ELISpot assay and prediction of organ transplant rejection.

The ELISpot assay is a sensitive technique applied to assess cytokine-producing memory/effector T cells and human leukocyte antigens (HLA)-specific IgG-producing B cells. Besides the fact that the method is laborious and is difficult to standardise between laboratories, it may provide valuable information on the immune response of recipients before and after organ transplantation. In this article, we briefly review the recent literature and discuss the clinical significance of the ELISpot assay in predicting the risk and incidence of allograft rejection and survival.

De novo HLA Class II antibodies are associated with the development of chronic but not acute antibody-mediated rejection after liver transplantation - a retrospective study.

Donor-specific antibodies (DSA) cause antibody-mediated rejection (AMR); however, their pathogenic role has not yet been adequately investigated after liver transplantation. The aim of our study was to analyse the clinical significance of DSA and complement-binding DSA for the prediction of AMR after liver transplantation. Our cohort included 120 liver recipients with assessed protocol biopsies one year post-transplant. All patients had defined HLA-specific and complement-binding (C1q + and C3d+) antibodies before and in regular intervals after transplantation. The incidence of DSA was evaluated in relation with clinical and histopathological data in the liver allografts. A higher occurrence of acute AMR was observed in recipients with preformed complement-binding DSA to HLA Class I antigens. Patients who developed chronic AMR had more frequently de novo-produced antibodies against HLA Class II antigens (P = 0.0002). A correlation was also found between de novo-formed C1q + and C3d+-binding antibodies to HLA Class II antigens and the development of chronic AMR (P = 0.043). Our study implies that preformed complement-binding DSA to HLA Class I antigens are related to increased risk of acute antibody-mediated rejection, while chronic AMR is more frequent in patients with de novo-produced antibodies to HLA Class II antigens after liver transplantation.

Crossing borders to facilitate live donor kidney transplantation: the Czech-Austrian kidney paired donation program - a retrospective study.

Kidney paired donation (KPD) is a valuable tool to overcome immunological barriers in living donor transplantation. While small national registries encounter difficulties in finding compatible matches, multi-national KPD may be a useful strategy to facilitate transplantation. The Czech (Prague) and Austrian (Vienna) KPD programs, both initiated in 2011, were merged in 2015. A bi-national algorithm allowed for ABO- and low-level HLA antibody-incompatible exchanges, including the option of altruistic donor-initiated domino chains. Between 2011 and 2019, 222 recipients and their incompatible donors were registered. Of those, 95.7% (Prague) and 67.9% (Vienna) entered into KPD registries, and 81 patients received a transplant (95% 3-year graft survival). Inclusion of ABO-incompatible pairs in the Czech program contributed to higher KPD transplant rates (42.6% vs. 23.6% in Austria). After 2015 (11 bi-national match runs), the median pool size increased to 18 pairs, yielding 33 transplants (8 via cross-border exchanges). While matching rates doubled in Austria (from 9.1% to 18.8%), rates decreased in the Czech program, partly due to implementation of more stringent HLA antibody thresholds. Our results demonstrate the feasibility of merging small national KPD programs to increase pool sizes and may encourage the implementation of multi-national registries to expand the full potential of KPD.

The possible critical role of T-cell help in DSA-mediated graft loss.

In this review, we discuss a possible central role of T-cell help in severe forms of graft damage mediated by donor-specific HLA antibodies (DSA). Some kidney transplant recipients with pretransplant DSA show a high graft failure rate, whereas in other patients DSA do not harm the transplanted kidney and in most cases, disappear shortly after transplantation. Analyzing 80 desensitized highly immunized kidney transplant recipients and another multicenter cohort of 385 patients with pretransplant HLA antibodies, we reported recently that an ongoing T-cell help from an activated immune system, as measured by an increased level of soluble CD30 in serum, might be necessary for the DSA to exert a deleterious effect. Patients positive for both pretransplant DSA and sCD30 appear to require special measures, such as the elimination of DSA from the circulation, potent immunosuppression, good HLA-matching, and intense post-transplant monitoring, whereas exclusion of DSA-positive patients from transplantation in the absence of high sCD30 may not be justified in all cases, even if the pretransplant DSA are strong and complement-activating.

