Consensus guidelines on the testing and clinical management issues associated with HLA and non-HLA antibodies in transplantation. Transplantation. 2013;95:19-47. [PMID: 23238534 DOI: 10.1097/tp.0b013e31827a19cc]

Concordance and discordance in anti-HLA antibody testing

BACKGROUND

Correct identification of the specificity of antibodies directed against HLA using single antigen Luminex beads (SALB) is essential in current HLA laboratory practice for transplantation. The aim of this study was to investigate the magnitude of concordance and discordance among laboratories in testing for anti-HLA antibodies using SALB.

METHOD

35 sera were distributed by the ASHI Proficiency Testing Program to HLA laboratories worldwide. We analyzed 4335 test results submitted between April 2010 and April 2013 by participating laboratories.

RESULTS

SALB was used by approximately 94% of the participating laboratories, yet concordant assignment of antibody specificity was imperfect. For each serum, the assignment of an average of 10 antibody specificities was discordant. Disagreement was observed for antibodies directed against common as well as uncommon antigens. The assignment of an average of 15 antibody specificities in each "positive" serum appeared to be influenced by vendor-dependent causes. Inter-vendor concordance was lower than intra-vendor concordance, indicating that vendor dependent factors may be a central cause for disagreement.

CONCLUSIONS

Our study illustrates the prevalence of concordance and discordance, also affected by unpremeditated causes, in reporting SALB antibody results. Insufficient concordance and standardization in antibody testing may have practical implications for organ allocation and organ sharing programs.

Clinical relevance of HLA antibody monitoring after kidney transplantation

In kidney transplantation, antibody-mediated allograft injury caused by donor HLA-specific antibodies (DSA) has recently been identified as one of the major causes of late graft loss. This paper gives a brief overview on the impact of DSA development on graft outcome in organ transplantation with a focus on risk factors for de novo alloantibody induction and recently published guidelines for monitoring of DSA during the posttransplant phase.

The significance of histological diagnosis in renal allograft biopsies in 2014

In 2014, the renal allograft biopsy still represents the best available diagnostic 'gold' standard to assess reasons for allograft dysfunction. However, it is well recognized that histological lesion observed in the biopsy is of limited diagnostic specificity and that the Banff classification as the international diagnostic standard represents mere expert consensus. Here, we review the role of the renal allograft biopsy in different clinical and diagnostic settings. To increase diagnostic accuracy and to compensate for lack of specificity, the interpretation of biopsy pathology needs to be within the clinical context, primarily defined by time post-transplantation and patient-specific risk profile. With this in mind, similar histopathological patterns will lead to different conclusions with regard to diagnosis, disease grading and staging and thus to patient-specific clinical decision-making. Consensus generation for such integrated diagnostic approach, preferably including new molecular tools, represents the next challenge to the transplant community on its way to precision medicine in transplantation.

Acute liver allograft antibody-mediated rejection: an inter-institutional study of significant histopathological features

Acute antibody-mediated rejection (AMR) occurs in a small minority of sensitized liver transplant recipients. Although histopathological characteristics have been described, specific features that could be used (1) to make a generalizable scoring system and (2) to trigger a more in-depth analysis are needed to screen for this rare but important finding. Toward this goal, we created training and validation cohorts of putative acute AMR and control cases from 3 high-volume liver transplant programs; these cases were evaluated blindly by 4 independent transplant pathologists. Evaluations of hematoxylin and eosin (H&E) sections were performed alone without knowledge of either serum donor-specific human leukocyte antigen alloantibody (DSA) results or complement component 4d (C4d) stains. Routine histopathological features that strongly correlated with severe acute AMR included portal eosinophilia, portal vein endothelial cell hypertrophy, eosinophilic central venulitis, central venulitis severity, and cholestasis. Acute AMR inversely correlated with lymphocytic venulitis and lymphocytic portal inflammation. These and other characteristics were incorporated into models created from the training cohort alone. The final acute antibody-mediated rejection score (aAMR score)--the sum of portal vein endothelial cell hypertrophy, portal eosinophilia, and eosinophilic venulitis divided by the sum of lymphocytic portal inflammation and lymphocytic venulitis--exhibited a strong correlation with severe acute AMR in the training cohort [odds ratio (OR) = 2.86, P < 0.001] and the validation cohort (OR = 2.49, P < 0.001). SPSS tree classification was used to select 2 cutoffs: one that optimized specificity at a score > 1.75 (sensitivity = 34%, specificity = 86%) and another that optimized sensitivity at a score > 1.0 (sensitivity = 81%, specificity = 71%). In conclusion, the routine histopathological features of the aAMR score can be used to screen patients for acute AMR via routine H&E staining of indication liver transplant biopsy samples; however, a definitive diagnosis requires substantiation by DSA testing, diffuse C4d staining, and the exclusion of other insults.

