Graft immunologic events in deceased donor kidney transplant recipients with preformed HLA-donor specific antibodies.

INTRODUCTION: Pretransplant donor-specific HLA alloantibodies detected with the Single Antigen Bead (SAB) assay reflect an increased risk for acute antibody-mediated rejection (AMR). We herein report the incidence of both acute AMR and acute cellular rejection (ACR) during the first year posttransplantation, in a cohort of kidney transplant recipients (KTR) of deceased donor (DD) grafts, according to their DSA status. Pretransplant DSA do not preclude DD-KT in negative CDC-XM recipients at our center. PATIENTS AND METHODS: 246 KT were performed at our center between 01/2012 and 12/2015 and 100 KTR obtained from a DD were analyzed; 24% harbored DSA by SAB assay, MFI values >500 were considered positive. All recipients received thymoglobulin induction and generic tacrolimus-based maintenance therapy. Graft biopsies were performed by protocol on months 3 and 12 as well as per indication. The incidence of AMR and ACR was correlated with the existence of pretransplant DSA. RESULTS: Overall, 34% of patients developed an acute rejection episode, 54.2% in the DSA group versus 27.6% in the non-DSA group (p=0.032), and most of these events were detected as subclinical conditions in protocol biopsies. AMR events developed in 33.3% and 19.7% (p=0.176) in the DSA and the non-DSA groups, respectively. ACR events were found in 16.6% and 6.6% (p=0.127) in the DSA and non-DSA groups, respectively. Graft function was similar between groups at the end of the 1st year posttransplant and no immunological graft loss occurred. CONCLUSION: Despite the use of depleting induction therapy and adequate tacrolimus trough levels along with MMF and steroids, a high rate of rejection events was observed during the first year post-transplantation.

Anti-HLA-DQ antibodies are highly and independently related to the C1q-binding capacity of HLA antibodies.

The complement-binding capacity of anti-HLA antibodies (HLAabs) is recognized as a key pathogenic factor. The aim of this study is to describe the patient characteristics associated to the presence of C1q+ as well as those of the Abs per se when associated to C1q binding. METHODOLOGY: This is a cross-sectional, observational, descriptive study of patients with previous sensitizing factors and awaiting a kidney transplant (KT). We determined anti-HLA antibodies and their C1q binding capacity with the C1q assay. RESULTS: Among the 55 included patients, 26 (47.2%) had at least one C1q+ anti-HLAab. A previous transplant history, a greater number of HLAabs, a greater % of class I or class II PRA, the average MFI of all HLAabs, the MFI of the dominant HLAab and the HLAab antigenic specificities against HLA-B, -C and -DQ, all proved to be risk factors associated to the presence of C1q binding HLAabs (C1q+). In the total population, were detected 1268 HLAabs, 230 (18.1%) of which were C1q+. On multivariate analysis, both HLAabs against the HLA-DQ antigenic specificity (OR 9.82 95% CI 5.4-17.6, p<0.001) and the MFI documented by LABScreen®SAB (OR 1.2% CI 1.22-1.3, p<0.001), proved to be risk factors. CONCLUSION: Anti-HLA-DQ antibodies and the MFI (LABScreen®SAB) are highly and independently related to the C1q-binding capacity of HLA antibodies.

C1Q Assay Results in Complement-Dependent Cytotoxicity Crossmatch Negative Renal Transplant Candidates with Donor-Specific Antibodies: High Specificity but Low Sensitivity When Predicting Flow Crossmatch.

The aim of the present study was to describe the association of positive flow cross match (FXM) and C1q-SAB. Methods. In this observational, cross-sectional, and comparative study, patients included had negative AHG-CDC-XM and donor specific antibodies (DSA) and were tested with FXM. All pretransplant sera were tested with C1q-SAB assay. Results. A total of 50 donor/recipient evaluations were conducted; half of them had at least one C1q+ Ab (n = 26, 52%). Ten patients (20.0%) had DSA C1q+ Ab. Twenty-five (50%) FXMs were positive. Factors associated with a positive FXM were the presence of C1q+ Ab (DSA C1q+ Ab: OR 27, 2.80-259.56, P = 0.004, and no DSA C1q+ Ab: OR 5, 1.27-19.68, P = 0.021) and the DSA LABScreen-SAB MFI (OR 1.26, 95% CI 1.06-1.49, P = 0.007). The cutoff point of immunodominant LABScreen SAB DSA-MFI with the greatest sensitivity and specificity to predict FXM was 2,300 (sensitivity: 72% and specificity: 75%). For FXM prediction, DSA C1q+ Ab was the most specific (95.8%, 85-100) and the combination of DSA-MFI > 2,300 and C1q+ Ab was the most sensitive (92.0%, 79.3-100). Conclusions. C1q+ Ab and LABScreen SAB DSA-MFI were significantly associated with FXM. DSA C1q+ Ab was highly specific but with low sensitivity.

