The enigma of sclera-specific autoimmunity in scleritis

Scleritis is a severe and painful ophthalmic disorder, in which a pathogenic role for collagen-directed autoimmunity was repeatedly suggested. We evaluated the presence of sclera-specific antibodies in a large cohort of patients with non-infectious scleritis. Therefore, we prospectively collected serum samples from 121 patients with non-infectious scleritis in a multicenter cohort study in the Netherlands. In addition, healthy (n = 39) and uveitis controls (n = 48) were included. Serum samples were tested for anti-native human type II collagen antibodies using a validated enzyme-linked immunosorbent assay (ELISA). Further, sclera-specific antibodies were determined using indirect immunofluorescence (IIF) on primate retinal/scleral cryosections. Lastly, human leukocyte antigen (HLA) typing was performed in 111 patients with scleritis. Anti-type II collagen antibodies were found in 13% of scleritis patients, in 10% of healthy controls and in 11% of uveitis controls (p = 0.91). A specific reaction to scleral nerve tissue on IIF was observed in 33% of patients with scleritis, which was higher than in healthy controls (11%; p = 0.01), but similar to uveitis controls (25%; p = 0.36). Reactivity to the scleral nerve tissue was significantly associated with earlier onset of scleritis (48 versus 56 years; p < 0.001), bilateral involvement (65% versus 42%; p = 0.01), and less frequent development of scleral necrosis (5% versus 22%; p = 0.02). HLA-B27 was found to be twice as prevalent in patients with scleritis (15.3%) compared to a healthy population (7.2%). In conclusion, scleral nerve autoantibody reactivity was more common in scleritis and uveitis patients in contrast to healthy controls. Further research is needed to characterize these scleral-nerve directed antibodies and assess their clinical value.

Multiomic profiling of transplant glomerulopathy reveals a novel T-cell dominant subclass

Kidney transplant (KTx) biopsies showing transplant glomerulopathy (TG) (glomerular basement membrane double contours (cg) > 0) and microvascular inflammation (MVI) in the absence of C4d staining and donor-specific antibodies (DSAs) do not fulfill the criteria for chronic active antibody-mediated rejection (CA-AMR) diagnosis and do not fit into any other Banff category. To investigate this, we initiated a multicenter intercontinental study encompassing 36 cases, comparing the immunomic and transcriptomic profiles of 14 KTx biopsies classified as cg+MVI DSA-/C4d- with 22 classified as CA-AMR DSA+/C4d+ through novel transcriptomic analysis using the NanoString Banff-Human Organ Transplant (B-HOT) panel and subsequent orthogonal subset analysis using two innovative 5-marker multiplex immunofluorescent panels. Nineteen genes were differentially expressed between the two study groups. Samples diagnosed with CA-AMR DSA+/C4d+ showed a higher glomerular abundance of natural killer cells and higher transcriptomic cell type scores for macrophages in an environment characterized by increased expression of complement-related genes (i.e., C5AR1) and higher activity of angiogenesis, interstitial fibrosis tubular atrophy, CA-AMR, and DSA-related pathways when compared to samples diagnosed with cg+MVI DSA-/C4d-. Samples diagnosed with cg+MVI DSA-/C4d- displayed a higher glomerular abundance and activity of T cells (CD3+, CD3+CD8+, and CD3+CD8-). Thus, we show that using novel multiomic techniques, KTx biopsies with cg+MVI DSA-/C4d- have a prominent T-cell presence and activity, putting forward the possibility that these represent a more T-cell dominant phenotype.

Imlifidase Desensitization in HLA-incompatible Kidney Transplantation: Finding the Sweet Spot

Imlifidase, derived from a Streptococcus pyogenes enzyme, cleaves the entire immunoglobulin G pool within hours after administration in fully cleaved antigen-binding and crystallizable fragments. These cleaved fragments can no longer exert their antibody-dependent cytotoxic functions, thereby creating a window to permit HLA-incompatible kidney transplantation. Imlifidase is labeled, in Europe only, for deceased donor kidney transplantation in highly sensitized patients, whose chances for an HLA-compatible transplant are negligible. This review discusses outcomes of preclinical and clinical studies on imlifidase and describes the phase III desensitization trials that are currently enrolling patients. A comparison is made with other desensitization methods. The review discusses the immunological work-up of imlifidase candidates and especially the "delisting strategy" of antigens that shift from unacceptable to acceptable with imlifidase desensitization. Other considerations for clinical implementation, such as adaptation of induction protocols, are also discussed. Imlifidase cleaves most of the currently used induction agents except for horse antithymocyte globulin, and rebound of donor-specific antibodies should be managed. Another consideration is the timing and interpretation of (virtual) crossmatches when bringing this novel desensitization agent into the clinic.

Comparison of 2 Immunosuppression Minimization Strategies in Kidney Transplantation: The ALLEGRO Trial

BACKGROUND

Evidence on the optimal maintenance of immunosuppressive regimen in kidney transplantation recipients is limited.

METHODS

The Amsterdam, LEiden, GROningen trial is a randomized, multicenter, investigator-driven, noninferiority, open-label trial in de novo kidney transplant recipients, in which 2 immunosuppression minimization strategies were compared with standard immunosuppression with basiliximab, corticosteroids, tacrolimus, and mycophenolic acid. In the minimization groups, either steroids were withdrawn from day 3, or tacrolimus exposure was reduced from 6 mo after transplantation. The primary endpoint was kidney transplant function at 24 mo.

RESULTS

A total of 295 participants were included in the intention-to-treat analysis. Noninferiority was shown for the primary endpoint; estimated glomerular filtration rate at 24 mo was 45.3 mL/min/1.73 m 2 in the early steroid withdrawal group, 49.0 mL/min/1.73 m 2 in the standard immunosuppression group, and 44.7 mL/min/1.73 m 2 in the tacrolimus minimization group. Participants in the early steroid withdrawal group were significantly more often treated for rejection ( P = 0.04). However, in this group, the number of participants with diabetes mellitus during follow-up and total cholesterol at 24 mo were significantly lower.

CONCLUSIONS

Tacrolimus minimization can be considered in kidney transplant recipients who do not have an increased immunological risk. Before withdrawing steroids the risk of rejection should be weighed against the potential metabolic advantages.

Determination of the clinical relevance of donor epitope-specific HLA-antibodies in kidney transplantation

In kidney transplantation, survival rates are still partly impaired due to the deleterious effects of donor specific HLA antibodies (DSA). However, not all luminex-defined DSA appear to be clinically relevant. Further analysis of DSA recognizing polymorphic amino acid configurations, called eplets or functional epitopes, might improve the discrimination between clinically relevant vs. irrelevant HLA antibodies. To evaluate which donor epitope-specific HLA antibodies (DESAs) are clinically important in kidney graft survival, relevant and irrelevant DESAs were discerned in a Dutch cohort of 4690 patients using Kaplan-Meier analysis and tested in a cox proportional hazard (CPH) model including nonimmunological variables. Pre-transplant DESAs were detected in 439 patients (9.4%). The presence of certain clinically relevant DESAs was significantly associated with increased risk on graft loss in deceased donor transplantations (p < 0.0001). The antibodies recognized six epitopes of HLA Class I, 3 of HLA-DR, and 1 of HLA-DQ, and most antibodies were directed to HLA-B (47%). Fifty-three patients (69.7%) had DESA against one donor epitope (range 1-5). Long-term graft survival rate in patients with clinically relevant DESA was 32%, rendering DESA a superior parameter to classical DSA (60%). In the CPH model, the hazard ratio (95% CI) of clinically relevant DESAs was 2.45 (1.84-3.25) in deceased donation, and 2.22 (1.25-3.95) in living donation. In conclusion, the developed model shows the deleterious effect of clinically relevant DESAs on graft outcome which outperformed traditional DSA-based risk analysis on antigen level.

Ellipro scores of donor epitope specific HLA antibodies are not associated with kidney graft survival

In kidney transplantation, donor HLA antibodies are a risk factor for graft loss. Accessibility of donor eplets for HLA antibodies is predicted by the ElliPro score. The clinical usefulness of those scores in relation to transplant outcome is unknown. In a large Dutch kidney transplant cohort, Ellipro scores of pretransplant donor antibodies that can be assigned to known eplets (donor epitope specific HLA antibodies [DESAs]) were compared between early graft failure and long surviving deceased donor transplants. We did not observe a significant Ellipro score difference between the two cohorts, nor significant differences in graft survival between transplants with DESAs having high versus low total Ellipro scores. We conclude that Ellipro scores cannot be used to identify DESAs associated with early versus late kidney graft loss in deceased donor transplants.