Molecular markers of systemic autoimmune disorders: the expression of MHC-located HSP70 genes is significantly associated with autoimmunity development.

OBJECTIVES: To analyse the expression regulation of two inducible HSP70 genes - HSPA1A and HSPA1B - located within the major histocompatibility complex (MHC) in patients with various systemic autoimmune diseases and to prove the reliability of MHC-located HSP70 genes as molecular markers reflecting the autoimmune process. METHODS: 94 adult patients with idiopathic inflammatory myopathy (IIM, n=31), systemic lupus erythematosus (SLE, n=31) or systemic sclerosis (SSc, n=32) and 37 healthy individuals were analysed. The mRNA expression level was determined using quantitative real-time PCR method. The expression of intracellular HSP70 was established by flow cytometry, the extracellular HSP70 protein was measured in plasma samples using a commercially available sandwich enzyme-linked immunosorbent assay (ELISA). RESULTS: The expression of HSPA1A gene was significantly up-regulated in patients with autoimmune diseases (SLE: p<0.01; SSc: p<0.01; IIM: p<0.0001) compared to healthy controls. The expression of HSPA1B gene was increased only in patients with myositis (p<0.05). Furthermore, the HSPA1B gene expression is associated with the HLA-DRB1*03 risk allele in patients with IIM. In addition, we have found a relation between HSPA1A gene expression regulation and the presence of disease specific autoantibodies in patients with SLE and myositis. The level of intracellular HSP70 was not increased; however, the level of extracellular HSP70 protein was increased in patients suffering from SSc and IIM as compared to controls. CONCLUSIONS: The results suggest an involvement of the MHC-linked HSP70 genes in the pathology of studied autoimmune disorders. Therefore, the HSPA1A and HSPA1B genes might serve as an interesting candidate molecule for development of distinct types of autoimmunities.

Novel insights into pretransplant allosensitization in heart transplant recipients in the contemporary era of immunosuppression and rejection surveillance.

Solid-phase assays (SPA) have facilitated detection and definition of antibodies to human leukocyte antigens (HLA) and major histocompatibility complex class I chain-related antigen A (MICA). However, clinical consequences of pretransplant SPA results in heart transplantation have been studied insufficiently in the current era of immunosuppression and rejection surveillance. Pretransplant sera, panel-reactive antibodies (PRA), pretransplant crossmatch, and clinical data were retrospectively analyzed in 264 adult heart transplant recipients. The specificity of HLA and MICA antibodies and C1q-binding activity of donor-specific antibodies (DSA) were defined using SPA. Pretransplant HLA antibodies were detected in 57 (22%) individuals, in 28 individuals (11%); these antibodies were DSA after transplant. Preformed DSA and elevated peak PRA were independent predictors of pathologic AMR, which occurred in 19 individuals (7%). The increasing number of DSA and the cumulative mean fluorescence intensity of DSA were associated with AMR. C1q-binding assay was a suboptimal predictor of AMR in our cohort. Pretransplant allosensitization and MICA antibodies were related neither to impaired graft survival nor to other adverse clinical events during a median follow-up of 39 months. Identification of preformed DSA by SPA, in addition to PRA monitoring, may predict AMR in the contemporary era of heart transplantation.

Safety and Immunogenicity of SARS-CoV-2 mRNA Vaccine Booster Doses in Kidney Transplant Recipients: Results of a 12-mo Follow-up From a Prospective Observational Study.