Impact of pretransplant exposure to allosensitization factors generating HLA antibodies in the Luminex era.

AIM: To identify the frequency of exposure to sensitizing factors and evaluate the risk ascribable to each sensitizing factor generating HLAabs measured by Luminex. METHODS: This is a retrospective cohort study that included 502 transplanted patients and 51 patients on the waiting list for a deceased donor graft. Patients were divided into 4 groups according to the %PRA: 0%, 1 to 19%, 20 to 49% and ≥50%. The OR attributable to each sensitizing factor or combination were calculated. RESULTS: Of the total 553 subjects, 53.5% were male, with an average age 35.42±12.96years. 69.1% were exposed to one or more sensitizing factors; 44.8% had %PRA class I≥1 and 38.9% had %PRA class II≥1. Independently or combined, sensitizing factors persist as a risk factor for the development of a %PRA >1%, >20% or >50%. After multivariate analysis, the three sensitizing factors remained significantly associated to HLAab development. CONCLUSIONS: In spite of using a most sensitive technique such as Luminex to measure the %PRA, a clear association persists between exposure to sensitizing factors and a high %PRA. The risk increases after exposure to more than one sensitizing factor.

Pretransplant angiotensin II type 1-receptor antibodies are a risk factor for earlier detection of de novo HLA donor-specific antibodies.

BACKGROUND: Angiotensin II type 1 receptor antibodies (AT1Rabs) have been associated with significantly reduced graft survival. Earlier graft loss has been observed in patients who had pretransplant AT1Rabs and posttransplant donor-specific antibodies (DSA). METHODS: The main goal of this retrospective cohort study was to examine the association between AT1Rabs and the time period to detection of de novo human leukocyte antigen (HLA-DSA) posttransplantation in living donor kidney transplant recipients (KTR). The analysis included 141 KTRs. Pretransplant frozen serum samples were tested for AT1Rabs by ELISA and HLA-DSA by SAB (Luminex) at both the pre- and post-KT time points. RESULTS: The median AT1Rab level was 9.13 U (interquartile range 5.22-14.33). After a mean follow-up period of 3.55 years, 48 patients were found to harbour de novo HLA-DSAs. The presence of AT1Rabs [hazard ratio (HR) 1.009, 95% confidence interval (CI) 1.002-1.01, P = 0.010], male-to-male transplantation (HR 2.57, 95% CI 1.42-4.67, P = 0.002) and antecedent borderline changes or acute cellular rejection (ACR) (HR 2.47, 95% CI 1.29-4.75, P = 0.006) were significantly associated with de novo DSA detection. A dose-dependent association between AT1Rab levels (<10 U, 10.1-16.9 U, 17-29.9 U and >30 U) and de novo DSA detection was observed (log-rank P = 0.0031). After multivariate analysis of AT1Rab levels (continuous variable), AT1Rabs >30 U, male-to-male transplantation, donor age, higher class I percentage of Panel Reactive Antibody and antecedent borderline changes or ACR remained as independent significant risk factors for the detection of de novo DSAs. CONCLUSIONS: The findings suggest that higher levels of pretransplant circulating antibodies against AT1R (>30 U) in kidney graft recipients constitute an independent risk factor for earlier de novo HLA-DSA detection during the posttransplant period.

C1q Assay Results in Complement-Dependent Cytotoxicity Crossmatch Negative Renal Transplant Candidates with Donor-Specific Antibodies: High Specificity But Low Sensitivity When Predicting Flow Crossmatch.

