Preformed anti-HLA Antibodies Research Articles

#1016 Kidney transplantation in highly sensitized patients with preformed donor-specific antibodies through personalized delisting strategies

Abstract Background and Aims This study explores a personalized delisting strategy enabling kidney transplantation in highly sensitized patients with preformed donor-specific anti-HLA antibodies (DSA) trying to minimize the risk of antibody-mediated rejection (ABMR). Method Retrospective single-centre analysis of 50 kidney transplant recipients with preformed DSA (preDSA) after employing a delisting strategy to enhance their access to transplantation, and without received a pre-transplant or immediate post-transplant desensitization protocol. The delisting approach focused on allowing less deleterious antibodies according to their mean fluorescence intensity (MFI), anti-HLA class and C1q study results. The strategy consisted on eliminating as prohibited HLA antigens those recognized by antibodies with the lowest MFI in the following order: 1st- MFI < 5000; 2nd- MFI < 10000; 3rd-Any MFI. Additionally, delisting prioritized a single locus in the following order: 1st- one of the HLA class I loci (A, B, or Cw); 2nd- the rest of the class I loci; 3rd- HLA-DP, followed by DR. C1q studies were performed before delisting and transplantation was contraindicated in the presence of DSA detected in the C1q assay. Two comparative cohorts included 50 sensitized recipients without pre-transplant DSA (SwoDSA) and 50 non-sensitized recipients (NS). Results The delisting strategy allowed transplantation with preformed DSA and demonstrated comparable rejection rates to SwoDSA and NS groups (16%, 14% and 8%, respectively; log-rank = 0.28). However, the occurrence of acute ABMR was 12% in the preDSA group, significantly higher than in SwoDSA (1%) and NS (0%) (log-rank = 0.0093). The immunological risk assumed in delisting correlated with ABMR incidence (patients with ABMR had significantly higher sum MFI [mean ± SD: 9301 ± 6340 vs 4492 ± 5641; p = 0.049]), emphasizing the importance of tailored strategies. DSA persistence after transplantation correlated with higher MFI and increased ABMR risk. Of note, 16% of preDSA patients developed de novo DSA versus only the 4% of SwoDSA and 0% of NS patients (p = 0.004). After a mean follow-up of 3.1 ± 2.1 years, the 1-, 3- and 5-year death-censored allograft survival rates were 100%, 90% and 78%, respectively, in the preDSA group; 98%, 84% and 84% in the SwoDSA group and 100% in NS group (log-rank = 0.02). Conclusion The present study demonstrates the feasibility and acceptable outcomes of kidney transplantation in highly sensitized patients with preformed DSA through a personalized delisting strategy without using desensitization protocols.

#4856 HISTOLOGICAL FINDINGS OF ACUTE HUMORAL REJECTION IN PATIENTS WITH STANDARD IMMUNOLOGICAL RISK: ANTIBODY-MEDIATED DAMAGE OR MICROVASCULAR INJURY?