Background: Booster doses of SARS-CoV-2 mRNA vaccines are commonly used in kidney transplant recipients (KTRs). However, there is uncertainty regarding the waning of vaccination responses and immunological safety in KTRs. Methods: A total of 123 KTRs were included in the final analysis of this prospective observational cohort study. The aim was to evaluate the immunogenicity and immunological safety. SARS-CoV-2 antispike IgG antibodies and anti-HLA antibodies were measured at baseline and then at months 3, 6, and 12 after vaccination with the first booster dose (ie, the third vaccine dose). Antibodies against S1 and S2 subunits of SARS-CoV-2 were evaluated using an immunochemiluminescent assay (cutoff 9.5 AU/mL, sensitivity 91.2%, and specificity 90.2%). Anti-HLA antibodies were analyzed using single-antigen bead technology. Results: Seroconversion was reached in 65% of KTRs previously nonresponding to 2-dose mRNA vaccination; the overall seroconversion rate 3 mo after the first booster dose was 83%. Vaccination induced a durable humoral response, and the antibody levels were stable during the 12-mo study follow-up. Higher age (exponentiated beta coefficient [eß] 0.97; 95% confidence interval [CI], 0.943-0.997) and a full dose of mycophenolate (eß 0.296; 95% CI, 0.089-0.984) were negatively associated with SARS-CoV-2 IgG antibody levels, whereas better graft function (eß1.021; 95% CI, 1.005-1.037) was associated positively. There were no systematic signs of anti-HLA antibody development after vaccination. However, during the follow-up, there was a nonsignificant signal of an increase in anti-HLA antibodies in those who developed COVID-19. Conclusions: Additional booster doses of SARS-CoV-2 mRNA vaccines induce durable antibody response even in a large subset of previous nonresponders and are not associated with the risk of allosensitization. Furthermore, a signal linking COVID-19 to the development of anti-HLA antibodies was observed, and this should be confirmed and further examined (NCT05483725).

Effect of SARS-CoV-2 infection on anti-HLA antibodies and de novo donor specific antibodies incidence in lung transplant recipients.

PURPOSE: There are no clear guidelines on how to handle immunosuppression in lung transplant recipients (LTRs) infected by SARS-CoV-2. Antimetabolite reduction with corticosteroid escalation is the most frequent strategy. The aim of this study was to determine the effect of this therapeutic approach on the incidence of de novo donor specific-antibodies (dnDSA). METHODS: We retrospectively analysed a cohort of 27 LTRs diagnosed with SARS-CoV-2 infection between September 2020 and April 2021 with available anti-HLA antibodies screening before and after infection. Managed as per the centre's SARS-CoV-2 protocol, the treatment modalities included specific virostatic treatment, convalescent plasma administration, reduction or discontinuation of mycophenolate and transient corticosteroid escalation initiated in the second week post-infection. RESULTS: All 27 patients received virostatics: 15 (55.6%) remdesivir and 12 (44.4%) favipiravir. In addition, 18 patients (66.7%) underwent convalescent plasma therapy. Of the 27 patients, 25 (92.6%) received mycophenolate as a part of their maintenance immunosuppressive regimen, which was temporarily reduced in 10 (37%) and discontinued in 15 LTRs (55.6%), the median resumption times for mycophenolate daily doses of at least 1000 mg being 13 days (IQR 11.0-63.5) and 59 days (IQR 26.0-130.0), respectively. Corticosteroids were escalated in 25 patients (92.6%), of whom 9 (33.3%) received IV methylprednisolone (median 80 mg/day; IQR 80-187.5) and 16 (59.3%) had oral prednisone adjusted (median 20 mg/day; IQR 16.3-38.8). The median time to revert to the corticosteroid dosage of ≤20 mg/day was 42 days (IQR 36.0-87.0). Notably, no dnDSA were detected in any LTR between 1 and 9 months from the onset of the SARS-CoV-2 infection. CONCLUSION: Our findings suggest that antimetabolite cessation with a transient corticosteroid escalation is a safe therapeutic strategy regarding anti-HLA dynamics in SARS-CoV-2 infected LTRs.