Histopathological diagnosis of acute and chronic rejection in pediatric kidney transplantation

ABO-compatible as well as ABO-incompatible kidney transplantation are well established in the pediatric population. There are particularities in the histopathological evaluation of pediatric kidney transplant biopsies as for example the recurrence of certain diseases different from the adult population. Furthermore, the challenging transition of pediatric renal transplant recipients to adulthood is associated with an increased rate of non-adherence triggered rejection episodes. With modern immunosuppressive drugs, T-cell-mediated rejection of renal allografts is well controlled. In contrast, antibody-mediated rejection (AMR) is increasingly recognized as one of the major reasons for allograft loss. However, the 2001 diagnostic Banff criteria for antibody-mediated rejection require further refinement, as the morphological spectrum of AMR expands while effective therapeutic strategies are lacking. For example, endarteritis, which traditionally has been attributed to T-cell-mediated rejection, has recently been shown to be part of the AMR spectrum in some cases. Many findings in transplant renal biopsies are not specific for a certain disease but need consideration of differential diagnoses. To use the term "chronic allograft nephropathy" as a diagnostic entity is no longer appropriate. Therefore, the precise identification of specific diseases is paramount in the assessment of transplant renal biopsies in order to enable tailored therapeutic management.

The clinical spectrum of de novo donor-specific antibodies in pediatric renal transplant recipients

The development of donor-specific HLA antibodies (DSA) is associated with worse renal allograft survival in adult patients. This study assessed the natural history of de novo DSA, and its impact on renal function in pediatric renal transplant recipients (RTR). HLA antibodies were measured prospectively using single-antigen-bead assays at 1, 3, 6 and 12 months posttransplant followed by 12-monthly intervals and during episodes of allograft dysfunction. Of 215 patients with HLA antibody monitoring, 75 (35%) developed DSA at median of 0.25 years posttransplant with a high prevalence of Class II (70%) and HLA-DQ (45%) DSA. DSA resolved in 35 (47%) patients and was associated with earlier detection (median, inter-quartile range 0.14, 0.09-0.33 vs. 0.84, 0.15-2.37 years) and lower mean fluorescence intensity (MFI) (2658, 1573-3819 vs. 7820, 5166-11 990). Overall, DSA positive patients had more rapid GFR decline with a 50% reduction in GFR at mean 5.3 (CI: 4.7-5.8) years versus 6.1 (5.7-6.4) years in DSA negative patients (p = 0.02). GFR decreased by a magnitude of 1 mL/min/1.73 m(2) per log10 increase in Class II DSA MFI (p < 0.01). Using Cox regression, independent factors predicting poorer renal allograft outcome were older age at transplant (hazard ratio 1.1, CI: 1.0-1.2 per year), tubulitis (1.5, 1.3-1.8) and microvasculature injury (2.9, 1.4-5.7). In conclusion, pediatric RTR with de novo DSA and microvasculature injury were at risk of allograft failure.

The PROCARE consortium: toward an improved allocation strategy for kidney allografts

Kidney transplantation is the best treatment option for patients with end-stage renal failure. At present, approximately 800 Dutch patients are registered on the active waiting list of Eurotransplant. The waiting time in the Netherlands for a kidney from a deceased donor is on average between 3 and 4 years. During this period, patients are fully dependent on dialysis, which replaces only partly the renal function, whereas the quality of life is limited. Mortality among patients on the waiting list is high. In order to increase the number of kidney donors, several initiatives have been undertaken by the Dutch Kidney Foundation including national calls for donor registration and providing information on organ donation and kidney transplantation. The aim of the national PROCARE consortium is to develop improved matching algorithms that will lead to a prolonged survival of transplanted donor kidneys and a reduced HLA immunization. The latter will positively affect the waiting time for a retransplantation. The present algorithm for allocation is among others based on matching for HLA antigens, which were originally defined by antibodies using serological typing techniques. However, several studies suggest that this algorithm needs adaptation and that other immune parameters which are currently not included may assist in improving graft survival rates. We will employ a multicenter-based evaluation on 5429 patients transplanted between 1995 and 2005 in the Netherlands. The association between key clinical endpoints and selected laboratory defined parameters will be examined, including Luminex-defined HLA antibody specificities, T and B cell epitopes recognized on the mismatched HLA antigens, non-HLA antibodies, and also polymorphisms in complement and Fc receptors functionally associated with effector functions of anti-graft antibodies. From these data, key parameters determining the success of kidney transplantation will be identified which will lead to the identification of additional parameters to be included in future matching algorithms aiming to extend survival of transplanted kidneys and to diminish HLA immunization. Computer simulation studies will reveal the number of patients having a direct benefit from improved matching, the effect on shortening of the waiting list, and the decrease in waiting time.

Preemptive treatment with therapeutic plasma exchange and rituximab for early donor-specific antibodies after lung transplantation

OBJECTIVE

De novo donor-specific anti-human leukocyte antigen antibodies develop in a high proportion of lung transplant recipients early after lung transplantation. We recently showed that de novo donor-specific antibodies (DSA) occurrence is associated with significantly increased mortality. Here, we studied the efficacy of a preemptive treatment protocol.

