Immunity to Human leukocyte antigen (HLA) cannot explain all cases of ABMR, nor the differences observed in the outcome of kidney recipients with circulating DSAs endowed with similar biologic ...characteristics. Thus, increasing attention has recently been focused on the role of immunity to non-HLA antigenic targets.
We analyzed humoral auto- and alloimmune responses to the non-HLA antigen glutathione S-transferase theta 1 (GSTT1), along with development of
(
)HLA-DSAs, in a cohort of 146 pediatric non-sensitized recipients of first kidney allograft, to analyze its role in ABMR and graft loss. A multiplex bead assay was employed to assess GSTT1 antibodies (Abs).
We observed development of GSTT1 Abs in 71 recipients after transplantation, 16 with MFI > 8031 (4th quartile: Q4 group). In univariate analyses, we found an association between Q4-GSTT1Abs and ABMR and graft loss, suggesting a potential role in inducing graft damage, as GSTT1 Abs were identified within ABMR biopsies of patients with graft function deterioration in the absence of concomitant intragraft HLA-DSAs. HLA-DSAs and GSTT1 Abs were independent predictors of graft loss in our cohort. As GSTT1 Ab development preceded or coincided with the appearance of
HLA-DSAs, we tested and found that a model with the two combined parameters proved more fit to classify patients at risk of graft loss.
Our observations on the harmful effects of GSTT1Abs, alone or in combination with HLA-DSAs, add to the evidence pointing to a negative role of allo- and auto-non-HLA Abs on kidney graft outcome.
De novo posttransplant donor-specific HLA-antibody (dnDSA) detection is now recognized as a tool to identify patients at risk for antibody-mediated rejection (AMR) and graft loss. It is still unclear ...whether the time interval from transplant to DSA occurrence influences graft damage. Utilizing sera collected longitudinally, we evaluated 114 consecutive primary pediatric kidney recipients grafted between 2002 and 2013 for dnDSA occurrence by Luminex platform. dnDSAs occurred in 39 patients at a median time of 24.6 months. In 15 patients, dnDSAs developed within 1 year (early-onset group), while the other 24 seroconverted after the first posttransplant year (late-onset group). The two groups were comparable when considering patient- and transplant-related factors, as well as DSA biological properties, including C1q and C3d complement-binding ability. Only recipient age at transplant significantly differed in the two cohorts, with younger patients showing earlier dnDSA development. Late AMR was diagnosed in 47% of the early group and in 58% of the late group. Graft loss occurred in 3/15 (20%) and 4/24 (17%) patients in early- and late-onset groups, respectively (p = ns). In our pediatric kidney recipients, dnDSAs predict AMR and graft loss irrespective of the time elapsed between transplantation and antibody occurrence.
Development of de novo donor-specific antibodies (dnDSA) is associated with late or chronic antibody-mediated rejection (CAMR) and poor graft outcome in low-risk kidney transplant recipients. ...High-level soluble B-cell activating factor (sBAFF) was observed in kidney recipients at higher risk of developing dnDSA.
We longitudinally analyzed sBAFF levels in 81 consecutive primary pediatric kidney recipients monitored for de novo human leukocyte antigen (HLA) antibody (Ab) occurrence to gain insight into the events conditioning B-cell activation posttransplant and to analyze the usefulness of paired DSA-sBAFF monitoring in this clinical setting.
At a median follow-up of 65 months, 23 patients (28%) developed dnDSA, with 13 of 23 developing CAMR. Irrespective of HLA Ab status, sBAFF levels progressively increased in all patients in the first posttransplant year, thereafter reaching a plateau. sBAFF levels were influenced by the degree of HLA class I antigen match and donor age. Despite higher levels of sBAFF in HLA Ab-positive patients (median and 95% confidence interval sBAFF in DSA+non-DSA patients: 568, 534-608 pg/mL vs. 502, 422-548 pg/mL in Ab-negative patients; P<0.05), we found that sBAFF monitoring could not predict DSA development by a time to event longitudinal analysis. Moreover, sBAFF kinetics up to CAMR onset could not anticipate CAMR development in the DSA cohort.
