Donor-specific Antibody Production Research Articles

Association of PIRCHE-II score with anti-donor T-cell response and risk of de novo donor-specific antibody production in kidney transplant recipients

BackgroundDe novo donor-specific antibodies (dnDSAs) affect long-term outcomes of kidney transplantation (KT). A higher Predicted Indirectly ReCognizable Human Leukocyte Antigen (HLA) Epitopes (PIRCHE-II) score correlates with various clinical outcomes, including dnDSA formation. However, a detailed analysis of the relationship between the PIRCHE-II score and anti-donor T-cell response is lacking. Therefore, this study investigated the relationship between PIRCHE-II scores associated with dnDSA formation and mixed lymphocyte reaction results of anti-donor T-cell response. MethodsData of 105 adult living-donor KT recipients were retrospectively assessed. ResultsOf the 105 patients, 13.3 % developed dnDSAs during the observation period. The PIRCHE-II score at the HLA-DQ locus (PIRCHE-DQ) was significantly higher in patients with dnDSA formation than in those without. The incidence of dnDSA formation was significantly higher in the PIRCHE-DQ ≥ 77 group than in the PIRCHE-DQ < 77 group. The proportion of patients with increased anti-donor T-cell response was significantly higher in the PIRCHE-DQ ≥ 77 group than in the PIRCHE-DQ < 77 group before KT and at 4 and 5 years after KT. ConclusionsPIRCHE-DQ may predict dnDSA formation and anti-donor T-cell response. Reducing the immunosuppressive drug dose in cases of high PIRCHE-DQ might not be prudent.

Oxymatrine attenuates chronic allograft rejection by modulating immune responses and inhibiting fibrosis

BackgroundChronic rejection (CR) is a significant obstacle to long-term allograft survival. Oxymatrine (OMT) is a prominent bioactive compound widely utilized in traditional Chinese medicine for the management of inflammatory disorders and it has considerable potential as a therapeutic candidate for the treatment of CR. MethodsWell-established major histocompatibility complex (MHC) class II mismatched B6 mice. C-H-2bm12-to-C57BL/6 mouse transplantation was used as a CR model. Hematoxylin and eosin (H&E) staining, immunohistochemistry, and Masson's trichrome staining were used to assess pathological changes in the grafts, and the percentages of immune cells were determined by flow cytometry. The effects of OMT on the regulation of CD4+ T cell differentiation and cytokine secretion were verified in vitro. ResultsOMT effectively alleviated pathological graft damage, characterized by chronic changes in intimal lesions, vasculopathy, and fibrosis and significantly prolonged cardiac allograft survival. OMT exerted its immunomodulatory effects by inhibiting T helper 1 (Th1) and T helper 17 (Th17) cell differentiation while promoting Treg differentiation both in vivo and in vitro. Further studies revealed that OMT inhibited the phosphorylation of mammalian target of rapamycin (mTOR), which is a potential mechanism underlying its immunosuppressive effects. OMT also inhibited the activation of B cells and the production of donor-specific antibody (DSA). In addition, OMT effectively alleviated chronic changes in fibrosis in cardiac allografts, and these changes may be related to the inhibition of the transforming growth factor-β (TGF-β)-Smad 2/3 pathway. ConclusionsOMT attenuated CR by modulating the immune response and inhibiting graft fibrosis. Further in-depth investigations of OMT may provide valuable insights into the development of novel therapeutic strategies for CR inhibition.