Abstract Background and Aims The development of acute humoral rejection (AHR) is increased in patients with high immunological risk. Taking into account the highly sensitivity from the techniques used to determine anti-HLA antibodies, the histological findings of AHR in the immediate post-transplantation period in patients without preformed anti-HLA antibodies (standard immunological risk) is unexpected. We propose the implication of non-immunological factors as the origin of these findings. Our aim was to evaluate the histological findings of AHR in the immediate post-transplantation period in patients with standard immunological risk and to analyze factors related to its appearance. Method A multicenter retrospective study was carried out including renal transplants performed between January-2014 and december-2022, excluding patients with pre-transplant HLA sensitization and failures due to thrombosis. A descriptive analysis of transplant recipients with standard immunological risk who developed histological findings of AHR was made (AHRh) .In addition, we performed a comparative analysis of this group with the patients who developed AHR with pre-transplant HLA sensitization (AHRs). Results Of the 351 patients, 18 (5.1%) presented AHRh, all were first transplants without pre-transplant anti-HLA antibodies. Fourteen donors were brain death and four due to controlled circulatory arrest. Banff AHR was grade I in 1 patient, grade II in 13 patients, and III in 3 cases. 50% showed thrombotic microangiopathy (TMA). Seven (38.9%) failed after a mean follow-up of 28.7±26.1 months. The failure etiologies were chronic rejection (3) and primary dysfunction (4). No patient presented anti-HLA antibodies during the follow-up and 3 have received a second transplant without complications. When comparing the AHRh group with the AHRs (n = 14), we observed a greater age of the donor in AHRh (median 71,5 vs 56.5, p = 0.02) a higher percentage of donor due to controlled circulatory arrest (22% vs 0%, p = 0.075) and with history of Hypertension (66.7% vs 42.9%, p = 0.09). Recipient age was higher in AHRh (median 64.5 vs 51, p = 0.025), with a higher proportion of retransplant in AHRs (42.9% vs 0, p = 0.002). In AHRh, DGF (100% vs 57.1%, p = 0.002) and thrombotic microangiopathy (50% vs 14.3%, p = 0.03) were more frequent. Renal function was worse during the follow-up in AHRh (p<0.05). No differences have been observed in graft and patient survival. Conclusion The histological finding of RAH in patients with standard immunological risk appears as an aggressive process with negative consequences on graft survival. The absence of anti-HLA antibodies in subsequent follow-up suggests the involvement of non-immunological factors in its developing. Processes related to the maintenance and/or extraction of organs could favor the appearance of microvascular damage, with histological findings suggestive of AHR especially in older grafts and with comorbidity. Studying these cases is essential to identify risk groups and establish appropriate therapeutic strategies.

Lung transplantation despite preformed donor-specific antihuman leukocyte antigen antibodies: a 9-year single-center experience

Pretransplant allosensitization to human leukocyte antigens (HLA) increases the recipient’s waiting list time and mortality in lung transplantation. Rather than waiting for crossmatch-negative donors, since 2013, recipients with preformed donor-specific antiHLA antibodies (pfDSA) have been managed with repeated IgA- and IgM-enriched intravenous immunoglobulin (IgGAM) infusions, usually in combination with plasmapheresis before IgGAM and a single dose of antiCD20 antibody. This retrospective study presents our 9-year experience with patients transplanted with pfDSA. Records of patients transplanted between February 2013 and May 2022 were reviewed. Outcomes were compared between patients with pfDSA and those without any de novo donor-specific antiHLA antibodies. The median follow-up time was 50 months. Of the 1,043 patients who had undergone lung transplantation, 758 (72.7%) did not develop any early donor-specific antiHLA antibodies, and 62 (5.9%) patients exhibited pfDSA. Among the 52 (84%) patients who completed treatment, pfDSA was cleared in 38 (73%). In pfDSA vs control patients and at 8-year follow-up, respectively, graft survival (%) was 75 vs 65 (P = .493) and freedom from chronic lung allograft dysfunction (%) was 63 vs 65 (P = .525). In lung transplantation, crossing the preformed HLA-antibody barrier is safe using a treatment protocol based on IgGAM. Patients with pfDSA have a good 8-year graft survival rate and freedom from chronic lung allograft dysfunction, similar to control patients.

Significance of pretransplant and de novo anti-HLA antibody detection after simultaneous pancreas-kidney transplantation

Introduction. Nowadays, there are few studies concerning assessment of the clinical significance of determining the level of pretransplant and de novo anti-HLA antibodies in patients after simultaneous pancreas-kidney transplantation.Aim. The study of the incidence, timing of formation and specificity of pretransplant and de novo anti-HLA antibodies in patients after simultaneous pancreas-kidney transplantation.Material and methods. We conducted a prospective and retrospective research to study the incidence, timing of formation and specificity of pretransplant and de novo anti-HLA antibodies in 55 patients after simultaneous pancreas-kidney transplantation performed at the N.V. Sklifosovsky Research Institute for Emergency Medicine from 2008 to 2022.Results. There were 4 patients with preformed anti-HLA antibodies (7%). The formation of de novo anti-HLA antibodies after simultaneous pancreas-kidney transplantation was observed in 17 patients (31%). There were 5 patients with antiHLA class I, 3 patients with anti-HLA class II, 3 patients with anti-HLA class I and II, 5 patients with anti-MICA and 1 patient with both classes of anti-HLA and anti-MICA. The formation of de novo anti-HLA antibodies significantly increased the incidence of acute rejection (47% compared with 13%, p=0.014).Conclusion. The frequency of pretransplant and de novo anti-HLA antibody detection in the recipients at our Center is comparable to published data from other transplant centers. We obtained evidence that the formation of de novo antiHLA antibodies increases the incidence of acute rejection after simultaneous pancreas-kidney transplantation.

