Anti-HLA alloantibodies of the IgA isotype in re-transplant candidates part II: Correlation with graft survival.

We reported previously on the widespread occurrence of anti-HLA alloantibodies of the IgA isotype (anti-HLA IgA) in the sera of solid-organ re-transplantation (re-tx) candidates (Arnold et al., ). Specifically focussing on kidney re-tx patients, we now extended our earlier findings by examining the impact of the presence and donor specificity of anti-HLA IgA on graft survival. We observed frequent concurrence of anti-HLA IgA and anti-HLA IgG in 27% of our multicenter collective of 694 kidney re-tx patients. This subgroup displayed significantly reduced graft survival as evidenced by the median time to first dialysis after transplantation (TTD 77 months) compared to patients carrying either anti-HLA IgG or IgA (TTD 102 and 94 months, respectively). In addition, donor specificity of anti-HLA IgA had a significant negative impact on graft survival (TTD 74 months) in our study. Taken together, our data strongly indicate that presence of anti-HLA IgA, in particular in conjunction with anti-HLA-IgG, in sera of kidney re-tx patients is associated with negative transplantation outcome.

16(th) IHIW: anti-HLA alloantibodies of the of IgA isotype in re-transplant candidates.

In this multicentre study, sera from 803 retransplant candidates, including 775 kidney transplant recipients, were analysed with regard to the presence and specificity of anti-HLA alloantibodies of the IgA isotype using a modified microsphere-based platform. Of the kidney recipients, nearly one-third (n = 237, 31%) had IgA alloantibodies. Mostly, these antibodies were found in sera that also harboured IgG alloantibodies that could be found in a total of 572 (74%) of patients. Interestingly, IgA anti-HLA antibodies were preferentially targeting HLA class I antigens in contrast to those of the IgG isotype, which targeted mostly both HLA class I and II antigens. Donor specificity of the IgA alloantibodies could be established for over half of the 237 patients with IgA alloantibodies (n = 124, 52%). A further 58 patients had specificities against HLA-C or HLA-DP, for which no information regarding donor typing was available. In summary, these data showed in a large cohort of retransplant candidates that IgA alloantibodies occur in about one-third of patients, about half of these antibodies being donor specific.

Successful Treatment of Anti-angiotensin II Type 1 Receptor Antibody-Associated Rejection in Kidney Transplantation: A Case Report.

Angiotensin II type 1 receptor (AT1R) antibody, a non-HLA antibody, has been found to have a detrimental effect on kidney allografts. Similarly to HLA antibodies, recipients who have AT1R antibodies are at risk for allograft rejection and poor long-term graft outcome. Besides mediating allograft rejections via direct effects on endothelial and vascular smooth muscle without complement activation, AT1R antibodies may lead to accelerated hypertension via the renin-angiotensin pathway. There has been no definite level of AT1R antibody that predicts allograft rejection. Because of a low incidence of AT1R antibody-associated rejection, there are few reports on specific treatment. The results of conventional treatment, which aims to remove these pathologic antibodies similarly to the treatment of HLA antibody-associated rejection, have been unsatisfactory. Some studies recommend using angiotensin receptor blocker to attenuate the adverse effects of AT1R antibody on kidney allograft. Herein we present a kidney transplant recipient with AT1R antibody-associated refractory allograft rejection who was successfully treated with the use of steroid, plasmapheresis, intravenous immunoglobulin, and rituximab.

Influence of HLA-DQ Matching on Allograft Outcomes in Deceased Donor Kidney Transplantation.

