Development Of Antibody-mediated Rejection Research Articles

HLA Mismatches Identified by a Novel Algorithm Predict Risk of Antibody-mediated Rejection From De Novo Donor-specific Antibodies.

The development of de novo donor-specific antibodies (dnDSA) and antibody-mediated rejection (AMR) remains a barrier to long-term graft and patient survival. Most dnDSA are directed against mismatched donor HLA-DQ antigens. Here, we describe a novel algorithm, which we have termed categorical amino acid mismatched epitope, to evaluate HLA-DQ mismatches. In this algorithm, amino acid residues of HLA-DQ protein were categorized into 4 groups based on their chemical characteristics. The likelihood of categorically mismatched peptides presented by the recipient's HLA-DRB1 was expressed as a normalized value, %Rank score. Categorical HLA-DQ mismatches were analyzed in 386 heart transplant recipients who were mismatched with their donors at the HLA-DQB1 locus. We found that the presence of DQB1 mismatches with %Rank score ≤1 was associated with the development of dnDSA (P = 0.002). Furthermore, dnDSA increased the risk of AMR only in recipients who had DQ mismatches with %Rank score ≤1 (hazard ratio = 5.8), but the freedom from AMR was comparable between recipients with dnDSA and those without dnDSA if %Rank scores of DQ mismatching were >1. These results suggest that HLA-DQ mismatches evaluated by the categorical amino acid mismatched epitope algorithm can stratify the risk of development of dnDSA and AMR in heart transplant recipients.

#2461 KIR-HLA-I genetic mismatch and the development of antibody-mediated rejection and microvascular inflammation after renal transplantation

Abstract Background and Aims Antibody-mediated rejection (ABMR) and microvascular inflammation (MVI) contribute to kidney transplant (KT) loss of function. The contribution of Natural Killer (NK) cells to the development of ABMR/MVI through inhibitory (iKIR) and activating (aKIR) HLA-I KIR (Killer-cell Immunoglobulin-like Receptors) has been proposed. The presence of an iKIR gene in the KT recipient (KTR) recognizing a self HLA-I ligand absent in the donor is defined as an iKIR-HLA-I mismatch (MM), and the presence of an aKIR gene in the KTR with HLA-I ligand in the graft absent in the KTR is defined as an aKIR-HLA-I MM. These MMs indicate the presence of potentially alloreactive NK cells that could contribute to the graft rejection, especially in the presence of NK receptor activating ligands or DSA. Our aim was to study the relationship between the number of KIR-HLA-I mismatches and ABMR/MVI. Method We selected 56 first KT, not treated with thymoglobulin or rituximab: 24 cases with ABMR/MVI and 32 controls without rejection in biopsies at 12-36 months. Donor and recipient HLA-I genotypes were determined by NGS, and recipient KIR genotypes by PCR-SSO (Luminex). The interactions considered were: KIR2DL1/HLA-C2, KIR2DL2&KIR2DL3/HLA-C1, KIR3DL1/HLA-Bw4, KIR3DL2/HLA-A*03, A*11, KIR2DS1/HLA-C2, KIR2DS2/HLA-C1, KIR3DS1/HLA-Bw4-I80 and KIR2DS4/HLA-A*11, C*02, C*04, C*05, C*16:01. Results KT recipients had a mean age of 54.55 years, 30.36% female and 8.92% living donor with no significant differences between ABMR/MVI and controls. The proportion of patients with ≥1 iKIR-HLA-I MM was higher in the ABMR/MVI group compared to controls (75% vs 56.25%, P = .1473), with a significant difference in the percentage of KIR3DL1 MM (29.17% vs 6.25%, P = .0296). The proportion of patients with at least one aKIR-HLA-I MM was non-significantly lower in ABMR/MVI compared to the control group (20.83% vs 28.13%, P = .5329). Overall, the proportion of KT recipients with ≥1 MM, either iKIR or aKIR, was 21% higher in the ABMR/MVI group (83.33% vs 68.75%, P = .2123). Conclusion In a population of immunologically low-risk KT recipients, we found a significantly greater proportion of patients with genetic iKIR-HLA-I MM in those with ABMR/MVI, but not of aKIR-HLA-I MM. NK cells with iKIR-HLA-I MM could contribute to antibody-mediated allograft damage together with other mechanisms.