Antibody verification of HLA class I and class II eplets by human monoclonal HLA antibodies

In solid organ transplantation, formation of de novo donor-specific HLA antibodies is induced by mismatched eplets on donor HLA molecules. While several studies have shown a strong correlation between the number of eplet mismatches and inferior outcomes, not every eplet mismatch is immunogenic. Eplets are theoretically defined entities, necessitating formal proof that they can be recognised and bound by antibodies. This antibody verification is pivotal to ensure that clinically relevant eplets are considered in studies on molecular matching. Recombinant human HLA-specific monoclonal antibodies (mAbs) were generated from HLA-reactive B cell clones isolated from HLA immunised individuals using recombinant HLA molecules. Subsequently, the reactivity patterns of the mAbs obtained from single antigen bead assay were analysed using HLA-EMMA software to identify single or configurations of solvent accessible amino acids uniquely present on the reactive HLA alleles and were mapped to eplets. Two HLA class I and seven HLA class II-specific human mAbs were generated from four individuals. Extensive mAb reactivity analysis, led to antibody verification of three HLA-DR-specific eplets, and conversion of five eplets (one HLA-A, one HLA-B, two HLA-DR, and one HLA-DP), from provisionally verified to truly antibody-verified. Finally, one HLA-DQ-specific eplet was upgraded from level A2 to level A1 verification evidence. The generation of recombinant human HLA-specific mAbs with different specificities contributes significantly to the antibody verification of eplets and therefore is instrumental for implementation of eplet matching in the clinical setting.

Repurposing HLA genotype data of renal transplant patients to prevent severe drug hypersensitivity reactions

Introduction: Specific alleles in human leukocyte antigens (HLAs) are associated with an increased risk of developing drug hypersensitivity reactions induced by abacavir, allopurinol, carbamazepine, oxcarbazepine, phenytoin, lamotrigine, or flucloxacillin. Transplant patients are genotyped for HLA as a routine practice to match a potential donor to a recipient. This study aims to investigate the feasibility and potential impact of repurposing these HLA genotype data from kidney transplant patients to prevent drug hypersensitivity reactions. Methods: A cohort of 1347 kidney transplant recipients has been genotyped in the Leiden University Medical Center (LUMC) using next-generation sequencing (NGS). The risk alleles HLA-A*31:01, HLA-B*15:02, HLA-B*15:11, HLA-B*57:01, and HLA-B*58:01 were retrieved from the NGS data. Medical history, medication use, and allergic reactions were obtained from the patient's medical records. Carrier frequencies found were compared to a LUMC blood donor population. Results: A total of 13.1% of transplant cohort patients carried at least one of the five HLA risk alleles and therefore had an increased risk of drug-induced hypersensitivity for specific drugs. HLA-A*31:01, HLA-B*15:02, HLA-B*57:01, and HLA-B*58:01 were found in carrier frequencies of 4.61%, 1.19%, 4.46%, and 3.35% respectively. No HLA-B*15:11 carrier was found. In total nine HLA-B*57:01 carriers received flucloxacillin and seven HLA-B*58:01 carriers within our cohort received allopurinol. Discussion: Our study shows that repurposing HLA genotype data from transplantation patients for the assignment of HLA risk alleles associated with drug hypersensitivity is feasible. The use of these data by physicians while prescribing drugs or by the pharmacist when dispensing drugs holds the potential to prevent drug hypersensitivity reactions. The utility of this method was highlighted by 13.1% of the transplant cohort patients carrying an actionable HLA allele.

Diagnosis and treatment of allograft rejection in islet transplantation

Islet transplantation stabilizes glycemic control in patients with complicated diabetes mellitus. Rapid functional decline could be due to islet allograft rejection. However, there is no reliable method to assess rejection, and treatment protocols are absent. We aimed to characterize diagnostic features of islet allograft rejection and assess effectiveness of high-dose methylprednisolone treatment. Over a median follow-up of 61.8 months, 22% (9 of 41) of islet transplant recipients experienced 10 suspected rejection episodes (SREs). All first SREs occurred within 18 months after transplantation. Important features were unexplained hyperglycemia (all cases), unexplained C-peptide decrease (ΔC-peptide, 77.1% [-59.1% to -91.6%]; ΔC-peptide:glucose, -76.3% [-49.2% to -90.4%]), predisposing event (5 of 10 cases), and increased immunologic risk (5 of 10 cases). At 6 months post-SRE, patients who received protocolized methylprednisolone (n = 4) had significantly better islet function than untreated patients (n = 4), according to C-peptide (1.39 ± 0.59 vs 0.14 ± 0.19 nmol/L; P = .007), Igls score (good [4 of 4 cases] vs failure [3 of 4 cases] or marginal [1 of 4 cases]; P = .018) and β score (6.0 [6.0-6.0] vs 1.0 [0.0-3.5]; P = .013). SREs are prevalent among islet transplant recipients and are associated with loss of islet graft function. Timely treatment with high-dose methylprednisolone mitigates this loss. Unexplained hyperglycemia, unexpected C-peptide decrease, a predisposing event, and elevated immunologic risk are diagnostic indicators for SRE.

Chronic Pancreas Allograft Rejection Followed by Successful HLA-Incompatible Islet Alloautotransplantation: A Novel Strategy?

The purpose of pancreas or islet transplantation is to restore glycemic control in order to mitigate diabetes-related complications and prevent severe hypoglycemia. Complications from chronic pancreas allograft rejection may lead to transplantectomy, even when the endocrine function remains preserved. We present first evidence of a successful HLA incompatible islet re-transplantation with islets isolated from a rejecting pancreas allograft after simultaneous kidney pancreas transplantation. The pancreas allograft was removed because of progressively painful pancreatic panniculitis from clinically uncontrolled chronic rejection. The endocrine function was preserved. Induction treatment for this "islet alloautotransplantation" consisted of plasmapheresis, IVIg and alemtuzumab. At 1 year, the patient retained islet graft function with good glycemic control and absence of severe hypoglycemia, despite persistent low-grade HLA donor-specific antibodies. His panniculitis had resolved completely. In our point of view, islet alloautotransplantation derived from a chronically rejecting pancreas allograft is a potential option to salvage (partial) islet function, despite preformed donor-specific antibodies, in order to maintain stable glycemic control. Thereby it protects against severe hypoglycemia, and it potentially mitigates kidney graft dysfunction and other diabetes-related complications in patients with continued need for immunosuppression and who are otherwise difficult to retransplant.

HLA-DQ eplet mismatch load may identify kidney transplant patients eligible for tacrolimus withdrawal without donor-specific antibody formation after mesenchymal stromal cell therapy

Recently, the randomized phase-II Triton study demonstrated that mesenchymal stromal cell (MSC) therapy facilitated early tacrolimus withdrawal in living donor kidney transplant recipients. The current sub-study analyzed formation of de novo donor-specific HLA antibodies (dnDSA) in the context of the degree of HLA eplet mismatches. At the time of protocol biopsy at 6 months, 7/29 patients (24%) in the MSC group and 1/27 patient (3.7%) in the control group had developed dnDSA. In the MSC group, all dnDSA were anti-HLA-DQ; two patients had anti-DQ alone and five patients combined with anti-class I, HLA-DR or -DP. Despite excess dnDSA formation in the MSC-arm of the study, the evolution of eGFR (CKD-EPI) and proteinuria were comparable 2 years posttransplant. All dnDSA were complement-binding and three patients had antibody-mediated rejection in the protocol biopsy, but overall rejection episodes were not increased. Everolimus had to be discontinued in nine patients because of toxicity, and tacrolimus was reintroduced in six patients because of dnDSA formation. The HLA-DQ eplet mismatch load independently associated with dnDSA (adjusted hazard ratio = 1.07 per eplet mismatch, p = 0.008). A threshold of ≥11 HLA-DQ eplet mismatches predicted subsequent dnDSA in all 11 patients in the MSC group, but specificity was low (44%). Further research is warranted to explore HLA molecular mismatch load as a biomarker to guide personalized maintenance immunosuppression in kidney transplantation.

Tacrolimus Monotherapy is Safe in Immunologically Low-Risk Kidney Transplant Recipients: A Randomized-Controlled Pilot Study

In this randomized-controlled pilot study, the feasibility and safety of tacrolimus monotherapy in immunologically low-risk kidney transplant recipients was evaluated [NTR4824, www.trialregister.nl]. Low immunological risk was defined as maximal 3 HLA mismatches and the absence of panel reactive antibodies. Six months after transplantation, recipients were randomized if eGFR >30 ml/min, proteinuria <50 mg protein/mmol creatinine, no biopsy-proven rejection after 3 months, and no lymphocyte depleting therapy given. Recipients were randomized to tacrolimus/mycophenolate mofetil (TAC/MMF) or to taper and discontinue MMF at month 9 (TACmono). 79 of the 121 recipients were randomized to either TACmono (n = 38) or TAC/MMF (n = 41). Mean recipient age was 59 years and 59% received a living donor transplant. The median follow-up was 62 months. After randomization, 3 TACmono and 4 TAC/MMF recipients experienced a biopsy-proven rejection. At 5 years follow-up, patient survival was 84% in TACmono versus 76% in TAC/MMF with death-censored graft survival of 97% for both groups and no differences in eGFR and proteinuria. Eleven TACmono recipients had an infectious episode versus 22 TAC/MMF recipients (p < 0.03). Donor-specific anti-HLA antibodies were not detected during follow-up in both groups. Tacrolimus monotherapy in selected immunologically low-risk kidney transplant recipients appears safe and reduces the number of infections.

Destructive inflammatory reaction after an autologous retinal pigment epithelium and choroid transplantation: no detection of an auto-immune response

Purpose

Five patients who underwent uncomplicated retinal pigment epithelium (RPE)-choroid transplantation for neovascular age-related macular degeneration developed a destructive inflammatory reaction causing subretinal fluid accumulation and extensive RPE atrophy in the graft. We hypothesized that this inflammation could be caused by an auto-immune response against the graft, resulting in circulating auto-antibodies. The aim of our study was to examine a potential autoimmune origin, which would allow a more targeted therapy approach.