MCPggaac haplotype is associated with poor graft survival in kidney transplant recipients with de novo thrombotic microangiopathy.

De novo thrombotic microangiopathy (TMA) is associated with poor kidney graft survival, and as we previously described, it is a recipient driven process with suspected genetic background. Direct Sanger sequencing was performed in 90 KTR with de novo TMA and 90 corresponding donors on selected regions in CFH, CD46, C3, and CFB genes that involve variations with a functional effect or confer a risk for aHUS. Additionally, 37 recipients of paired kidneys who did not develop TMA were analyzed for the MCPggaac haplotype. Three-years death-censored graft survival was assessed using Kaplan-Meier and Cox regression models. The distribution of haplotypes in all groups was in the Hardy-Weinberg equilibrium and there was no clustering of haplotypes in any group. In the TMA group, we found that MCPggaac haplotype carriers were at a significantly higher risk of graft loss compared to individuals with the wild-type genotype. Worse 3-year death-censored graft survival was associated with longer cold ischemia time (HR 1.20, 95% CI 1.06, 1.36) and recipients' MCPggaac haplotype (HR 3.83, 95% CI 1.42, 10.4) in the multivariable Cox regression model. There was no association between donor haplotypes and kidney graft survival. Similarly, there was no effect of the MCPggaac haplotype on 3-year graft survival in recipients of paired kidneys without de novo TMA. Kidney transplant recipients carrying the MCPggaac haplotype with de novo TMA are at an increased risk of premature graft loss. These patients might benefit from therapeutic strategies based on complement inhibition.

Intimal Arteritis and Microvascular Inflammation Are Associated With Inferior Kidney Graft Outcome, Regardless of Donor-Specific Antibodies.

Background: The prognostic role of intimal arteritis of kidney allografts in donor-specific antibody negative (DSA-) antibody-mediated rejection (ABMR) remains unclear. Methods: Seventy-two out of 881 patients who had undergone kidney transplantation from 2014 to 2017 exhibited intimal arteritis in biopsies performed during the first 12 months. In 26 DSA negative cases, the intimal arteritis was accompanied by tubulointerstitial inflammation as part of T cell-mediated vascular rejection (TCMRV, N = 26); intimal arteritis along with microvascular inflammation occurred in 29 DSA negative (ABMRV/DSA-) and 19 DSA positive cases (ABMRV, DSA+, N = 17). In 60 (83%) patients with intimal arteritis, the surveillance biopsies after antirejection therapy were performed. Hundred and two patients with non-vascular ABMR with DSA (ABMR/DSA+, N = 55) and without DSA (ABMR/DSA-, N = 47) served as controls. Time to transplant glomerulopathy (TG) and graft failure were the study endpoints. Results: Transplant glomerulopathy -free survival at 36 months was 100% in TCMRV, 85% in ABMR/DSA-, 65% in ABMRV/DSA-, 54% in ABMR/DSA+ and 31% in ABMRV/DSA+ (log rank p < 0.001). Death-censored graft survival at 36 months was 98% in ABMR/DSA-, 96% in TCMRV, 86% in ABMRV/DSA-, 79% in ABMR/DSA+, and 64% in ABMRV/DSA+ group (log rank p = 0.001). In surveillance biopsies, the resolution of rejection was found in 19 (90%) TCMRV, 14 (58%) ABMRV/DSA-, and only 4 (27%) ABMRV/DSA+ patients (p = 0.006). In the multivariable model, intimal arteritis as part of ABMR represented a significant risk for TG development (HR 2.1, 95% CI 1.2-3.8; p = 0.012) regardless of DSA status but not for graft failure at 36 months. Conclusions: Intimal arteritis as part of ABMR represented a risk for early development of TG regardless of the presence or absence of DSA. Intimal arteritis in DSA positive ABMR represented the high-risk phenotype.