Marginal zone B cells are required for optimal humoral responses to allograft

Antibody-mediated rejection (AMR) is among the leading causes of graft failure in solid organ transplantation. However, AMR treatment options are limited by an incomplete understanding of the mechanisms underlying de novo donor-specific antibody (DSA) generation. The development of pathogenic isotype-switched DSA in response to transplanted allografts is typically attributed to follicular B cells undergoing germinal center reaction whereas the contribution of other B cell subsets has not been previously addressed. The current study investigated the role of recipient marginal zone B cells (MZ B cells) in DSA responses using mouse models of heart and renal allotransplantation. MZ B cells rapidly differentiate into antibody-secreting cells in response to allotransplantation. Despite the selective depletion of follicular B cells in heart allograft recipients, MZ B cells are sufficient for T-dependent IgM and early IgG DSA production. Furthermore, the presence of intact MZ B cell subset is required to support the generation of pathogenic isotype-switched DSA in renal allograft recipients containing donor-reactive memory helper T cells. These findings are the first demonstration of the role of MZ B cells in humoral alloimmune responses following solid organ transplantation and identify MZ B cells as a potential therapeutic target for minimizing de novo DSA production and AMR in transplant recipients.

Oxidized ATP Suppresses B Lymphocyte Activity to Attenuate Antibody-mediated Rejection of Kidney Allografts in Mice

Background. Antibody-mediated rejection (AMR) is a major cause of renal allograft dysfunction and loss. Targeting B cells and/or donor-specific antibody removal using plasma exchange and anti-CD20 antibodies are increasingly used in clinical practice, but the efficacy remains limited. Recent studies suggest that targeting purinergic P2X7 receptor/ATP axis can have profound immune regulatory effects in transplant models, but the mechanisms involved remain incompletely defined. Methods. Purified B cells were isolated from the spleen of Balb/C mice and cultured with oxidized ATP at different concentrations. Proliferation and differentiation of B cells were examined. Effects of oxidized ATP were examined in a presensitized animal model where kidney allograft rejection mimics aspects of clinical AMR. Histopathology was assessed at the time of rejection or on day 5 after kidney transplantation. Infiltrating immune cells in renal allografts were detected by flow cytometry. Results. Oxidized ATP inhibited B-cell activation and proliferation in vitro, significantly attenuated histological signs of graft injury and prolonged kidney allograft survival. Mechanistically, oxidized ATP inhibited antibody secretion by activated B cells in response to lipopolysaccharide stimulation and markedly suppressed the production of donor-specific antibody in kidney allograft recipients. Oxidized ATP also reduced graft infiltration by other inflammatory cells. Conclusions. These findings provide evidence for the involvement of the purinergic P2X7 receptor pathway in AMR and suggest that targeting this pathways may have important clinical implications.

Graft protective effects and donor-specific antibody suppression by CD4+CD25+Foxp3+ regulatory T cell induced by HMG-CoA reductase inhibitor rosuvastatin in a murine heart transplant model

BackgroundWe previously demonstrated that the hydroxymethylglutaryl-CoA (HMG-CoA) reductase inhibitor (statins) play an important role in the regulation of alloimmune responses. However, little is known regarding the effects of statin on allograft protection or donor-specific antibodies (DSA). In this study, we investigated the graft-protective and immunomodulatory effects of rosuvastatin in a model of fully major histocompatibility complex-mismatched murine cardiac allograft transplantation.MethodsCBA mice underwent transplantation of C57BL/6 (B6) hearts and received 50 and 500 μg/kg/day of rosuvastatin from the day of transplantation until seven days after the completion of transplantation. To confirm the requirement for regulatory T cells (Tregs), we administered an anti-interleukin-2 receptor alpha antibody (PC-61) to rosuvastatin-treated CBA recipients. Additionally, histological and fluorescent staining, cell proliferation analysis, flow cytometry, and DSA measurements were performed.ResultsCBA recipients with no treatment rejected B6 cardiac graft acutely (median survival time [MST], 7 days). CBA mice treated with 500 μg/kg/day of rosuvastatin prolonged allograft survival (MSTs, 77 days). Fluorescent staining studies showed that rosuvastatin-treated recipients had strong aggregation of CD4+Foxp3+ cells in the myocardium and around the coronary arteries of cardiac allografts two weeks after grafting. Flow cytometry studies performed two weeks after transplantation showed an increased number of splenic CD4+CD25+Foxp3+ T cells in rosuvastatin-treated recipients. The addition of rosuvastatin to mixed leukocyte cultures suppressed cell proliferation by increasing the number of CD4+CD25+Foxp3+ Tregs. Additionally, Tregs suppressed DSA production in rosuvastatin-treated recipients.ConclusionRosuvastatin treatment may be a complementary graft-protective strategy for suppressing DSA production in the acute phase, driven by the promotion of splenic and graft-infiltrating CD4+CD25+Foxp3+ Tregs.