Methods

Five above-mentioned patients and four control groups of five patients each were included: 1) after uncomplicated RPE-choroid transplantation, 2) after full macular translocation, 3) treated with anti-vascular endothelial growth factor, and 4) healthy controls. Histopathology of rejected graft tissue was performed using standard procedures. Presence of RPE-choroid autoantibodies in serum was examined by indirect immunofluorescence and Western blot, and human leukocyte antigen (HLA) typing was performed.

Results

Histopathological examination of an explanted graft showed infiltration of T-lymphocytes and macrophages in the choroid and RPE, and an increased number of B-cell lymphocytes were found in the choroid. Indirect immunofluorescence showed weak RPE-choroid autoantibody immunoreactivity in three patients of different groups. Western blot did not show specific RPE-choroid autoantibody immunoreactivity and no difference of HLA genotypes between the groups was found.

Conclusions

Although local mononuclear inflammatory cell infiltration and a high number of B-lymphocytes were observed in an explanted graft, we did not detect serological evidence of an autoimmune origin of the postoperative inflammation using direct immunofluorescence and Western Blot. Alternatively, the graft failure may have been caused by local innate inflammation, triggered by breakdown of tolerance. Based on our current findings of this small study group, we have no rationale to pursue therapies targeted towards autoreactive graft failure. More research is needed to confirm our findings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12348-022-00305-2.

Causes of Kidney Graft Failure in a Cohort of Recipients With a Very Long-Time Follow-Up After Transplantation

Background

Biopsy-proven causes of graft loss many years after kidney transplantation are scarcely documented.

Methods

Patients transplanted between 1995 and 2005 (n = 737) in a single center were followed on a regular basis until 2021. The recipients were divided according to age at transplantation into 3 groups; 18–39 years (young), 40–55 years (middle age), and older than 55 years (elderly). For cause biopsies of renal transplants were clustered into the categories, rejection, IFTA, return original disease, and diagnosis of de novo kidney disease.

Results

Rejection was the main cause of graft failure censored for death at every time period after transplantation. The incidence of T cell-mediated rejection (TCMR) became rare 6 years after transplantation while the cumulative incidence of antibody-mediated rejection (ABMR) increased over time (1.1% per year). ABMR was not diagnosed anymore beyond 15 years of follow-up in recipients without pre-transplant donor-specific antibodies (DSA). An episode of TCMR was associated with an increased incidence of ABMR diagnosis in the short-term but did not increase the overall incidence of AMBR not in the long-term. Death as a cause of graft failure was an important competitive risk factor long after transplantation and resulted in a significantly lower frequency of rejection-related graft loss in the elderly group (11 vs. 23% in the young group at 15 year follow-up).

Conclusion

Rejection is a major cause of graft loss but recipient’s age, time after transplantation, and the presence of DSA before transplantation determine the relative contribution to overall graft loss and the type of rejection involved.

HLA-DQ-Specific Recombinant Human Monoclonal Antibodies Allow for In-Depth Analysis of HLA-DQ Epitopes

HLA-DQ donor-specific antibodies (DSA) are the most prevalent type of DSA after renal transplantation and have been associated with eplet mismatches between donor and recipient HLA. Eplets are theoretically defined configurations of surface exposed amino acids on HLA molecules that require verification to confirm that they can be recognized by alloantibodies and are therefore clinically relevant. In this study, we isolated HLA-DQ specific memory B cells from immunized individuals by using biotinylated HLA-DQ monomers to generate 15 recombinant human HLA-DQ specific monoclonal antibodies (mAb) with six distinct specificities. Single antigen bead reactivity patterns were analyzed with HLA-EMMA to identify amino acids that were uniquely shared by the reactive HLA alleles to define functional epitopes which were mapped to known eplets. The HLA-DQB1*03:01-specific mAb LB_DQB0301_A and the HLA-DQB1*03-specific mAb LB_DQB0303_C supported the antibody-verification of eplets 45EV and 55PP respectively, while mAbs LB_DQB0402_A and LB_DQB0602_B verified eplet 55R on HLA-DQB1*04/05/06. For three mAbs, multiple uniquely shared amino acid configurations were identified, warranting further studies to define the inducing functional epitope and corresponding eplet. Our unique set of HLA-DQ specific mAbs will be further expanded and will facilitate the in-depth analysis of HLA-DQ epitopes, which is relevant for further studies of HLA-DQ alloantibody pathogenicity in transplantation.

Activated CD4+ T Cells and Highly Differentiated Alloreactive CD4+ T Cells Distinguish Operationally Tolerant Liver Transplantation Recipients

Spontaneous operational tolerance to the allograft develops in a proportion of liver transplantation (LT) recipients weaned off immunosuppressive (IS) drugs. Several studies have investigated whether peripheral blood circulating T cells could play a role in the development or identify operational tolerance, but never characterized alloreactive T cells in detail due to the lack of a marker for these T cells. In this study, we comprehensively investigated phenotypic and functional characteristics of alloreactive circulating T cell subsets in tolerant LT recipients (n = 15) using multiparameter flow cytometry and compared these with LT recipients on IS drugs (n = 23) and healthy individuals (n = 16). Activation-induced CD137 was used as a marker for alloreactive T cells upon allogenic stimulation. We found that central and effector memory CD4+ T cells were hyporesponsive against donor and third-party splenocyte stimulation in tolerant LT recipients, whereas an overall hyperresponsiveness was observed in alloreactive terminally differentiated effector memory CD4+ T cells. In addition, elevated percentages of circulating activated T helper cells were observed in these recipients. Lastly, tolerant and control LT recipients did not differ in donor-specific antibody formation. In conclusion, a combination of circulating hyperresponsive highly differentiated alloreactive CD4+ T cells and circulating activated T helper cells could discriminate tolerant recipients from a larger group of LT recipients.

T-Cell Epitopes Shared Between Immunizing HLA and Donor HLA Associate With Graft Failure After Kidney Transplantation

CD4⁺ T-helper cells play an important role in alloimmune reactions following transplantation by stimulating humoral as well as cellular responses, which might lead to failure of the allograft. CD4⁺ memory T-helper cells from a previous immunizing event can potentially be reactivated by exposure to HLA mismatches that share T-cell epitopes with the initial immunizing HLA. Consequently, reactivity of CD4⁺ memory T-helper cells toward T-cell epitopes that are shared between immunizing HLA and donor HLA could increase the risk of alloimmunity following transplantation, thus affecting transplant outcome. In this study, the amount of T-cell epitopes shared between immunizing and donor HLA was used as a surrogate marker to evaluate the effect of donor-reactive CD4⁺ memory T-helper cells on the 10-year risk of death-censored kidney graft failure in 190 donor/recipient combinations using the PIRCHE-II algorithm. The T-cell epitopes of the initial theoretical immunizing HLA and the donor HLA were estimated and the number of shared PIRCHE-II epitopes was calculated. We show that the natural logarithm-transformed PIRCHE-II overlap score, or Shared T-cell EPitopes (STEP) score, significantly associates with the 10-year risk of death-censored kidney graft failure, suggesting that the presence of pre-transplant donor-reactive CD4⁺ memory T-helper cells might be a strong indicator for the risk of graft failure following kidney transplantation.

Uncomplicated oocyte donation pregnancies display an elevated CD163-positive type 2 macrophage load in the decidua, which is associated with fetal-maternal HLA mismatches

PROBLEM

The embryo of an oocyte donation (OD) pregnancy is completely allogeneic to the mother, which may challenge the maternal immune system to tolerize the fetus. Decidual macrophages are essential in maintaining a healthy pregnancy, and type 2 macrophages may exhibit immune suppressive activity. We hypothesized that the composition of decidual macrophages is different between uncomplicated OD pregnancies and non-OD in vitro fertilization (IVF) pregnancies, and is related to fetal-maternal incompatibility.

METHOD OF STUDY

Women with uncomplicated pregnancy were enrolled: 25 singleton OD pregnancies and 17 non-OD IVF pregnancies. The extent of immunohistochemical staining of CD14 (pan-macrophage marker) and CD163 (type 2 macrophage marker) in both decidua basalis and parietalis was quantitated by digital image analysis. Maternal and fetal DNA was typed for human leukocyte antigen (HLA)-A, -B, C, -DRB1, and -DQB1, and fetal-maternal HLA mismatches were calculated.

RESULTS

OD pregnancies showed a higher percentage of CD163+ staining (P = .040) and higher CD163/CD14 ratio (P = .032) in the parietalis than non-OD IVF. The OD group was separated into a semi-allogeneic group (≤5 fetal maternal HLA mismatches) and a fully allogeneic group (> 5 mismatches). The HLA-fully-allogeneic OD group, but not the HLA-semi-allogeneic OD group, showed significantly elevated CD163/CD14 ratio in the parietalis compared with the non-OD IVF group (P < .05).

CONCLUSIONS

Uncomplicated OD pregnancies display a higher CD163-positive cell fraction in the total decidual macrophage population compared to autologous pregnancies, which may suggest that a local type 2 macrophage-related mechanism is needed to compensate for the higher fetal-maternal HLA mismatch load.