BACKGROUND AND OBJECTIVES: HLA matching at the A, B, and DR loci influences the graft survival rate of deceased donor kidney transplants. The effect of HLA-DQB1 matching on transplant outcomes is still controversial. The aim of this study was to investigate the association of HLA-DQB1 matching with allograft outcomes in deceased donor kidney transplant recipients. METHODS: A retrospective analysis of deceased donor kidney transplant recipients between 2008 and 2014 at the Faculty of Medicine Ramathibodi Hospital, Bangkok, Thailand, was performed. Donor-recipient HLA matching at DQB1 locus was analyzed. The association between HLA-DQB1 mismatches and transplant outcomes was investigated using adjusted Cox regression analysis. RESULTS: A total of 383 deceased donor kidney transplants were performed during the study period, of which 297 with complete clinical and laboratory data were analyzed. The median follow-up time of all patients was 41 months (range, 16.4-65.6 months). Of the 297 recipients, 107 (36.03%) received 0 HLA-DQB1 mismatched kidneys and 190 (63.97%) received 1 or 2 HLA-DQB1 mismatched kidneys. Recipients who have received 1 or 2 HLA-DQB1 mismatched kidneys had a higher risk of acute rejection, with the adjusted hazard ratio of 4.35 (95% CI, 1.41-13.42; P = .01). However, HLA-DQB1 mismatching was not associated with chronic rejection and graft survival. CONCLUSION: Donor-recipient HLA-DQB1 mismatching is associated with acute rejection in deceased donor kidney transplants. However HLA-DQB1 mismatching does not have a negative impact on chronic rejection or graft survival.

Acute Antibody-Mediated Rejection by De Novo Anti-HLA-DPß and -DPα Antibodies After Kidney Transplantation: A Case Report.

The presence of isolated de novo anti-DP antibodies is uncommon, making it difficult to determine the impact of anti-DP antibodies on graft outcome. We describe a case of acute antibody-mediated rejection mediated by de novo donor-specific anti-HLA-DP antibodies. Furthermore, the generation of non-donor-specific anti-DP antibodies (NDSAs) detected in the patient's sera was investigated. An 18-year-old woman with pretransplant 0% panel-reactive antibody received kidney transplantation from a living donor. She experienced combined acute T-cell-mediated and antibody-mediated rejection at 15 months after transplantation. High resolution HLA typing of the donor and the patient revealed that they were mismatched at both DPB1 (DPB1*31:01) and DPA1 (DPA1*02:02) loci. The single antigen bead (SAB) testing of patient's sera revealed antibodies against donor's DPB1*31:01 and DPA1*02:02 alleles. Antibodies against several non-donor-specific DP antigens were also detected. No antibodies against other HLA class I and II antigens were detected. In order to explain the reactivity pattern of NDSAs, HLAMatchmaker program was used to identify immunizing eplets shared between donor alleles and reactive beads. The analysis showed 84DEAV, a DPB1 eplet, as a shared eplet found on DPB1*31:01 (mismatched donor allele) and on DPB1-reactive alleles in SAB assay. Additionally, 50RA, a DPA1 eplet, was identified as a shared eplet found on DPA1*02:02 (mismatched donor allele) and on DPA1-reactive alleles in SAB assay. This case highlights the clinical significance of HLA-DP antibodies. Furthermore, the generation of NDSA anti-DP antibodies by epitope sharing underscores the importance of HLA-DP epitope matching in kidney transplantation.

Outcome of Pretransplantation Therapeutic Plasma Exchange in Highly Sensitized Deceased-donor Kidney Transplant Recipients.

