Pretransplant Human Leukocyte Antigen Research Articles

Trends in the Perioperative Practices for Immunological Assessment and Immunosuppression Strategies for Patients Undergoing Intestinal Transplantation at American Transplant Centers.

Intestinal transplantation (IT) is a complex procedure that requires nuanced immunosuppressive strategies to optimize patient outcomes. Despite advancements, significant variability remains in immunosuppressive protocols across transplant centers due to a lack of consensus on the optimal approaches for induction, maintenance, and clinical testing. This variability complicates standardization and identification of best practices for IT recipients. A descriptive survey study was conducted to characterize immunosuppressive and testing strategies in IT at major transplant centers in the United States. Ten centers known to have performed over 10 ITs since 2015 were selected from the Scientific Registry of Transplant Recipients database. A 22-question survey was distributed to surgical directors, collecting data on pre-, peri-, and post-transplant immunological testing, desensitization strategies, immunosuppressive regimens, and management of antibody-mediated rejection (AMR) and acute cellular rejection (ACR). Nine centers (90%) responded. All centers conducted pretransplant human leukocyte antigen (HLA) and donor-specific antibody (DSA) testing, with varying frequencies and methodologies. Desensitization was reported by 44% of centers for isolated IT and by 22% for multivisceral transplants. Induction therapy predominantly involved antithymocyte globulin (89%) and rituximab (44%). Tacrolimus was universally used for maintenance, with varying trough level targets across centers. Post-transplant DSA testing was performed by all centers, and protocol-driven endoscopic bowel biopsies were routine at 67% of centers. AMR was diagnosed at 89% of centers, with plasmapheresis and IVIG being the most common treatments. Variability was noted in desensitization practices and AMR management. This survey highlights considerable consistency in pre- and post-transplant testing and immunosuppressive regimens for IT recipients, while significant variability exists in desensitization strategies and AMR management. Further research is needed to standardize these practices to improve patient outcomes across transplant centers.

Human leukocyte antigen mismatch and circulating donor-specific antibodies predict graft loss after kidney transplantation: A retrospective study from Campania region – Italy

Donor-specific antibodies (DSA) are an established biomarker predicting antibody-mediated rejection, as the leading cause of graft loss after kidney transplantation. Furthermore, human leukocyte antigen (HLA) matching offers a more precise assessment of donor-recipient HLA compatibility and may prevent more effectively sensitization against allograft tissue. Indeed, increased number of HLA mismatches (MM) is significantly associated with a higher risk of immunological rejection, de novo DSA (dnDSA) development, and graft failure. Over the last decade, a comprehensive approach to optimize kidney matching and monitor transplant recipients for acute and chronic graft dysfunction was the goal for the success of the kidney transplantation. In our long-term retrospective study, we have found that pre- and post-transplantation HLA antibodies were significantly associated with de novo dnDSA occurrence (pre-transplant HLA Class I antibodies p = 0.039p < 0.05; pre-transplant HLA Class II antibodies p = 0.011p < 0.05; post-transplant HLA Class I non-DSA antibodies p < 0.01; post-transplant HLA Class II non-DSA antibodies p < 0.01). In addition, HLA MM at locus A (hazard ratio (HR), 2.44; 95 % confidence interval (CI): 1.15–5.16; p = 0.01 hazard ratio (HR), 2.33; 95 % confidence interval (CI):1.132–4.805; p = 0.02) and DSA Class I (HR, 10.24; 95 % CI: 1.44–72.62; p = 0.02 HR, 5.539; 95 % CI: 1.264–24.272; p = 0.02) appeared to be significant predictors of poorer graft survival. Our investigation demonstrates the long medium-term experience of DSA development occurrence in patients with after kidney transplantation in Campania region – Italy.

Exploring the immunological relevance of pre-transplant donor-specific antibody in intestinal transplantation, with special consideration to the liver.