Role of HLA matching and donor specific antibody development in long-term survival, acute rejection and cardiac allograft vasculopathy

Although there are different data supporting benefits of HLA matching in kidney transplantation, its role in heart transplantation is still unclear. HLA mismatch (MM) between donor and recipient can lead to the development of donor-specific antibodies (DSA) which produces negative events on the outcome of heart transplantation. Moreover, DSAs are involved in the development of antibody-mediated rejection (AMR) and are associated with an increase in cardiac allograft vasculopathy (CAV). In this study it is analyzed retrospectively the influence of HLA matching and anti-HLA antibodies on overall survival, AMR and CAV in heart transplantation. For this retrospective study are recruited heart transplanted patients at the Cardiac Transplantation Centre of Naples between 2000 and 2019. Among the 155 heart transplant patients, the mean number of HLA-A, B, -DR MM (0 to 6) between donor and recipient was 4.5 ± 1.1. The results show a negative association between MM HLA-DR and survival (p = 0.01). Comparison of patients with 0–1 MM at each locus to all others with 2 MM, for both HLA class I and class II, has not showed significant differences in the development of CAV. Our analysis detected DSA in 38.1% of patients. The production of de novo DSA reveals that there is not an influence on survival (p = 0.72) and/or AMR (p = 0.39). Instead, there is an association between the production of DSA class II and the probability of CAV development (p = 0.03). Mean fluorescence intensity (MFI) values were significantly higher in CAV-positive patients that CAV-negative patients (p = 0.02). Prospective studies are needed to evaluate HLA class II matching as an additional parameter for heart allocation, especially considering the increment of waiting list time.

Organizing pneumonia is associated with molecular allograft injury and the development of antibody-mediated rejection

The association between organizing pneumonia (OP) after lung transplantation with the development of acute rejection (AR) remains undefined. In addition, molecular allograft injury, as measured by donor-derived cell-free DNA (dd-cfDNA), during episodes of OP and its relationship to episodes of AR, chronic lung allograft dysfunction (CLAD), or death is unknown. This multicenter, prospective cohort study collected serial plasma samples from 188 lung transplant recipients for dd-cfDNA at the time of bronchoscopy with biopsy. Multivariable Cox regression was used to analyze the association between OP with the development of AR (antibody-mediated rejection (AMR) and acute cellular rejection (ACR)), CLAD, and death. Multivariable models were performed to test the association of dd-cfDNA at OP with the risk of AR, CLAD, or death. In multivariable analysis, OP was associated with increased risk of AMR (hazard ratio (HR)=2.26, 95% confidence interval (CI) 1.04-4.92, p=0.040) but not ACR (HR=1.29, 95% CI: 0.66-2.5, p=0.45) or the composite outcome of CLAD or death (HR=0.88, 95% CI, 0.47-1.65, p=0.69). Median levels of dd-cfDNA were higher in OP compared to stable controls (1.33% vs 0.43%, p=0.0006). Multivariable analysis demonstrated that levels of dd-cfDNA at diagnosis of OP were associated with increased risk of both AMR (HR=1.29, 95% CI 1.03-1.62, p=0.030) and death (HR=1.16, 95% CI, 1.02-1.31, p=0.026). OP is independently associated with an increased risk of AMR but not CLAD or death. The degree of molecular allograft injury at the diagnosis of OP may further predict the risk of AMR and death.

(1283) Covid-19 Associated Development of Antibody Mediated Rejection in Orthotopic Heart Transplantation Patients

(1283) Covid-19 Associated Development of Antibody Mediated Rejection in Orthotopic Heart Transplantation Patients

The human cytomegalovirus-specific and UL40-mediated imprint in the natural killer cell repertoire is associated with antibody-mediated rejection in lung transplant recipients.