In complement dependent cytotoxicity crossmatch negative renal transplant candidates with human leukocyte antigen donor-specific antibodies (DSA), both the presence of DSA C1q+ and the dominant DSA fluorescence were significantly associated with a positive flow cytometry crossmatch (FXM+). The C1q+ assay was highly specific, but had low sensitivity when predicting FXM+, so the clinical significance of a FXM+ in the absence of DSA C1q+ remains to be clarified in future studies.

Pre-transplant angiotensin II type 1receptor antibodies: a risk factor for decreased kidney graft function in the early post-transplant period?

Angiotensin II type 1 receptor antibodies (AT1Rab) are associated to a significantly lower graft survival and a higher risk of acute rejection after kidney transplantation. This study aimed to evaluate graft function and BPAR during the 1st year post-transplant (PT) in adult kidney transplant recipients (KTR), between 03/2009 and 08/2012. Pre-KT sera were screened for AT1Rab (ELISA) and HLA-DSA (Luminex). Three groups were analyzed: AT1Rab only (n = 13); HLA-DSA only (n = 8); and no AT1Rab or HLA-DSA (n = 90). No differences were observed in clinical characteristics across groups. A higher percentage of BPAR was observed in the AT1Rab positive group, but this difference was not significant. KTR with AT1Rab had a lower mean eGFR (20 mL/min/1.73m2) when compared to KTR with no Abs at 12 months. The significant difference in eGFR was observed since the 1st month PT. Multivariate analysis showed 4 factors independently and significantly associated with eGFR at 12mos PT: BPAR (-18.7 95%, CI -28.2 to -9.26, p<0.001), AT1Rab (-10.51, CI -20.9 to -0.095, p = 0.048), donor age (-0.42, CI -0.75 to -0.103 p = 0.010), and recipient age (-0.36, CI -0.67 to -0.048, p = 0.024). In this study AT1Rab in pre-transplant sera from KTR, was an independent and significant risk factor contributing to a lower eGFR 12 months. PT. This finding deserves to be confirmed in a larger KTR population.

Pre-transplant angiotensin II type 1 receptor antibodies: A risk factor for decreased kidney graft function in the early post-transplant period?

Angiotensin II type 1 receptor antibodies (AT,Rab) are associated with a significantly lower graft survival and a higher risk of acute rejection after kidney transplantation. This study aimed to evaluate graft function and biopsy proven acute rejection (BPAR) during the first year post-transplant in adult renal transplant recipients (RTR), between 03/2009 and 08/2012. Pre-transplant sera were screened for AT1Rab (via enzyme linked immunosorbent assay) and donor specific anti-human leukocyte antigen antibodies (HLA-DSA, via Luminex). Three groups were analyzed: AT1Rab only (n=13); HLA-DSA only (n=8); and no AT1Rab or HLA-DSA (n=90). No differences were observed in clinical characteristics across groups. A higher percentage of BPAR was observed in the AT1Rab positive group, but this difference was not significant. RTR with AT1Rab had a lower median estimated glomerular filtration rate (eGFR=20 ml/min/1.73m2) when compared to RTR with no antibodies at 12 months. A significant difference in eGFR was observed since the first month post-transplant. Multivariate analysis showed four factors independently and significantly associated with eGFR at 12 months post-transplant: BPAR (beta -18.7, 95% CI -28.2 to -9.26, p<0.001), AT,Rab (beta -10.51, 95% CI -20.9 to -0.095 p=0.048), donor age (beta -0.42, 95% CI -0.75 to -0.103, p=0.010), and recipient age (3 -0.36, 95% CI -0.67 to -0.048, p= 0.024). In this study, AT1Rab in pre-transplant sera from RTR was an independent and significant risk factor contributing to a lower eGFR at 12 months posttransplant. This finding deserves to be confirmed in a larger RTR population.

Pre-nephrectomy angiotensin II type 1 receptor antibodies in living kidney donors: A concern?