Despite recent advances that have improved outcomes following intestinal transplantation (ITx), achieving long-term patient survival and rejection-free survival is still challenging. Understanding the relevance of pre-transplant human leukocyte antigen (HLA) donor-specific antibody (DSA) in ITx and the immunomodulatory potential of the liver within the allograft is crucial to providing an accurate assessment of pre-transplant immunological risk, which could influence and improve post-transplant outcomes further. This was the primary objective of this retrospective study of 95 adult ITx transplants which took place at Cambridge University Hospitals (United Kingdom) between 2007 and 2019. Two novel programs were developed and validated to identify DSA (tested by Luminex single antigen beads) in this dataset. Data analysis utilised Kaplan-Meier survival methods, and statistical analysis was performed using log-rank tests and adjusted Cox models. Fifty-four (57%) ITx cases contained a liver, and 36 (38%) were sensitised to HLA. Pre-transplant DSA >500 mean fluorescent intensity appeared to negatively affect post-ITx patient survival and rejection outcomes. Additionally, liver-inclusive allografts seemed to show particular resistance to HLA class I DSA. Our data hints towards consistency with other ITx studies where deleterious effects of DSA have been demonstrated, and where liver inclusion is protective from HLA class I DSA. This is in line with current national guidelines for immunological risk. Our publicly available research programs could support future large or multicentre studies where statistically relevant data might be gained.

Utilizing proficiency testing survey data to create advanced educational content: the virtual crossmatch challenge model.

Proficiency testing (PT) surveys include data from laboratories across the world and are ideal for creating advanced educational content, beyond just consensus grading. Educational challenges provide a unique opportunity to probe common laboratory practices and risk assessment, especially in cases where there is no "analyte" tested. Human leukocyte antigen (HLA) compatibility evaluation between donor and recipient pairs has been traditionally assessed using T-cell and B-cell physical crossmatches. However, advancements in our ability to identify and characterize HLA antibodies using solid phase assays, in combination with changing deceased donor allocation schemes and improved HLA typing, have shifted the paradigm from performing physical crossmatches to the use of the virtual crossmatch (VXM). VXM is a compatibility assessment relying on the interpretation of pre-transplant HLA laboratory data and as such, it is not an "analyte". However, VXM results are used in clinical decision-making. The VXM assessment depends on patient characteristics as well as laboratory and transplant center practices but must ensure safe transplantation outcomes while maintaining equity in access to transplantation. In this manuscript, we describe the American Society for Histocompatibility and Immunogenetics (ASHI) PT Educational VXM Challenge, as a model for creating educational content using PT survey data. We discuss the different components of the VXM Challenge and highlight major findings and learning points acquired from ASHI VXM Challenges performed between 2018-2022, such as the lack of correlation between the VXM and the physical crossmatch in the presence of low level donor-specific antibodies (DSA), or when the DSA were aimed against donor alleles that are not present on the antibody panel, and in the presence of an antibody to a shared eplet. Finally, we show that the VXM Educational Challenge serves as a valuable tool to highlight the strengths and pitfalls of the VXM assessment and reveals differences in testing and result interpretation among participating HLA laboratories.

Living Donor Kidney Transplantation in Patients With Donor-Specific HLA Antibodies After Desensitization With Immunoadsorption.

Due to the current organ shortage, living donor kidney transplantation is increasingly performed across HLA (human leukocyte antigen) or ABO antibody barriers. There is still uncertainty about the risk of antibody-mediated rejection (AMR) episodes, which may limit long-term graft survival. From March 2007 to December 2016, 58 sensitized living donor kidney transplant candidates were identified and 38 patients eventually included in the study: 36 patients (95%) had pre-transplant and pre-desensitization Luminex-detected donor-specific HLA antibodies (DSA), and 17/36 patients (47%) in addition had a positive crossmatch result. Two patients had no detectable DSA but a positive CDC B-cell crossmatch result. Patients were treated with pre- and post-transplant apheresis and powerful immunosuppression including the anti-CD20 antibody rituximab (N = 36) in combination with thymoglobulin (N = 20) or anti-IL2 receptor antibody (N = 18). The results of the 38 successfully desensitized and transplanted patients were retrospectively compared to the results of 76 matched standard-risk recipients. Desensitized patients showed patient and graft survival rates similar to that of standard-risk recipients (P = 0.55 and P = 0.16, respectively). There was a trend toward reduced death-censored graft survival in desensitized patients (P = 0.053) which, however, disappeared when the 34 patients who were transplanted after introduction of sensitive Luminex testing were analyzed (P = 0.43). The incidence of rejection episodes without borderline changes were in desensitized patients with 21% similar to the 18% in standard-risk patients (P = 0.74). Thirty-six patients had pre-transplant HLA class I and/or II DSA that were reduced by 85 and 81%, respectively, during pre-transplant desensitization (P < 0.001 for both). On day 360 after transplantation, 20 of 36 (56%) patients had lost their DSA. The overall AMR rate was 6% in these patients, but as high as 60% in 5 (14%) patients with persistent and de novo DSA during year 1; 2 (40%) of whom lost their graft due to AMR. Eleven (31%) patients with persistent DSA but without de novo DSA had an AMR rate of 18% without graft loss while one patient lost her graft without signs of AMR. Our desensitization protocol for pre-sensitized living donor kidney transplant recipients with DSA resulted in good graft outcomes with side effects and rejection rates similar to that of standard-risk recipients. Adequate patient selection prior to transplantation and frequent immunological monitoring thereafter is critical to minimize rejection episodes and subsequent graft loss.