BACKGROUND: Sensitization is associated with a high rate of post-transplantation rejection. A desensitization protocol using therapeutic plasma exchange (TPE) was proposed to reduce anti-HLA antibody before transplantation, but there has been limited data regarding the efficacy of pretransplantation TPE in highly sensitized deceased-donor kidney transplantation (DDKT). METHODS: A retrospective cohort study of 142 patients who received DDKT was conducted and divided into two groups: a high-panel-reactive antibody (PRA) >50% group and a low-PRA ≤50% group. The high-PRA group was sub-divided into those who received and did not receive pretransplantation TPE. Donor-specific anti-HLA antibodies (DSA) were also collected pretransplantation in the high-PRA group. RESULTS: The probability of acute rejection was 26, 4, and 9 cases/1000/person month in the high-PRA group with no TPE, the high-PRA group receiving TPE, and the low-PRA group, respectively (P = .0208). In the multivariable logistic regression analysis, the hazard ratio for graft rejection was 2.37 (95% confidence interval: 0.89 to 6.35) and 2.22 (95% confidence interval: 0.54 to 9.13) in the group of high-PRA who received TPE and high-PRA with no TPE, compared with the low-PRA group, respectively (P value not significant). The incidence of antibody-mediated rejection in 6 months in the DSA-positive subgroup was not different between those who received TPE or no TPE. CONCLUSION: Desensitization with TPE is a reasonable alternative for highly sensitized DDKT. Patients who received pretransplantation TPE had a lower incidence of acute rejection compared to the group that did not receive TPE. However, pretransplantation TPE alone was not effective in the prevention of acute rejection in recipients with DSA.

A Rare HLA-DRB1*14:22-DQB1*04:01 Haplotype in a Kidney Donor: Implication in the Interpretation of Donor-Specific Antibody in Kidney Transplantation-A Case Report.

BACKGROUND: The presence of donor-specific human leukocyte antigen antibodies (HLA-DSA) can be determined by performing Luminex assay with single-antigen beads. The single-antigen beads' panels cover the most frequent HLA alleles of the HLA-A, B, C, DRB1, DRB3/4/5, DQB, and DP loci, although the HLA typing for deceased donors often includes only HLA-A, B, and DR. Therefore, the information of haplotypic association between DRB1 and DQB1 is essential for the analysis of HLA-DSA, especially when HLA-DQ antibodies are identified in the patient's serum. CASE REPORT: We report the finding of a rare HLA-DRB1*14:22-DQB1*04:01 haplotype in a Thai potential kidney donor. HLA class I and class II high-resolution typing were performed by a method of polymerase chain reaction with the use of sequence-specific primers. The HLA-A*24:02-C*04:06-B*13:01-DRB3*02:02-DRB1*14:22-DQA1*05:05-DQB1*04:01 haplotype in the kidney donor was confirmed by segregation analysis in the kidney donor's family. This rare haplotype was also identified in her father and the 2 of her offspring. CONCLUSIONS: To our knowledge, this is the 1st report of the rare HLA-DRB1*14:22-DQB1*04:01 haplotype in Thai individuals. The information of the rare HLA-DR-DQ haplotypic association provides a caution for HLA laboratory personnel when analyzing HLA-DSA in a patient with HLA-DQ antibodies and the HLA-DQ typing of a deceased donor is unavailable.

Significance of HLA Antibody Detected by PRA-Bead Method in Kidney Transplant Outcomes.

BACKGROUND: The impact of specific HLA antibodies on the allograft function in the Luminex era is not clearly known. This study aimed to investigate kidney transplantation outcomes in patients with different anti-HLA antibody status as detected by Luminex PRA. METHODS: This retrospective study included 106 deceased-donor kidney transplantation (DDKT) patients divided into 3 groups by PRA status as detected by PRA-bead: (1) PRA = 0; (2) positive PRA but with negative antibody against donor's HLA antigens; and (3) positive PRA with positive anti-HLA antibody specificity against donor's HLA antigens. RESULTS: There were 65, 23, and 18 patients in groups 1, 2, and 3, respectively. Early allograft rejections were highest in group 3 (22.2%) (P = .02). In multivariate analysis, delayed graft function was the only factor that was associated with allograft rejection (hazard ratio, 8.9; 95% confidence interval, 1.9-39.8; P = .004). Estimated glomerular filtration rates at 1 year of the 3 groups were 54.6, 55.8, and 60.0 mL/min (P = .71). One-year allograft failure and death were not different among the 3 groups. Expanded-criteria deceased donors were associated with both allograft failure (P = .003) and patient death (P = .02). CONCLUSIONS: Anti-HLA antibody as detected by Luminex PRA was associated with early allograft rejection but not graft or patient survival. The effect of newer treatment modalities can improve the outcomes of PRA-positive patients to be similar to nonsensitized patients at 1 year.