Risk factors for delayed kidney graft function from a deseased donor

Aim. To determine statistically significant risk factors for delayed renal graft function. To assess the impact of delayed kidney graft function on the development of other complications, graft and recipient survival.Material and methods. In 237 consecutive kidney transplant recipients (from June 2018 to December 2021), we assessed its function in the early postoperative period. Delayed function was considered to be the need for hemodialysis in the first week after surgery. Among the donor factors, the type of donor, age, body mass index, the presence of vasopressor support, the time the donor was in intensive care, and the maximum level of creatinine during the follow-up were evaluated. Recipient risk factors include age, gender, body mass index, presence/absence and amount of urine, presence of preformed anti-HLA antibodies and/or repeated kidney transplantation, number of mismatches for six HLA antigens, number of mismatches for HLA-DR, presence and type of renal replacement therapy, etiology of end stage kidney disease. Among the perioperative risk factors are the duration of cold preservation, the time of second warm ischemia, the volume of intraoperative blood loss, the intraoperatively determined renal arterial resistive index of the renal graft, and the maximum concentration of tacrolimus in the first 4 days after kidney transplantation. After that the relationship between the presence of delayed kidney graft function and the development of early postoperative complications was assessed and its effect on the long-term survival of grafts and recipients was analyzed.Results. Out of 237 cases, 9 showed no function of the transplanted kidney, and therefore the grafts were removed. The incidence of delayed renal graft function was 24.5% (58/237). According to the results of a univariate analysis, a statistically significant relationship with the development of delayed kidney graft function had donor body mass index (p=0.019), male gender of the recipient (p=0.048), recipient body mass index (p=0.038), amount of urine (p=0.003), anuria (p=0.002), presence of preformed antibodies (p=0.025), repeated transplantation (p=0.002), time of second warm ischemia (p=0.036), intraoperative renal arterial resistive index (p=0.004) and maximum tacrolimus concentration in the first 4 days (p=0.022). In the multivariate model, donor body mass index >30 kg/m2 and peak tacrolimus concentration >23 ng/mL in the first 4 days were statistically significant (p=0.018 and p=0.025, respectively). A trend towards statistical significance was noted in the presence of oligoanuria before kidney transplantation (p=0.066) and resistance index >0.75 after surgery (p=0.056). One-year renal transplant survival in the absence and presence of delayed kidney graft function was 92.4% and 87.7%, two-year survival was 89.4% and 76.1%, respectively. The effect of delayed kidney graft function on graft survival was statistically significant (p=0.01), while overall recipient survival did not differ between the groups.Conclusion. During the univariate analysis, we identified 9 statistically significant factors, of which at least 3 are potentially modifiable. In the multivariate model, the most significant modifiable risk factor was an increased concentration of tacrolimus, which prompted the authors to reconsider the existing immunosuppressive protocol at the City Clinical Hospital n.a. S.P. Botkin. We consider the search for modifiable statistically significant risk factors for patients, their analysis and implementation of preventive measures to be an important task for each kidney transplant center.

The oxygen carrier M101 alleviates complement activation, which may be beneficial for donor organ preservation.

During organ transplantation, ischemia/reperfusion injury and pre-formed anti-HLA antibodies are the main cause of delayed graft function and recovery through the activation of the complement system. By supplying oxygen during transplantation, M101 is suspected to avoid complement activation, however, a direct effect exerted by M101 on this pathway is unknown. This was tested by using functional assays (lymphocytotoxic crossmatch test, C3d Luminex-based assay, 50% complement hemolysis [CH50], and 50% alternative complement pathway [AP50/AH50]), and quantitative assays (C3, C3a, C4, C5, C5a, C6, C7, C8, C9 and sC5b-9). M101 interferes with the anti-HLA lymphocytotoxic crossmatch assay, and this effect is complement-dependent as M101 inhibits the classical complement pathway (CH50) in a dose-dependent and stable manner. Such inhibition was independent from a proteolytic effect (fractions C3 to C9) but related to a dose-dependent inhibition of the C3 convertase as demonstrated by exploring downstream the release of the anaphylatoxins (C3a and C5a), C3d, and sC5b-9. The C3 convertase inhibition in the presence of M101 was further demonstrated in the AP50/AH50 assay. In conclusion, the use of M101 avoids the activation of the complement pathway, which constitutes an additional advantage for this extracellular hemoglobin to preserve grafts from ischemia/reperfusion injury and preformed anti-HLA antibodies.

