Evidence Of Antibody-mediated Rejection Research Articles

Heart transplantation and anti-HLA antibodY: myocardial dysfunction and prognosis - HeartLAy study.

The presence of anti-human leucocyte antigen (HLA) antibodies has been implicated in a higher incidence of complications as well as mortality rate in heart transplantation. The aim of the study was to identify through non-invasive parameters early signs of myocardial dysfunction in the presence of anti-HLA antibodies but without evidence of antibody-mediated rejection (AMR) and its possible prognostic impact. A total of 113 heart-transplanted patients without acute cellular rejection (ACR) and AMR or cardiac allograft vasculopathy (CAV) were prospectively enrolled and divided into two groups ['HLA+' (50 patients) and 'HLA-' (63 patients)], based on the presence of anti-HLA antibodies. Each patient was followed for 2years after the enrolment, recording episodes of AMR, ACR, CAV, and mortality. Clinical characteristics were similar between the two groups. Among laboratory data, N-terminal pro-B-type natriuretic peptide and high-sensitivity cardiac troponin values were significantly higher in the presence of anti-HLA antibodies (P<0.001 and P=0.003, respectively). The echocardiographic parameters that showed a statistically significant difference between the two groups were deceleration time of E wave (DecT E, P<0.001), left ventricular global longitudinal strain (P<0.001), tricuspid annular plane systolic excursion (P=0.011), tricuspid S' wave (P=0.002), and free wall right ventricular longitudinal strain (fwRVLS, P=0.027), whereas left atrial strain did not differ significantly (P=0.408). Univariate analysis showed that anti-HLA antibodies were associated with the development of CAV at both 1 and 2year follow-up [odds ratio (OR) 11.90, 95% confidence interval (CI) 1.43-90.79, P=0.022 and OR 3.37, 95% CI 1.78-9.67, P=0.024, respectively]. Bivariate analysis demonstrated that both fwRVLS and DecT E were predictors of CAV development independently from HLA status. The presence of circulating anti-HLA antibodies is correlated with a mild cardiac dysfunction, even in the absence of AMR, and CAV development. Interestingly, reduced values of DecT E and fwRVLS were predictors of future development of CAV, independently from anti-HLA antibody.

Treatment of De Novo DSA with IVIG Monotherapy After Lung Transplantation

<h3>Purpose</h3> The development of de novo donor-specific anti-HLA antibodies (DSA) is associated with worse outcomes in lung transplant recipients (LTxR). The purpose of this study is to evaluate IVIG monotherapy for de novo DSA in the absence of allograft dysfunction or clinical antibody-mediated rejection (AMR). <h3>Methods</h3> Adult LTxR between 2/2013 and 3/2021 treated with IVIG monotherapy for de novo DSA with no evidence of AMR were included. IVIG was initiated at 2g/kg followed by 1g/kg monthly for a minimum of 3 months or until clearance (up to 6 months). HLA Ab is routinely checked by Luminex SAB post-transplant at day 14, months 1, 3, 6, 9, 12, and 18, and monthly during IVIG treatment. Primary outcome was change in DSA after IVIG therapy. DSA clearance was defined as sum MFI less than 1000. <h3>Results</h3> 32 LTxR developed de novo DSA at a median of 33 days (18,143) post-transplant and were treated with IVIG. Mean follow-up time was 1330 days (861-1910). The median sum MFI for DSA at baseline was 4782 (2927,7490). DQ was the immunodominant DSA in 24 (75%) and only 2 (6%) patients had isolated class I DSA. MFI of sum DSA decreased by a median of 2993 (2051, 6358) after IVIG therapy; p < 0.0001. Eighteen (56%) cleared de novo DSA (Group 1) versus 14 (44%) did not clear (Group 2) at the end of IVIG therapy. There was no significant difference in age, gender, race, transplant indication or type, cPRA, HLA mismatch, or PGD. ACR and AMR tended to be more frequent in Group 2; ACR: 92.9% vs 61.1%, p=0.053; and AMR: 35.7% vs 5.6%, p=0.063. Overall survival for the entire cohort at 1, 3 and 5 years was 100%, 86%, 60%, respectively. There was no significant difference in chronic lung allograft dysfunction (CLAD) or survival between Groups (Table 1). <h3>Conclusion</h3> In LTxR, IVIG monotherapy is associated with significant reduction in de novo DSA. DSA clearance may result in less acute rejection. Randomized controlled trials are needed to determine the optimal strategy for managing de novo DSA.