#3105 Tocilizumab for treatment of antibody mediated rejection in kidney transplant patients

Abstract Background and Aims Chronic active antibody-mediated rejection (caABMR) causes 40% of long-term graft failure after kidney transplantation (KT). Early treatment is of great importance, however, hard clinical evidence is still lacking. Currently the combination of plasmapheresis (PF), rituximab and intravenous immunoglobulin is used as standard treatment. Tocilizumab (TCZ) is a monoclonal antibody, IL-6 receptor antagonist, and it inhibits the production of donor-specific antibodies (DSA). We hypothesized that tocilizumab administration has an additional effect on graft survival and non-inferior to standard therapy in KT patients with ABMR. Method Retrospective single-center noninferiority case-control study was performed by involving 73 KT patients (43.5 ± 14.3 years, females 31, eGFR 19.5 ± 13.4) with biopsy proven ABMR diagnosed between June 2017 and May 2022. 19 patients received 8 mg/kg intravenous TCZ therapy for 6 months (12 aABMR, 7 caABMR, 38.6 ± 12.8 years, females 6). In the control group (C, n=54, 10 aABMR, 44 caABMR, 45.2 ± 14.5 years, females 25), 20 patients received plasmapheresis treatment, the rest stayed on optimized maintenance therapy (tacrolimus, mycophenolic acid, prednisolone). Baseline demographic data, standard laboratory data, proteinuria and DSA level were also monitored and analyzed. Results Graft loss occurred in 13 cases (6 aABMR, 7 caABMR) in KT on TCZ therapy and 43 (6 aABMR, 37 caABMR) in C group, meaning significantly lower risk of graft loss in the TCZ group (RR 0.69, p=0.036) during the median follow-up of 11.3 (IQR 2.5-23.1) months. In TCZ group, all caABMR patients lost their graft during the observation. In TCZ group, 1 year after the TCZ treatment, DSA (pooled) was lower (7028 (575-17782) versus 1605 (551-16903), p&amp;lt;0.05). Conclusion Early administration of TCZ seems to be noninferior to standard therapy and effective to prevent early graft loss as part of standard therapy in aABMR. Further clinical studies are needed to clarify clinical indications of TCZ and its long-term effects on the course of chronic active ABMR.

#715 Adiponectin / leptin ratio as an index to determine the risk of metabolic and rejection complications in patients after kidney transplantation