CD16+ natural killer (NK-) cells play, together with donor-specific antibodies (DSA) and via antibody-dependent cellular cytotoxicity (ADCC), an important role in the pathogenesis of antibody-mediated rejection (ABMR) in lung-transplant recipients (LTRs). Cytotoxic CD16+NKG2C+ NK cells proliferate in response to human Cytomegalovirus (HCMV) infections via the presentation of HCMV-encoded and highly polymorphic UL40 peptides. In our study, we aimed to clarify whether infections with HCMV-strains carrying different UL40 peptide variants are associated with the shift of the NK cell repertoire and the development of ABMR in LTRs. We included 30 DSA+ABMR+, 30 DSA+ABMR- and 90 DSA-ABMR- LTRs. In all patients, 1 episode of high-level HCMV-replication occurred. In all DSA+ABMR+ LTRs, HCMV-replication occurred prior to ABMR diagnosis. The association of HCMV UL40 variants with the expansion of CD16+ NK cell subsets and ABMR was assessed in NK cell proliferation and ADCC assays. Our study revealed that the VMAPRTLIL and VMTPRTLVL UL40 variants were significantly overrepresented in DSA+ABMR+ LTRs. Both peptides were associated with a pronounced proliferation of cytotoxic and proinflammatory CD16+NKG2C+ NK cells. The stimulation with both peptides led to a shift of the NK cell repertoire towards CD16+NKG2C+ NK cells, which was associated with strong ADCC responses after stimulation with endothelial cells and plasma from DSA+ABMR+ LTRs. Distinct UL40 peptide variants of the infecting HCMV-strain are associated with the development of ABMR after lung transplantation, due to a shift towards a highly cytotoxic CD16+NKG2C+ NK cell population. These peptides are thus potential prognostic markers for ABMR.

Impact of Low-Level Donor-Specific Anti-HLA Antibody on Posttransplant Clinical Outcomes in Kidney Transplant Recipients.

The clinical significance of low-level donor-specific anti-HLA antibody (low-DSA) remains controversial. We investigated the impact of low-DSA on posttransplant clinical outcomes in kidney transplant (KT) recipients. We retrospectively reviewed 1,027 KT recipients, namely, 629 living donor KT (LDKT) recipients and 398 deceased donor KT (DDKT) recipients, in Seoul St. Mary's Hospital (Seoul, Korea) between 2010 and 2018. Low-DSA was defined as a positive anti-HLA-DSA result in the Luminex single antigen assay (LABScreen single antigen HLA class I - combi and class II - group 1 kits; One Lambda, Canoga Park, CA, USA) but a negative result in a crossmatch test. We compared the incidence of biopsy-proven allograft rejection (BPAR), changes in allograft function, allograft survival, patient survival, and posttransplant infections between subgroups according to pretransplant low-DSA. The incidence of overall BPAR and T cell-mediated rejection did not differ between the subgroups. However, antibody-mediated rejection (ABMR) developed more frequently in patients with low-DSA than in those without low-DSA in the total cohort and the LDKT and DDKT subgroups. In multivariate analysis, low-DSA was identified as a risk factor for ABMR development. Its impact was more pronounced in DDKT (odds ratio [OR]: 9.60, 95% confidence interval [CI]: 1.79-51.56) than in LDKT (OR: 3.76, 95% CI: 0.99-14.26) recipients. There were no significant differences in other outcomes according to pretransplant low-DSA. Pretransplant low-DSA has a significant impact on the development of ABMR, and more so in DDKT recipients than in LDKT recipients, but not on long-term outcomes.