ABO-Incompatible Living Donor Liver Transplantation with Reduced Rituximab Dose: A Retrospective Analysis of 65 Patients - Can We Fast-Track Liver Transplant Surgery and Improve Long-Term Survival?

BackgroundABO-incompatible (ABO-i) living donor liver transplantation (LDLT) is a feasible alternative for donor liver allograft in emergency situations, especially in Asia, where deceased-donor organs remain scarce. The reported outcomes of ABO-i LDLT after optimal desensitization are comparable to those of ABO-compatible LDLT. In this retrospective study, we found improved outcomes after ABO-i LDLT with a low-dose rituximab in combination with double-filtration plasmapheresis (DFPP) and prophylactic antibiotic therapy.Material/MethodsBetween January 2006 and December 2018, a total of 65 recipients underwent ABO-i LDLT surgeries at our center. The study cohort consisted of 50 recipients (Era III) who underwent ABO-i LDLT using the recently updated desensitization protocol, which included rituximab 200 mg intravenous injection once a week prior to LDLT, 4 sessions of DFPP in all patients, and prophylactic antibiotics for 3 months.ResultsThe 3-year overall survival rate achieved in ABO-i LDLT patients was 72.7% (66.6% for Era I and 33.3% for Era II patients). In the study population, 11 patients developed complications due to infection. Five of these patients (10%) died due to overwhelming sepsis. Four patients (8%) were diagnosed with multiple strictures and diffusely scattered dilatation of intrahepatic bile ducts on computed tomography, without vascular complications. Three of them had evidence of antibody-mediated rejection (AMR).ConclusionsOur experience shows that the ABO-i LDLT protocol of lowered rituximab combined with pre-transplant sessions of plasmapheresis and a quadruple immunosuppressive regimen can be effective in chronic liver failure patients with clinical urgency in the absence of an ABO-compatible donor. Fast-tracking the use of ABO-i LDLT is feasible in patients with an acute liver failure (ALF) and can safely increase the donor liver pool, with an acceptable outcome.

Complement Component C4d Deposition in the Placenta of Preeclampsia Patients and Renal Glomeruli in 1 Postpartum Renal Biopsy.

The classic disorder of placental malperfusion is preeclampsia (PE), in which the kidney is also a target organ, leading to renal dysfunction. Although the precise pathogenesis of PE is unknown, increasing evidence suggests that PE is associated with complement dysregulation. The maternal immune response to an allogenic fetus and excessive activation of the complement system may both be involved in the pathogenesis of PE. C4d deposition is considered to be evidence of antibody-mediated rejection in an allograft. This study investigated a correlation between C4d expression in the placenta and clinicopathologic features of PE patients. Immunohistochemical staining for C4d was performed on placental tissue of PE patients (n=70) and normal pregnancy patients (n=30). Clinicopathologic features, such as maternal age and parity, placental weight, proteinuria, and histologic features of the placenta were evaluated. One PE patient who suffered from proteinuria after delivery received a renal biopsy. C4d expression was demonstrated in syncytiotrophoblast of chorionic villi. The expression of C4d was significantly more frequent in the placenta with PE (50%) than in the placenta lacking complications (14.3%) (P=0.001). C4d expression was significantly accompanied by increased syncytial knots in PE (P=0.045). Among PE patients, C4d expression was significantly correlated with low placental weight (P=0.001) and high proteinuria (P=0.018, Mann-Whitney U test). Renal biopsy of a PE patient after delivery also showed deposition of C4d along the glomerular capillary walls. C4d may play an important role in placental tissue injury and in renal complications in PE.