Our findings provide evidence of early posttransplant B-cell activation even in unsensitized recipients of first kidney allograft. The significance of this activation, likely induced by exposition to the allograft, is yet unclear.
While de novo donor-specific HLA antibodies (dnDSAs) have a detrimental impact on kidney graft outcome, the clinical significance of de novo non donor-specific antibodies (dnNDSAs) is more ...controversial. We retrospectively evaluated for Ab development and characteristics of dnNDSAs serially collected post-transplant sera and, when available, graft biopsy eluates, from 144 non-sensitized, primary pediatric kidney recipients, consecutively transplanted at a single center between 2003 and 2017, using HLA class I and class II single-antigen flow-bead assays (SAB). The results were compared with clinical-pathologic data from HLA antibody negative and HLA dnDSA-positive patients.
Forty-five out of 144 patients developed dnNDSAs (31%). Among the dnNDSA-positive patients, 86% displayed one or more class I/II antibodies recognizing antigens included in the CREG/shared epitope groups that also comprise the mismatched donor HLA antigens. Despite potential pathogenicity, as suggested by their occasional presence within the graft, dnNDSAs displayed significantly lower MFI, and limited complement binding and graft homing properties, when compared with dnDSAs. In parallel, the graft survival probability was significantly lower in patients with dnDSA than in those with dnNDSA or without HLA antibodies (p < 0.005). Indeed, the dnNDSA-positive patients remaining dnDSA-negative throughout the posttransplant period did not develop clinical antibody mediated rejection and graft loss, and maintained good graft function at a median follow-up of 9 years. The biological characteristics of dnNDSAs may account for the low graft damaging capability when compared to dnDSAs.
•More than 30% of our non-sensitized pediatric kidney recipients developed dnNDSAs.•dnNDSAs did not induce clinically relevant graft damage at a medium-term follow-up.•Low MFI and poor C1q binding ability support the lack of pathogenicity of dnNDSAs.
Highlights • We investigated gene expression in highly sensitized patients waiting for a kidney graft. • Cytokines involved in B cell activation and antibody production were increased in these ...patients. • Cytokine blockade may be an additional desensitizing strategy in this risk category.
Summary
Data on the different HLA‐antibody (Ab) categories in pediatric kidney recipients developing de novo donor‐specific Abs (DSA) after transplantation are scarce. We retrospectively evaluated 82 ...consecutive nonsensitized pediatric recipients of a first kidney graft for de novo HLA Ab occurrence and antigen specificity. At a median follow‐up of 6 years, 29% of patients developed de novo DSA, while 45% had de novo non‐DSA. DSA appeared at 25‐month median time post‐transplant and were mostly directed toward HLA‐DQ antigens. Considering each HLA antigen, the estimated rate of DQ DSA (7.55 per 100 person‐years) was much higher than the rates observed for non‐DQ DSA. The HLA‐DQ Ab recognized determinants of the DQβ chain in 70% of cases, α chain in 25% of cases, and both chains in one patient. Non‐DSA peaked earlier than DSA, and were largely directed against HLA class I specificities that belonged to HLA‐A‐ and HLA‐B‐related cross‐reacting epitope groups (CREG) in 56% of cases. Our results indicate a need for evaluating HLA‐DQ compatibilities in kidney allocation, in order to minimize post‐transplant development of de novo DSA, known to be responsible for antibody‐mediated rejection and graft loss.