METHODS

A retrospective observational study was conducted on all lung transplantations at Hanover Medical School between January 2009 and May 2013.

RESULTS

Among the 500 transplant recipients, early DSA developed in 86 (17%). Of these, 56 patients (65%; Group A) received therapeutic plasma exchange, and 30 patients (35%; Group B) did not. Among Group A patients, 51 also received rituximab. Between groups, there was no statistically significant difference in mortality, incidence of pulsed steroid therapies, rejections diagnosed by biopsy specimen, incidence of bronchitis obliterans syndrome (BOS), or infections requiring hospitalization at 1 year and 3 years. Also, there were no statistically significant differences after matching 21 Group A with 21 Group B patients through propensity score analysis. Significantly more Group A patients (65%) than Group B patients (34%) cleared DSA at hospital discharge (p = 0.01). At the last control after transplantation (median, 14 months; interquartile range, 5-24 months), 11 Group A (22%) and 9 Group B patients (33%) still showed DSA (p = 0.28).

CONCLUSIONS

Preemptive treatment with therapeutic plasma exchange and rituximab led to improved elimination of DSA early after lung transplantation (p = 0.01). However, spontaneous elimination in untreated Group B patients also occurred frequently. This treatment protocol was not associated with significantly improved outcome.

Methodological aspects of anti-human leukocyte antigen antibody analysis in solid organ transplantation

Donor human leukocyte antigen (HLA)-specific antibodies (DSA) play an important role in solid organ transplantation. Preexisting IgG isotype DSA are considered a risk factor for antibody mediated rejection, graft failure or graft loss. The post-transplant development of DSA depends on multiple factors including immunogenicity of mismatched antigens, HLA class II typing of the recipient, cytokine gene polymorphisms, and cellular immunoregulatory mechanisms. De novo developed antibodies require special attention because not all DSA have equal clinical significance. Therefore, it is important for transplant clinicians and transplant immunologists to accurately characterize DSA. In this review, the contemporary immunological techniques for detection and characterization of anti-HLA antibodies and their pitfalls are described.

Human leukocyte antigens and alloimmunization in heart transplantation: an open debate

Considerable advances in heart transplantation outcome have been achieved through the improvement of donor-recipient selection, better organ preservation, lower rates of perioperative mortality and the use of innovative immunosuppressive protocols. Nevertheless, long-term survival is still influenced by late complications. We support the introduction of HLA matching as an additional criterion in the heart allocation. Indeed, allosensitization is an important factor affecting heart transplantation and the presence of anti-HLA antibodies causes an increased risk of antibody-mediated rejection and graft failure. On the other hand, the rate of heart-immunized patients awaiting transplantation is steadily increasing due to the limited availability of organs and an increased use of ventricular assist devices. Significant benefits may result from virtual crossmatch approach that prevents transplantation in the presence of unacceptable donor antigens. A combination of both virtual crossmatch and a tailored desensitization therapy could be a good compromise for a favorable outcome in highly sensitized patients. Here, we discuss the unresolved issue on the clinical immunology of heart transplantation.

HLA antibody detection with solid phase assays: great expectations or expectations too great?

Alloantibodies directed against HLA antigens, are a barrier to long-term solid organ allograft survival. The clinical impact of preformed, donor-directed HLA alloantibodies range from acceptable risk to unequivocal contraindication for organ transplantation. HLA antibodies are key factors that limit patient access to donor organs. Serological methods were once the only approach to identify HLA antigens and antibodies. Limitations in these technologies led to the development of solid phase approaches. In the early 1990s, the development of the polymerase chain reaction enabled DNA-based HLA antigen testing to be performed. By the mid-1990s, microparticle-based technology that utilized flow cytometry for analysis was developed to detect both classes I and II HLA antibodies. These methodologies revolutionized clinical histocompatibility testing. The strengths and weaknesses of these assays are described in detail in this review.

De novo donor-specific HLA antibodies are associated with early and high-grade bronchiolitis obliterans syndrome and death after lung transplantation

BACKGROUND

The development of human leukocyte antigen (HLA) antibody responses has been associated with worse clinical outcomes, such as bronchiolitis obliterans syndrome (BOS) and death, in lung transplant recipients (LTRs). However, the role of donor-specific HLA antibody (DSA) responses as a risk factor for poor outcomes remains controversial.

METHODS

We prospectively screened 445 LTRs for DSA at our institution at the time of surveillance bronchoscopies for the first 2 years after transplantation between 2003 and 2008, and evaluated clinical outcomes. For this purpose, we used the combination of panel-reactive antibodies (PRA) by enzyme-linked immunosorbent assay (ELISA) and the Luminex single-antigen bead (SAB) assay (One Lambda, Canoga Park, CA).