Pre-transplant AT1R antibodies and long-term outcomes in kidney transplant recipients with a functioning graft for more than 5 years.

There is conflicting data regarding the association of pre-transplant AT1R antibody levels and long-term outcomes following kidney transplantation. We examined the association between pre-transplant antibodies and long-term graft outcome by assaying pre-transplant sera from 125 kidney transplant recipients from 1999 to 2009. The mean age at transplant was 55.7±13 years; 67.2% were male, 87.2% were Caucasian, and 67.2% received a deceased donor transplant. Induction therapy included 44.8% thymoglobulin. Human leukocyte antigen (HLA) donor-specific antibodies (DSA) were present in 22 (17.6%) patients, while AT1R antibodies >17U/mL were present in 24 (19.2%). The mean AT1R antibodies level was 13±7.2 U/mL. Patients were followed-up for 7.1±1.9 years after transplant. Pre-transplant AT1R antibodies were associated with rejection (p<0.0001), antibody-mediated rejection (ABMR) (p<0.0001), and death-censored graft failure (DCGF) (p=0.01). This was confirmed by univariate Cox regression analyses for AT1R antibodies >10U/mL (HR 2.64, 95% Cl 1.35 - 5.17, p=0.04) and AT1R antibodies >17U/mL (HR=1.74, 95% Cl 1.061-2.98, p=0.04). Multivariable analyses did not retain AT1R antibodies as independent predictors of DCGF; however, pre-transplant HLA, DSA, and acute rejection during the first year were associated with DCGF (HR 2.07, 95% Cl 1.13 - 3.78, p=0.02 and HR 3.03, 95% Cl 1.13 - 3.78, p=0.0002, respectively). Our study indicates that in patients with a functioning kidney allograft >5years, pre-transplant AT1R antibodies may be associated with a greater risk of rejection and late graft failure.

Pre-transplant HLA Antibodies and Delayed Graft Function in the Current Era of Kidney Transplantation.

Delayed graft function (DGF) occurs in a significant proportion of deceased donor kidney transplant recipients and was associated with graft injury and inferior clinical outcome. The aim of the present multi-center study was to identify the immunological and non-immunological predictors of DGF and to determine its influence on outcome in the presence and absence of human leukocyte antigen (HLA) antibodies. 1,724 patients who received a deceased donor kidney transplant during 2008–2017 and on whom a pre-transplant serum sample was available were studied. Graft survival during the first 3 post-transplant years was analyzed by multivariable Cox regression. Pre-transplant predictors of DGF and influence of DGF and pre-transplant HLA antibodies on biopsy-proven rejections in the first 3 post-transplant months were determined by multivariable logistic regression. Donor age ≥50 years, simultaneous pre-transplant presence of HLA class I and II antibodies, diabetes mellitus as cause of end-stage renal disease, cold ischemia time ≥18 h, and time on dialysis >5 years were associated with increased risk of DGF, while the risk was reduced if gender of donor or recipient was female or the reason for death of donor was trauma. DGF alone doubled the risk for graft loss, more due to impaired death-censored graft than patient survival. In DGF patients, the risk of death-censored graft loss increased further if HLA antibodies (hazard ratio HR=4.75, P < 0.001) or donor-specific HLA antibodies (DSA, HR=7.39, P < 0.001) were present pre-transplant. In the presence of HLA antibodies or DSA, the incidence of biopsy-proven rejections, including antibody-mediated rejections, increased significantly in patients with as well as without DGF. Recipients without DGF and without biopsy-proven rejections during the first 3 months had the highest fraction of patients with good kidney function at year 1, whereas patients with both DGF and rejection showed the lowest rate of good kidney function, especially when organs from ≥65-year-old donors were used. In this new era of transplantation, besides non-immunological factors, also the pre-transplant presence of HLA class I and II antibodies increase the risk of DGF. Measures to prevent the strong negative impact of DGF on outcome are necessary, especially during organ allocation for presensitized patients.