The Importance of Non-HLA Antibodies After Heart Transplant

Antibodies to human leukocyte antigens (HLA) are associated with adverse patient and allograft outcomes after heart transplantation. Non-HLA antibodies have increasingly been recognized as important mediators of rejection, cardiac allograft vasculopathy (CAV), and allograft injury. In particular, these antibodies have been implicated in a subset of heart transplant recipients who have clinical and/or pathologic evidence of antibody-mediated rejection in the absence of detectable antibodies against HLA. Non-HLA antigens have been identified to have important roles in both the innate and adaptive immune response in transplantation. These antigens are predominantly expressed on vascular endothelium of the donor heart and include major histocompatibility class I related chain A (MICA), G protein coupled receptor angiotensin II type 1 receptor (AT1R), cytoskeletal elements such as myosin and vimentin. A growing number of studies have demonstrated antibodies to these antigens in rejection and development of CAV. At present, non-HLA antibodies are not routinely monitored post-transplant, and laboratory evaluation remains non-standardized. Further investigation is required to improve the detection of non-HLA antibodies, define pathophysiological mechanisms involved in allograft injury, and better understand their impact on clinical outcomes. Non-HLA antibodies have been identified as important mediators of rejection, allograft dysfunction, and CAV in heart transplantation. Ongoing investigations and improving laboratory detection methods will determine their potential role in post-transplant risk stratification and management.

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.

Antibody-mediated rejection 16 years post-cardiac transplantation: a case report of an uncommon late presentation in a middle-aged woman.

Background Very late antibody-mediated rejection (AMR) in heart transplant patients (over 10 years post-transplant) is very rare. It is associated with high mortality, graft dysfunction, and fulminant coronary artery vasculopathy (CAV) and should remain in the differential for patients presenting with late graft dysfunction.Case summary A 57-year-old woman 16 years of post-heart transplant with a previously unremarkable post-transplant course including protocol driven biopsies showing no rejection and a recent unremarkable screening nuclear stress test presented to our institution with clinical heart failure. Echocardiogram revealed graft dysfunction and endomyocardial biopsy showed no signs of cellular rejection, but evidence of AMR. The patient was treated with steroid and immunotherapy with clinical improvement but suffered several infectious complications and renal dysfunction requiring haemodialysis related to her immunotherapy treatment. Despite aggressive AMR management, donor-specific antibodies and symptoms persisted and CAV progressed.Discussion This case illustrates the poor diagnostic yield of non-invasive testing for AMR, and highlights importance to clinicians of considering AMR even if the patient over 10 years post-transplant when the diagnosis is rare.

P040 Post-transplant De-novo donor specific antibody to HLA-B8, of unknown clinical significance

Clinical History: A 62 year-old male with chronic glomerulonephritis underwent kidney transplant from a donation after cardiac death donor in Jan 2017. Cold ischemia time was 8 h. The recipient had no donor specific antibody detected in any pretransplant sera tested since 2012. Flow-cytometric crossmatch (FCXM) was negative with the day of transplant sample. He received induction with Thymoglobulin, methylprednisolone, mycophenolate mofetil, and tacrolimus. Post-op day (POD)#1 creatinine was 7.90 mg/dl. He experienced delayed graft function, but otherwise no complications. He was discharged on POD#7 with a creatinine of 2.82 mg/dl. On POD#8 his creatinine was 1.7 mg/dl. De novo HLA-B8 antibody (14,365 MFI) was detected on a Thymo-absorbed and heat inactivated sample from the same day. The patient began therapeutic plasma exchange (TPE) and IVIG treatments on an every other day schedule. The kidney biopsy showed no evidence of antibody-mediated rejection. The Anti-HLA-B8 levels decreased to ∼ 2,000MFI. To understand the nature of this antibody, the FCXM was repeated using the POD#8 sample and was negative (T cell channel shift = 36 and B cell = 65). Therefore TPE/IVIG was stopped after 2 cycles. An incidental cavitary lesion was identified in the mid lobe of his right lung post-transplant. Quantiferon gold test was intermediate positive, but AFB culture was negative. 15 months post transplant, he continues to have HLA-B8 antibody 1500–3000 MFI, a stable creatinine ∼ 1.2 mg/dl, no proteinuria, and protocol biopsy in March 2018 showed no evidence of rejection. Discussion: The single antigen bead (SAB) assay is a very sensitive and specific antibody assay. During the manufacturing process, HLA antigens can become denatured and unfolded. This artificial unfolding allows for unmasking of cryptic epitopes on the recombinant HLA antigens. These cryptic epitopes may cross-react with epitopes found in microorganisms or allergens and may generate antibodies that react with denatured HLA proteins. False positive SAB assay may lead to unnecessary procedures in patients, and may limit patients’ to access to organ transplantation. Therefore, it is of utmost importance to recognize these artifacts and when possible utilize different platforms of testing to confirm the presence of artifactually denatured antibodies.