Predictive Potential of Flow Cytometry Crossmatching in Deceased Donor Kidney Transplant Recipients Subjected to Peritransplant Desensitization.

Recipient sensitization is a major risk factor of antibody-mediated rejection (ABMR) and inferior graft survival. The predictive effect of solid-phase human leukocyte antigen antibody testing and flow cytometry crossmatch (FCXM) in the era of peritransplant desensitization remains poorly understood. This observational retrospective single-center study with 108 donor-specific antibody (DSA)-positive deceased donor kidney allograft recipients who had undergone peritransplant desensitization aimed to analyze variables affecting graft outcome. ABMR rates were highest among patients with positive pretransplant FCXM vs. FCXM-negative (76 vs. 18.7%, p < 0.001) and with donor-specific antibody mean fluorescence intensity (DSA MFI) > 5,000 vs. <5,000 (54.5 vs. 28%, p = 0.01) despite desensitization. In univariable Cox regression, FCXM positivity, retransplantation, recipient gender, immunodominant DSA MFI, DSA number, and peak panel reactive antibodies were found to be associated with ABMR occurrence. In multivariable Cox regression adjusted for desensitization treatment (AUC = 0.810), only FCXM positivity (HR = 4.6, p = 0.001) and DSA number (HR = 1.47, p = 0.039) remained significant. In conclusion, our data suggest that pretransplant FCXM and DSA number, but not DSA MFI, are independent predictors of ABMR in patients who received peritransplant desensitization.

Chronic Active Antibody-Mediated Rejection Is Associated With the Upregulation of Interstitial But Not Glomerular Transcripts.

Molecular assessment of renal allografts has already been suggested in antibody-mediated rejection (ABMR), but little is known about the gene transcript patterns in particular renal compartments. We used laser capture microdissection coupled with quantitative RT-PCR to distinguish the transcript patterns in the glomeruli and tubulointerstitium of kidney allografts in sensitized retransplant recipients at high risk of ABMR. The expressions of 13 genes were quantified in biopsies with acute active ABMR, chronic active ABMR, acute tubular necrosis (ATN), and normal findings. The transcripts were either compartment specific (TGFB1 in the glomeruli and HAVCR1 and IGHG1 in the tubulointerstitium), ABMR specific (GNLY), or follow-up specific (CXCL10 and CX3CR1). The transcriptional profiles of early acute ABMR shared similarities with ATN. The transcripts of CXCL10 and TGFB1 increased in the glomeruli in both acute ABMR and chronic active ABMR. Chronic active ABMR was associated with the upregulation of most genes (SH2D1B, CX3CR1, IGHG1, MS4A1, C5, CD46, and TGFB1) in the tubulointerstitium. In this study, we show distinct gene expression patterns in specific renal compartments reflecting cellular infiltration observed by conventional histology. In comparison with active ABMR, chronic active ABMR is associated with increased transcripts of tubulointerstitial origin.

A Europe wide acceptable mismatch program will enable transplantation of long waiting highly sensitised patients with a compatible donor.

Immunisation against Human Leucocyte Antigens (HLA) can be caused by pregnancy, blood transfusion, or organ transplants. The HLA antibody status of a given patient significantly influences their access and waiting time to transplant. For some highly sensitised patients (HSP) there is hardly any suitable donor available in the deceased donor pool of their allocation organisation and therefore they wait a very long time before being offered a kidney for transplant. Especially patients with rare HLA phenotypes in relation to the actual donor pool are waiting extremely long. As HLA phenotypes are different in the various European populations, we hypothesized that extension of the donor pool outside the respective allocation system will increase the chance of receiving a compatible transplant for this subgroup of highly sensitised patients. One of the objectives of the EUROSTAM project, (a Europe-wide Strategy to enhance Transplantation of highly sensitised patients on the basis of Acceptable HLA Mismatches) was to develop a tool to compare the chance of transplanting HSP in different European populations with donor organs from within and outside their own donor pool. Information on the HLA type and ABO blood group of the actual donor population, as well as the acceptable mismatches of long waiting HSP were obtained from the EUROSTAM partner organizations i.e. Eurotransplant (ET), UK National Health Service Blood and Transplant (NHSBT), Barcelona, Prague and Athens. Results from simulations using the newly developed tool shows that 195 (27%) of the 724 long waiting highly sensitised patients registered at each partner organisation have increased chances of transplant in a different European donor pool. This makes a strong case for sharing kidneys between European countries for selected difficult to transplant patients.