Angiotensin II type 1 receptor (AT1R) autoantibodies (AT1Rab) have been associated with pre-eclampsia and malignant hypertension. Overactivity of the angiotensin-II/AT1R complex has also been implicated in cardiac, renal, and vascular remodeling, leading to mortality and morbidity from cardiovascular disease. Pre-donation prevalence and possible post-donation effects of AT1Rab in living kidney donors (LKD) are unknown. In this study, sera obtained the day before nephrectomy and kept frozen at -70 degrees C from 113 strictly normotensive and non-obese LKD were tested for AT1Rab by OneLambda detection assay. AT1Rab titers >or=17 international units were considered positive. Pre-donation renal function [estimated glomerular filtration rate (eGFR)] and blood pressure at 1 and 12 months post-donation were recorded in every patient. Ten of 113 (8.8%) LKD yielded a positive AT1Rab result. History of sensitization events was similar in both groups. There was no difference in renal function between LKD with positive and negative AT1Rab results, 1 (mean eGFR 73.8 versus 72.4 mL/min/1.73m2) and 12 months post-donation (mean eGFR 74.1 versus 74.5 mL/min/1.73m2). During follow-up, none of the LKD developed hypertension (defined as blood pressure >130/85), nor did they require antihypertensive drugs. AT1Rab are apparently indolent in healthy adults after short-term follow-up. Longer observation of all LKD will be necessary to draw final conclusions.

[Husband to wife kidney transplantation in five multiparous women: sensitization or tolerance after pregnancy?]. / Trasplante renal de esposo a esposa en cinco mujeres multíparas. Efecto sensibilizante o efecto "tolerogénico" de la gestación?

BACKGROUND: Pregnancy is a known cause of immunological sensitization and it has been reported graft survival to be lower in husband to wife kidney transplantation if the wife had been pregnant (mutual children) as compare to those cases without pregnancies. Previous exposure to husband HLA antigens during pregnancies may lead to specific sensitization to subsequent allografts. AIM: To communicate the fate of kidney allograft in husband to wife transplantation when the recipient had been pregnant. PATIENTS AND METHODS: From 682 renal transplants performed at INCMNSZ 5 corresponded to husband to wife transplants. All the recipients were multiparous and had received multiple blood transfusions. Pretransplantation lymphocytotoxic cross-match testing were performed by complement dependent citotoxicity with antihuman globulin added (AHG-CDC), being negative in all cases for T and B cells. All the patients received triple-drug immunosuppressive therapy, additionally, anti-IL2R monoclonal antibodies were used in two cases. RESULTS: Two patients developed: accelerated acute rejection (case 1), and acute humoral rejection (case 5), respectively. Graft in these patients were loss to rejection and transplant nephrectomy accomplished. The remaining three patients (cases 2, 3, and 4) has not had any rejection episode, and have had excellent graft outcome at 34, 30, and 21 months posttransplant, respectively. CONCLUSIONS: Why under similar conditions some husband to wife kidney transplant recipients developed an adverse humoral immunological events while others maintain excellent long-term graft outcome? Is it possible to speculate that for some women pregnancy is in fact a sensitizing event, while in others it promotes "immunological acceptance"? At present there is no a test that characterized one and other group. Even though pretransplantation cross-match testing by flow cytometry is more sensitive than AHG-CDC, its negative result is by no means an absolute guarantee that an adverse anamnestic immunological event will not occur.

Frequencies of HLA-A and HLA-B alleles in a Mexico City mestizo sample.

The aim of the present study was to evaluate the frequency of HLA-A and HLA-B antigens in a sample of the Mexico City Mestizo population. Previous similar studies were done by other authors in nonrelated individuals, while the present investigation was performed in families (parents and offspring), and therefore, a more accurate estimate of gene and haplotype frequencies was obtained. The predominant antigens in descending order are A2, A24, and A28 at the A locus, whereas B39 and B35 are at the B locus, all with gene frequencies above 0.1. As expected, the two more frequent haplotypes were A2-B16 and A2-B35 (considering main specificities), both with frequencies of 0.056. Seven of the 18 significant delta values of the haplotypes (observed vs. expected) remained significant after correcting for the number of comparisons, indicating the presence of linkage disequilibrium between the HLA-A and HLA-B regions. However, only A1-B8 and A19-B13 were found to be in disequilibrium in another Mexico City Mestizo sample which had very similar HLA-A and HLA-B allele frequencies to those in the present survey, suggesting that the biological significance of the other associations is rather doubtful. Am. J. Hum. Biol. 9:1-5 © 1997 Wiley-Liss, Inc.