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.

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.

Ten-Year Follow-up of Pharmacokinetics-Guided Very Early Cyclosporine Minimization Synchronized With Everolimus Initiation in De Novo Kidney Transplantation.

BACKGROUND: Minimization of calcineurin inhibitor (CNI) from the 1st week after kidney transplantation (KT) may reduce the risk of CNI nephrotoxicity. METHODS: Ten de novo KT recipients who received full exposure cyclosporine (CsA) and prednisolone as initial therapy were enrolled. Initial CsA minimization was 50% and started at day 7 after KT. This was synchronized with everolimus (EVL) initiation. Target trough level of EVL was 3-8 ng/mL. Pharmacokinetics studies of CsA and EVL were studied at week 4. The CsA dosage was further reduced to keep a lowest value of serum creatinine and a target EVL level. Primary outcomes were estimated glomerular filtration rate (eGFR) at baseline and last follow-up. RESULTS: Patients' mean age at last follow-up was 60.6 ± 11.7 years. Follow-up duration was 121.6 ± 12.8 months. Pharmacokinetics study found that Cmax of CsA ranged from 309 to 1,896 ng/mL, mean area under the receiver operating characteristic curve (AUC) of CsA was 3,449 ± 1,402 ng·h/mL, C0 of EVL was 5.2 ± 1.5 ng/mL, Cmax of EVL was 15.4 ± 4.6 ng/mL, and AUC of EVL was 99.7 ± 26.1 ng·h/mL. Achieved nadir serum creatinine was 1.03 ± 0.33 mg/dL. Achieved best eGFR (Modification of Diet in Renal Disease formula) was 99.7 ± 26 mL/min. eGFR at 12 months was 82 ± 25 mL/min. Last serum creatinine was 1.32 ± 0.45 mg/dL. Last eGFR was 57.2 ± 13.55 mL/min. Actuarial death-censored 10-year graft survival was 100%. Actuarial 10-year patient survival was 80%. CONCLUSIONS: Our intervention can lead to an average of 75% CsA minimization and a very good eGFR at 10 years.

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.