Heart transplantation across preformed donor-specific antibody barriers using a perioperative desensitization protocol

Heart transplantation across preformed donor-specific HLA-antibody barriers is associated with impaired short- and long-term survival. Therefore, in recipients with preformed anti-HLA antibodies, waiting for crossmatch-negative donors is standard practice. As an alternative strategy, recipients with preformed anti-HLA donor specific antibodies have been managed at our institutions with a perioperative desensitization regimen. A retrospective analysis was performed comparing heart transplant recipients with preformed donor-specific HLA-antibodies to recipients without donor-specific antibodies. Recipients with a positive virtual crossmatch received a perioperative desensitization protocol including tocilizumab intraoperatively, plasma exchange and rituximab followed by a six-month course of IgGAM. Among the 117 heart-transplanted patients, 19 (16%) patients underwent perioperative desensitization, and the remaining 98 (84%) patients did not. Cold ischemic time, posttransplant extracorporeal life support for primary graft dysfunction, and intensive care unit stay time did not differ between groups. At 1-year follow-up, freedom from pulsed steroid therapy for presumed rejection and biopsy-confirmed acute cellular or humoral rejection did not differ between groups. One-year survival amounted to 94.7% in the treated patients and 81.4% in the control group. Therefore, heart transplantation in sensitized recipients undergoing a perioperative desensitization appears safe with comparable postoperative outcomes as patients with a negative crossmatch.

Perioperative Desensitization with IgA- and IgM-Enriched Human Immunoglobulins Allows Safe Lung Transplantation in Patients with Preformed Donor Specific Antibodies

<h3>Purpose</h3> Pretransplant sensitization to human leukocyte antigens (HLA) increases the recipient waiting list time and mortality in lung transplantation. Instead of awaiting crossmatch-negative donors, since 2013, recipients with preformed anti-HLA donor specific antibodies (pfDSA) have been managed peri-transplant at our institution with repeated IgA- and IgM-enriched intravenous immunoglobulin infusions (IgGAM, first infusion: 2gr/kg, then 0.5gr/kg every 4 weeks thereafter to a maximum of 6 months), usually in combination with plasmapheresis (PE) before IgGAM and a single dose of anti-CD20 antibody (375mg/m², Rituximab) after the first IgGAM infusion. This study presents the 8-year results of this protocol in patients transplanted with pfDSA. <h3>Methods</h3> Records of patients transplanted at our institution between 02/2013 and 10/2021 were reviewed. Outcomes were compared between patients with pfDSA (pfDSA group) and those without any early DSA (control group)<i>.</i> Patients without pfDSA who developed DSA only post transplantation (n=219) were excluded from the analysis. Median follow-up was 47 (21-73) months. <h3>Results</h3> Of the 994 transplanted patients, 55 (5%) patients exhibited pfDSA and 721 (73%) did not develop any early DSA. Among these 55 patients, 40 (73%) patients possessed pfDSA against class II HLA antigens and 17 (31%) patients against class I antigens (2 patients against both classes). Twelve (22%) patients showed a positive retrospective CDC crossmatch and 21 (38%) patients developed additional de-novo DSA after transplantation. Forty-four (80%) patients were treated with PE and 45 (82%) patients with Rituximab. At follow-up end, treatment was completed in 45 (82%) patients (still on treatment, n=4; in-hospital deaths, n=2; treatment interrupted earlier as intended by protocol, n=4). In these 45 patients, IgGAM treatment cleared DSA in 33 (73%) patients, with 4 (12%) patients showing the same DSA recurrence. In pfDSA vs. control patients and at 5-year follow-up, respectively, graft survival (%) was 83 vs. 76 (p=0.40) and freedom from chronic lung allograft dysfunction (%) 72 vs. 72 (p=0.62). <h3>Conclusion</h3> In lung transplantation, a treatment protocol based on IgGAM allowed transplanting patients with preformed DSA with good 5-year graft survival similar to control patients.