Role of Autoimmunity in Patients Transplanted for Acute Liver Failure of Unknown Origin: A Clinical and Graft Biopsy Analysis.

The etiology and prognosis of acute liver failure (ALF) remains unknown in a significant proportion of cases. Signs of autoimmunity may be present, but no consistent pattern has been observed. We aimed to analyze if pretransplant immunological findings, human leukocyte antigen (HLA) haplotypes, and clinical features among patients with an unknown etiology differ from those of autoimmune or other known etiologies. We also analyzed whether such signs impact posttransplant biopsy findings or complications. All adult ALF patients undergoing liver transplantation (LT) in Finland during 1987-2015 were followed to 2016. Data were collected from the LT registry, pathology database, and patient records. A total of 124 patients were included in the analysis. Study subgroups were acute autoimmune hepatitis (AIH; n=25), known non-AIH etiology (n=54), and unknown etiology (n=45). The unknown etiology group differed from the known non-AIH group with regard to the following pretransplant autoimmunity-associated features: positive perinuclear anti-neutrophil cytoplasmic antibodies (36% versus 8%; P=0.02) and higher mean immunoglobulin A (IgA; 3.2±1.7 versus 2.1±1.4, P=0.006) and immunoglobulin G (IgG; 12.7±4.3 versus 8.5±3.6, P=0.001). AIH-associated HLA haplotypes B8, DR3, and B8DR3 were more common in the AIH group (40%, 44%, and 36%, respectively) and in the unknown group (29%, 33%, and 29%, respectively) than in the known non-AIH group (11%, 17%, and 11%, respectively) or in the Finnish general population (17%, 18%, and 8%, respectively). However, these findings had no association with protocol biopsies, extrahepatic autoimmune diseases, or survival. Patients with≥1 rejection episode had higher pretransplant IgA (3.7±2.3 versus 2.6± 1.2; P=0.02) and IgG (16.4±10.2 versus 12.4±6.8; P=0.03) than those without rejections. Autoimmunity-associated pretransplant laboratory findings and HLA haplotypes were common in ALF of unknown etiology, but they showed minimal predictive value for posttransplant biopsy findings, clinical complications, or survival.

Donor-specific and -nonspecific HLA antibodies and outcome post lung transplantation.

Donor-specific antibodies (DSAs) against human leukocyte antigen (HLA) are associated with chronic lung allograft dysfunction (CLAD) and mortality post lung transplantation, but data concerning prevalence, time of onset, persistence and effects on long-term outcome remain scarce.We assessed the association between HLA antibodies and CLAD-free and graft survival in a cohort of 362 patients. We stratified our analysis according to DSA status, persistence of antibodies and timing of antibodies (pre-transplant, early or late post-transplant).Within our cohort, 61 (17%) patients developed DSAs (mostly against HLA-DQ), which was associated with worse CLAD-free and graft survival (p<0.0001 and p=0.059, respectively). Persistent (hazard ratio (HR) 3.386, 95% CI 1.928-5.948; p<0.0001) as well as transient (HR 2.998, 95% CI 1.406-6.393; p=0.0045) DSAs were associated with shorter CLAD-free survival compared with patients without DSAs. Persistent DSAs (HR 3.071, 95% CI 1.632-5.778; p=0.0005) but not transient DSAs were negatively associated with graft survival compared with patients without DSAs, likely due to the higher incidence of restrictive CLAD. HLA non-DSAs and pre-transplant HLA antibodies had no effect on post-transplant outcome.We demonstrated an important difference in prognosis between persistent and transient DSAs. Moreover, the observed association between DSAs and restrictive CLAD suggests an overlap between antibody-mediated rejection and restrictive CLAD that needs further investigation.

Pre-transplant Sensitization for Patient Awaiting Lung Transplant: Are We Concerned?

The goal of this paper is to highlight the changes in detection, management, and prognosis of pre-transplant sensitized candidates and recipients. With improvements in technology, human leukocyte antigen (HLA) antibody testing has identified a significant proportion of lung transplant candidates with pre-transplant HLA antibody detection. Pre-transplant antibodies are associated with worse early outcomes after lung transplant if not addressed with targeted antibody therapy. There are promising new therapy plans to address pre-transplant HLA antibodies and potentially ameliorate the early risk of antibody-mediated graft injury. Pre-transplant sensitization continues to be a difficult problem in lung transplant. Detailed HLA antibody reports allow for precise identification of antibodies. The future challenge is how to manage these antibodies pre- and peri-transplant.