Summary
Current research is focusing on identifying bioclinical parameters for risk stratification of renal allograft loss, largely due to antibody‐mediated rejection (AMR). We retrospectively ...investigated graft outcome predictors in 24 unsensitized pediatric kidney recipients developing HLA de novo donor‐specific antibodies (dnDSAs), and treated for late AMR with plasmapheresis + low‐dose IVIG + Rituximab or high‐dose IVIG + Rituximab. Renal function and DSA properties were assessed before and longitudinally post treatment. The estimated GFR (eGFR) decline after treatment was dependent on a negative % eGFR variation in the year preceding treatment (P = 0.021) but not on eGFR at treatment (P = 0.74). At a median follow‐up of 36 months from AMR diagnosis, 10 patients lost their graft. Altered eGFR (P < 0.001) and presence of C3d‐binding DSAs (P = 0.005) at treatment, and failure to remove DSAs (P = 0.01) were negatively associated with graft survival in the univariable analysis. Given the relevance of DSA removal for therapeutic success, we analyzed antibody properties dictating resistance to anti‐humoral treatment. In the multivariable analysis, C3d‐binding ability (P < 0.05), but not C1q‐binding, and high mean fluorescence intensity (P < 0.05) were independent factors characterizing DSAs scarcely susceptible to removal. The poor prognosis of late AMR is related to deterioration of graft function prior to treatment and failure to remove C3d binding and/or high‐MFI DSAs.
It is well known that the presence of alloantibodies against human HLA class I (A, B, C) and class II (DR, DQ) antigens in transplant recipients waiting for a first or subsequent kidney transplant ...has a significant negative impact on graft outcome, with increased acute and chronic rejection rates. HLA antibodies, present in hyperimmunized patients (PRA > 80%) as a result of pregnancies, blood transfusions and previous failed grafts, once thought to be a formidable barrier to renal transplantation, can now be overcome with excellent results by means of desensitization protocols in kidney transplant recipients from living or cadaver donors. Such pretransplant desensitization protocols consist of high-dose intravenous immunoglobulin infusions (IVIg-HD), plasmapheresis associated with low-dose IVIg (IVIg-LD) and immunoabsorption by protein-A sepharose or Ig-sepharose columns. All of the above treatments, associated in many cases with the anti-CD20 monoclonal antibody Rituximab, have been widely applied in living donor kidney transplant recipients showing donor-specific anti-HLA antibodies. Similar desensitization protocols have been used for non-A2 AB0-incompatible living donor kidney transplants. These techniques have allowed successful transplantation in this high-risk patient category by providing live donor kidneys that function promptly with minimal risk of early loss, and have consequently increased the organ donor pool. Long-term follow- up of these patients and the application on a wider scale of these techniques, which for many patients may represent the only realistic chance of a successful transplant, will provide the definitive answers about their real efficacy.
Development of anti-human leukocyte antigen donor-specific antibodies (DSAs) is associated with antibody-mediated rejection (AMR) and reduced allograft survival in kidney transplant recipients. ...Whether changes in circulating lymphocytes anticipate DSA or AMR development is unclear.
We used time-of-flight mass cytometry to analyze prospectively collected peripheral blood mononuclear cells (PBMC) from pediatric kidney transplant recipients who developed DSA (DSA-positive recipients DSA
, n = 10). PBMC were obtained at 2 months posttransplant, 3 months before DSA development, and at DSA detection. PBMC collected at the same time points posttransplant from recipients who did not develop DSA (DSA-negative recipients DSA
, n = 11) were used as controls.
DSA
and DSA
recipients had similar baseline characteristics and comparable frequencies of total B and T cells. Within DSA
recipients, there was no difference in DSA levels (mean fluorescence intensity MFI: 13 687 ± 4159 vs 11 375 ± 1894 in DSA
AMR-positive recipients (AMR
) vs DSA
AMR-negative recipients (AMR
), respectively;
= 0.630), C1q binding (5 DSA
AMR
100% vs 4 DSA
AMR
80%;
= 1.000), or C3d binding (3 DSA
AMR
60% vs 1 DSA
AMR
20%;
= 0.520) between patients who developed AMR and those who did not. However, DSA
patients who developed AMR (n = 5; 18.0 ± 3.6 mo post-DSA detection) had increased B cells with antibody-secreting (IgD
CD27
CD38
;
= 0.002) and memory (IgD
CD27
CD38
;
= 0.003) phenotypes compared with DSA
and DSA
AMR
recipients at DSA detection.
Despite the small sample size, our comprehensive phenotypic analyses show that circulating B cells with memory and antibody-secreting phenotypes are present at DSA onset, >1 year before biopsy-proven AMR in pediatric kidney transplant recipients.
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