RESULTS

We detected de novo DSA (dnDSA) in 58 of 445 (13%) LTRs in our cohort. Freedom from BOS was significantly reduced in LTRs with dnDSA versus those without dnDSA (p < 0.001). Using a Cox proportional hazards model, the development of dnDSA was associated with a significantly increased hazard ratio (HR = 6.59 [4.53 to 9.59]; p < 0.001) for BOS and high-grade BOS (Stage ≥ 2) (HR = 5.76 [3.48 to 9.52]; p < 0.001). Freedom from death was significantly reduced in LTRs with dnDSA (p < 0.001), including mortality attributable to BOS (HR = 9.86 [4.91 to 19.78]; p < 0.001).

CONCLUSIONS

Taken together, our findings provide evidence that dnDSA is associated with accelerated BOS kinetics and severity, as well as death due to BOS after lung transplantation. In addition, these data support regular monitoring for the development of dnDSA in LTRs and underscore the need for novel strategies to mitigate the increased risk of poor outcomes associated with dnDSA.

Polyclonal B cell activation for accurate analysis of pre-existing antigen-specific memory B cells

The enzyme-linked immunospot (ELISPOT) assay is a widely used tool for enumeration of antigen-specific memory B cells in several disciplines, such as vaccination, cancer immunotherapy and transplantation. For the accurate estimation of antigen-specific memory B cell frequencies, a well-defined B cell activation protocol is pivotal. In this study, we aimed to characterize a polyclonal B cell activation protocol to facilitate optimal monitoring of antigen-specific memory B cell frequencies. Total, naive and memory B cells were activated polyclonally with an α-CD40 monoclonal antibody, cytosine-phosphate-guanine (CPG) oligodeoxynucleotide (ODN) 2006, interleukin (IL)-2, IL-10 and IL-21. Polyclonal activation of B cells resulted in equal cell death ratios in naive and memory B cells. When tested in an antigen-specific system, immunoglobulin (Ig)G spots were detected only in the memory fraction. There was no change in B cell polyclonality due to in-vitro activation. Our data show that the current polyclonal activation protocol may be used reliably to estimate the frequency of memory B cells in ELISPOT assays.

De novo donor-specific HLA antibodies: biomarkers of pancreas transplant failure

This study assesses the role of posttransplant HLA antibody monitoring in the surveillance of pancreas transplant recipients. Four hundred thirty-three pancreas transplants were performed at the Oxford Transplant Centre 2006-2011 (317 simultaneous pancreas kidney [SPK] and 116 isolated pancreas [IP]). HLA antibody monitoring was performed at 0, 6 and 12 months and annually and during clinical events. There was no association between pancreas graft failure and recipient or donor characteristics. Posttransplant antibody status, available for 354 (81.8%) of recipients, demonstrated that 141 (39.8%) developed de novo HLA antibodies, of which 52 (36.9%) were de novo donor-specific HLA antibodies (DSA) (34 SPK, 18 IP). The development of antibodies to donor HLA, but not to nondonor HLA, was significantly associated with poorer graft outcomes, with 1- and 3-year graft survival inferior in SPK recipients (85.2% vs. 93.5%; 71.8% vs. 90.3%, respectively; log-rank p = 0.002), and particularly in IP recipients (50.0% vs. 82.9%; 16.7 vs. 79.4%, respectively; log-rank p = 0.001). In a multivariate analysis, development of de novo DSA emerged as a strong independent predictor of pancreas graft failure (hazard ratio 4.66, p < 0.001). This is the largest study to examine de novo HLA antibodies following pancreas transplantation and clearly defines a high-risk group in need of specific intervention.

Quantifying the risk of incompatible kidney transplantation: a multicenter study

Incompatible live donor kidney transplantation (ILDKT) offers a survival advantage over dialysis to patients with anti-HLA donor-specific antibody (DSA). Program-specific reports (PSRs) fail to account for ILDKT, placing this practice at regulatory risk. We collected DSA data, categorized as positive Luminex, negative flow crossmatch (PLNF) (n = 185), positive flow, negative cytotoxic crossmatch (PFNC) (n = 536) or positive cytotoxic crossmatch (PCC) (n = 304), from 22 centers. We tested associations between DSA, graft loss and mortality after adjusting for PSR model factors, using 9669 compatible patients as a comparison. PLNF patients had similar graft loss; however, PFNC (adjusted hazard ratio [aHR] = 1.64, 95% confidence interval [CI]: 1.15-2.23, p = 0.007) and PCC (aHR = 5.01, 95% CI: 3.71-6.77, p < 0.001) were associated with increased graft loss in the first year. PLNF patients had similar mortality; however, PFNC (aHR = 2.04; 95% CI: 1.28-3.26; p = 0.003) and PCC (aHR = 4.59; 95% CI: 2.98-7.07; p < 0.001) were associated with increased mortality. We simulated Centers for Medicare & Medicaid Services flagging to examine ILDKT's effect on the risk of being flagged. Compared to equal-quality centers performing no ILDKT, centers performing 5%, 10% or 20% PFNC had a 1.19-, 1.33- and 1.73-fold higher odds of being flagged. Centers performing 5%, 10% or 20% PCC had a 2.22-, 4.09- and 10.72-fold higher odds. Failure to account for ILDKT's increased risk places centers providing this life-saving treatment in jeopardy of regulatory intervention.