Abstract Background and Aims Adipose tissue, as an endocrine and paracrine organ, produces several hormones that are involved in the regulation of metabolic and inflammatory processes or immune system activity. While leptin is the main pro-inflammatory marker of adipose tissue, adiponectin is characterized by its anti-inflammatory effects. The adiponectin / leptin (A/L) ratio had been shown to correlate better with the occurrence of cardiometabolic risk factors than hormone concentrations alone. Results in the general population suggest that an A/L ratio &amp;gt; 1 can be considered normal, an A/L ratio of 0.5-1 indicates a moderate increase, and an A/L ration &amp;lt; 0.5 a high increase in cardiometabolic risk. The first aim of our study was to determine the risk of developing post-transplant diabetes mellitus (PTDM), prediabetes and other metabolic risk factors in relation to the A/L ratio in patients after kidney transplantation (KT). The second aim was to determine the risk of developing acute graft rejection in relation to the A/L ratio in patients after KT. Method A total of 104 patients were included in our prospective analysis after applying inclusion and exclusion criteria. Pre-transplantation and subsequently at 3, 6 and 12 months after KT, we recorded baseline characteristics of donors and recipients, including parameters characterizing graft function, metabolic (lipid profile, indices of glucose metabolism) and anthropometric parameters. At the same time, we examined serum adipocytokine concentrations (adiponectin, leptin) and calculated the A/L ratio. In the third month after KT, all patients underwent protocol graft biopsy and donor specific antibody (DSA) testing by Luminex method. Results We found that during the follow-up period, there was a significant increase in the A/L ratio in the control group (p = 0.0013) and, on the other hand, a significant decrease in the group who developed PTDM (p = 0.0003). Comparing the different subgroups divided on the A/L ratio one year after KT, we found that patients with an A/L &amp;lt; 0.5 were significantly longer in the dialysis program, had higher body mass index (BMI), waist circumference, worse graft function, and a higher prevalence of prediabetes and PTDM compared with those whose A/L ratio was &amp;gt; 1. Using logistic regression in multivariate analysis, we identified age at the time of KT [OR 1.0709, (p = 0.0337)], triglycerides level at 1 year after KT [OR 2.7735, (p = 0.446)] and A/L ratio &amp;lt; 0.5 [OR 3.1724, (p = 0.014)] as independent risk factors for the development of prediabetes and PTDM 1 year after KT. At the same time, after adjusting for differences in baseline donor and recipient characteristics, we identified the subgroup with an A/L ratio &amp;lt; 0.5 pre-transplant [HR 1.6126, (p = 0.0133)] and 3 months after KT [HR 1.3150, (p = 0.0172)] as an independent risk factor for the development of acute graft rejection. In the subsequent specification of the rejection episode, we found that A/L ratio &amp;lt; 0.5 pre-transplant [HR 2.2353, (p = 0.0357)] and 3 months after KT [HR 3.0954, (p = 0.0237)] is and independent risk factor for the occurrence of acute humoral rejection with DSA positivity. Conclusion In our study, we found that an A/L ratio &amp;lt; 0.5 is an independent risk factor for the development of prediabetes, PTDM 1 year after KT and acute humoral graft rejection with de novo DSA production in the third month after KT. This is the first study to investigate the correlation of the A/L ratio with the risk of developing metabolic and immunological complications in patients after KT.

Impact of donor-specific antibody with low mean fluorescence intensity on allograft outcomes in kidney transplant

BackgroundImmune-mediated rejection is the most common cause of allograft failure in kidney transplant (KT) patients. Exposure to alloantigen, including human leukocyte antigen (HLA), results in the production of donor-specific antibodies (DSA). There are limited data about low levels of mean fluorescence intensity (MFI) DSA, especially post-transplantation. This study evaluated allograft outcomes in KT patients with low MFI DSA. MethodsFrom January 2007 to December 2021, KT patients who were tested for post-transplant DSA at Ramathibodi Hospital, Bangkok, Thailand, with the DSA MFI ≤ 1000 were evaluated. These KT patients were categorized into two groups: very low DSA (VLL; MFI = 1–500) and low DSA (LL; MFI = 501–1000). All KT patients were evaluated for the primary outcomes, such as the incidence of acute rejection, serum creatinine levels at one and five years after transplantation as well as allograft and patient survivals. ResultsAmong 36 KT patients 25 were included as those with VLL and 11 as those with LL. The LL group had significantly higher T-cell mediated allograft rejection (TCMR) than the VLL group (45% vs. 12%, P = 0.04). In addition, 10 patients, 5 in the VLL group and 5 in the LL group developed antibody-mediated allograft rejection (ABMR). Both TCMR and ABMR were confirmed by biopsy results. There was a trend toward higher MFI in KT patients with ABMR than without ABMR (P = 0.22). At 5 post-transplant years, serum creatinine, allograft and patient survivals were comparable between these two groups. Furthermore, the univariate and multivariate analyzes revealed that the LL group was a high risk for rejection. ConclusionLow MFI DSA values after transplantation may be associated with a higher incidence of rejection, but this finding did not show differences in allograft and patient survival in this study's analysis.