Glomerulocapillary miRNA response to HLA-class I antibody in vitro and in vivo

Changes in miRNA expression of glomerular capillaries during antibody-mediated rejection (ABMR) are poorly understood and could contribute to the deleterious inflammation and fibrosis of ABMR via suppression of target genes. A better understanding could lead to novel diagnostic tools and reveal novel therapeutic targets. We explored deregulated miRNAs in an glomeruloendothelial in vitro model of ABMR due to class I human leukocyte antigen (HLA) with and without complement activation. We studied a set of 16 promising candidate miRNAs in microdissected glomeruli a confirmation set of 20 human transplant biopsies (DSA+) compared to 10 matched controls without evidence for ABMR. Twelve out of these 16 glomerulocapillary miRNAs could successfully be confirmed as dysregulated in vivo with 10 upregulated (let-7c-5p, miR-28-3p, miR-30d-5p, miR-99b-5p, miR-125a-5p, miR-195-5p, miR-374b-3p, miR-484, miR-501-3p, miR-520e) and 2 downregulated (miR29b-3p, miR-885-5p) in DSA+ vs. controls. A random forest analysis based on glomerular miRNAs identified 18/20 DSA+ and 8/10 controls correctly. This glomerulocapillary miRNA signature associated with HLA class I-DSA could improve our understanding of ABMR and be useful for diagnostic or therapeutic purposes.

Baseline anti-blood group antibody titers and their response to desensitization and kidney transplantation

In recent years, immunological barriers historically considered as absolute contraindications to transplantation are being reevaluated. One such barrier is the ABO blood group incompatibility. With better understanding of immunological mechanisms and effective various regimens for controlling it, ABO-incompatible (ABO-I) kidney transplantation is now being performed with increasing frequency. For good outcome, most important is to achieve and maintain low anti-blood group antibody titers (ABGATs). Twenty-two patients with ABO-I donors have been studied. The anti-A and anti-B antibody titers (IgG and IgM) were estimated by column agglutination technology using Automated Ortho BioVue System. For desensitization, pretransplant plasmapheresis and/or immunoadsorption and rituximab were used. ABGAT was determined before transplant and periodically after transplant. It was observed that one-third of the patients have low baseline ABGAT. In these cases with low ABGAT, transplant can be performed without any desensitization. In those with titers <1:256, rituximab (two doses of 200 mg weekly) and 3–6 sessions of plasmapheresis can bring down titers to <1:32. In those with titers >1:256, immunoadsorption may be used from the beginning to reduce ABGAT. After transplant, the titers drop to <1:8 in majority. Rise in titers to >1:64 require close observation and biopsy. If there is evidence of antibody-mediated rejection, treatment should be promptly started. Rise in titers 4–6 weeks after transplant is not associated with any graft dysfunction, and hence not of any clinical significance.

Borderline rejection in ABO-incompatible kidney transplantation.

The clinical results of ABO-incompatible (ABOi) and ABO-compatible (ABOc) kidney transplantation (KT) are similar. Protocol kidney biopsies (PKB) of ABOi transplant recipients show positivity for C4d without evidence of antibody-mediated rejection (ABMR), but little is known about the histologic progression. We evaluated histologic parameters in PKB at 12months and also compared clinical outcome at 1year. This is a prospective observational study conducted between 2009 and 2013. We performed 146/30 ABOc/ABOi consecutive living-donor KT with PKB as well as additional indication biopsies. In the ABOi group, the desensitization protocol consisted of rituximab, plasma exchange or immunoadsorption, and immunoglobulins. In indication biopsies during the first year, T-cell-mediated rejection Banff ≥immunoadsorption was 8.2% vs 6.7% (P=.561) and ABMR 4.8% vs 13.3% (P=.095). At 1year, PKB (ABOc/ABOi) showed differences in borderline rejection lesions (6.8% vs 23.3% [P=.012]) and in C4d positivity in the ABOi group (P=.001). Interstitial fibrosis and tubular atrophy (IFTA) lesions (ABOc/ABOi) were 68.4% vs 63.2% (P=.348). Transplant glomerulopathy was 0.7% vs 3.3% (P=.373) at 1year. Our PKB ABOi series shows at 1year more borderline lesions independent of ABO titers, HLA incompatibility, and the presence of antidonor antibody, but do not show more IFTA nor transplant glomerulopathy. No clinical differences were observed between ABOi and ABO transplants.

