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Despite the growing use of desensitization strategies, hyperimmune patients remain at high risk of antibody-mediated rejection suggesting that, even when donor-specific antibodies (DSA) are effectively depleted, anti-donor specific B cells persist. We included 10 highly sensitized recipients that underwent desensitization with plasmapheresis and B cell depletion prior to kidney transplantation. We quantified changes in DSA (luminex), total B-cell subsets (flow cytometry), anti-donor HLA B cells (fluorospot), and single-cell metabolism in serially collected samples before desensitization, at the time of transplant, and at 6 and 12 months thereafter. Desensitization was associated with a decrease in DSA and total memory B cell and naive B cell percentage, while plasma cells and memory anti-donor HLA circulating B cells persisted up to 12 months after transplant. At 12-month post-transplantation, memory B cells increased their glycolytic capacity, while proliferative KI67+ plasma cells modified their metabolism by increasing fatty acid and amino acid oxidation capacity and decreasing their glucose dependence. Despite effective DSA depletion, anti-donor B cells persist in kidney transplant recipients. Due to the reliance of these cells on glycolysis, glycolysis-targeting therapies might represent a valuable treatment strategy. [ABSTRACT FROM AUTHOR]

Despite the growing use of desensitization strategies, hyperimmune patients remain at high risk of antibody-mediated rejection suggesting that, even when donor-specific antibodies (DSA) are effectively depleted, anti-donor specific B cells persist. We included 10 highly sensitized recipients that underwent desensitization with plasmapheresis and B cell depletion prior to kidney transplantation. We quantified changes in DSA (luminex), total B-cell subsets (flow cytometry), anti-donor HLA B cells (fluorospot), and single-cell metabolism in serially collected samples before desensitization, at the time of transplant, and at 6 and 12 months thereafter. Desensitization was associated with a decrease in DSA and total memory B cell and naive B cell percentage, while plasma cells and memory anti-donor HLA circulating B cells persisted up to 12 months after transplant. At 12-month post-transplantation, memory B cells increased their glycolytic capacity, while proliferative KI67+ plasma cells modified their metabolism by increasing fatty acid and amino acid oxidation capacity and decreasing their glucose dependence. Despite effective DSA depletion, anti-donor B cells persist in kidney transplant recipients. Due to the reliance of these cells on glycolysis, glycolysis-targeting therapies might represent a valuable treatment strategy.

Summary: Preformed donor‐specific antibodies (DSAs) limit access to transplantation for thousands of renal transplant patients. While kidney paired donation offers the best strategy for patients with a living donor, for very highly sensitized patients and those without living donors, a strategy of desensitization offers the best hope of transplantation. Removal of DSAs with plasmapheresis, intravenous immunoglobulin and anti‐CD20 antibodies can permit successful transplantation. While the clinical outcomes remain inferior to compatible transplant and the costs are significantly greater, when compared with long‐term dialysis treatment, these strategies are offer improved survival and are cost‐effective given nationally accepted benchmarks. [ABSTRACT FROM AUTHOR]

Summary: There are conflicting data about the role of transplant nephrectomy and immunosuppression withdrawal on the development of allosensitization and the impact on re‐transplantation. We divided 109 first graft recipients into two groups according to whether they underwent nephrectomy (NX+, n = 61) or their graft was left in situ (NX−, n = 48). Sera were assessed for HLA‐A/B/Cw/DR/DQ antibodies at the time of NX/transplant failure and after 3, 6, 12, 24 months. The NX+ group showed a higher rate of donor specific antibody (DSA) and non‐DSA human leukocyte antigen (HLA) antibody production at all the time points. Multivariable analysis showed that nephrectomy was a strong, independent risk factor for the development of DSAs after 12 and 24 months (P = 0.005 and 0.008). In the NX− group, low tacrolimus levels correlated with DSA formation (AUC 0.817, P = 0.002; best cut‐off level 2.9 ng/ml). Analysis with a standardized pool of UK donors showed a more difficult grade of HLA matchability following nephrectomy compared with the NX− group. Nephrectomy is followed by the long‐term production of DSA and non‐DSA HLA antibodies and negatively impacts on the chances of finding a HLA‐compatible kidney. Tacrolimus levels ≥3 ng/ml are protective against the development of allosensitization and could facilitate re‐transplantation in the NX− group. [ABSTRACT FROM AUTHOR]