Sequential administration of anti-complement component C5 eculizumab and type-2 anti-CD20 obinutuzumab for the treatment of early antibody-mediated rejection after kidney transplantation: A proof of concept

Kidney transplant (KT) candidates with donor-specific antibodies (DSA) exhibit exceedingly high antibody-mediated rejection (ABMR) and allograft loss rates. Currently, treatment of ABMR remains an unmet clinical need. We report the use of the anti-C5 eculizumab and the type-2 anti-CD20 obinutuzumab in two patients with early ABMR. Eculizumab (900 mg IV) led to complete inhibition of the terminal complement cascade (unremarkable AP50 and CH50 activity) and prompt stoppage of complement-dependent antibody-mediated allograft injury (clearance of intra-graft C4d and C5b-9 deposition). Despite complement inhibition, obinutuzumab (1000 mg IV) determined full and long-lasting peripheral B-cell depletion, with significant reduction in all DSA. Graft function improved, remaining stable up to three years of follow-up. No signs of active ABMR and rebound DSA were detected. Obinutuzumab B-cell depletion and inhibition of DSA production were not affected by complement blockage. Further studies are needed to confirm the potential benefit of obinutuzumab in association with complement inhibitors.

RORγt inverse agonist TF-S14 inhibits Th17 cytokines and prolongs skin allograft survival in sensitized mice

Chronic antibody mediated rejection (AMR) is the major cause of solid organ graft rejection. Th17 contributes to AMR through the secretion of IL17A, IL21 and IL22. These cytokines promote neutrophilic infiltration, B cell proliferation and donor specific antibodies (DSAs) production. In the current study we investigated the role of Th17 in transplant sensitization. Additionally, we investigated the therapeutic potential of novel inverse agonists of the retinoic acid receptor-related orphan receptor gamma t (RORγt) in the treatment of skin allograft rejection in sensitized mice. Our results show that RORγt inverse agonists reduce cytokine production in human Th17 cells in vitro. In mice, we demonstrate that the RORγt inverse agonist TF-S14 reduces Th17 signature cytokines in vitro and in vivo and leads to blocking neutrophilic infiltration to skin allografts, inhibition of the B-cell differentiation, and the reduction of de novo IgG3 DSAs production. Finally, we show that TF-S14 prolongs the survival of a total mismatch grafts in sensitized mice. In conclusion, RORγt inverse agonists offer a therapeutic intervention through a novel mechanism to treat rejection in highly sensitized patients.

Oxymatrine combined with rapamycin to attenuate acute cardiac allograft rejection

Background and aimSolid organ transplantation remains a life-saving therapeutic option for patients with end-stage organ dysfunction. Acute cellular rejection (ACR), dominated by dendritic cells (DCs) and CD4+ T cells, is a major cause of post-transplant mortality. Inhibiting DC maturation and directing the differentiation of CD4+ T cells toward immunosuppression are keys to inhibiting ACR. We propose that oxymatrine (OMT), a quinolizidine alkaloid, either alone or in combination with rapamycin (RAPA), attenuates ACR by inhibiting the mTOR–HIF–1α pathway. MethodsGraft damage was assessed using haematoxylin and eosin staining. Intragraft CD11c+ and CD4+ cell infiltrations were detected using immunohistochemical staining. The proportions of mature DCs, T helper (Th) 1, Th17, and Treg cells in the spleen; donor-specific antibody (DSA) secretion in the serum; mTOR–HIF–1α expression in the grafts; and CD4+ cells and bone marrow-derived DCs (BMDCs) were evaluated using flow cytometry. ResultsOMT, either alone or in combination with RAPA, significantly alleviated pathological damage; decreased CD4+ and CD11c+ cell infiltration in cardiac allografts; reduced the proportion of mature DCs, Th1 and Th17 cells; increased the proportion of Tregs in recipient spleens; downregulated DSA production; and inhibited mTOR and HIF-1α expression in the grafts. OMT suppresses mTOR and HIF-1α expression in BMDCs and CD4+ T cells in vitro. ConclusionsOur study suggests that OMT-based therapy can significantly attenuate acute cardiac allograft rejection by inhibiting DC maturation and CD4+ T cell responses. This process may be related to the inhibition of the mTOR–HIF–1α signaling pathway by OMT.