Autologous bone marrow-derived mesenchymal stromal cell therapy with early tacrolimus withdrawal: The randomized prospective, single-center, open-label TRITON study

After renal transplantation, there is a need for immunosuppressive regimens which effectively prevent allograft rejection, while preserving renal function and minimizing side effects. From this perspective, mesenchymal stromal cell (MSC) therapy is of interest. In this randomized prospective, single-center, open-label trial, we compared MSCs infused 6 and 7 weeks after renal transplantation and early tacrolimus withdrawal with a control tacrolimus group. Primary end point was quantitative evaluation of interstitial fibrosis in protocol biopsies at 4 and 24 weeks posttransplant. Secondary end points included acute rejection, graft loss, death, renal function, adverse events, and immunological responses. Seventy patients were randomly assigned of which 57 patients were included in the final analysis (29 MSC; 28 controls). Quantitative progression of fibrosis failed to show benefit in the MSC group and GFR remained stable in both groups. One acute rejection was documented (MSC group), while subclinical rejection in week 24 protocol biopsies occurred in seven patients (four MSC; three controls). In the MSC group, regulatory T cell numbers were significantly higher compared to controls (p = .014, week 24). In conclusion, early tacrolimus withdrawal with MSC therapy was safe and feasible without increased rejection and with preserved renal function. MSC therapy is a potentially useful approach after renal transplantation.

P–420 uncomplicated oocyte donation pregnancies display elevated CD163 positive type 2 macrophage load in the decidua, which is associated with fetal-maternal HLA class II mismatches

Study question

Do quantity and composition of decidual macrophages differ between uncomplicated oocyte donation (OD) pregnancies and non-OD in vitro fertilization (IVF) pregnancies?

Summary answer

OD placentas show higher decidual CD163 positive fraction within the total macrophage population compared to non-OD IVF placentas.

What is known already

The embryo of an OD pregnancy is completely allogeneic to the mother, which may lead to a bigger challenge for the maternal immune system to tolerize the fetus compared to autologous pregnancies. Placental macrophages may be essential in maintaining a healthy pregnancy. Macrophages can be classified into different categories based on phenotype and characteristics, in which type 2 macrophages are thought to exhibit immune suppressive activity.

Study design, size, duration

This retrospective case-control study included patients who delivered in the Leiden University Medical Center between January 1st 2006 and July 1st 2016. A total of 42 pregnancies were enrolled in this study, conceived by uncomplicated singleton OD pregnancies (n = 25) or non-OD IVF pregnancies (n = 17). Medical records were reviewed and clinical data were collected. Placental tissue samples were collected for immunohistochemical staining and blood samples were collected for HLA typing.

Participants/materials, setting, methods

Placentas were collected and immunohistochemically stained for CD14 (pan-macrophage marker) and CD163 (type 2 macrophage marker). The extent of staining was quantitated by digital image analysis software. To assess mismatching, maternal and fetal DNA was typed for HLA-A, -B, C, -DRB1, and -DQB1.

Main results and the role of chance

A significantly lower percentage of CD14 positive staining was observed in the decidua basalis of OD pregnancies compared to non-OD IVF pregnancies (p = 0.030). Consequently, the CD163/CD14 ratio in OD group was higher than in non-OD IVF group (p = 0.243). In the parietalis, OD pregnancies demonstrated a significantly higher percentage of CD163+ staining (p = 0.040) and a significantly higher CD163/CD14 ratio (p = 0.032) compared to non-OD IVF group. The reproducibility of this quantitative analysis was found to be high. OD group was separated into a syngeneic group (number of mismatches lower than half of the antigens per HLA locus) and an allogeneic group (number of mismatches higher than half of the antigens per HLA locus). Significant differences of CD163+ and CD163/CD14 ratio were found in the decidua parietalis when comparing the HLA-classII-allogeneic OD group with the non-OD IVF group (p = 0.047). This difference was not found for the HLA-class-II-syngeneic OD group.

Limitations, reasons for caution

Our study only focused on decidua basalis and parietalis, no other locations in the placentas. Larger sample size might be needed to verify the association between macrophages and HLA mismatches.

Wider implications of the findings: To our knowledge, this study is the first to quantify a higher CD163 positive M2 macrophages load within the total decidual macrophages of uncomplicated OD pregnancy compared to non-OD IVF pregnancies.

Trial registration number

Not applicable

P-420 Pre-selected for an award: Uncomplicated oocyte donation pregnancies display elevated CD163 positive type 2 macrophage load in the decidua, which is associated with fetal-maternal HLA class II mismatches

Study question

Do quantity and composition of decidual macrophages differ between uncomplicated oocyte donation (OD) pregnancies and non-OD in vitro fertilization (IVF) pregnancies?

Summary answer

OD placentas show higher decidual CD163 positive fraction within the total macrophage population compared to non-OD IVF placentas.

What is known already

The embryo of an OD pregnancy is completely allogeneic to the mother, which may lead to a bigger challenge for the maternal immune system to tolerize the fetus compared to autologous pregnancies. Placental macrophages may be essential in maintaining a healthy pregnancy. Macrophages can be classified into different categories based on phenotype and characteristics, in which type 2 macrophages are thought to exhibit immune suppressive activity.

Study design, size, duration

This retrospective case-control study included patients who delivered in the Leiden University Medical Center between January 1st 2006 and July 1st 2016. A total of 42 pregnancies were enrolled in this study, conceived by uncomplicated singleton OD pregnancies (n = 25) or non-OD IVF pregnancies (n = 17). Medical records were reviewed and clinical data were collected. Placental tissue samples were collected for immunohistochemical staining and blood samples were collected for HLA typing.

Participants/materials, setting, methods

Placentas were collected and immunohistochemically stained for CD14 (pan-macrophage marker) and CD163 (type 2 macrophage marker). The extent of staining was quantitated by digital image analysis software. To assess mismatching, maternal and fetal DNA was typed for HLA-A, -B, C, -DRB1, and -DQB1.

Main results and the role of chance

A significantly lower percentage of CD14 positive staining was observed in the decidua basalis of OD pregnancies compared to non-OD IVF pregnancies (p = 0.030). Consequently, the CD163/CD14 ratio in OD group was higher than in non-OD IVF group (p = 0.243). In the parietalis, OD pregnancies demonstrated a significantly higher percentage of CD163+ staining (p = 0.040) and a significantly higher CD163/CD14 ratio (p = 0.032) compared to non-OD IVF group. The reproducibility of this quantitative analysis was found to be high. OD group was separated into a syngeneic group (number of mismatches lower than half of the antigens per HLA locus) and an allogeneic group (number of mismatches higher than half of the antigens per HLA locus). Significant differences of CD163+ and CD163/CD14 ratio were found in the decidua parietalis when comparing the HLA-classII-allogeneic OD group with the non-OD IVF group (p = 0.047). This difference was not found for the HLA-class-II-syngeneic OD group.

Limitations, reasons for caution

Our study only focused on decidua basalis and parietalis, no other locations in the placentas. Larger sample size might be needed to verify the association between macrophages and HLA mismatches.

Wider implications of the findings

To our knowledge, this study is the first to quantify a higher CD163 positive M2 macrophages load within the total decidual macrophages of uncomplicated OD pregnancy compared to non-OD IVF pregnancies.

Trial registration number

not applicable

Maternal-Fetal HLA Compatibility in Uncomplicated and Preeclamptic Naturally Conceived Pregnancies

Introduction

In pregnancy, the mother and fetus differ in HLA antigens, and yet the maternal immune system generally tolerates the fetus. KIR receptors expressed by maternal uterine NK cells at the maternal-fetal interface directly interact with HLA-C on extravillous trophoblast cells for optimal placental development. In this study, we aimed to determine whether there is a preferential selection for HLA compatibility and specific KIR/HLA-C combinations in uncomplicated and preeclamptic naturally conceived pregnancies compared to what would be expected by chance.

Methods

Genotyping for maternal and fetal HLA-A, -B, -C, -DR, and -DQ, and maternal KIR was performed for 451 uncomplicated pregnancies and 77 pregnancies complicated with preeclampsia. The number of HLA antigen (mis)matches between mother and fetus was calculated and compared to expected values obtained by randomization of the HLA haplotype, inherited from the father, over the existing maternal haplotype of the fetuses. A similar methodology was executed for analysis of the KIR/HLA-C data (n=309).

Results

In uncomplicated pregnancies, the degree of maternal-fetal HLA matching was not different than expected-by-chance values. In preeclamptic pregnancies, the degree of maternal-fetal HLA matching was different in observed compared to expected-by-chance values (p=0.012). More specifically, the degree of maternal-fetal matching of HLA-C was higher in the actual preeclamptic pregnancies than was expected-by-chance (p=0.007). Preeclamptic pregnancies showed an overall tendency towards higher maternal-fetal HLA compatibility, for total HLA matches (p=0.021), HLA class I (p=0.038) and HLA-C (p=0.025) compared to uncomplicated pregnancies.

Conclusion

The data suggest that there is no preferential selection of maternal-fetal HLA compatibility in uncomplicated pregnancies. In contrast, increased total HLA, HLA class I and, especially, HLA-C compatibility is associated with preeclampsia, suggestive for a role of HLA mismatches in immune regulation leading to uncomplicated pregnancy.