Summary: Luminex single antigen bead assays revolutionized human leukocyte antigen (HLA) antibody detection owing to their superior sensitivity compared to conventional methods. Nevertheless, the advent of higher sensitivity came at the expense of difficulty in clinical decision‐making, since not all luminex detectable antibodies are clinically relevant. Therefore, new tools such as C1q/C3d assays and IgG subclass analysis emerged with the aim to discriminate the inert antibodies from the deleterious ones. Here, we provide an overview on the technical challenges related to these different HLA antibody detection systems and briefly refer to the recent literature regarding the clinical relevance of these assays, mainly in the field of kidney transplantation. [ABSTRACT FROM AUTHOR]

Summary: Acceptable outcomes of donor‐specific antibody (DSA)‐positive living kidney transplantation (LKT) have recently been reported. However, LKT in crossmatch (XM)‐positive patients remains at high‐risk and requires an optimal desensitization protocol. We report our intermediate‐term outcomes of XM‐positive LKT vs. XM‐negative LKT in patients who underwent LKT between January 2012 and June 2015 in our institution. The rate of acute antibody‐mediated rejection (ABMR) within 90 days postoperation, graft function, and patient, and graft survival rates at 4 years were investigated. Patients were divided into three groups: XM−DSA− (n = 229), XM−DSA+ (n = 36), and XM + DSA+ (n = 15). The XM + DSA+ group patients underwent desensitization with high‐dose intravenous immunoglobulin, plasmapheresis, and rituximab. The rates of ABMR within 90 days in the XM−DSA−, XM−DSA+, and XM + DSA+ groups were 1.3%, 9.4%, and 60.0%, respectively (P < 0.001). There were no significant differences in the graft function throughout the observational period, the 4‐year patient or graft survival rates among three groups. This study showed that intermediate‐term outcomes of XM‐positive LKT were comparable to XM‐negative LKT. However, our current desensitization protocol cannot avert ABMR within 90 days, and XM positivity is still a significant risk factor for ABMR. Further refinement of the current desensitization regimen is required. [ABSTRACT FROM AUTHOR]

Donor-specific antibodies ( DSA) increase the risk of allograft rejection and graft failure. They may be present before transplant or develop de novo after transplantation. Here, we studied the evolution of preformed DSA and their impact on graft outcome in kidney transplant recipients. Using the Luminex Single Antigen assay, we analyzed the sera on the day of transplantation of 239 patients who received a kidney transplant. Thirty-seven patients (15.5%) had pre-existing DSA detected the day of transplantation. After 5 years, the pre-existing DSA disappeared in 22 patients whereas they persisted in 12. Variables associated with DSA persistence were age <50 years ( P = 0.009), a history of previous transplantation ( P = 0.039), the presence of class II DSA ( P = 0.009), an MFI of preformed DSA >3500 ( P < 0.001), and the presence of two or more DSA ( P < 0.001). DSA persistence was associated with a higher risk of graft loss and antibody-mediated rejection. Previously undetected preformed DSA are deleterious to graft survival only when they persist after transplantation. [ABSTRACT FROM AUTHOR]

The use of generic formulations of immunosuppressive drugs in renal transplantation has been and still is a controversial subject. The lack of clinical studies about safety and efficacy in transplant patients is one of the factors restricting the diffusion of generic drugs in the renal transplant field. Since March 2013, our transplant unit has incorporated generic tacrolimus (Adoport®; Sandoz), replacing the one we were currently using (Prograf®; Astellas). When carrying out our retrospective analysis comparing the two different formulations, we evaluated several clinical results: tacrolimus trough concentrations ( C0) at 5-7 days; 1, 3, and 6 months post-transplantation; concentration/dose ratio at 6 months; acute rejection incidence; delayed graft function ( DGF); renal function (as CKD- EPI); and proteinuria at 6 months in 120 patients (1:1 ratio of Prograf® versus Adoport®), noticing no important differences. We also evaluated the results of protocol biopsies at 6 months in a subgroup of patients, thus verifying the safety and efficacy of this particular generic drug versus the reference product on a histological basis as well. No difference in the development of dn DSA ( de novo donor-specific antibody) was found between the two groups. [ABSTRACT FROM AUTHOR]

Living-donor lobar lung transplantation ( LDLLT) is an established therapy for patients with end-stage lung disease, but living-donor lobar lung retransplantation (re- LDLLT) is rarely reported. We previously reported a case of unilateral antibody-mediated rejection after LDLLT in the presence of newly formed donor-specific antibodies against a right-lobe donor. The same patient developed contralateral bronchiolitis obliterans, resulting in bilateral bronchiolitis obliterans, but re- LDLLT was successful. Pathological findings of the explanted lungs were consistent with the clinical course of the patient. One year after re- LDLLT, the patient is doing well without any anti-human leukocyte antigen antibodies. Four lobes from four different donors were transplanted in this patient. The first two lobes were rejected eventually, but the two lobes implanted later presented no signs of rejection at least for 1 year after the transplant. Herein, we report this rare case and compare the clinical course and pathological findings. [ABSTRACT FROM AUTHOR]