Pretransplant human leukocyte antigen antibodies detected by single-antigen bead assay are a risk factor for long-term kidney graft loss even in the absence of donor-specific antibodies.

Clinical relevance of ELISA- and single-antigen bead assay (SAB)-detected pretransplant HLA antibodies (SAB-HLA-Ab) for kidney graft survival was evaluated retrospectively in 197 patients transplanted between 2002 and 2009 at the University Clinic Frankfurt. Having adjusted for retransplantation and delayed graft function, a significantly increased risk for death-censored graft loss was found in patients with pretransplant SAB-HLA-Ab [HR: 4.46; 95% confidence interval (CI): 1.47-13.48; P = 0.008]. The risk for increased graft loss was also significant in patients with pretransplant SAB-HLA-Ab but without SAB-detected donor-specific Ab (SAB-DSA) (HR: 4.91; 95% CI of 1.43-16.991; P = 0.012). ELISA was not sufficient to identify pretransplant immunized patients with an increased risk for graft loss. In immunized patients, graft loss was predominantly present in patients who received transplants with a mismatch on the HLA-DR locus. In conclusion, even if our study is limited due to small sample size, the results show an increased risk for long-term graft loss in patients with pretransplant SAB-HLA, even in the absence of DSA. SAB-HLA-Ab-positive patients, being negative in ELISA or CDC assay, might profit from a well-HLA-DR-matched graft and intensified immunosuppression.

The impact of pre-transplant allosensitization on outcomes after lung transplantation

Allosensitization can be a significant barrier to transplantation for some patients, and previous studies suggested that pre-transplant allosensitization was associated with worse outcomes after lung transplantation. However, human leukocyte antigen (HLA) antibody testing has evolved significantly over the past 10 years, and current assays are highly sensitive and specific. We examined the impact of pre-transplant allosensitization on post-transplant outcomes in the era of solid-phase multiplex HLA antibody detection assays in this retrospective, single-center study of 304 adult transplant recipients between January 1, 2006, and December 31, 2012. We accepted donor organs for allosensitized patients if a virtual crossmatch was compatible with all previously identified antibodies. In univariate and multivariate Cox proportional hazards models, pre-transplant allosensitization, the calculated panel reactive antibody, and the number of pre-transplant HLA antibodies were not associated with the development of acute cellular rejection, lymphocytic bronchiolitis, donor-specific HLA antibodies, chronic lung allograft dysfunction, or graft failure. Pre-transplant allosensitization does not adversely affect outcomes after lung transplantation when the potentially reactive HLAs are avoided in the donor by a virtual crossmatch with the recipient.

Creatinine and cytokines plasma levels related to HLA compatibility in kidney transplant patients

Introduction:The success of kidney transplantation depends on prevention of organ rejection by the recipient’s immune system, which recognizes alloantigens present in transplanted tissue. Human leukocyte antigen (HLA) typing is one of the tests used in pre-renal transplantation and represents one of the most important factors for a successful procedure.Objective:The present study evaluated creatinine and cytokines plasma levels in kidney transplant patients according to pre-transplant HLA typing.Methods:We assessed 40 renal transplanted patients selected in two transplant centers in Belo Horizonte (MG).Results:Patients were distributed into three groups according to HLA compatibility and, through statistical analysis, the group with more than three matches (H3) was found to have significantly lower post-transplant creatinine levels, compared to groups with three or fewer matches (H2 and H1, respectively). The median plasma levels of cytokines interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-α), and interleukin 10 (IL-10) were evaluated according to the number of matches. Pro-inflammatory cytokines (IL-6 and TNF-α) were significantly higher in groups with lower HLA compatibility. On the other hand, the regulatory cytokine IL-10 had significantly higher plasma levels in the group with greater compatibility between donor and recipient.Conclusion:These findings allow us to infer that pre-transplant HLA typing of donors and recipients can influence post-transplant renal graft function and may contribute to the development and choice of new treatment strategies.

Pretransplant DSA But Not Complement Fixing HLA Antibodies Are Associated with Increased Risk for Antibody Mediated Rejection in Kidney Transplantation.