Preemptive treatment of de novo donor-specific antibodies in lung transplant patients reduces subsequent risk of chronic lung allograft dysfunction or death

The development of donor-specific antibodies after lung transplantation is associated with downstream acute cellular rejection, antibody-mediated rejection (AMR), chronic lung allograft dysfunction (CLAD), or death. It is unknown whether preemptive (early) treatment of de novo donor-specific antibodies (dnDSAs), in the absence of clinical signs and symptoms of allograft dysfunction, reduces the risk of subsequent CLAD or death. We performed a multicenter, retrospective cohort study to determine if early treatment of dnDSAs in lung transplant patients reduces the risk of the composite endpoint of CLAD or death. In the cohort of 445 patients, 145 patients developed dnDSAs posttransplant. Thirty patients received early targeted treatment for dnDSAs in the absence of clinical signs and symptoms of AMR. Early treatment of dnDSAs was associated with a decreased risk of CLAD or death (hazard ratio, 0.36; 95% confidence interval, 0.17-0.76; P < .01). Deferring treatment until the development of clinical AMR was associated with an increased risk of CLAD or death (hazard ratio, 3.00; 95% confidence interval, 1.46-6.18; P < .01). This study suggests that early, preemptive treatment of donor-specific antibodies in lung transplant patients may reduce the subsequent risk of CLAD or death.

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.

Antibody-Mediated Rejection of the Lung in Patients with Short Telomeres

PurposeShort telomeres are associated with interstitial lung disease (ILD) and immune dysregulation. Prior studies have suggested that lung transplant recipients with short telomeres experience high rates of renal dysfunction, cytopenias, and infections and may have reduced survival and time to onset of chronic lung allograft dysfunction. It is unknown whether immune dysfunction related to short telomeres contributes to post-transplant complications such as antibody-mediated rejection (AMR). We investigated whether leukocyte telomere length (LTL) is a risk factor for developing AMR.MethodsThis is a single-center retrospective cohort study of 114 ILD patients who underwent lung transplantation between January 1, 2008 and December 31, 2017. Pre-transplant leukocyte telomere length (LTL) was measured using qPCR. Age-adjusted telomere length was calculated by comparing against a reference population, and dichotomized above and below the 10th percentile. Each patient underwent serial testing for donor-specific antibodies (DSA) and transbronchial biopsies per institutional protocol. AMR was graded according to the 2016 ISHLT consensus report and graded as definite and probable AMR. The acute cellular rejection (ACR) score was computed as the sum of the total numeric Grade A ACR in the follow up period. Multivariable logistic regression was used to assess potential predictors of AMR and included age, sex, ACR score, transplant type and LTL as covariates.ResultsThere were 35 (30.7%) patients with age-adjusted LTL < 10th percentile. DSA was positive in 67 (58.8%) patients. Definite and probable AMR occurred in 11 (9.6%) and 16 patients (14.0%), respectively. Development of AMR was not associated with LTL < 10th percentile (p=0.274). After adjustment, LTL < 10th percentile does not increase the odds of AMR (OR 0.70; 95% CI, 0.24-2.04; P=0.516). However, ACR score was associated with AMR (OR 1.25; 95% CI 1.04-1.51; P=0.020).ConclusionPre-transplant LTL < 10th percentile does not appear to be a risk factor for development of AMR. Short telomeres are associated with interstitial lung disease (ILD) and immune dysregulation. Prior studies have suggested that lung transplant recipients with short telomeres experience high rates of renal dysfunction, cytopenias, and infections and may have reduced survival and time to onset of chronic lung allograft dysfunction. It is unknown whether immune dysfunction related to short telomeres contributes to post-transplant complications such as antibody-mediated rejection (AMR). We investigated whether leukocyte telomere length (LTL) is a risk factor for developing AMR. This is a single-center retrospective cohort study of 114 ILD patients who underwent lung transplantation between January 1, 2008 and December 31, 2017. Pre-transplant leukocyte telomere length (LTL) was measured using qPCR. Age-adjusted telomere length was calculated by comparing against a reference population, and dichotomized above and below the 10th percentile. Each patient underwent serial testing for donor-specific antibodies (DSA) and transbronchial biopsies per institutional protocol. AMR was graded according to the 2016 ISHLT consensus report and graded as definite and probable AMR. The acute cellular rejection (ACR) score was computed as the sum of the total numeric Grade A ACR in the follow up period. Multivariable logistic regression was used to assess potential predictors of AMR and included age, sex, ACR score, transplant type and LTL as covariates. There were 35 (30.7%) patients with age-adjusted LTL < 10th percentile. DSA was positive in 67 (58.8%) patients. Definite and probable AMR occurred in 11 (9.6%) and 16 patients (14.0%), respectively. Development of AMR was not associated with LTL < 10th percentile (p=0.274). After adjustment, LTL < 10th percentile does not increase the odds of AMR (OR 0.70; 95% CI, 0.24-2.04; P=0.516). However, ACR score was associated with AMR (OR 1.25; 95% CI 1.04-1.51; P=0.020). Pre-transplant LTL < 10th percentile does not appear to be a risk factor for development of AMR.