Early donor-specific antibodies in lung transplantation: risk factors and impact on survival

BACKGROUND

The impact of early donor-specific anti-HLA antibodies (DSA) on patient and graft survival after lung transplantation remains controversial. In this study we analyzed risk factors for DSA that developed before initial hospital discharge after lung transplantation (early DSA) and compared mid-term outcomes in patients with or without DSA.

METHODS

Between January 2009 and August 2013, 546 patients underwent lung transplantation at our institution. One hundred (18%) patients developed early DSA (Group A) and 446 (82%) patients (Group B) did not. Patient records were retrospectively reviewed.

RESULTS

Retransplantation (odds ratio [OR] = 2.7, 95% confidence interval [CI] 1.1 to 6.5, p = 0.03), pre-operative HLA antibodies (OR = 2.1, 95% CI 1.2 to 3.4, p = 0.003) and primary graft dysfunction (PGD) score Grade 2 or 3 at 48 hours (OR = 2.6, 95% CI 1.5 to 4.6, p = 0.001) were associated with early DSA development. Overall, 1- and 3-year survival in Group A and B patients was 79 ± 4% vs 88 ± 2% and 57 ± 8% vs 74 ± 3%, respectively (p = 0.019). Eleven Group A (11%) and 32 Group B (7%) patients died before hospital discharge (p = 0.34). Among patients surviving beyond discharge, 1- and 3-year survival in Group A and B patients was 89 ± 4% vs 95 ± 1% and 65 ± 8% vs 80 ± 3% in Group A and B patients, respectively (p = 0.04). Multivariate analysis identified early anti-HLA Class II DSA (OR = 1.9, 95% CI 1.0 to 3.4, p = 0.04) as an independent risk factor for post-discharge mortality but not for in-hospital mortality.

CONCLUSIONS

Pre-operative HLA antibodies, retransplantation or post-operative PGD increase the risk of developing early DSA, which were independently associated with an increased risk for mortality.

Immunosuppression and allograft rejection following lung transplantation: evidence to date

The enduring success of lung transplantation is built on the use of immunosuppressive drugs to stop the immune system from rejecting the newly transplanted lung allograft. Most patients receive a triple-drug maintenance immunosuppressive regimen consisting of a calcineurin inhibitor, an antiproliferative and corticosteroids. Induction therapy with either an antilymphocyte monoclonal or an interleukin-2 receptor antagonist are prescribed by many centres aiming to achieve rapid inhibition of recently activated and potentially alloreactive T lymphocytes. Despite this generic approach acute rejection episodes remain common, mandating further fine-tuning and augmentation of the immunosuppressive regimen. While there has been a trend away from cyclosporine and azathioprine towards a preference for tacrolimus and mycophenolate mofetil, this has not translated into significant protection from the development of chronic lung allograft dysfunction, the main barrier to the long-term success of lung transplantation. This article reviews the problem of lung allograft rejection and the evidence for immunosuppressive regimens used both in the short- and long-term in patients undergoing lung transplantation.

Predictive factors of allosensitization in renal transplant patients switched from calcineurin to mTOR inhibitors

Conversion of kidney-transplant recipients from calcineurin inhibitors to mTOR inhibitors has been suggested to be a risk factor for increased alloimmune response. We have analyzed the development of new HLA-antibodies (HLA-Abs) early after conversion in 184 patients converted in stable phase at our hospital and compared with a control group of nonconverted comparable 63 transplants. Using single-antigen solid-phase immunoassay analysis, a preconversion and a 3-6 months postconversion sera were prospectively analyzed in every patient for the appearance of new HLA-Abs. Renal function at 2 years postconversion and cumulative graft survival were compared between groups. In 16 patients, new HLA-Abs (3-DSA and 13-NonDSA), not present at the moment of conversion, were detected (8.7% vs. 3.1% in the control group). The type of mTORi used, type of CNI preconversion, the presence of steroids, time of conversion, or indication for conversion did not have influence on this effect but the presence of HLA-Abs before conversion highly correlated with the appearance of new specificities. Patients with de novo HLA-Abs showed a trend to worst graft function and survival. In conclusion, conversion to mTORi can be followed by early appearance of de novo HLA-Abs, especially in patients with HLA-Abs preconversion, and this complication should be screened early after conversion.

Antithymocyte globulin is associated with a lower incidence of de novo donor-specific antibodies in moderately sensitized renal transplant recipients

BACKGROUND

Recent evidence suggests that de novo donor-specific antibodies (dnDSA) are associated with antibody-mediated rejection (ABMR) and graft failure after kidney transplantation. The effects of induction immunosuppression on dnDSA are unknown.