It is still not fully elucidated whether kidney transplant recipients with preformed donor-specific human leukocyte antigen (HLA) antibodies (DSA) detectable by Luminex Single Antigen Beads (SAB) are at increased risk of reduced allograft function early after transplantation. Especially the effect of complement fixing DSA detected by the C1q SAB assay remains unclear. Regarding the C1q assay recent studies indicated controversial results, possibly related to centre effects or the size of the patient cohorts analyzed. The aim of our retrospective analysis was to evaluate the early impact of C1q fixing DSA in a large single centre study. We included a cohort of 262/289 renal transplant recipients transplanted in a short period between January 2011 and December 2012 at the local kidney transplantation program in this analysis. All transplantations were performed with a CDC negative crossmatch. For living donation also flow cytometric crossmatches were performed. The pretransplant HLA antibody status determined by Luminex SAB was not systematically considered for transplant decisions. In addition, we analysed all indication biopsies performed within the first one to two years of follow-up for histological signs of antibody mediated rejection (AMR). Pretransplant SAB DSA were present in 40 patients (25 with anti-HLA-class I, 11 with class II, and 4 with class I+II specificities, respectively). In total 27/262 patients showed signs of AMR, 14 of 222 patients without DSA (6.3%, RR 0.2) compared to 13/40 patients with DSA (32.5%, RR 5.2). The C1q fixing capacity was positive in 6/40 patients with DSA, but only in 1/27 patients with AMR. Follow-up data for graft survival and function are pending. Although still preliminary, our study could clearly confirm pretransplant Luminex DSA as a significant risk factor for the occurrence of early AMR after renal transplantation. C1q-binding capacity of DSA at the time of transplantation seems to be not predictive for the occurrence of AMR during early follow-up.

Peripheral B-cell phenotype and BAFF levels are associated with HLA immunization in patients awaiting kidney transplantation.

The role of B-cell subsets in human leukocyte antigen (HLA)-specific humoral responses in patients with end-stage renal disease is poorly documented. The objective of this study was to analyze the potential association between B-cell subsets distribution and anti-HLA antibodies before kidney transplantation. The authors studied by flow cytometry peripheral B-cell subsets and serum levels of BAFF, the main homeostatic cytokine for peripheral B cells, in 101 consecutive end-stage renal disease patients admitted for transplantation. In patients with HLA antibodies detected with Luminex single antigen, the proportion of activated naive B cells (Bm2) was significantly higher (64.4 ± 15.1% vs. 52.5 ± 19.1% in HLA antibody-negative patients, P=0.0008) at the expense of memory B cells, as were BAFF serum levels (1,651 ± 1,297 vs. 1,139 ± 693 pg/mL, P<0.0001). Proportion of Bm2 and BAFF levels were positively associated with the diversity of anti-HLA antibodies. In multivariate analysis, besides HLA-immunizing events (pregnancy and previous transplantation), proportion of Bm2 cells but not of other B-cell subsets or BAFF levels was independently associated with the presence and diversity of anti-HLA antibodies. High proportion of Bm2 cells before transplantation was associated with an increased risk of developing de novo donor-specific antibodies during the first year posttransplant. The authors did not find any association between the frequency of antibody-mediated rejection and pretransplant proportion of any B-cell subset or BAFF serum levels. Increased proportions of activated naive B cells are linked with pretransplant HLA immunization and the development of posttransplant donor-specific antibodies.

Graft-Specific HLA-Antibodies Do Not Influence Unit Dominance and Do Not Prevent High Rates of Sustained Donor Engraftment in Recipients of Double-Unit Cord Blood Transplantation