A Diagnostic Biomarker Model Associated with Immune Infiltration in Patients with Antibody-Mediated Rejection after Kidney Transplantation

Background: In spite of advances in development and application of immunosuppressive agents, the long-term survival of grafts still needs to be advanced caused by antibody-mediated rejection (ABMR). Many researchers have paid attention to this area. However, little was known about the role of genes and immune cells in the development of ABMR. Methods: In total, 2533 biopsy cases from four different cohorts were collected. Three Gene Expression Omnibus (GEO) datasets (GSE36059, GSE98320 and GSE12403) were used as the training set, and one GEO dataset and twenty biopsy samples from our center were used for validation. The potential diagnostic prediction value of the signature and immune profiles were also explored. Findings: The LASSO regression model and PPI network were performed to search candidate biomarkers. LAPTM5, GBP2, CCL5 and KLRD1 were obtained as diagnostic biomarkers (AUC = 0·934, 95% CI 0·923-0·943). Immune cell infiltration analysis revealed that γδ T cells which could secrete IL-17A were most related with four biomarkers. The infiltration of γδ T cells and IL-17A were significantly higher in ABMR group than that in ST group. Interpretation: We have identified and established a diagnostic model containing four transcripts as diagnostic biomarkers of ABMR following kidney transplantation. Several types of immune cells were inferred to be involved in the process of ABMR. Among these, γδ T cells were most related with four biomarkers, which may promote ABMR by producing IL-17A. Funding: This work was supported by the National Natural Science Foundation of China [grant numbers 82070769, 81900684, 81870512, 81770751, 81570676, 81470981, 81100532], Project of Jiangsu Province for Important Medical Talent [grant number ZDRCA2016025], the “333 High Level Talents Project” in Jiangsu Province [grant numbers BRA2017532, BRA2016514, BRA2015469], the Standardized Diagnosis and Treatment Research Program of Key Diseases in Jiangsu Province [grant number BE2016791], the Open Project Program of Health Department of Jiangsu Province [grant number JSY-2-2016-099], Jiangsu Province Natural Science Foundation Program [grant number BK20191063]. Declaration of Interest: None to declare. Ethical Approval: This study was approved by the local ethics committee of the First Affiliated Hospital of Nanjing Medical University (2016-SR-029).

A Comprehensive Overview of the Clinical Relevance and Treatment Options for Antibody-mediated Rejection Associated With Non-HLA Antibodies.

Although solid organ transplant results have improved significantly in recent decades, a pivotal cause of impaired long-term outcome is the development of antibody-mediated rejection (AMR), a condition characterized by the presence of donor-specific antibodies to HLA or non-HLA antigens. Highly HLA-sensitized recipients are treated with desensitization protocols to rescue the transplantation. These and other therapies are also applied for the treatment of AMR. Therapeutic protocols include removal of antibodies, depletion of plasma and B cells, inhibition of the complement cascade, and suppression of the T-cell–dependent antibody response. As mounting evidence illustrates the importance of non-HLA antibodies in transplant outcome, there is a need to evaluate the efficacy of treatment protocols on non-HLA antibody levels and graft function. Many reviews have been recently published that provide an overview of the literature describing the association of non-HLA antibodies with rejection in transplantation, whereas an overview of the treatment options for non-HLA AMR is still lacking. In this review, we will therefore provide such an overview. Most reports showed positive effects of non-HLA antibody clearance on graft function. However, monitoring non-HLA antibody levels after treatment along with standardization of therapies is needed to optimally treat solid organ transplant recipients.