Role of Pretransplant Complement-fixing Donor-specific Antibodies Identified by C1q Assay in Kidney Transplantation.

BACKGROUND: Kidney transplant recipients who have pretransplant donor-specific human leukocyte antigen (HLA) antibodies have greater risk for developing allograft rejection and allograft loss. However, there is a varied effect of graft injury among patients with pretransplantation donor-specific antibodies (DSA). The difference of complement activating ability may be the reason why some DSA are detrimental to kidney allograft. This study aimed to investigate the association between pretransplantation C1q-binding DSA and clinical outcomes. METHODS: This retrospective study included 48 pretransplant sera from kidney transplant recipients who had pretransplant DSA with negative complement-dependent cytotoxic (CDC) crossmatches. The IgG DSA testing and C1q testing were performed on a Luminex platform with single antigen bead assay. The clinical outcomes between C1q-positive and C1q-negative groups were compared. RESULTS: C1q-positive DSA were detected in 12 out of 48 patients (25%). The incidences of antibody-mediated rejection (AMR) were higher among patients with C1q-positive DSA than patients with C1q-negative DSA (66.7% vs 41.7%). Nevertheless, there were no statistically significant associations between C1q-DSA and AMR (odds ratio 2.8, 95% CI 0.68-11.6, P = .13) and between C1q-DSA and graft loss (odds ratio 0.52, 95% CI 0.09-2.89, P = .44). The C1q-positive DSA group had significantly higher IgG DSA MFI than the C1q-negative DSA group (P < .001). CONCLUSION: C1q-binding ability of DSA in pretransplant sera of kidney recipients was not associated with antibody-mediated rejection and graft loss post-transplantation. In contrast with the clinical relevance of C1q testing in the post-transplantation setting, C1q testing in pretransplant sera has limited use for immunological risk assessment.

Significance of C1q-fixing donor-specific antibodies after kidney transplantation.

OBJECTIVES: De novo donor-specific HLA antibodies (DSA) are associated with allograft rejection and allograft loss. However, not all DSA are equally detrimental to allograft function. The ability to activate complement may be an important factor differentiating clinically relevant DSA from nonrelevant DSA. The C1q assay detects a subset of HLA antibodies that can fix complement. This study aimed to investigate the correlation between C1q-fixing de novo DSA (dnDSA) and clinical outcomes posttransplant. METHODS: This retrospective study included 193 sera from kidney transplant recipients who underwent posttransplant DSA testing and/or kidney biopsy for clinical causes. Thirty-five of the 193 (18.1%) had immunoglobulin G DSA. Seventeen of the 35 patients were excluded owing to the presence of pretransplant HLA antibodies. We then analyzed C1q DSA at the time of biopsy in 18 recipients who developed dnDSA. The clinical outcomes of patients with C1q-positive DSA and C1q-negative DSA were compared. RESULTS: C1q-positive DSA were detected in 10 of 18 patients (55.6%). The incidences of transplant glomerulopathy were significantly higher among patients with C1q-positive DSA than patients with C1q-negative DSA (80% vs 0%; P = .001). Although patients with C1q-positive DSA experienced more chronic antibody-mediated rejection and graft loss (80% vs 37.5% [P = .145]; 60% vs 25% [P = .188]), the differences were not significant. The receiver operating characteristic curve analysis showed that the C1q assay was an excellent predictor of transplant glomerulopathy with area under the curve of 0.9 (95% CI, 0.769-1.000). CONCLUSION: The presence of C1q-positive dnDSA was associated with an increased risk of transplant glomerulopathy. The C1q assay is potentially a powerful method for identifying patients at risk for transplant glomerulopathy.