Single antigen testing to reduce early antibody-mediated rejection risk in female recipients of a spousal donor kidney

Female recipients of a spousal donor kidney transplant are at greater risk of donor-specific pre-immunization, which may increase the risk of acute antibody-mediated rejection (ABMR). We assessed the incidence of early ABMR (within two weeks after transplantation), risk factors for ABMR and graft function in 352 complement-dependent cytotoxicity test-negative LURD transplant recipients, transplanted between 1997 and 2014 at the Leiden University Medical Center in The Netherlands. Risk factors for immunization were retrieved from the health records. As methods to screen for preformed donor-specific antibodies (pDSA) have developed through time, we retrospectively screened those with ABMR for pDSA using pooled-antigen bead (PAB) and single-antigen bead (SAB) assays. The cumulative incidence of rejection in the first six months after transplantation was 18% (TCMR 15%; early ABMR 3%). Early ABMR resulted in inferior graft survival and was more common in women who received a kidney from their spouse (10%) than in other women (2%) and men (<1%). The SAB assay retrospectively identified pDSA in seven of nine cases of early ABMR (78%), while the PAB detected pDSA in only three cases (33%). Seeing that early ABMR occurred in 10% of women who received a kidney from their spouse, a SAB assay should be included in the pre-transplant assessment of this group of women, regardless of the result of the PAB assay.

Low incidence of IgA isotype of HLA antibodies in alloantigen exposed individuals

Human leukocyte antigen (HLA) antibodies are induced by pregnancy, transfusion, or transplantation. Serum from transplant recipients is regularly screened for IgG HLA antibodies because of their clinical relevance for transplant outcome. While other isotypes of HLA antibodies, such as IgA may also contribute to the alloimmune response, validated detection assays for IgA HLA antibody detection are lacking. Therefore, we modified the commonly used luminex screening assay for IgG HLA antibody detection (IgG-LMX) into an IgA HLA antibody screening assay (IgA-LMX). Optimization and validation was performed with IgG, IgA1, and IgA2 isotype variants of HLA-specific human recombinant monoclonal antibodies (mAbs). Reactivity patterns of IgA1 and IgA2 isotype HLA-specific mAbs in IgA-LMX were identical to those of the IgG isotype. Cross-reactivity with IgG and IgM antibodies and nonspecific binding to the beads were excluded. Further assay validation showed the absence of IgA HLA antibodies in serum from individuals without alloantigen exposure (n = 18). When the IgA-LMX assay was applied to sera from 289 individuals with known alloantigen exposure through pregnancy (n = 91) or kidney transplantation (n = 198), IgA HLA antibodies were detected in 3.5% of individuals; eight patients on the kidney retransplant waitlist and two women immunized through pregnancy. The majority (90%) of IgA HLA antibodies were directed against HLA class II and were always present in conjunction with IgG HLA antibodies. Results of this study show that this validated IgA-LMX method can serve as a screening assay for IgA HLA antibodies and that the incidence of IgA HLA antibodies in alloantigen exposed individuals is low.

Generation and reactivity analysis of human recombinant monoclonal antibodies directed against epitopes on HLA-DR

In kidney transplantation, eplet mismatches between donor and recipient have been associated with de novo donor-specific antibody development. Eplets are theoretically defined configurations of polymorphic amino acids and require experimental verification to establish whether they can be bound by alloantibodies. Human HLA-specific monoclonal antibodies (mAbs) have been instrumental for this purpose but are largely lacking for HLA class II. In this study, we isolated single HLA-DR-specific memory B cells from peripheral blood of immunized individuals (n = 3) using HLA class II tetramers to generate recombinant human HLA-DR antigen-reactive mAbs (n = 5). Comparison of the amino acid composition of the reactive HLA alleles in relation to the antibody reactivity patterns led to identification of 3 configurations, 70Q 73A, 31F 32Y 37Y, and 14K 25Q recognized, respectively, by HLA-DRB1*01:01, HLA-DRB1*04:01, and HLA-DRB1*07:01 antigen-reactive mAbs. The first 2 correspond to eplets 70QA and 31FYY and can now be considered antibody verified. The latter indicates that eplet 25Q needs to be redefined before being considered as antibody verified. Generation and reactivity analysis of human HLA-DR mAbs allowed for identification of amino acid configurations corresponding to known eplets, whereas the other patterns may be used to redefine eplets with similar, but not identical predicted amino acid composition.

Human leukocyte antigen selected allogeneic mesenchymal stromal cell therapy in renal transplantation: The Neptune study, a phase I single-center study

Mesenchymal stromal cells (MSC) hold promise as a novel immune-modulatory therapy in organ transplantation. First clinical studies have used autologous MSCs; however, the use of allogeneic "off-the-shelf" MSCs is more sustainable for broad clinical implementation, although with the risk of causing sensitization. We investigated safety and feasibility of allogeneic MSCs in renal transplantation, using a matching strategy that prevented repeated mismatches. Ten patients received two doses of 1.5 × 10⁶ /kg allogeneic MSCs 6 months after transplantation in a single-center nonrandomized phase Ib trial, followed by lowering of tacrolimus (trough level 3 ng/mL) in combination with everolimus and prednisone. Primary end point was safety, measured by biopsy proven acute rejection (BPAR) and graft loss 12 months after transplantation. Immune monitoring was performed before and after infusion. No BPAR or graft loss occurred and renal function remained stable. One patient retrospectively had DSAs against MSCs, formed before infusion. No major alterations in T and B cell populations or plasma cytokines were observed upon MSC infusion. Administration of HLA selected allogeneic MSCs combined with low-dose tacrolimus 6 months after transplantation is safe at least in the first year after renal transplantation. This sets the stage to further explore the efficacy of third-party MSCs in renal transplantation.

Immunosuppression Has Long-Lasting Effects on Circulating Follicular Regulatory T Cells in Kidney Transplant Recipients

Background: FoxP3⁺ follicular regulatory T cells (Tfr) have been identified as the cell population controlling T follicular helper (Tfh) cells and B cells which, are both involved in effector immune responses against transplanted tissue.

Methods: To understand the biology of Tfr cells in kidney transplant patients treated with tacrolimus and mycophenolate mofetil (MMF) combination immunosuppression, we measured circulating (c)Tfh and cTfr cells in peripheral blood by flow cytometry in n = 211 kidney transplant recipients. At the time of measurement patients were 5–7 years after transplantation. Of this cohort of patients, 23.2% (49/211) had been previously treated for rejection. Median time after anti-rejection therapy was 4.9 years (range 0.4–7 years). Age and gender matched healthy individuals served as controls.

Results: While the absolute numbers of cTfh cells were comparable between kidney transplant recipients and healthy controls, the numbers of cTfr cells were 46% lower in immunosuppressed recipients (p < 0.001). More importantly, in transplanted patients, the ratio of cTfr to cTfh was decreased (median; 0.10 vs. 0.06), indicating a disruption of the balance between cTfr and cTfh cells. This shifted balance was observed for both non-rejectors and rejectors. Previous pulse methylprednisolone or combined pulse methylprednisolone + intravenous immunoglobulin anti-rejection therapy led to a non-significant 30.6% (median) and 51.2% (median) drop in cTfr cells, respectively when compared to cTfr cell numbers in transplant patients who did not receive anti-rejection therapy. A history of alemtuzumab therapy did lead to a significant decrease in cTfr cells of 85.8% (median) compared with patients not treated with anti-rejection therapy (p < 0.0001). No association with tacrolimus or MMF pre-dose concentrations was found.

Conclusion: This cross-sectional study reveals that anti-rejection therapy with alemtuzumab significantly lowers the number of cTfr cells in kidney transplant recipients. The observed profound effects by these agents might dysregulate cTfr functions.

Comparison of Alemtuzumab and Anti-thymocyte Globulin Treatment for Acute Kidney Allograft Rejection

Rabbit anti-thymocyte globulin (rATG) is currently the treatment of choice for glucocorticoid-resistant, recurrent, or severe acute allograft rejection (AR). However, rATG is associated with severe infusion-related side effects. Alemtuzumab is incidentally given to kidney transplant recipients as treatment for AR. In the current study, the outcomes of patients treated with alemtuzumab for AR were compared with that of patients treated with rATG for AR. The patient-, allograft-, and infection-free survival and adverse events of 116 alemtuzumab-treated patients were compared with those of 108 patients treated with rATG for AR. Propensity scores were used to control for differences between the two groups. Patient- and allograft survival of patients treated with either alemtuzumab or rATG were not different [hazard ratio (HR) 1.14, 95%-confidence interval (CI) 0.48–2.69, p = 0.77, and HR 0.82, 95%-CI 0.45–1.5, p = 0.52, respectively). Infection-free survival after alemtuzumab treatment was superior compared with that of rATG-treated patients (HR 0.41, 95%-CI 0.25–0.68, p < 0.002). Infusion-related adverse events occurred less frequently after alemtuzumab treatment. Alemtuzumab therapy may therefore be an alternative therapy for glucocorticoid-resistant, recurrent, or severe acute kidney transplant rejection.