AbstractAbstract 960 Background:Pre-transplant human leukocyte antigen (HLA)-antibodies have an established role in failed engraftment after single-unit cord blood (CB) transplantation (CBT). Their role in double-unit CBT (DCBT) engraftment, however, is more controversial. Some transplant centers advocate pre-transplant screening of the recipient for HLA-antibodies, and avoidance of units with the corresponding antigens if antibodies are detected. Methods:We evaluated the influence of pre-transplant HLA-antibodies on sustained donor neutrophil engraftment and unit dominance in 82 recipients (median 48 years, range 2–69) of 4–6/6 HLA-A, B antigen, DRB1 allele matched double-unit CB grafts, and transplanted for hematologic malignancies at MSKCC from July 2008 to July 2012. HLA-antibodies were measured by the HLA Laboratory of the American Red Cross Blood Service using Single Antigen Luminex beads and analyzed by HLA Fusion software. The cut-off for positive results was a normalized mean fluorescence intensity value > 1000. Results:Overall, 28/82 (34%) patients were positive for HLA-antibodies [16 (19.5%) had antibodies without graft specificity, and 12 (14.5%) had antibodies with graft specificity]. These patients were more likely to be female with acute leukemia and cytomegalovirus seropositive. All patients with graft-specific antibodies received myeloablative conditioning; 5 had antibodies against class I HLA, 6 against class II, and one patient had antibodies to both Class I/II. Moreover, of these 12 patients, 6 had antibodies against one unit, and 6 had antibodies against both units. Neutrophil engraftment according to antibody presence is summarized in the Table. 64 of 66 (97%) evaluable myeloablative DCBT recipients (Table 1A) engrafted at a median of 24 days (range 12–40); one patient without antibodies and one with antibodies against both units had primary graft failure, both in the setting of early onset multi-organ failure. Both patients were 100% donor with one unit but did not recover counts. Of the 6 patients with antibodies to one unit, 3 engrafted with that unit and 3 with the opposite unit. Of the 6 patients with antibodies against both units, one had clinical graft failure as described above, and the 5 others had sustained donor engraftment (4 with one unit and one with both). In engrafting myeloablative recipients, the median time to neutrophil recovery was 8 days slower in patients with graft-specific antibodies, but the engrafting unit in these patients also had the lowest infused dose: median CD34+ cell dose/kg if no antibodies 0.83 × 105/kg, non-specific antibodies 1.09 × 105/kg, and antibodies specific to graft 0.65 × 105/kg. In non-myeloablative recipients, 15/16 (94%) engrafted (Table 1B). The single patient with graft rejection and autologous recovery had HLA-antibodies that were not graft specific. Conclusions:11 of 12 double-unit CBT recipients with graft-specific antibodies engrafted successfully. While myeloablative recipients with graft-specific antibodies engrafted more slowly, this may be explained by a lower infused CD34+ cell dose of their engrafting units. Multivariate analysis of larger patient numbers will be required to further evaluate the effect of graft-specific antibodies on engraftment speed. At this time, however, the presence of graft-specific antibodies should not preclude DCBT, and whether their presence should influence graft selection is not clear. Furthermore, there is no suggestion that the presence of HLA-antibodies influences unit dominance after DCBT.TableSustained Donor Neutrophil Engraftment According to HLA-antibodies1A) Myeloablative Conditioning (n=67)Median (Range) Time to Neutrophil Recovery (> 0.5)N (%) Sustained EngraftmentNo antibodies (n=41)23 days (range 12–38)39/40 (1 non-evaluable)Antibodies: not graft-specific (n=14)23 days (range 12–37)14/14Antibodies: graft-specific (n=12)31 days (range 13–40)11/12Against engrafting unit (n=3)28 days (range 24–31)3/3Against non-engrafting unit (n=3)31 days (range 25–32)3/3Antibodies against both units (n=6)33 days (range 13–40)5/61B) Non-Myeloablative Conditioning (n=15)Median (Range) Time to Neutrophil Recovery (> 0.5)N (%) Sustained EngraftmentNo antibodies (n=13)10 days (range 8–20)13/13Antibodies: not graft specific (n=2)19 days in 1 patient (other had graft failure/autologous recovery)1/2Antibodies: graft specific (n=0)-- Disclosures:Giralt:Celgene: Honoraria, Research Funding.

The Clinical Significance of Human Leukocyte Antigen Antibody Development in Kidney Transplantation

BackgroundThis retrospective study uses the LAT-M (One Lambda Inc., Calif) screen assay to reexamine the impacts (a), of pretransplant human leukocyte antigen (HLA) antibody on long-term graft survival; (b) posttransplant HLA antibody on long-term graft survival and (c) immunosuppressive regimen on posttransplant HLA antibody development. Patients and methodsPretransplant sera from 222 renal transplant recipients and posttransplant sera from 216 renal transplant recipients were studied for the impact of HLA antibody on long-term graft survival. ResultsAmong the patients who did not display pretransplant HLA antibodies, 85% enjoyed 5-year and 59% 10-year graft survival, whereas the patients who tested positive were 83% and 83% (P = .5596). Among the patients who did not show posttransplant HLA antibodies, 99% enjoyed 5-, 91% 10-, and 65% 15-year graft survival, whereas for the 44 patients who tested positive they were 59%, 44%, and 30%, respectively (P < .0001). Patients prescribed cyclosporine + myfortic (odds ratio 0.17, P = .05) or FK + Cellcept (odds ratio 0.36, P = .04) showed the lowest posttransplant HLA antibody development. ConclusionBoth regimens improve graft survival.