In this study, we retrospectively investigated the relationship between the presence/titers of donor-specific (DSA)/nondonor-specific antibody (NDSA) and the rate of graft rejection after transplantation. The subjects comprised 34 recipients who tested positive by FlowPRA Screening. The recipients were divided into two groups; 22 recipients with DSA and 12 recipients with NDSA, as detected using FlowPRA Single Antigen I and II beads. The antibodies were also quantitatively examined using the molecules of equivalent soluble fluorochrome (MESF) method. Nine of the 22 recipients with DSA (9/22, 40%) developed antibody-mediated rejection (AMR), while none of the 12 recipients with NDSA (0/12, 0%) developed AMR ( P < 0.01). In a quantitative analysis of the MESF data, patients with DSA with MESF values of over 3000 frequently showed AMR (8/11, 73%). In contrast, one of the patients with DSA with MESF values of <3000 showed AMR (1/11, 9%). One of the 12 patients (1/12, 8%) with NDSA showed cellular rejection (T-cell-mediated rejection), regardless of the MESF values. In patients with DSA, an MESF value of 3000 may be a useful cutoff value for identifying patients at a high risk for AMR. [ABSTRACT FROM AUTHOR]

Donor-specific alloantibodies (DSA), especially those fixing complement, may pose a particular immunologic risk to transplant recipients. To assess the clinical impact of C4d- or non-C4d-fixing (IgG) HLA sensitization, pretransplant sera obtained from 338 kidney allograft recipients prescreened by FlowPRA were retrospectively evaluated by Luminex single antigen (SA) testing using a novel fluorescent-labeled anti-C4d reagent for detection of antibody-triggered C4d deposition in addition to IgG binding. Recipients with [IgG]DSA ( n = 39) showed a substantially higher rate of C4d positive rejection (33%) than 16 patients with [IgG] non-DSA (0%) or 283 antibody-negative patients (4%, multivariate analysis excluding retransplantation because of high co-linearity: P < 0.0001), and adversely affected 5-year death-censored graft survival  (74% vs. 81% and 90%, respectively, multivariate model: P < 0.05). [C4d] DSA ( n = 21) and [C4d] non-DSA ( n = 25) increased rates of C4d positive rejections to a similar extent (24% and 28% vs. 4% in recipients without C4d-fixing reactivity; multivariate analysis: P ≤ 0.002) with a trend towards adverse 5-year graft survival (76% and 76% vs. 90%; P ≤ 0.2). In conclusion, Luminex-based characterization of HLA sensitization may be a useful strategy for risk stratification. Possibly as a result of intensified immunosuppression in presensitized recipients, identification of C4d-fixing DSA was not associated with a further increase of rejection and graft loss rates. [ABSTRACT FROM AUTHOR]

We sought to clarify the controversial issue of whether detecting low-level anti-donor-specific HLA antibody (HLA-DSA) by single-antigen flow-bead assay (SAFB) may have a potential role in reducing acute and chronic antibody-mediated rejection (AMR). We retrospectively studied the preoperative serum of ABO-compatible living kidney transplantation recipients transplanted between 2001 and 2004 by SAFB using a Luminex platform. HLA-DSA was detected only by SAFB in 24 patients, although all of them showed negative T-cell and B-cell complement-dependent cytotoxicity (CDC) crossmatches. The HLA-DSA patients went on to have surprisingly high levels of acute and chronic AMR despite being only weakly sensitized (acute AMR, 33.3%; chronic AMR, 41.7%). After 2005, we implemented SAFB routinely and any patient having a positive HLA-DSA was considered to be a desensitization candidate. The 52 patients found to have HLA-DSA underwent kidney transplantation after prior treatment with a single dose of rituximab (RIT) and three or four sessions of double-filtration plasmapheresis (DFPP) in addition to regimens commonly used between 2001 and 2004. After 2005, there was a significant reduction in the occurrence of acute and chronic AMR (acute AMR, 4.7%, P < 0.001; chronic AMR, 4.7%, P < 0.001). The 5-year graft survival rate also improved after implementing SAFB (83.3-98.1%, P = 0.032). The RIT/DFPP-induction protocol may improve graft survival even in patients with low-level DSA. [ABSTRACT FROM AUTHOR]