HLA-EMMA: A user-friendly tool to analyse HLA class I and class II compatibility on the amino acid level

In renal transplantation, polymorphic amino acids on mismatched donor HLA molecules can lead to the induction of de novo donor‐specific antibodies (DSA), which are associated with inferior graft survival. To ultimately prevent de novo DSA formation without unnecessarily precluding transplants it is essential to define which polymorphic amino acid mismatches can actually induce an antibody response. To facilitate this, we developed a user‐friendly software program that establishes HLA class I and class II compatibility between donor and recipient on the amino acid level. HLA epitope mismatch algorithm (HLA‐EMMA) is a software program that compares simultaneously the HLA class I and class II amino acid sequences of the donor with the HLA amino acid sequences of the recipient and determines the polymorphic solvent accessible amino acid mismatches that are likely to be accessible to B cell receptors. Analysis can be performed for a large number of donor‐recipient pairs at once. As proof of principle, a previously described study cohort of 191 lymphocyte immunotherapy recipients was analysed with HLA‐EMMA and showed a higher frequency of DSA formation with higher number of solvent accessible amino acids mismatches. Overall, HLA‐EMMA can be used to analyse compatibility on amino acid level between donor and recipient HLA class I and class II simultaneously for large cohorts to ultimately determine the most immunogenic amino acid mismatches.

Apparent Lack of BRAF V600E Derived HLA Class I Presented Neoantigens Hampers Neoplastic Cell Targeting by CD8+ T Cells in Langerhans Cell Histiocytosis

Langerhans Cell Histiocytosis (LCH) is a neoplastic disorder of hematopoietic origin characterized by inflammatory lesions containing clonal histiocytes (LCH-cells) intermixed with various immune cells, including T cells. In 50-60% of LCH-patients, the somatic BRAF ^V600E driver mutation, which is common in many cancers, is detected in these LCH-cells in an otherwise quiet genomic landscape. Non-synonymous mutations like BRAF ^V600E can be a source of neoantigens capable of eliciting effective antitumor CD8⁺ T cell responses. This requires neopeptides to be stably presented by Human Leukocyte Antigen (HLA) class I molecules and sufficient numbers of CD8⁺ T cells at tumor sites. Here, we demonstrate substantial heterogeneity in CD8⁺ T cell density in n = 101 LCH-lesions, with BRAF ^V600E mutated lesions displaying significantly lower CD8⁺ T cell:CD1a⁺ LCH-cell ratios (p = 0.01) than BRAF wildtype lesions. Because LCH-lesional CD8⁺ T cell density had no significant impact on event-free survival, we investigated whether the intracellularly expressed BRAF ^V600E protein is degraded into neopeptides that are naturally processed and presented by cell surface HLA class I molecules. Epitope prediction tools revealed a single HLA class I binding BRAF ^V600E derived neopeptide (KIGDFGLATEK), which indeed displayed strong to intermediate binding capacity to HLA-A^*03:01 and HLA-A^*11:01 in an in vitro peptide-HLA binding assay. Mass spectrometry-based targeted peptidomics was used to investigate the presence of this neopeptide in HLA class I presented peptides isolated from several BRAF ^V600E expressing cell lines with various HLA genotypes. While the HLA-A^*02:01 binding BRAF wildtype peptide KIGDFGLATV was traced in peptides isolated from all five cell lines expressing this HLA subtype, KIGDFGLATEK was not detected in the HLA class I peptidomes of two distinct BRAF ^V600E transduced cell lines with confirmed expression of HLA-A^*03:01 or HLA-A^*11:01. These data indicate that the in silico predicted HLA class I binding and proteasome-generated neopeptides derived from the BRAF ^V600E protein are not presented by HLA class I molecules. Given that the BRAF ^V600E mutation is highly prevalent in chemotherapy refractory LCH-patients who may qualify for immunotherapy, this study therefore questions the efficacy of immune checkpoint inhibitor therapy in LCH.

Long-term Evaluation of Allogeneic Bone Marrow-derived Mesenchymal Stromal Cell Therapy for Crohn's Disease Perianal Fistulas

BACKGROUND AND AIMS

The long-term safety and efficacy of allogeneic bone marrow-derived mesenchymal stromal cell [bmMSC] therapy in perianal Crohn's disease [CD] fistulas is unknown. We aimed to provide a 4-year clinical evaluation of allogeneic bmMSC treatment of perianal CD fistulas.

METHODS

A double-blind dose-finding study for local bmMSC therapy in 21 patients with refractory perianal fistulising Crohn's disease was performed at the Leiden University Medical Center in 2012-2014. All patients treated with bmMSCs [1 x 107 bmMSCs cohort 1, n = 5; 3 × 107 bmMSCs cohort 2, n = 5; 9 × 107 bmMSCs cohort 3, n = 5] were invited for a 4-year evaluation. Clinical events were registered, fistula closure was evaluated, and anti-human leukocyte antigen [HLA] antibodies were assessed. Patients were also asked to undergo a pelvic magnetic resonance imaging [MRI] and rectoscopy.

RESULTS

Thirteen out of 15 patients [87%] treated with bmMSCs were available for long-term follow-up. Two non-MSC related malignancies were observed. No serious adverse events thought to be related to bmMSC therapy were found. In cohort 2 [n = 4], all fistulas were closed 4 years after bmMSC therapy. In cohort 1 [n = 4] 63%, and in cohort 3 [n = 5] 43%, of the fistulas were closed, respectively. In none of the patients anti-HLA antibodies could be detected 24 weeks and 4 years after therapy. Pelvic MRI showed significantly smaller fistula tracts after 4 years.

CONCLUSIONS

Allogeneic bmMSC therapy for CD-associated perianal fistulas is also in the long-term a safe therapy. In bmMSC-treated patients, fistulas with closure at Week 24 were still closed after 4 years.

Antibodies against ARHGDIB are associated with long-term kidney graft loss

The clinical significance of non-HLA antibodies on renal allograft survival is a matter of debate, due to differences in reported results and lack of large-scale studies incorporating analysis of multiple non-HLA antibodies simultaneously. We developed a multiplex non-HLA antibody assay against 14 proteins highly expressed in the kidney. In this study, the presence of pretransplant non-HLA antibodies was correlated to renal allograft survival in a nationwide cohort of 4770 recipients transplanted between 1995 and 2006. Autoantibodies against Rho GDP-dissociation inhibitor 2 (ARHGDIB) were significantly associated with graft loss in recipients transplanted with a deceased-donor kidney (N = 3276) but not in recipients of a living-donor kidney (N = 1496). At 10 years after deceased-donor transplantation, recipients with anti-ARHGDIB antibodies (94/3276 = 2.9%) had a 13% lower death-censored covariate-adjusted graft survival compared to the anti-ARHGDIB-negative (3182/3276 = 97.1%) population (hazard ratio 1.82; 95% confidence interval, 1.32-2.53; P = .0003). These antibodies occur independently from donor-specific anti-HLA antibodies (DSA) or other non-HLA antibodies investigated. No significant relations with graft loss were found for the other 13 non-HLA antibodies. We suggest that pretransplant risk assessment can be improved by measuring anti-ARHGDIB antibodies in all patients awaiting deceased-donor transplantation.

Allocation to highly sensitized patients based on acceptable mismatches results in low rejection rates comparable to nonsensitized patients

Whereas regular allocation avoids unacceptable mismatches on the donor organ, allocation to highly sensitized patients within the Eurotransplant Acceptable Mismatch (AM) program is based on the patient's HLA phenotype plus acceptable antigens. These are HLA antigens to which the patient never made antibodies, as determined by extensive laboratory testing. AM patients have superior long-term graft survival compared with highly sensitized patients in regular allocation. Here, we questioned whether the AM program also results in lower rejection rates. From the PROCARE cohort, consisting of all Dutch kidney transplants in 1995-2005, we selected deceased donor single transplants with a minimum of 1 HLA mismatch and determined the cumulative 6-month rejection incidence for patients in AM or regular allocation. Additionally, we determined the effect of minimal matching criteria of 1 HLA-B plus 1 HLA-DR, or 2 HLA-DR antigens on rejection incidence. AM patients showed significantly lower rejection rates than highly immunized patients in regular allocation, comparable to nonsensitized patients, independent of other risk factors for rejection. In contrast to highly sensitized patients in regular allocation, minimal matching criteria did not affect rejection rates in AM patients. Allocation based on acceptable antigens leads to relatively low-risk transplants for highly sensitized patients with rejection rates similar to those of nonimmunized individuals.

Recombinant human monoclonal HLA antibodies of different IgG subclasses recognising the same epitope: Excellent tools to study differential effects of donor-specific antibodies

In the field of transplantation, the humoural immune response against mismatched HLA antigens of the donor is associated with inferior graft survival, but not in every patient. Donor‐specific HLA antibodies (DSA) of different immunoglobulin G (IgG) subclasses may have differential effects on the transplanted organ. Recombinant technology allows for the generation of IgG subclasses of a human monoclonal antibody (mAb), while retaining its epitope specificity. In order to enable studies on the biological function of IgG subclass HLA antibodies, we used recombinant technology to generate recombinant human HLA mAbs from established heterohybridomas. We generated all four IgG subclasses of a human HLA class I and class II mAb and showed that the different subclasses had a comparable affinity, normal human Fc glycosylation, and retained HLA epitope specificity. For both mAbs, the IgG1 and IgG3 isotypes were capable of binding complement component 3d (C3d) and efficient in complement‐dependent cell lysis against their specific targets, while the IgG2 and IgG4 subclasses were not able to induce cytotoxicity. Considering the fact that the antibody‐binding site and properties remained unaffected, these IgG subclass HLA mAbs are excellent tools to study the function of individual IgG subclass HLA class I and class II‐specific antibodies in a controlled fashion.