Increased Levels of sCD30 Have No Impact on the Incidence of Early ABMR and Long-Term Outcome in Intermediate-Risk Renal Transplant Patients With Preformed DSA.

Background: It is still incompletely understood why some patients with preformed donor-specific anti-HLA antibodies (DSA) have reduced kidney allograft survival secondary to antibody-mediated rejection (ABMR), whereas many DSA-positive patients have favorable long-term outcomes. Elevated levels of soluble CD30 (sCD30) have emerged as a promising biomarker indicating deleterious T-cell help in conjunction with DSA in immunologically high-risk patients. We hypothesized that this would also be true in intermediate-risk patients.Methods: We retrospectively analyzed pre-transplant sera from 287 CDC-crossmatch negative patients treated with basiliximab induction and tacrolimus-based maintenance therapy for the presence of DSA and sCD30. The incidence of ABMR according to the Banff 2019 classification and death-censored allograft survival were determined.Results: During a median follow-up of 7.4 years, allograft survival was significantly lower in DSA-positive as compared to DSA-negative patients (p < 0.001). In DSA-positive patients, most pronounced in those with strong DSA (MFI > 5,000), increased levels of sCD30 were associated with accelerated graft loss compared to patients with low sCD30 (3-year allograft survival 75 vs. 95%). Long-term survival, however, was comparable in DSA-positive patients irrespective of sCD30 status. Likewise, the incidence of early ABMR and lesion score characteristics were comparable between sCD30-positive and sCD30-negative patients with DSA. Finally, increased sCD30 levels were not predictive for early persistence of DSA.Conclusion: Preformed DSA are associated with an increased risk for ABMR and long-term graft loss independent of sCD30 levels in intermediate-risk kidney transplant patients.

Immunological considerations-HLA matching and management of high immunological risk recipients.

Lung transplant outcomes remain inferior largely due to mismatching in human leukocyte antigens (HLAs) that leads to chronic rejection and chronic allograft dysfunction. The mismatched donor HLAs can be recognized by the effector T cells or donor-specific HLA antibodies. This review summarizes mechanisms leading to immune responses as a result of HLA mismatching. It specifically focuses on sensitized lung transplant candidates with preformed anti-HLA antibodies, which represent a significant management challenge for physicians. In this review, we describe the diagnostic histocompatibility testing and therapeutic options for managing the sensitized lung transplant patients and discuss how multidisciplinary approach may help to improve lung transplantation outcomes.

Rituximab Desensitization in Liver Transplant Recipients With Preformed Donor-specific HLA Antibodies: A Japanese Nationwide Survey.

Background.The significance of preformed donor-specific anti-HLA antibodies (DSAs) in liver transplant recipients is controversial. Moreover, there has been no established desensitization protocol for DSA-positive recipients.Methods.A Japanese nationwide survey was performed to investigate the clinical practice among preformed DSA-positive patients with special reference to rituximab desensitization.Results.There was a total of 47 cases, including 2 pediatric cases, in which rituximab (287 ± 159 mg [319 (50–916)/m2]) was administered to desensitize preformed DSA. The decision for the indication of rituximab desensitization was based on a single-antigen assay in the majority of cases (83%, 39/47), and the most frequent protocol was rituximab monotherapy (n = 12) followed by quadruple treatment with rituximab tacrolimus, mycophenolate mofetil, and plasmapheresis (n = 11). The overall 1-, 3-, and 5-y graft and patient survival rates among adult patients were 85%, 83%, 83%, and 81%, 77%, 74%, respectively, while neither graft loss nor death was observed in the 2 pediatric cases. The 1-, 3-, and 12-mo cumulative incidence of antibody-mediated rejection (AMR) was 11%, 13%, and 13%, respectively. The incidence of AMR was significantly higher in the lower rituximab dose group than in the higher rituximab dose group (cutoff 300 mg/m2, 4% versus 24%, P = 0.041). The rate of infusion-related adverse drug reactions (ADRs) was 4.4%, and all ADRs were mild and self-limiting. A total of 99 ADRs among 27 patients were reported, none of which were severe adverse events associated with rituximab.Conclusions.The rituximab induction was well tolerated among DSA-positive liver transplant recipients with a satisfactory outcome. A rituximab dose >300 mg/m2 was observed to achieve less incidence of the development of AMR.

