute AMR, but also chronic graft dysfunction, graft loss and death. Antibody burden quantified by SAB assay may identify patients at highest immunological risk and therefore influence patient management and improve long-term patient outcome.

Fidler SJ ，Irish AB ，Lim W ，Ferrari P ，Witt CS ，Christiansen FT ... -  《-》

Peri-operative third party red blood cell transfusion in renal transplantation and the risk of antibody-mediated rejection and graft loss.

Historic red blood cell transfusion (RBCT) may induce anti-HLA antibody which, if donor specific (DSA), is associated with increased antibody-mediated rejection (AMR). Whether post-operative RBCT influences this risk is unknown. We examined the RBCT history in 258 renal transplant recipients stratified according to prevalent recipient HLA antibody (DSA, Non-DSA or No Antibody). AMR occurred more frequently in patients who received RBCT both pre and post transplant compared with all other groups (Pre+Post-RBCT 21%, Pre-RBCT 4%, Post-RBCT 6%, No-RBCT 6%, HR 4.1 p=0.004). In the 63 patients who received Pre+Post-RBCT, 65% (13/20) with DSA developed AMR compared with 0/6 in the Non-DSA group and 2/37 (5%) in the No-Antibody group (HR 13.9 p<0.001). In patients who received No-RBCT, Pre-RBCT or Post-RBCT there was no difference in AMR between patients with DSA, Non-DSA or No-Antibody. Graft loss was independently associated with Pre+Post-RBCT (HR 6.5, p=0.001) AMR (HR 23.9 p<0.001) and Non-AMR (6.0 p=0.003) after adjusting for DSA and delayed graft function. Re-exposure to RBCT at the time of transplant is associated with increased AMR only in patients with preformed DSA, suggesting that RBCT provides additional allostimulation. Patients receiving Pre+Post-RBCT also had an increased risk of graft loss independently of AMR or DSA. Both pre and post procedural RBCT in renal transplantation is associated with modification of immunological risk and warrants additional study.

Fidler S ，Swaminathan R ，Lim W ，Ferrari P ，Witt C ，Christiansen FT ，D'Orsogna LJ ，Irish AB ... -  《-》