Effect of initial immunosuppression on long-term kidney transplant outcome in immunological low-risk patients

BACKGROUND

Few studies have evaluated the effect of different immunosuppressive strategies on long-term kidney transplant outcomes. Moreover, as they were usually based on historical data, it was not possible to account for the presence of pretransplant donor-specific human-leukocyte antigen antibodies (DSA), a currently recognized risk marker for impaired graft survival. The aim of this study was to evaluate to what extent frequently used initial immunosuppressive therapies increase graft survival in immunological low-risk patients.

METHODS

We performed an analysis on the PROCARE cohort, a Dutch multicentre study including all transplantations performed in the Netherlands between 1995 and 2005 with available pretransplant serum (n = 4724). All sera were assessed for the presence of DSA by a luminex single-antigen bead assay. Patients with a previous kidney transplantation, pretransplant DSA or receiving induction therapy were excluded from the analysis.

RESULTS

Three regimes were used in over 200 patients: cyclosporine (CsA)/prednisolone (Pred) (n = 542), CsA/mycophenolate mofetil (MMF)/Pred (n = 857) and tacrolimus (TAC)/MMF/Pred (n = 811). Covariate-adjusted analysis revealed no significant differences in 10-year death-censored graft survival between patients on TAC/MMF/Pred therapy (79%) compared with patients on CsA/MMF/Pred (82%, P = 0.88) or CsA/Pred (79%, P = 0.21). However, 1-year rejection-free survival censored for death and failure unrelated to rejection was significantly higher for TAC/MMF/Pred (81%) when compared with CsA/MMF/Pred (67%, P < 0.0001) and CsA/Pred (64%, P < 0.0001).

CONCLUSION

These results suggest that in immunological low-risk patients excellent long-term kidney graft survival can be achieved irrespective of the type of initial immunosuppressive therapy (CsA or TAC; with or without MMF), despite differences in 1-year rejection-free survival.

Reciprocal HLA-DR allogenicity between mother and child affects pregnancy outcome parameters

Successful pregnancy outcome depends on local immunoregulatory mechanisms preventing a detrimental immune response towards the semi-allogeneic fetus. We investigated the influence of HLA-DR (in)compatibility on pregnancy outcome parameters in 480 women. The parameters tested were birth weight, individualized birthweight ratio (IBR), gestational age, and maternal highest diastolic blood pressure. Irrespective of pregnancy complications, maternal-fetal HLA-DR incompatibility resulted in increased IBR. We conclude that reciprocal HLA-DR allogenicity between mother and child positively affect pregnancy outcome parameters.

The Number of Donor-Specific IL-21 Producing Cells Before and After Transplantation Predicts Kidney Graft Rejection

Interleukin (IL)-21 supports induction and expansion of CD8⁺ T cells, and can also regulate the differentiation of B cells into antibody-producing plasma cells. We questioned whether the number of circulating donor-specific IL-21 producing cells (pc) can predict kidney transplant rejection, and evaluated this in two different patient cohorts. The first analysis was done on pre-transplantation samples of 35 kidney transplant recipients of whom 15 patients developed an early acute rejection. The second study concerned peripheral blood mononuclear cell (PBMC) samples from 46 patients obtained at 6 months after kidney transplantation of whom 13 developed late rejection. Significantly higher frequencies of donor-specific IL-21 pc were found by Elispot assay in both patients who developed early and late rejection compared to those without rejection. In addition, low frequencies of donor-specific IL-21 pc were associated with higher rejection-free survival. Moreover, low pre-transplant donor-specific IL-21 pc numbers were associated with the absence of anti-HLA antibodies. Donor-reactive IL-21 was mainly produced by CD4⁺ T cells, including CD4⁺ follicular T helper cells. In conclusion, the number of donor-specific IL-21 pc is associated with an increased risk of both early and late rejection, giving it the potential to be a new biomarker in kidney transplantation.

Presence of intragraft B cells during acute renal allograft rejection is accompanied by changes in peripheral blood B cell subsets

B cells have various functions, besides being plasma cell precursors. We determined the presence of intragraft B cells at time of acute rejection (AR) and looked for correlates of B cell involvement in peripheral blood. Renal biopsies at time of AR or stable graft function were analysed for the presence of B cells and B cell‐related gene expression, as well as C4d staining. Peripheral blood B cell subset distribution was analysed at various time‐points in patients with AR and controls, alongside serum human leucocyte antigen (HLA) antibodies. AR was accompanied by intragraft CD20⁺ B cells, as well as elevated CD20 (MS4A1) and CD19 gene expression compared to controls. B cell infiltrates were proportional to T cells, and accompanied by the chemokine pair C‐X‐C motif chemokine ligand 13 (CXCL13)–C‐X‐C motif chemokine receptor 5 (CXCR5) and B cell activating factor (BAFF). Peripheral blood memory B cells were decreased and naive B cells increased at AR, in contrast to controls. While 22% of patients with AR and 5% of controls showed de‐novo donor‐specific antibodies (DSA), all biopsies were C4d‐negative. These results suggest a role for B cells in AR by infiltrating the graft alongside T cells. We hypothesize that the shift in peripheral blood B cell composition is related to the graft infiltration at time of AR.

Development and Validation of a Multiplex Non-HLA Antibody Assay for the Screening of Kidney Transplant Recipients

The best treatment for patients with end-stage renal disease is kidney transplantation. Although graft survival rates have improved in the last decades, patients still may lose their grafts partly due to the detrimental effects of donor-specific antibodies (DSA) against human leukocyte antigens (HLA) and to a lesser extent also by antibodies directed against non-HLA antigens expressed on the donor endothelium. Assays to detect anti-HLA antibodies are already in use for many years and have been proven useful for transplant risk stratification. Currently, there is a need for assays to additionally detect multiple non-HLA antibodies simultaneously in order to study their clinical relevance in solid organ transplantation. This study describes the development, technical details and validation of a high-throughput multiplex assay for the detection of antibodies against 14 non-HLA antigens coupled directly to MagPlex microspheres or indirectly via a HaloTag. The non-HLA antigens have been selected based on a literature search in patients with kidney disease or following transplantation. Due to the flexibility of the assay, this approach can be used to include alternative antigens and can also be used for screening of other organ transplant recipients, such as heart and lung.

Cross-Reactivity of Virus-Specific CD8+ T Cells Against Allogeneic HLA-C: Possible Implications for Pregnancy Outcome

Heterologous immunity of virus-specific T cells poses a potential barrier to transplantation tolerance. Cross-reactivity to HLA-A and -B molecules has broadly been described, whereas responses to allo-HLA-C have remained ill defined. In contrast to the transplant setting, HLA-C is the only polymorphic HLA molecule expressed by extravillous trophoblasts at the maternal-fetal interface during pregnancy. Uncontrolled placental viral infections, accompanied by a pro-inflammatory milieu, can alter the activation status and stability of effector T cells. Potential cross-reactivity of maternal decidual virus-specific T cells to fetal allo-HLA-C may thereby have detrimental consequences for the success of pregnancy. To explore the presence of cross-reactivity to HLA-C and the other non-classical HLA antigens expressed by trophoblasts, HLA-A and -B-restricted CD8+ T cells specific for Epstein-Barr virus, Cytomegalovirus, Varicella-Zoster virus, and Influenza virus were tested against target cells expressing HLA-C, -E, and -G molecules. An HLA-B^*08:01-restricted EBV-specific T cell clone displayed cross-reactivity against HLA-C^*01:02. Furthermore, cross-reactivity of HLA-C-restricted virus-specific CD8+ T cells was observed for HCMV HLA-C^*06:02/TRA CD8+ T cell lines and clones against HLA-C^*03:02. Collectively, these results demonstrate that cross-reactivity against HLA-C can occur and thereby may affect pregnancy outcome.

Pretransplant C3d-Fixing Donor-Specific Anti-HLA Antibodies Are Not Associated with Increased Risk for Kidney Graft Failure

Background Complement-fixing antibodies against donor HLA are considered a contraindication for kidney transplant. A modification of the IgG single-antigen bead (SAB) assay allows detection of anti-HLA antibodies that bind C3d. Because early humoral graft rejection is considered to be complement mediated, this SAB-based technique may provide a valuable tool in the pretransplant risk stratification of kidney transplant recipients.Methods Previously, we established that pretransplant donor-specific anti-HLA antibodies (DSAs) are associated with increased risk for long-term graft failure in complement-dependent cytotoxicity crossmatch-negative transplants. In this study, we further characterized the DSA-positive serum samples using the C3d SAB assay.Results Among 567 pretransplant DSA-positive serum samples, 97 (17%) contained at least one C3d-fixing DSA, whereas 470 (83%) had non-C3d-fixing DSA. At 10 years after transplant, patients with C3d-fixing antibodies had a death-censored, covariate-adjusted graft survival of 60%, whereas patients with non-C3d-fixing DSA had a graft survival of 64% (hazard ratio, 1.02; 95% confidence interval, 0.70 to 1.48 for C3d-fixing DSA compared with non-C3d-fixing DSA; P=0.93). Patients without DSA had a 10-year graft survival of 78%.Conclusions The C3d-fixing ability of pretransplant DSA is not associated with increased risk for graft failure.