Donor specific anti-HLA antibodies and cardiac allograft vasculopathy: A prospective study using highly automated 3-D optical coherence tomography analysis.

INTRODUCTION: Recent studies suggested potential positive correlations between HLA-specific antibodies and development of cardiac allograft vasculopathy (CAV). METHODS: This prospective two-center study investigated early progression of CAV by coronary optical coherence tomography in 1 month and 12 months after heart transplantation (HTx) in 104 patients. Detection and characterization of donor specific (DSA) and MHC class-I polypeptide-related sequence A (MICA) antibodies were performed before, 1, 6 and 12 months after transplantation. RESULTS: During the first post-HTx year, we observed a significant reduction in the mean coronary luminal area (P < .001), and progression in mean intimal thickness (IT) (P < .001). DSA and anti-MICA occurred in 17% of all patients, but no significant relationship was observed between presence of DSA/anti-MICA and IT progression within 12 months after HTx. In contrast, we observed significant association between presence of DSA (p=0.031), de-novo DSA (p=0.031), HLA Class II DSA (p=0.017) and media thickness (MT) progression. CONCLUSION: Results of our study did not identify a direct association between presence of DSA/anti-MICA and intimal thickness progression in an early period after HTx. However, we found significant relationships between DSA and media thickness progression that may identify a newly recognized immune-pathological aspect of CAV.

Data and optimisation requirements for Kidney Exchange Programs.

Kidney Exchange Programs (KEP) are valuable tools to increase the options of living donor kidney transplantation for patients with end-stage kidney disease with an immunologically incompatible live donor. Maximising the benefits of a KEP requires an information system to manage data and to optimise transplants. The data input specifications of the systems that relate to key information on blood group and Human Leukocyte Antigen (HLA) types and HLA antibodies are crucial in order to maximise the number of identified matched pairs while minimising the risk of match failures due to unanticipated positive crossmatches. Based on a survey of eight national and one transnational kidney exchange program, we discuss data requirements for running a KEP. We note large variations in the data recorded by different KEPs, reflecting varying medical practices. Furthermore, we describe how the information system supports decision making throughout these kidney exchange programs.

Towards uniformity in the definition of acceptable mismatches for highly sensitized patients.

The Eurotransplant (The Eurotransplant International Foundation) acceptable mismatch programme has been shown to be a successful tool to enhance transplantation of highly sensitized patients(HSPs). However, patients with rare HLA phenotypes in relation to the Eurotransplant donor population remain on the waiting list. EUROSTAM is an European Union funded project to explore the feasibility of a Europe-wide acceptable mismatch programme enabling transplantation of HSPs with rare HLA phenotypes within their own organ exchange organization. The present study, which forms part of the EUROSTAM project, assesses the differences in the practices of the laboratories in different countries with respect to their HLA antibody profiling and risk adverseness. In the serum exchange exercises of 18 samples, a high level of variability has been shown in both assays and interpretation of results. In the data exchange exercise when all participants were given the same Luminex raw data for analysis, a high degree of consensus was reached where the median fluorescent intensity values of beads were <500 and >2000 for standard single antigen bead assays, or <500 and >5000 for assignment of acceptable mismatches. The risk adverseness analysis has showed distinct patterns of attitudes towards the perceived risks based on HLA antibody assay results, most probably influenced by the local protocols of the clinical transplant programme of each laboratory. In order to ensure fairness and maintain consistencies of organ exchange among partner transplant centres, a centralized facility will be instrumental for a uniform definition of acceptable mismatches.