Role of HLA in cardiothoracic transplantation.

In current clinical practice, transplant clinicians create collaborative working relationships with histocompatibility laboratory scientists to identify the risk of long-term graft failure, which may assist in establishing strategies for treatment and surveillance. Transplant immunology research also focuses on optimizing human leukocyte antibody tissue typing and defines the most effective test for detecting the presence of donor-specific antibodies. Although several studies have been conducted, data on pediatric heart transplant recipients are limited. Epitope load information may be utilized to identify donors with permissible human leukocyte antibody mismatches to increase transplant success. Although current guidelines do not consider human leukocyte antibody epitope-based matching tools, these guidelines could be useful for identifying recipients at a high risk of donor-specific antibody production, which would be appropriate for routine donor-specific antibody screening to initiate early interventions to prevent antibody-mediated rejection. Human leukocyte antibody matching at the epitope level offers an effective approach for identifying acceptable mismatches in sensitized patients and provides information about epitope loads. In the future, eplet matching may be used to define the best immunosuppressive therapy protocol for cardiothoracic organ transplantation. This report provides an overview of the role of human leukocyte antibodies in heart and lung transplantation.

Graft Protective and Intercellular Immunomodulatory Effects by Adoptive Transfer of an Agonistic Anti-BTLA mAb (3C10) Induced CD4+CD25+ Regulatory T Cells in Murine Cardiac Allograft Transplant Model

We demonstrated that an agonistic anti-B and T lymphocyte attenuator antibody (3C10) prolonged cardiac survival by inducing regulatory T cells (Treg). However, the mechanisms of immune tolerance in the recipients remained unclear. In this study, we investigated the graft-protective and intercellular immunomodulatory effects of adoptive transfer (AT) of 3C10-induced Tregs in a murine cardiac allograft transplant model. Thirty days after transplantation of a C57BL/6 heart into the primary 3C10-treated CBA recipients, splenic CD4+CD25+ cells from these recipients (3C10/AT group) or naïve CBA mice (no-treatment group) were adoptively transferred into secondary CBA recipients with a C57BL/6 heart. To confirm the requirement for 3C10-induced Tregs, we administered an anti-interleukin-2 receptor alpha antibody (PC-61) to secondary CBA recipients. Additionally, histologic and fluorescent staining, cell proliferation analysis, flow cytometry, and donor-specific antibody (DSA) measurements were performed. 3C10/AT-treated CBA recipients resulted in significantly prolonged allograft survival (median survival time [MST], >50 days). Allografts displayed prolonged function with preservation of vessel structure by maintaining high numbers of splenic CD4+CD25+Foxp3+ Treg and intramyocardial CD4+Foxp3+ cells. DSA levels were suppressed in 3C10/AT-treated CBA recipients. Moreover, PC-61 administration resulted in a shorter MSTs of cardiac allograft survivals, a detrimental increase in DSA production, and enhanced expression of programmed cell death (PD)-1. AT of 3C10-induced Tregs may be a promising graft-protective strategy to prolong allograft survival and suppress DSA production, driven by the promotion of splenic and graft-infiltrating Tregs and collaboration with PD-1+ T cells and Treg.

Early allogeneic immune modulation after establishment of donor hematopoietic cell-induced mixed chimerism in a nonhuman primate kidney transplant model.