Exploring the causes of the high incidence of delayed graft function after kidney transplantation in Brazil: a multicenter study.

This retrospective multicenter (n=18) cohort study evaluated the incidence, risk factors, and the impact of delayed graft function (DGF) on 1-year kidney transplant (KT) outcomes. Of 3992 deceased donor KT performed in 2014-2015, the incidence of DGF was 54%, ranging from 29.9% to 87.7% among centers. Risk factors (lower-bound-95%CI OR upper-bound-95%CI ) were male gender (1.066 1.2491.463 ), diabetic kidney disease (1.053 1.2961.595 ), time on dialysis (1.005 1.0071.009 ), retransplantation (1.035 1.3971.885 ), preformed anti-HLA antibodies (1.011 1.3831.892 ), HLA mismatches (1.006 1.0661.130 ), donor age (1.011 1.0171.023 ), donor final serum creatinine (sCr) (1.239 1.3171.399 ), cold ischemia time (CIT) (1.031 1.0431.056 ), machine perfusion (0.401 0.5420.733 ), and induction therapy with rabbit antithymocyte globulin (rATG) (0.658 0.8000.973 ). Duration of DGF>4days was associated with inferior renal function and DGF>14days with the higher incidences of acute rejection, graft loss, and death. In conclusion, the incidence and duration of DGF were high and associated with inferior graft outcomes. While late referral and poor donor maintenance account for the high overall incidence of DGF, variability in donor and recipient selection, organ preservation method, and type of induction agent may account for the wide variation observed among transplant centers.

Donor-specific antibody and sensitized patients in intestinal transplantation.

It has been well established that antibody to donor HLA pretransplant and the development of anti-human leukocyte antigen (HLA) antibodies posttransplant contribute to inferior graft survival outcomes. This article serves to review the current status of the management of pretransplant sensitized intestinal transplant candidate as well as to review posttransplant care of patients that harbor antidonor HLA antibodies. The intestinal transplant candidate oftentimes presents for transplant listing with high levels of anti-HLA antibodies that necessitate a careful preoperative strategy to avoid a donor-recipient pair that would result in a positive crossmatch. In the end, donor intestine offer acceptance is based on a balance between recipient clinical needs and allowable immunologic risk tolerance. The use of virtual crossmatching (VXM) enables the transplant center to effectively gauge the immunologic risk of each potential donor-recipient pair far in advance of allocating resources toward pursuing a donor organ. In those candidates with high levels of preformed donor anti-HLA antibodies, desensitization with a novel technique of donor splenic perfusion has been described as well as a single-center experience with a conventional desensitizing protocol. Posttransplant, with the use of a denovo donor-specific antibody (dnDSA) monitoring and treatment protocol, the well known deleterious effects of dnDSA can potentially be ameliorated, thus improving outcome. Efforts to establish a formal histologic criteria for antibody-mediated rejection (ABMR) in the intestinal graft continues to evolve with recent findings describing the relationship between DSA and histopathologic findings. Techniques such as the use of VXM, novel desensitization methods and protocols, monitoring and eradicating dnDSA, along with establishing new criteria for ABMR have all contributed to improving the outcomes in transplanting the immunologically challenging intestine.

Böbrek Transplant Alıcılarında HLA Hassasiyetinin Greft Fonksiyonuna ve Hayatta Kalmaya Etkisi

Objective: Anti-human leukocyte antibodies (HLA) play an important role in graft survival, particularly in kidney transplantation. Preformed anti-HLA antibodies, especially donor specific antibodies can cause acute and chronic rejections. In this study, it was aimed to assess the effects of anti-HLA antibodies in kidney patients before transplant on graft function, failure, and patient survival. Methods: PRA (Panel Reactive Antibody) levels were monitored using bead based methods such as Luminex and flow cytometry. Post-transplant estimated glomerular filtration ratios (eGFR) among first, third, and fifth year patient survivals and graft failures were statistically analyzed. Results: In this study, it was observed that related transplants had low levels of PRAs, and their eGFRs were at normal reference range. The patients without acute rejection episode (ARE) had higher eGFR values than those with ARE. When five year-graft survival terms were evaluated, it was found that 65.6±9.8% and 86.5±3.2% graft survival terms were detected in anti-HLA Class I/II positive and negative patients, whereas 74.8±6.4% and 84.3 ±2.6% graft survival terms were observed in ARE positive and negative patients, respectively. eGFR value is a predictor of graft failure and patient survival. Our Cox regression analyses (HR=0.843, p=0.00) also supported this information. Conclusion: The study concluded that although the correlation between PRA positivity and graft survival were not significant, the shortest graft survival was observed in PRA positive patients in the whole cohort and ARE positive patients. The importance and requirement of pre- and post-transplant PRA tests continue.