Abstract 13048: Do Anti-HLA Antibodies Pre-heart Transplant Truly Impact Post-transplant Outcomes?

Introduction: Antibody-mediated rejection (AMR) continues to be a major barrier to favorable long-term outcomes and long-term survival. Sensitized pre-heart transplant (HTx) patients, those with anti-HLA antibodies, have previously demonstrated increased post-HTx rejection risk as well as increased mortality. In the current era, there is contention as to whether pre-HTx antibodies result in poor outcome after HTx. Methods: Between 2010 and 2015, 580 HTx patients were assessed for pre-HTx panel reactive antibodies (PRA). PRA levels were measured by the Luminex Single Antigen assay. Patients were divided into 5 groups of PRA levels including 0%, n=423 (Control); PRA 1-10%, n= 21; PRA 11-25%, n=24; PRA 26-50%, n=49; PRA 51-75%, n=32; and PRA &gt;75%, n=35. Endpoints included 5-year survival, freedom from cardiac allograft vasculopathy (CAV), freedom from non-fatal major adverse cardiac events (NF-MACE), freedom from donor specific antibody (DSA) development, and freedom from LV dysfunction (LV ejection fraction ≤40%) and 1-year freedom from rejection (any treated rejection (ATR), acute cellular rejection (ACR), AMR). Results: All groups with PRA &gt;10% had significantly lower 1-year freedom from AMR and 5-year freedom from DSA compared to the control, worsening with higher the PRA group. There was no significant difference in 5-year survival, 5-year freedom from CAV, NF-MACE, or LV dysfunction and 1-year freedom from ATR or ACR. Conclusions: Patients with increased anti-HLA antibody levels pre-HTx do not appear to have lower 5-year survival compared to patients without anti-HLA antibody levels. However, the development of 1-year AMR and 5-year DSA increased progressively with higher the PRA group. Further studies and longer follow-up are needed to better understand the effects of elevated pre-HTx PRA, immune therapies (desensitization) and post-HTx outcomes.

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.

Is Anti-Thymocyte Globulin for Sensitized Patients Undergoing Heart Transplantation Effective?

Anti-thymocyte globulin (ATG) has been used as an induction agent in heart transplant (HTx). Early studies suggest that ATG can decrease de novo donor specific antibody (DSA) production after HTx. It has not been established as to the efficacy of ATG in various levels of sensitized pts undergoing HTx. Between 2010-18, we assessed 370 sensitized pts who were divided into panel reactive antibody (PRA) groups including a control group without sensitization but who received ATG: Group A: 0% (control); Group B: 1-25%; Group C: 26-50%; and Group D: >50%. Pts received ATG immediately post-transplant x5 days. Blood was drawn for antibody detection at baseline, 1, 3, 6, and 12 months after HTx. Groups were assessed for freedom from 1-year survival, rejection (any treated rejection (ATR), acute cellular rejection (ACR), and antibody mediated rejection (AMR)), freedom from non-fatal major adverse cardiac events (NF-MACE: myocardial infarction, percutaneous coronary intervention/angioplasty, new congestive heart failure, pacemaker/implantable cardioverter-defibrillator placement, and stroke), and freedom from cardiac allograft vasculopathy (CAV). Pts in Groups C and D had decreased freedom from DSA compared to the Control. Furthermore, there was lower freedom from AMR in pts in Group D compared to Control. There were no differences in outcome between each Group and the Control in 1-year survival, freedom from CAV, freedom from NF-MACE, freedom from any treated rejection, and freedom from ACR (see Table). ATG induction may be beneficial in sensitized patients with PRA under 50% but did not appear to decrease the development of AMR and DSA in those pts with PRA >50% compared to control. Larger studies and longer follow-up will need to be performed to assess ATG's impact on antibodies and the development of chronic rejection (CAV).