Effect of Pretransplant Human Leukocyte Antigen Antibodies Detected by Solid-Phase Assay on Heart Transplant Outcomes

Introduction The significance of pretransplant human leukocyte antigen antibodies (HLA-Abs), especially donor-specific HLA-Abs (DSA), as detected by single antigen bead assay (SAB), is not well characterized in cardiac transplantation (CTX). We analyzed the significance of DSA detected by SAB in predicting crossmatch (XM) results and post-transplant rejection. Materials and methods We performed a retrospective study of 85 CTX with negative cytotoxicity XM. We tested pretransplant sera collected within 24 hours of transplantation by flow cytometric XM (FXM) and SAB. DSA identified by SAB were utilized to perform a virtual crossmatch (VXM). Positive VXM was defined as the presence of DSA at mean fluorescence intensity (DMFI) > 1500. Additionally, to analyze the significance of low-level DSA weakly positive VXM was DMFI 300 to 1500. We defined a negative VXM as MFI < 300. VXM results were correlated with FXM results and with posttransplant rejection. Results Patients in the weakly positive and negative VXM had similar posttransplant rejections. DMFI > 1500 correlates well with FXM results (accuracy = 90%). Patients with DMFI > 1500 had a higher incidence of antibody-medicated rejection (AMR; P = .0052), AMR grade I ( P < .0001), cell-mediated rejection (CMR) grade > 1R/1A ( P = .018), and CMR grade > 2R/3A ( P = .057). Similarly patients with positive FXM had a higher incidence of AMR ( P = .091), AMR grade 1 ( P < .0001), CMR grade > 1R/1A ( P = .05), and CMR grade > 2R/3A ( P = .56). Conclusions In conclusion, SAB defined DMFI > 1500 can be used as a surrogate for FXM. Recipients with DMFI > 1500 pretransplant and positive FXM have significantly higher rates of AMR and CMR compared to recipients with DMFI < 1500 or negative FXM.

HLA Antibodies and the Occurrence of Early Adverse Events in the Modern Era of Transplantation: A Collaborative Transplant Study Report

Adverse events occurring early after kidney transplantation were reported to influence graft outcome. In a prospective multicenter study initiated in 2001, we investigated the relationship between human leukocyte antigen (HLA) alloantibodies, early adverse events, and graft outcome. Pretransplant presence of HLA class I antibodies was associated with a higher rate of no immediate function (NIF) of the graft (odds ratio [OR] 1.78, P=0.023) and acute rejection episodes (ARE) during the first 3 months after transplantation (OR 2.53, P<0.001). NIF and ARE during posttransplant days 15 to 90 were associated with increased risk of graft loss to year 3 (OR 2.06 and 3.75, P=0.006 and P<0.001, respectively). ARE within the first 2 posttransplant weeks did not increase the risk significantly, especially if they occurred in nonsensitized patients without antibodies. Graft survival at 3 years in patients with both NIF and ARE during the first 3 months was significantly lower (81.3%+/-6.2%) than in patients who did not experience NIF or ARE (95.1%+/-1.0%, P<0.001). Importantly, neither NIF nor ARE had an impact on subsequent graft survival if good graft function (serum creatinine <130 mumol/L) was observed at the end of the third month. Our results show that NIF and ARE associated with pretransplant antibodies against HLA class I, and they suggest that early diagnosis and treatment of adverse events with the aim of obtaining normal 3-month graft function should be pursued rigorously. Good 3-month graft function is associated with excellent long-term survival, even in patients with pretransplant HLA antibodies and posttransplant adverse events.

Clinical relevance of pretransplant human leukocyte antigen donor-specific antibodies in renal patients waiting for a transplant: A risk factor

The use of highly sensitive solid-phase antibody detection assays, including x-MAP multiple bead-based technology (Luminex), has greatly enhanced our ability to accurately detect and define very low levels of HLA antibodies. These developments have led to patients having increasing lists of antibody specificities (which may not be clinically relevant), resulting in a new “technological barrier” to transplantation in sensitized patients. Alloantibodies play a major role in all types of solid organ rejection; the presence of low-titer donor-specific antigen (DSA) identified pretransplant is associated with an increased risk of antibody-mediated rejection (AMR). However, these low-titer antibodies do not represent an absolute contraindication to transplant. Improvement in the diagnosis and treatment of AMR will allow sensitized patients with DSA to be successfully transplanted in the short term, but extended follow-up is required to ensure acceptable long-term graft survival in this group. These factors must be integrated into the decision algorithms for immunosuppressive treatment in patients at immunologic risk.