METHODS

The study population comprised 114 consecutive moderately sensitized (positive DSA and negative flow crossmatch) recipients who received deceased donor renal transplants between December 2009 and November 2011. Patients were divided into two groups based on induction immunosuppression: antithymocyte globulin (ATG) (n=85) or basiliximab (n=29) and were followed up for 36 months.

RESULTS

Patients in the ATG group received a mean dose of 4.98 mg/kg ± 7.9 mg/kg, had a significantly higher PRA, and received more plasmapheresis and IVIG at the time of transplant. The incidence of dnDSA (P=0.02, HR=0.33, 95% CI 0.09-1.24) and ABMR (P=0.002, HR=0.2, 95% CI 0.04-0.87) was significantly lower in the ATG group. In multivariate regression analyses, ATG induction was the single most important variable associated with both ABMR and dnDSA.

CONCLUSIONS

In moderately sensitized deceased donor renal transplant recipients, induction with ATG is associated with a reduction in the occurrence of dnDSA and ABMR when compared with basiliximab.

Preformed donor-specific antibodies and risk of antibody-mediated rejection in repeat renal transplantation

BACKGROUND

Allograft outcomes in patients undergoing repeat renal transplantation are inferior compared to first-time transplant recipient outcomes. Donor-specific antibodies detected by solid-phase assays (DSA-SPA) may contribute to the worse prognosis. The influence of DSA-SPA on repeat renal transplantation outcomes has not been previously studied in detail.

DESIGN

This study reports the findings in 174 patients who underwent repeat renal transplantation between years 2007 and 2012. These included 62 patients with preformed DSA-SPA detected by Luminex at the time of transplantation. Patients received standard and consistent immunosuppression and were monitored closely for evidence of rejection. Recipients who underwent desensitization were excluded from this analysis. Endpoints included development of biopsy-proven acute rejection and analysis of graft survival and function.

RESULTS

Patients in the DSA-SPA-positive and DSA-SPA-negative groups received similar immunosuppression, and a similar proportion of recipients had a peak panel reactive antibody greater than 20%; the two groups differed with respect to human leukocyte antigen mismatches (4.7 ± 1.1 vs. 4.1 ± 1.7, P=0.024). Recipients with preformed DSA-SPA had higher rejection rates (54.8% vs. 34.8%, P=0.01), including higher rates of antibody-mediated rejection (AMR) (32.3% vs. 7.1%, P<0.001). Recipients who were DSA-SPA-positive and flow cytometry crossmatch (FCXM)-positive had a higher incidence of both AMR (OR 4.6, P=0.009) and of acute rejection (OR 3.57, P=0.02) as compared to those who were DSA-SPA-positive and FCXM-negative. Overall allograft survival was similar in the DSA-SPA-positive and DSA-SPA-negative groups (log-rank test=0.63, P=0.428). Differences in allograft function were detectable after 2 years (32.8 ± 13.1 vs. 47 ± 20.2 mL/min/1.73 m(2), P=0.023) and may be reflective of more AMR among DSA-SPA-positive patients.

CONCLUSIONS

This analysis suggests that DSA-SPA increases the overall risk of acute rejection but does not appear to adversely impact allograft survival during the early follow-up period. Close monitoring of renal function and early biopsy for AMR detection appear to allow for satisfactory short-term allograft outcomes in repeat transplant recipients.

The management of antibody-mediated rejection in the first presensitized recipient of a full-face allotransplant

We report on the management of the first full-face transplantation in a sensitized recipient with a positive preoperative crossmatch and subsequent antibody-mediated rejection (AMR). The recipient is a 45-year-old female who sustained extensive chemical burns, with residual poor function and high levels of circulating anti-HLA antibodies. With a clear immunosuppression plan and salvage options in place, a full-face allotransplant was performed using a crossmatch positive donor. Despite plasmapheresis alongside a standard induction regimen, clinical signs of rejection were noted on postoperative day 5 (POD5). Donor-specific antibody (DSA) titers rose with evidence of C4d deposits on biopsy. By POD19, biopsies showed Banff Grade III rejection. Combination therapy consisting of plasmapheresis, eculizumab, bortezomib and alemtuzumab decreased DSA levels, improved clinical exam, and by 6 months postop she had no histological signs of rejection. This case is the first to demonstrate evidence and management of AMR in face allotransplantation. Our findings lend support to the call for an update to the Banff classification of rejection in vascularized composite tissue allotransplantation (VCA) to include AMR, and for further studies to better classify the histology and mechanism of action of AMR in VCA.

Detection of donor-specific antibodies in kidney transplantation

INTRODUCTION

Precise and timely detection of human leukocyte antigen (HLA) donor-specific antibodies (DSAs) is vital for evaluating humoral immune status of patients pre- and post-transplantation.

SOURCE OF DATA

Clinically relevant articles on theory, development, methodology and application of HLA-DSA testing in kidney transplantation.

AREAS OF AGREEMENT AND CONTROVERSY

The availability of solid phase HLA-antibody testing revolutionized our ability to detect HLA-DSA and to appreciate their significance in kidney transplant outcome. The best approach to determine the strength, immunogenicity and pathogenicity of HLA antibodies still remains controversial.