Shared molecular eplet stimulates acute antibody-mediated rejection in a kidney transplant recipient with low-level donor-specific antibodies: a case report.

HLA antibodies usually recognize epitopes rather than antigens. This case report reveals that acute antibody-mediated rejection (AMR) that occurred in a kidney transplant recipient with low-level donor-specific antibodies (DSAs) could be explained by shared epitope. A 39-year-old woman received a first kidney transplant from a deceased donor (HLA-DRB1 11:06, 12:02, DRB3 02:02, 03:01). She developed acute AMR confirmed by kidney biopsy on day 4 after transplantation. Antibody testing with pretransplant serum showed anti-DR11 DSA below cutoff level (mean fluorescence intensity [MFI], 702; cutoff >1,000). However, high-level DSAs were detected on day 5 after transplantation (anti-DR11 MFI, 8,531; anti-DR12 MFI, 3,146). We hypothesized that the sharp rise in DSA levels was a result of anamnestic response with donor-antigen sensitization that occurred during pregnancy. High-resolution HLA-DR typing of her husband showed HLA-DRB1 03:01, 15:02:01, DRB3 02:02, DRB5 01:02. No sharing between donor HLAs eliciting reactive antibodies and her husband's HLAs was detected. Nevertheless, we speculated that shared epitope, not antigen, was the cause of allosensitization. To identify the shared epitope recognized by patient's antibodies, we used HLAmatchmaker, a computer algorithm that considers small configurations of polymorphic residues referred to as eplets as essential components of HLA epitopes for analysis. The results showed that 149H, which was the eplet shared by HLA-DRB1 03:01 (from her husband) and DRB1 11:06, DRB1 12:02, DRB3 03:01 (from donor), was the most prevalent eplet on DRB1 reactive alleles in Luminex assay. In conclusion, pretransplant low-level DSAs can induce AMR early after transplantation as a result of shared epitopes with a previous immunizer.

Cytotoxic flow cytometric crossmatch in renal transplantation: a single assay to simultaneously detect antibody binding and cytotoxicity.

OBJECTIVES: The complement-dependent lymphocytotoxicity crossmatch (CDC-XM) detects cytotoxic parameters of preformed antibodies. The flow cytometric crossmatch (FCXM) is used to detect the binding of recipient antibodies to donor cells. Because these two assays provide different information, both methods are often performed to assess the compatibility of donor-recipient pairs. The aim of this study was to develop a single assay that can simultaneously detect antibody binding and cytotoxicity. METHODS: A procedure called cytotoxic flow cytometric crossmatch (cFCXM) that determines cell death and antibody binding simultaneously was developed. The assay was validated in parallel with extended incubation CDC-XM. Receiver operating characteristic analysis was used to determine the cut-off level. Furthermore, pretransplantation sera from seven recipients with pretransplantation donor-specific antibodies (DSA) and negative CDC-XM were retrospectively tested for cFCXM (4 without antibody-mediated rejection (AMR) and three with AMR). RESULTS: The optimal method for the simultaneous detection of antibody binding and cytotoxicity in a single assay has been determined. Four of four patients (100%) with pretransplantation DSA and without AMR had negative cFCXM in both parameters. Of three patients with pretransplantation DSA who developed AMR, two patients (66.7%) had positive B-cell cFCXM in both parameters, and 1 patient (33.3%) had positive T-cell cFCXM in a binding parameter only. The first patient had anti-DR9, DR53, DQ9, the second patient had anti-A11, DR12 and the last one had an anti-B46 in their pretransplantation sera. These 3 cases experienced biopsy-proven AMR after living-donor kidney transplantation. CONCLUSION: The newly developed assay, cFCXM, can simultaneously determine cytoxicity and antibody binding using a single platform. Furthermore, this assay can detect clinically significant HLA alloantibodies undetectable by conventional crossmatches. The cFCXM could serve as a new tool for the detection of a recipient's alloantibodies.