Early graft losses in paired kidney exchange: Experience from 10years of the National Kidney Registry.

Cooperative kidney paired donation (KPD) networks account for an increasing proportion of all living donor kidney transplants in the United States. There are sparse data on the rate of primary nonfunction (PNF) losses and their consequences within KPD networks. We studied National Kidney Registry (NKR) transplants (February 14, 2009 to December 31, 2017) and quantified PNF, graft loss within 30days of transplantation, and graft losses in the first-year posttransplant and assessed potential risk factors. Of 2364 transplants, there were 38 grafts (1.6%) lost within the first year, 13 (0.5%) with PNF. When compared to functioning grafts, there were no clinically significant differences in blood type compatibility, degree of HLA mismatch, number of veins/arteries, cold ischemia, and travel times. Of 13 PNF cases, 2 were due to early venous thrombosis, 2 to arterial thrombosis, and 2 to failure of desensitization and development of antibody-mediated rejection (AMR). Given the low rate of PNF, the NKR created a policy to allocate chain-end kidneys to recipients with PNF following event review and attributable to surgical issues of donor nephrectomy. It is expected that demonstration of low incidence of poor early graft outcomes and the presence of a "safety net" would further encourage program participation in national KPD.

Exploring pre-surgery donor-specific antibodies in the context of organ shortage in liver transplant.

There is a growing disparity between the number of liver transplant (LT) candidates and availability of suitable liver allografts. Antibody-mediated rejection (AMR), secondary to positive donor-specific antibodies (DSA), remains a concern in liver transplantation. This study aimed to correlate expression of DSA on pre-transplant screening and outcomes of LT, specifically development of AMR in liver allografts and liver function profile in the post-operative period. Data of consecutive patients undergoing orthotopic LT (OLT) at the South Australian Liver Transplant Unit was analysed. All patients underwent DSA testing pre-transplant. Within a cohort of 96 patients, over a post-OLT median follow-up of 849 days, only 2 patients (2%) developed AMR. While both patients had a positive DSA test preoperatively, overall DSA positivity was noted in 31% patients, with a specificity for prediction of AMR of 0.708. No significant association was noted between AMR (p = 0.092), T cell-mediated rejection/TCMR (p = 0.797) or late hepatic artery thrombosis/LHAT (p = 0.521). There was no significant interaction effect between DSA positivity and serum bilirubin or transaminases over a period of 100 days. AMR following LT is uncommon. A positive DSA pre-transplant does not imply a definite risk of AMR. Also, there does not exist a significant interaction in time between DSA expression and serum bilirubin or transaminase levels. Until there emerges evidence to the contrary, it appears reasonable to consider DSA-positive donors within the broad context of marginal donors in the context of a worldwide shortage of LT donor allografts.

Circulating B Cells With Memory and Antibody-Secreting Phenotypes Are Detectable in Pediatric Kidney Transplant Recipients Before the Development of Antibody-Mediated Rejection.