The clinical utility of preformed C1q-binding donor-specific anti-HLA antibodies in kidney transplantation

The clinical utility of preformed C1q-binding donor-specific anti-HLA antibodies in kidney transplantation

Reassessment of the clinical impact of preformed donor-specific anti-HLA-Cw antibodies in kidney transplantation.

Anti-denatured HLA-Cw antibodies are highly prevalent, whereas anti-native HLA-Cw antibodies seem to lead to random flow cytometry crossmatch results. We aimed to reassess crossmatch prediction for anti-HLA-Cw using 2 types of single antigen flow beads (classical beads and beads with diminished expression of denatured HLA), and to compare the pathogenicity of preformed anti-denatured and anti-native HLA-Cw antibodies in kidney transplantation. We performed 135 crossmatches with sera reacting against donor HLA-Cw (classical beads fluorescence ≥500); only 20.6% were positive. Forty-three (31.6%) were anti-denatured HLA antibodies (beads with diminished expression of denatured HLA fluorescence <300); all were crossmatch negative. The correlation between classical beads fluorescence and the crossmatch ratio was low (ρ=0.178), and slightly higher with beads with diminished expression of denatured HLA (ρ=0.289). We studied 52 kidney recipients with preformed anti-HLA-Cw donor-specific antibodies. Those with anti-native HLA antibodies experienced more acute and chronic antibody-mediated rejections (P=.006 and .03, respectively), and displayed a lower graft survival (P=.04). Patients with anti-native HLA-Cw antibodies more frequently had previous sensitizing events (P<.000001) or plausibility of their antibody profile according to known anti-native HLA-Cw eplets (P=.0001). Anti-native but not anti-denatured HLA-Cw antibodies are deleterious, which underscores the need for reagents with diminished expression of denatured HLA.

Renal transplant patients with preformed anti-HLA antibodies: early biopsy findings and clinical outcomes.

Introduction:Renal fibrosis is the end point of a process that begins at transplant, with ischemia reperfusion and early inflammation, and progresses over time with immunological and non-immunological phenomena. Early identification of morphological markers and intervention could improve graft function and survival.Objective:to evaluate the correlation between intensity and specificity of pre-transplant anti-HLA antibodies and kidney allograft pathology in order to identify early risk factors or markers of allograft dysfunction.Methods:A retrospective cohort of kidney transplant recipients with pre-transplant anti-HLA antibodies who underwent graft biopsy within the first two years post-transplant was divided into two groups according to the specificity of anti-HLA antibodies: nonspecific (non-DSA, n = 29) and specific (DSA+, n = 16). Kidney graft pathology, renal function, and proteinuria were analyzed.Results:general characteristics were similar in both groups, except for the higher dose of thymoglobulin in DSA+ group (p < 0.05). The non-DSA group had higher scores for glomerulosclerosis, interstitial inflammation (i) and interstitial fibrosis (ci) (p < 0.05) and higher incidence of cell-mediated acute rejection. No statistical difference in incidence of antibody-mediated rejection, renal function, and proteinuria was observed during follow up.Discussion and conclusions:the difference in inflammation scores and interstitial fibrosis may be associated to the higher incidence of acute cell-mediated rejection and polyomavirus nephropathy in the Non-DSA group. We also should take into account the protective effect of higher doses of thymoglobulin, reducing ischemia reperfusion injury in the DSA+ group. The short follow-up might have been insufficient to detect long-term changes in allograft tissue, renal function, and proteinuria.

Characterization of the C1q-Binding Ability and the IgG1-4 Subclass Profile of Preformed Anti-HLA Antibodies by Solid-Phase Assays.