GROWING POINTS

Assays to identify complement-binding antibodies were developed. Their clinical utilization, pre- and post-transplantation, is currently under investigation. Appreciation of the complexity of HLA-DQ antibodies should lead to better assignment of unacceptable antibodies and cPRA calculation.

AREAS TIMELY FOR DEVELOPING RESEARCH

Characterization of HLA-antibody epitopes, and utilization of epitope matching to better define compatible donors could contribute to better transplant outcomes.

Current status of the organ replacement approach for malignancies and an overture for organ bioengineering and regenerative medicine

Significant achievements in the organ replacement approach for malignancies over the last 2 decades opened new horizons, and the age of "Transplant Oncology" has dawned. The indications of liver transplantation for malignancies have been carefully expanded by a strict patient selection to assure comparable outcomes with non-malignant diseases. Currently, the Milan criteria, gold standard for hepatocellular carcinoma, are being challenged by high-volume centers worldwide. Neoadjuvant chemoradiation therapy and liver transplantation for unresectable hilar cholangiocarcinoma has been successful in specialized institutions. For other primary and metastatic liver tumors, clinical evidence to establish standardized criteria is lacking. Intestinal and multivisceral transplantation is an option for low-grade neoplasms deemed unresectable by conventional surgery. However, the procedure itself is in the adolescent stage. Solid organ transplantation for malignancies inevitably suffers from "triple distress," i.e., oncological, immunological, and technical. Organ bioengineering and regenerative medicine should serve as the "triple threat" therapy and revolutionize "Transplant Oncology."

Combined liver and kidney transplantation in children

Simultaneous combined liver-kidney transplantation (CLKT) is a rare operation in pediatric patients so that annually only 10-30 operations are performed worldwide. The main indications for CLKT are primary hyperoxaluria type 1 and autosomal recessive polycystic kidney disease. In addition, CLKT is indicated in individual patients with metabolic or cirrhotic liver diseases and end-stage kidney disease. The surgery and immediate post-operative management of CLKT remain challenging in infants and small children. The patients should be operated on before they become severely ill or develop major systemic manifestations of their metabolic disorder. The liver allograft is immunologically protective of the kidney graft in simultaneous CLKT, often resulting in well-preserved kidney function. The long-term outcome after CLKT is nowadays comparable to that of isolated liver and kidney transplantations.

Early acute antibody-mediated rejection of a negative flow crossmatch 3rd kidney transplant with exclusive disparity at HLA-DP

Donor-specific alloantibodies (DSA) to HLA-DP may cause antibody-mediated rejection (AMR), especially in re-transplants. We describe the immunization history of a patient who received 3 kidney transplants; the 3rd kidney was completely matched except at DPA1 and DPB1. Prior to the 3rd transplant, single antigen bead analysis (SAB) showed DSA reactivity against DPA1 shared by the 1st and 3rd donors, but B and T flow crossmatch (FXM) results were negative. Within 11 days the 3rd transplant underwent acute C4d+ AMR which coincided with the presence of complement (C1q)-binding IgG1 DSA against donor DPA1 and DPB1. Using HLAMatchmaker and SAB, we provide evidence that eplet (epitope) spreading on DPA1 and eplet sharing on differing DPB1 alleles of the 1st and 3rd transplants was associated with AMR. Since weak DSA to DPA1/DPB1 may induce acute AMR with negative FXM, donor DPA1/DPB1 high resolution typing should be considered in sensitized patients with DP-directed DSA.

Posttransplant allosensitization in low immunological risk kidney and kidney-pancreas graft recipients

Introduction. Posttransplantation allosensitization prevalence and effect on kidney grafts outcomes remain unsettled. Methods. Between 2007 and 2012, 408 patients received a primary kidney graft (with 68 patients also receiving a pancreas graft) after a negative cytotoxic crossmatch. All patients had a pretransplant negative anti-HLA screening and 0% panel reactive antibodies. We analyzed retrospectively the results of anti-HLA antibodies screening by Luminex assay, performed between 6 and 24 months after transplant, and searched for the risk factors for antibody positivity and its impact on kidney graft outcomes. Results. Anti-HLA antibodies prevalence at 6 months was 17.4%. Previous steroid-insensitive acute rejection was the only risk factor for both anti-HLA classes detected antibodies. Antithymocyte globulin induction was also a risk factor for anti-HLA-I antibodies. Antibody positivity status was associated with reduced graft function at 12 months and graft survival at 5 years (91.5% versus 96.4%, P = 0.03). In multivariable Cox analysis, delayed graft function (HR = 6.1, P < 0.01), HLA mismatches >3 (HR = 10.2, P = 0.03), and antibody positivity for anti-HLA class II (HR = 5.1, P = 0.04) or class I/II (HR = 13.8, P < 0.01) were independent predictors of graft loss. Conclusions. Allosensitization against HLA class II ± I after transplant was associated with adverse kidney graft outcomes. A screening protocol seems advisable within the first year in low immunological risk patients.