We used time-of-flight mass cytometry to analyze prospectively collected peripheral blood mononuclear cells (PBMC) from pediatric kidney transplant recipients who developed DSA (DSA-positive recipients [DSAPOS], n = 10). PBMC were obtained at 2 months posttransplant, 3 months before DSA development, and at DSA detection. PBMC collected at the same time points posttransplant from recipients who did not develop DSA (DSA-negative recipients [DSANEG], n = 11) were used as controls. DSAPOS and DSANEG recipients had similar baseline characteristics and comparable frequencies of total B and T cells. Within DSAPOS recipients, there was no difference in DSA levels (mean fluorescence intensity [MFI]: 13 687 ± 4159 vs 11 375 ± 1894 in DSAPOSAMR-positive recipients (AMRPOS) vs DSAPOSAMR-negative recipients (AMRNEG), respectively; P = 0.630), C1q binding (5 DSAPOSAMRPOS [100%] vs 4 DSAPOSAMRNEG [80%]; P = 1.000), or C3d binding (3 DSAPOSAMRPOS [60%] vs 1 DSAPOSAMRNEG [20%]; P = 0.520) between patients who developed AMR and those who did not. However, DSAPOS patients who developed AMR (n = 5; 18.0 ± 3.6 mo post-DSA detection) had increased B cells with antibody-secreting (IgD-CD27+CD38+; P = 0.002) and memory (IgD-CD27+CD38-; P = 0.003) phenotypes compared with DSANEG and DSAPOSAMRNEG recipients at DSA detection. Despite the small sample size, our comprehensive phenotypic analyses show that circulating B cells with memory and antibody-secreting phenotypes are present at DSA onset, >1 year before biopsy-proven AMR in pediatric kidney transplant recipients.

What Stimulates the Development of De Novo Donor Specific Antibodies in Cardiac Transplant Recipients?

Introduction The formation of de novo donor specific antibodies (dDSAs) has been implicated in the development of antibody-mediated rejection (AMR) and coronary allograft vasculopathy (CAV) after cardiac transplantation. dDSAs can develop at any time following transplantation and are associated with a poor prognosis, but the reason dDSAs develop after the initial injury of the transplant surgery is unknown. Since the detection of dDSAs often triggers the use of potentially toxic therapies to reduce these antibodies, it is important to understand whether dDSAs are a mediator of poor outcomes or a marker of a harmful underlying process. Hypothesis In some cases, the development of dDSAs is precipitated by the development of CAV or other myocardial injury which can expose myocardial cell epitopes. Methods We reviewed the medical record of 217 patients followed at our institution who underwent heart transplantation between 2014 and 2017, were not desensitized prior to transplant and did not have pre-transplant donor specific antibodies. Of these, we identified 36 patients with dDSAs, 16 of whom did not develop dDSAs until ≥ 6 months post-transplant, as detected by the modern bead-based multiplex assay on routine measurement every 3 months. Results Major findings are shown in Figure 1. In 10 of 16 patients with dDSAs but without evidence of AMR, CAV diagnosis or significant elevation in BNP suggestive of myocardial injury preceded dDSA development. Conclusions These findings suggest that CAV or other myocardial injury may precede the development of dDSAs in some cardiac transplant recipients and would explain why dDSAs signal a poor prognosis. These findings may shift the therapeutic focus from direct suppression of dDSAs to earlier detection, prevention and therapy of CAV or other injury that may trigger these antibodies' delayed appearance.

AGT haplotype in ITGA4 gene is related to antibody-mediated rejection in heart transplant patients.

IntroductionOne of the main problems involved in heart transplantation (HT) is antibody-mediated rejection (AMR). Many aspects of AMR are still unresolved, including its etiology, diagnosis and treatment. In this project, we hypothesize that variants in genes involved in B-cell biology in HT patients can yield diagnostic and prognostic information about AMR.MethodsGenetic variants in 61 genes related to B-cell biology were analyzed by next generation sequencing in 46 HT patients, 23 with and 23 without AMR.ResultsWe identified 3 single nucleotide polymorphisms in ITGA4 gene (c.1845G>A, c.2633A>G, and c.2883C>T) that conformed the haplotype AGT-ITGA4. This haplotype is associated with the development of AMR. Moreover, AMR patients with the haplotype AGT-ITGA4 present lower levels of integrin α-4 in serum samples compared to the reference GAC haplotype in control patients.ConclusionWe can conclude that polymorphisms in genes related to the biology of B-cells could have an important role in the development of AMR. In fact, the AGT haplotype in ITGA4 gene could potentially increase the risk of AMR.