Acute Cellular Rejection and C4d Positivity in Heart Transplantation : A Manifestation of Asymptomatic Antibody-Mediated Rejection?

The role of routine C4d staining in endomyocardial biopsy specimens is uncertain. The implications of a diagnosis of acute cellular rejection (ACR) with a positive C4d with or without any evidence of antibody-mediated rejection (AMR) are unclear. This study sought to evaluate a distinct phenotype of ACR+/C4d+ in AMR- patients. Data on C4d, ACR, and AMR were collected. Donor-specific antibody (DSA), panel-reactive antibody (PRA), flow crossmatch, and data on ACR and AMR episodes were also reviewed. Thirty-five patients were followed. Group I with C4d+ biopsy specimens was compared with group II with C4d- biopsy specimens. ACR greater than 1R was higher in group I compared with group II (50% vs 7.4%; P = .01). Clinical suspicion of AMR, positive retrospective crossmatches, and detection of de novo DSA were also higher in group I. Our result indicate that C4d and ACR positivity in posttransplant patients may be a harbinger of a subclinical form of asymptomatic AMR.

Association between flow cytometric crossmatching and graft survival in Thai cadaveric-donor kidney transplantation.

The flow cytometry cross-match (FCXM) technique is a sensitive method and has been reported to predict and protect graft rejection more efficiently than the conventional complement-dependent cytotoxicity cross-match (CDCXM) and the anti-human globulin-complement dependent cytotoxicity (AHG-CDC) methods. We performed retrospective FCXM in 270 cadaveric donor kidney transplant patients with negative CDC and AHG. The correlation between FCXM with graft rejection and graft survival within 1 year to 3 years was analysed. There were 97 (35.9%) samples with positive FCXM. Only 7 (2.6%) of the 270 samples had evidence of antibody-mediated rejection (AMR) at the first year, which increased to 10 (3.7%) AMR samples after 3 years. Interestingly, there was a significant association between FCXM results with the graft outcome at 1 year (P = 0.046). However, when the association was analysed at 3 years after transplantation, it did not reach statistical significance. FCXM detected concordant positive results in 4 out of 8 samples. These samples had mean fluorescence intensity (MFI) of the donor-specific antibody (DSA) higher than 2,000. The DSA was identified by a single antigen bead. Although positive FCXM, particularly for HLA class I, was significantly associated with graft loss from AMR within 1 year of transplantation in this study, there were a lot of FCXM false positives, as high as 35.9%. Additional studies are required to further assess the usefulness of FCXM in Thailand.

Primary Graft Dysfunction After Zero-Mismatch Kidney Transplantation Secondary to Early Biopsy-Proven Acute Cell-Mediated Rejection: Case Report

We report a case of primary renal allograft dysfunction and early acute cell-mediated rejection after a 12/12 HLA antigen zero-mismatch (0MM) transplant. The recipient was a 40-year-old white man who was highly allosensitized, with a calculated panel reactive antibody score of 100%. In posteroperative day 1 the recipient remained anuric and underwent dialysis because of hyperkalemia. Graft biopsy showed early acute cellular rejection, Banff grade 2B. No evidence of antibody-mediated rejection was observed. To our knowledge, this case is the 1st to report early cell-mediated rejection after 12/12 HLA antigen 0MM kidney transplantation. This case suggests that highly sensitized candidates are at high immunologic risk even in the context of 0MM kidney transplantation.