Heterologous Cytomegalovirus and Allo-Reactivity by Shared T Cell Receptor Repertoire in Kidney Transplantation.

Cytomegalovirus (CMV) infection is associated with allograft rejection but the mechanisms behind are poorly defined yet. Although cross-reactivity of T cells to alloantigen and CMV has been hypothesized, direct evidence in patients is lacking. In this observational cohort study, we tested the pre-transplant effector/memory T cell response to CMV peptide pools and alloantigen in 78 living donor/recipient pairs using the interferon-gamma Enzyme-Linked ImmunoSpot (ELISPOT) assay. To prove the hypothesis of cross-reactivity, we analyzed by applying next-generation sequencing the T cell receptor ß (TCR- ß) repertoire of CMV- and alloantigen-reactive T cells enriched from peripheral pre-transplant blood of 11 CMV-seropositive and HLA class I mismatched patients. Moreover, the TCR-repertoire was also analyzed in the allograft biopsies of those patients. There was a significant association between the presence of pre-transplant CMV immediate-early protein 1 (IE-1)-specific effector/memory T cells and acute renal allograft rejection and function (p = 0.01). Most importantly, we revealed shared TCR-ß sequences between CMV-IE1 and donor alloantigen-reactive T cells in all pre-transplant peripheral blood samples analyzed in CMV-seropositive patients who received HLA class I mismatched grafts. Identical TCR sequences were also found in particular in post-transplant allograft biopsies of patients with concomitant CMV infection and rejection. Our data show the presence of functional, cross-reactive T cells and their clonotypes in peripheral blood and in kidney allograft tissue. It is therefore likely that CMV-donor cross-reactivity as well as CMV specific T cell elicited inflammation is involved in the processes that affect allograft outcomes.

Antibody-mediated rejection after liver transplantation-relevance of C1q and C3d-binding antibodies.

The aim of our study was to evaluate the relevance of complement-binding donor-specific antibodies (DSA) for prediction of antibody-mediated rejection (AMR) after liver transplantation. Sera from 123 liver transplant recipients were retrospectively defined for HLA specificity and complement-fixing activity using the single antigen beads, C1q and C3d techniques. Liver-recipients' sera were tested before transplantation, 3, 6 months and 1 year after transplantation. Patients were followed up for graft survival and rejection incidence for 1 year after transplantation. All patients with pretransplant complement-binding DSA developed severe AMR after transplantation, while three recipients out of four, who produced de novo complement-fixing DSA, developed AMR. Definition of DSA with respect to complement-fixing activity may provide clinically relevant information about the risk of AMR after liver transplantation.

Efficacy and safety of BORTEZOMIB treatment for refractory acute antibody-mediated rejection-a pilot study.

A novel therapeutic approach to refractory acute antibody-mediated rejection (AMR) in kidney transplant recipients was applied in 23 patients based on administration of Bortezomib, intravenous corticosteroids, plasmapheresis and Rituximab. Application of Bortezomib regimen led to diminishing of donor-specific antibodies (DSA) to HLA-B (P = 0.004) and HLA-DR (P = 0.0005), but not to HLA-A (P = 0.106) and HLA-DQ antigens (P = 0.18). Patients with good clinical response to treatment had significantly better allograft survival than recipients with continuing deterioration of graft function (P = 0.019). Graft survival after therapy of refractory AMR was significantly worse than survival after first transplantation and was comparable with outcomes after retransplantation. In conclusion, therapy with Bortezomib was well tolerated and effective in decreasing the levels of HLA-B and -DR antibodies, however, was not successful in depleting HLA-A and -DQ DSA.