Humoral alloimmunity, particularly that triggered by preformed antibodies against human leukocyte antigens (HLA), is associated with an increased prevalence of rejection and reduced transplant survival. The high sensitivity of solid phase assays, based on microbeads coated with single antigens (SAB), consolidated them as the gold-standard method to characterize anti-HLA antibodies, ensuring a successful allograft allocation. Mean fluorescence intensity (MFI) provided by SAB is regularly used to stratify the immunological risk, assuming it as a reliable estimation of the antibody-level, but it is often limited by artifacts. Beyond MFI, other properties, such as the complement-binding ability or the IgG1-4 subclass profile have been examined to more accurately define the clinical relevance of antibodies and clarify their functional properties. However, there are still unresolved issues. Neat serum-samples from 20 highly-sensitized patients were analyzed by SAB-panIgG, SAB-IgG1-4 subclass and SAB-C1q assays. All 1:16 diluted serum-samples were additionally analyzed by SAB-panIgG and SAB-IgG1-4 subclass assays. A total of 1,285 anti-HLA antibodies were identified as positive, 473 (36.8%) of which were C1q-binding. As expected, serum-dilution enhanced the correlation between the C1q-binding ability and the antibody-strength, measured as the MFI (rneat = 0.248 vs. rdiluted = 0.817). SAB-subclass assay revealed at least one IgG1-4 subclass in 1,012 (78.8%) positive antibody-specificities. Among them, strong complement-binding subclasses, mainly IgG1, were particularly frequent (98.9%) and no differences were found between C1q- and non-C1q-binding antibodies regarding their presence (99.4 vs. 98.5%; p = 0.193). In contrast, weak or non-C1q-binding subclasses (IgG2/IgG4) were more commonly detected in C1q-binding antibodies (78.9 vs. 38.6%; p < 0.001). Interestingly, a strong association was found between the C1q-binding ability and the IgG1 strength (rIgG1dil = 0.796). Though lower, the correlation between the IgG2 strength and the C1q-binding ability was also strong (rIgG2dil = 0.758), being both subclasses closely related (rIgG1−IgG2 = 0.817). We did not find any correlation with the C1q-binding ability considering the remaining subclasses. In conclusion, we demonstrate that a particular profile of IgG subclasses (IgG1/IgG3) itself does not determine at all the ability to bind complement of anti-HLA antibodies assessed by SAB-C1q assay. It is the IgG subclass strength, mainly of IgG1, which usually appears in combination with IgG2, that best correlates with it.

Favorable Outcome of an Exclusively Posttransplant Prophylactic Strategy After Heart Transplantation in Recipients With High Immunological Risk.

Management of the increasing number of sensitized heart transplant candidates has become a recurrent issue. Rather than using pretransplant desensitization therapies, we used a posttransplant prophylactic strategy. Our aim was to describe outcomes in transplant recipients with preformed donor-specific anti-HLA antibodies (pfDSA) managed with this strategy. A posttransplant protocol was applied to patients transplanted with pfDSA, consisting of perioperative management of DSA (polyvalent immunoglobulins +/- perioperative plasmapheresis sessions, according to DSA level, as well as induction therapy) and systematic treatment of subsequent antibody-mediated rejection (AMR), even when subclinical. We performed a retrospective analysis of this prospective protocol. The study included all consecutive first recipients of a noncombined heart transplant performed between 2009 and 2015 at our center. The primary endpoint was all-cause mortality. Secondary endpoints included primary graft dysfunction, early posttransplant bleeding, rejection, and cardiac allograft vasculopathy-free survival. A total of 523 patients were studied, including 88 (17%) and 194 (37%) transplanted with DSA mean fluorescence intensity (MFI) of 500 to 1000 and greater than 1000, respectively. The median follow-up period was 4.06 years. Survival was not significantly different between groups. Rejection-free survival was worse in patients with pfDSA MFI >1000, evidenced by a fourfold increase in the risk of antibody-mediated rejection. The incidence of primary graft dysfunction and cardiac allograft vasculopathy-free survival did not significantly differ between groups. Perioperative plasmapheresis increased the risk for transfusion of packed red blood cells. This exclusively posttransplant prophylactic strategy achieved favorable outcomes in heart transplant recipients with pfDSA.

Late impact of preformed anti-HLA antibodies on kidney graft outcome

Late impact of preformed anti-HLA antibodies on kidney graft outcome