Renal Allograft Rejection

Renal Allograft Rejection

Outcomes in Kidney Transplant Recipients With Post-Transplant DSA in the Absence of Antibody Mediated Rejection.

There is limited information on the significance of HLA-DSA (human leukocyte antigen donor-specific antibody) on outcomes in kidney transplant recipients with no histopathological evidence of Antibody Mediated Rejection (ABMR). We addressed this question in patients who underwent a kidney allograft biopsy between 01/2009 and 06/2012(n=1470). There were 75 patients with DSA (+) ABMR (-) biopsies (5.1%). 489 patients (33.2%) were DSA (-) ABMR (-) [table 1]. We evaluated patient and allograft survival through 3 years post biopsy.Table: No Caption available.Patients with DSA (+) ABMR (-) were more sensitized as evidence by higher PRA and re-transplant rates. DSA in this group were directed against class II in 55%, class I - 36%, class I and II - 8.5, respectively. In 49% of cases DSA were found to be de novo DSA. Regression analysis demonstrated that anti-HLA DSA were significantly associated with graft loss (HR 2.7, 95% CI 1.67-4.42, p = 0.000) [figure 1], although they were not significantly associated with patient survival (HR 1.8, 95% CI 0.88-3.81, p = 0.14).Figure: No Caption available.Conclusion The observation that DSA is an independent risk factor for graft loss even in the absence of histological evidence of ABMR indicates that the pathologic effects of such DSA may be significant and warrant follow-up biopsies and/or therapeutic interventions.

Acute Humoral Rejection in the Absence of Anti-HLA Antibodies, a French Nation-Wide Study.

Antibody mediated rejection (ABMR) is usually associated with donor-specific anti-HLA antibodies (DSA). Evidence of ABMR in patients with no DSA strongly suggests the implication of non-HLA antibodies. We implemented a retrospective nation-wide study to improve undertanding of non-HLA ABMR. Inclusion criteria were: first or re-transplantion, deceased or living-donor; acute allograft dysfunction during the first three months; allograft biopsy showing a total score of glomerulitis and peritubular capillaritis≥3 according to the Banff classification; absence of identified anti-HLA DSAs using Luminex®. Demographical and clinical parameters were collected for 36 cases. Recipient age was 53±19 yrs. Donor age was 53±12 yrs. Cold ischemia time was 12±8 hrs. All patients received induction therapy (94% basiliximab, 6% thymoglobuline), a CNI (69% tacrolimus, 31% cyclosporine), MPA and steroids. Rejection was diagnosed at day 12±9 in the absence of graft function recovery in 30% of patients. The remaining 25 patients defined a poor serum creatinine nadir of 289±169 μmol/L at day 15±22. Acute graft dysfunction (393±230 μmol/L) led to the diagnosis of acute rejection at day 25±34. No anti-HLA DSA were observed. Mean g+ptc score was 3,8 [3-6]. In addition, intimal arteritis and interstitial inflammation (i ≥1) were observed in 50% and 69% of cases, respectively. Additional lesions included haemorragic suffusion and thrombotic microangiopathy in 26% and 9% of cases, respectively. Therapeutic strategies included steroids pulses (86%), thymoglobulines (37%), rituximab (31%), IVIG (49%) and plasmapheresis (49%). Primary non function was observed in 2 cases. At last follow up (3±1 yrs) serum creatinine was 178±92 μmol/l. 6% of patients were back to dialysis. This study provides a close clinico-pathological description of non-HLA ABMR, and will be followed by additional histological and mechannistic analyses.

The use of ABO-incompatible grafts in living donor liver transplantation—First report from India