Chronic-active antibody-mediated rejection with or without donor-specific antibodies has similar histomorphology and clinical outcome - a retrospective study

Chronic-active antibody-mediated rejection (c-aABMR) is defined as histological evidence of chronic endothelial injury (cg), also known as transplant glomerulopathy, and either microvascular inflammation (MVI) or positivity for C4d. Importantly, the presence of donor-specific antibodies (DSA) is currently still mandatory for the diagnosis of c-aABMR. This retrospective study of 41 c-aABMR patients investigates whether cases suspicious for c-aABMR (DSA negative, n = 24) differ from cases of c-aABMR (DSA positive, n = 17) with respect to renal histology, allograft function and long-term graft survival. All included patients had progressive loss of allograft function and were diagnosed by for cause biopsy and scored according to the Banff '15 criteria. In all DSApos cases, DSA were de novo and the majority was directed against HLA-II being mostly anti-HLA-DQ antibodies. There were no statistically significant differences in clinical characteristics, decline in allograft function and renal allograft survival in cases with or without DSAs. All cases showed chronic histomorphological damage and inflammation, irrespective of the presence of DSA. Renal histology and clinical outcome of patients suspicious for c-aABMR (DSAneg) do not significantly differ from patients with a diagnosis of c-aABMR (DSApos). We believe that our study adds to the ongoing debate regarding the need for DSAs to be present for the diagnosis of c-aABMR.

PIRCHE-II Is Related to Graft Failure after Kidney Transplantation

Individual HLA mismatches may differentially impact graft survival after kidney transplantation. Therefore, there is a need for a reliable tool to define permissible HLA mismatches in kidney transplantation. We previously demonstrated that donor-derived Predicted Indirectly ReCognizable HLA Epitopes presented by recipient HLA class II (PIRCHE-II) play a role in de novo donor-specific HLA antibodies formation after kidney transplantation. In the present Dutch multi-center study, we evaluated the possible association between PIRCHE-II and kidney graft failure in 2,918 donor–recipient couples that were transplanted between 1995 and 2005. For these donors–recipients couples, PIRCHE-II numbers were related to graft survival in univariate and multivariable analyses. Adjusted for confounders, the natural logarithm of PIRCHE-II was associated with a higher risk for graft failure [hazard ratio (HR): 1.13, 95% CI: 1.04–1.23, p = 0.003]. When analyzing a subgroup of patients who had their first transplantation, the HR of graft failure for ln(PIRCHE-II) was higher compared with the overall cohort (HR: 1.22, 95% CI: 1.10–1.34, p < 0.001). PIRCHE-II demonstrated both early and late effects on graft failure in this subgroup. These data suggest that the PIRCHE-II may impact graft survival after kidney transplantation. Inclusion of PIRCHE-II in donor-selection criteria may eventually lead to an improved kidney graft survival.

Congenital Cytomegalovirus Infection: Maternal-Child HLA-C, HLA-E, and HLA-G Affect Clinical Outcome

Congenital CMV infection (cCMV) is the most common congenital infection causing permanent long-term impairments (LTI). cCMV immunopathogenesis is largely unknown due to the complex interplay between viral, maternal, placental, and child factors. In this study, a large retrospective nationwide cohort of children with cCMV and their mothers was used. HLA-C, HLA-E, and HLA-G were assessed in 96 mother–child pairs in relation to symptoms at birth and LTI at 6 years of age. The mothers were additionally typed for killer cell immunoglobulin-like receptors. The maternal HLA-G 14 bp deletion/deletion polymorphism was associated with a worse outcome, as the immunomodulation effect of higher protein levels may induce less CMV control, with a direct impact on placenta and fetus. The absence of maternal HLA-C belonging to the C2 group was associated with symptoms at birth, as activating signals on decidual NK may override inhibitory signals, contributing to a placental pro-inflammatory environment. Here, the increased HLA-E*0101 and HLA-C mismatches, which were associated with symptoms at birth, may enhance maternal allo-reactivity to fetal Ags, and cause suboptimal viral clearance. Finally, HLA-C non-inherited maternal antigens (NIMAs) were associated with LTI. The tolerance induced in the fetus toward NIMAs may indirectly induce a suboptimal CMV antiviral response throughout childhood. In light of our findings, the potential role of maternal–child HLA in controlling CMV infection and cCMV-related disease, and the clinical value as predictor for long-term outcome certainly deserve further evaluation.

Pretransplant Numbers of CD16+ Monocytes as a Novel Biomarker to Predict Acute Rejection After Kidney Transplantation: A Pilot Study

Acute rejection is one of the major immunological determinants of kidney graft function and survival. Early biomarkers to predict rejection are lacking. Emerging evidence reveals a crucial role for the monocyte/macrophage lineage cells in the pathogenesis of rejection. We hypothesized that higher pretransplant numbers of proinflammatory CD16+ monocytes can predict rejection. The study cohort consisted of 104 kidney transplant recipients (58 with no rejection and 46 with biopsy-proven rejection) and 33 healthy persons. Posttransplant median follow-up time was 14.7 mo (interquartile range 0.3-34 mo). Pretransplantation blood samples were analyzed by flow cytometry for monocyte immunophenotypes. Groups were compared by Cox regression models for the occurrence of acute rejection. We documented a significantly increased absolute number of pretransplant CD16+ monocytes in patients who developed biopsy-proven rejection after transplantation compared with those with no rejection (hazard ratio [HR] 1.60, 95% CI 1.28-2.00, p < 0.001) and healthy persons (HR 1.47, 95% CI 1.18-1.82, p < 0.001). In parallel, significantly fewer absolute numbers of CD16- monocytes were observed at pretransplant time points in rejectors versus nonrejectors (HR 0.74, 95% CI 0.58-0.94, p < 0,014). A higher pretransplant number of CD16+ monocytes is significantly associated with a higher risk of acute rejection after kidney transplantation.

A Memory B Cell Crossmatch Assay for Quantification of Donor-Specific Memory B Cells in the Peripheral Blood of HLA-Immunized Individuals

Humoral responses against mismatched donor HLA are routinely measured as serum HLA antibodies, which are mainly produced by bone marrow-residing plasma cells. Individuals with a history of alloimmunization but lacking serum antibodies may harbor circulating dormant memory B cells, which may rapidly become plasma cells on antigen reencounter. Currently available methods to detect HLA-specific memory B cells are scarce and insufficient in quantifying the complete donor-specific memory B cell response due to their dependence on synthetic HLA molecules. We present a highly sensitive and specific tool for quantifying donor-specific memory B cells in peripheral blood of individuals using cell lysates covering the complete HLA class I and class II repertoire of an individual. Using this enzyme-linked immunospot (ELISpot) assay, we found a median frequency of 31 HLA class I and 89 HLA class II-specific memory B cells per million IgG-producing cells directed at paternal HLA in peripheral blood samples from women (n = 22) with a history of pregnancy, using cell lysates from spouses. The donor-specific memory B cell ELISpot can be used in HLA diagnostic laboratories as a cross-match assay to quantify donor-specific memory B cells in patients with a history of sensitizing events.

A Randomized Controlled Clinical Trial Comparing Belatacept With Tacrolimus After De Novo Kidney Transplantation

BACKGROUND

Belatacept, an inhibitor of the CD28-CD80/86 costimulatory pathway, allows for calcineurin-inhibitor free immunosuppressive therapy in kidney transplantation but is associated with a higher acute rejection risk than ciclosporin. Thus far, no biomarker for belatacept-resistant rejection has been validated. In this randomized-controlled trial, acute rejection rate was compared between belatacept- and tacrolimus-treated patients and immunological biomarkers for acute rejection were investigated.

METHODS

Forty kidney transplant recipients were 1:1 randomized to belatacept or tacrolimus combined with basiliximab, mycophenolate mofetil, and prednisolone. The 1-year incidence of biopsy-proven acute rejection was monitored. Potential biomarkers, namely, CD8CD28, CD4CD57PD1, and CD8CD28 end-stage terminally differentiated memory T cells were measured pretransplantation and posttransplantation and correlated to rejection. Pharmacodynamic monitoring of belatacept was performed by measuring free CD86 on monocytes.

RESULTS

The rejection incidence was higher in belatacept-treated than tacrolimus-treated patients: 55% versus 10% (P = 0.006). All 3 graft losses, due to rejection, occurred in the belatacept group. Although 4 of 5 belatacept-treated patients with greater than 35 cells CD8CD28 end-stage terminally differentiated memory T cells/μL rejected, median pretransplant values of the biomarkers did not differ between belatacept-treated rejectors and nonrejectors. In univariable Cox regressions, the studied cell subsets were not associated with rejection-risk. CD86 molecules on circulating monocytes in belatacept-treated patients were saturated at all timepoints.

CONCLUSIONS

Belatacept-based immunosuppressive therapy resulted in higher and more severe acute rejection compared with tacrolimus-based therapy. This trial did not identify cellular biomarkers predictive of rejection. In addition, the CD28-CD80/86 costimulatory pathway appeared to be sufficiently blocked by belatacept and did not predict rejection.