The role of donor-specific HLA alloantibodies in liver transplantation

The impact of donor-specific HLA alloantibodies (DSA) on short- and long-term liver transplant outcome is not clearly defined. While it is clear that not all levels of allosensitization produce overt clinical injury, and that liver allografts possess some degree of alloantibody resistance, alloantibody-mediated adverse consequences are increasingly being recognized. To better define the current state of this topic, we assembled experts to provide insights, explore controversies and develop recommendations for future research on the consequences of DSA in liver transplantation. This article summarizes the proceedings of this inaugural meeting. Several insights emerged. Acute antibody-mediated rejection (AMR), although rarely diagnosed, is increasingly understood to overlap with T cell-mediated rejection. Isolated liver allograft recipients are at increased risk of early allograft immunologic injury when preformed DSA are high titer and persist posttransplantation. Persons who undergo simultaneous liver-kidney transplantation are at risk of renal AMR when Class II DSA persist posttransplantation. Other under-appreciated DSA associations include ductopenia and fibrosis, plasma cell hepatitis, biliary strictures and accelerated fibrosis associated with recurrent liver disease. Standardized DSA testing and diagnostic criteria for both acute and chronic AMR are needed to distil existing associations into etiological processes in order to develop responsive therapeutic strategies.

Antibody desensitization therapy in highly sensitized lung transplant candidates

As HLAs antibody detection technology has evolved, there is now detailed HLA antibody information available on prospective transplant recipients. Determining single antigen antibody specificity allows for a calculated panel reactive antibodies (cPRA) value, providing an estimate of the effective donor pool. For broadly sensitized lung transplant candidates (cPRA ≥ 80%), our center adopted a pretransplant multi-modal desensitization protocol in an effort to decrease the cPRA and expand the donor pool. This desensitization protocol included plasmapheresis, solumedrol, bortezomib and rituximab given in combination over 19 days followed by intravenous immunoglobulin. Eight of 18 candidates completed therapy with the primary reasons for early discontinuation being transplant (by avoiding unacceptable antigens) or thrombocytopenia. In a mixed-model analysis, there were no significant changes in PRA or cPRA changes over time with the protocol. A sub-analysis of the median fluorescence intensity (MFI) change indicated a small decline that was significant in antibodies with MFI 5000-10,000. Nine of 18 candidates subsequently had a transplant. Posttransplant survival in these nine recipients was comparable to other pretransplant-sensitized recipients who did not receive therapy. In summary, an aggressive multi-modal desensitization protocol does not significantly reduce pretransplant HLA antibodies in a broadly sensitized lung transplant candidate cohort.

Impact of donor-specific antibodies on the outcomes of kidney graft: Pathophysiology, clinical, therapy

Allo-antibodies, particularly when donor specific, are one of the most important factors that cause both early and late graft dysfunction. The authors review the current state of the art concerning this important issue in renal transplantation. Many antibodies have been recognized as mediators of renal injury. In particular donor-specific-Human Leukocyte Antigens antibodies appear to play a major role. New techniques, such as solid phase techniques and Luminex, have revealed these antibodies from patient sera. Other new techniques have uncovered alloantibodies and signs of complement activation in renal biopsy specimens. It has been acknowledged that the old concept of chronic renal injury caused by calcineurine inhibitors toxicity should be replaced in many cases by alloantibodies acting against the graft. In addition, the number of patients on waiting lists with preformed anti-human leukocyte antigens (HLA) antibodies is increasing, primarily from patients with a history of renal transplant failure already been sensitized. We should distinguish early and late acute antibody-mediated rejection from chronic antibody-mediated rejection. The latter often manifets late during the course of the post-transplant period and may be difficult to recognize if specific techniques are not applied. Different therapeutic strategies are used to control antibody-induced damage. These strategies may be applied prior to transplantation or, in the case of acute antibody-mediated rejection, after transplantation. Many new drugs are appearing at the horizon; however, these drugs are far from the clinic because they are in phase I-II of clinical trials. Thus the pipeline for the near future appears almost empty.

Immunology of liver transplantation

In comparison with other solid-organ transplants, liver allografts are immunologically privileged. Allografts are rejected by immune reactions of the host, and clinical therapy for liver allografts includes immunosuppression to prevent rejection. Orthotopic liver transplant causes systemic donor-specific T-cell tolerance. In addition, antigens introduced into hepatocytes or the portal vein cause tolerance. The basic mechanism in liver tolerance may include continuous exposure of diverse liver cell types to endotoxin derived from intestinal bacteria. This exposure promotes the expression of cytokines, antigen-presenting molecules, and costimulatory signals that inactivate T cells, partly by effects on liver antigen-presenting cells. A simple, reliable, noninvasive assay to evaluate antidonor alloreactivity may be important in implementing these approaches in the laboratory and clinic.