ABO incompatibility is the commonest reason for rejection of donors in living donor liver transplantation (LDLT). The donor pool could be expanded by 25 % to 35 % if the ABO barrier is overcome. In the absence of pre-conditioning, transplantation across the blood groups is fraught with the almost universal risk of antibody-mediated rejection (AMR) that rapidly leads to graft loss. However, AMR can be prevented by removal of preformed antibodies and reducing their production by B cells. We describe our initial experience of three cases of ABO-incompatible (ABO-i) LDLT: a 42-year-old male, an 8-month-old male and a 28-month-old female, all of blood group O+ who received blood group B + right lobe, B + left lateral segment, and A + left lateral segment liver grafts, respectively. Pre-LDLT conditioning included administration of anti-CD20 antibody (Rituximab(®)) to the adult 4 weeks prior, and four to seven sessions of double-filtration plasmapheresis to all, to remove preformed antibodies and achieve anti-donor blood group antibody (ADA) titers of ≤ 1:16 IgG and ≤ 1:8 IgM, respectively. In addition, cases 1 and 3 received mycophenolate mofetil for 7 days prior to LDLT. After LDLT, all three patients achieved normal graft function over 8-17 days with no evidence of AMR and without the need for further plasmapheresis. Postoperative complications included portal vein thrombosis (one successfully re-explored), CMV (one), Pseudomonas and Klebsiella sepsis (one each), and abdominal collection (one treated with percutaneous drainage). All are currently well with normal graft function and low ADA titers at 8, 16, and 19 months after ABO-i LDLT.

52-P: DE NOVO DEVELOPMENT OF DONOR SPECIFIC HLA ANTIBODIES IS STRONGLY ASSOCIATED WITH ANTIBODY MEDIATED REJECTION FOLLOWING LIVE DONOR RENAL TRANSPLANTATION

The harmful effects of preformed and de novo development of donor specific anti HLA antibodies in solid organ transplantation have been extensively reviewed and are found to be associated with allograft dysfunction. The spectrum of antibody mediated insult ranges from hyperacute rejection to chronic antibody mediated rejection (AMR) leading ultimately to graft loss. With the advent of solid phase assays, the sensitivity and specificity of antibody detection have increased. We studied 105 renal transplant recipients who had undergone live donor renal transplantation at this hospital. None of the recipients were sensitized. The recipients were longitudinally followed-up for a period of 60 months after transplantation. Serum samples collected serially at pre-transplant, at least one time during the post-transplant period and at the time of rejection were analyzed by the solid-phase immunoassay system on a Luminex 200 Platform using OneLambda SAB kits. Of the total patients, 79 did not show any evidence of AMR. The remaining 26 (24.7%) recipients had evidence of AMR as characterized by donor specific antibodies, histopathological changes and C4D staining on biopsy as per the Banff 2007 criteria. Luminex SAB analysis revealed that out of the 26 patients experiencing AMR, 80.7% had DSA compared to recipients who had no evidence of AMR (12.6%). The study highlights the relevance of de novo development of donor specific HLA antibodies with AMR in the renal allograft recipients.

Influence of preformed donor-specific antibodies and C4d on early liver allograft function

Introduction. The impact of preformed donor-specific antibodies (DSA) is incompletely understood in liver transplantation. The incidence and impact of preformed DSA on early post liver transplant were assessed and these were correlated with compliment fragment C4d on allograft biopsy. Methods. Pretransplant serum from 41 consecutive liver transplant recipients (brain dead donors; DBD = 27 and cardiac death donors; DCD = 14) were tested for class-specific anti-human leukocyte antigen (HLA) and compared against donor HLA types. Liver biopsies were taken during cold storage (t-1) and post-reperfusion (t0) stained with C4d and graded for preservation-reperfusion injury (PRI). Results. Of the 41 recipients, 8 (20%) had anti-HLA class I/II antibodies pretransplant, 3 (7%) were confirmed preformed DSA; classes I and II (n=1) and class I only (n=2). No biopsies showed definite evidence of antibody-mediated rejection. Graft biopsies in overall showed only mild PRI with ischemic hepatocyte C4d pattern similar in both positive and negative DSA patients. One DSA-positive (33%) compared with four DSA-negative patients (10%) had significant early graft dysfunction; severe PRI causing graft loss from primary nonfunction was seen only in DSA-negative group. Allograft biopsy of preformed DSA-positive patient demonstrated only minimal PRI; however, no identifiable cause could be attributed to graft dysfunction other than preformed DSA. Conclusion. Preformed DSA are present in 5–10% liver transplant recipients. There is no association between anti-HLA DSA and PRI and C4d, but preformed DSA may cause early morbidity. Larger studies on the impact of DSA with optimization of C4d techniques are required.