Mixed lymphohematopoietic chimerism is a proven strategy for achieving operational transplant tolerance, though the underlying immunologic mechanisms are incompletely understood. A post-transplant, non-myeloablative, tomotherapy-based total lymphoid (TLI) irradiation protocol combined with anti-thymocyte globulin and T cell co-stimulatory blockade (belatacept) induction was applied to a 3-5 MHC antigen mismatched rhesus macaque kidney and hematopoietic cell transplant model. Mechanistic investigations of early (60 days post-transplant) allogeneic immune modulation induced by mixed chimerism were conducted. Chimeric animals demonstrated expansion of circulating and graft-infiltrating CD4+CD25+Foxp3+ regulatory T cells (Tregs), as well as increased differentiation of allo-protective CD8+ T cell phenotypes compared to naïve and non-chimeric animals. In vitro mixed lymphocyte reaction (MLR) responses and donor-specific antibody production were suppressed in animals with mixed chimerism. PD-1 upregulation was observed among CD8+ T effector memory (CD28-CD95+) subsets in chimeric hosts only. PD-1 blockade in donor-specific functional assays augmented MLR and cytotoxic responses and was associated with increased intracellular granzyme B and extracellular IFN-γ production. These studies demonstrated that donor immune cell engraftment was associated with early immunomodulation via mechanisms of homeostatic expansion of Tregs and early PD-1 upregulation among CD8+ T effector memory cells. These responses may contribute to TLI-based mixed chimerism-induced allogenic tolerance.

Interleukin-37 contributes to endometrial regenerative cell–mediated immunotherapeutic effect on chronic allograft vasculopathy

Background aimsChronic allograft vasculopathy (CAV) remains a predominant contributor to late allograft failure after organ transplantation. Several factors have already been shown to facilitate the progression of CAV, and there is still an urgent need for effective and specific therapeutic approaches to inhibit CAV. Human mesenchymal-like endometrial regenerative cells (ERCs) are free from the deficiencies of traditional invasive acquisition methods and possess many advantages. Nevertheless, the exact immunomodulation mechanism of ERCs remains to be elucidated. MethodsC57BL/6 (B6) mouse recipients receiving BALB/c mouse donor abdominal aorta transplantation were treated with ERCs, negative control (NC)-ERCs and interleukin (IL)-37−/−ERCs (ERCs with IL-37 ablation), respectively. Pathologic lesions and inflammatory cell infiltration in the grafts, splenic immune cell populations, circulating donor-specific antibody levels and cytokine profiles were analyzed on postoperative day (POD) 40. The proliferative capacities of Th1, Th17 and Treg subpopulations were assessed in vitro. ResultsAllografts from untreated recipients developed typical pathology features of CAV, namely endothelial thickening, on POD 40. Compared with untreated and IL-37−/−ERC-treated groups, IL-37–secreting ERCs (ERCs and NC-ERCs) significantly reduced vascular stenosis, the intimal hyperplasia and collagen deposition. IL-37–secreting ERCs significantly inhibited the proliferation of CD4+T cells, reduced the proportions of Th1 and Th17 cells, but increased the proportion of Tregs in vitro. Furthermore, in vitro results also showed that IL-37–secreting ERCs significantly inhibited Th1 and Th17 cell responses, abolished B-cell activation, diminished donor-specific antibody production and increased Treg proportions. Notably, IL-37–secreting ERCs remarkably downregulated the levels of pro-inflammatory cytokines (interferon-γ, tumor necrosis factor-α, IL-1β, IL-6 and IL-17A) and increased IL-10 levels in transplant recipients. ConclusionsThe knockdown of IL-37 dramatically abrogates the therapeutic ability of ERCs for CAV. Thus, this study highlights that IL-37 is indispensable for ERC-mediated immunomodulation for CAV and improves the long-term allograft acceptance.

Blockade of BLyS inhibits B-cell responses and antibody production for the prevention of chronic transplant rejection

BACKGROUNDChronic rejection, closely related to the activation of B cells and donor-specific antibody (DSA) production, has unsatisfactory therapeutic outcomes. B lymphocyte stimulator (BLyS) is a major regulatory factor that controls the activation and differentiation of B cells. However, it remains unclear whether BLyS blockade can regulate B and plasma cells in the transplantation setting and affect chronic rejection. Here, we investigated the efficacy of the BLyS inhibitors belimumab and telitacicept in controlling B-cell response and preventing chronic rejection. METHODSThe effects of belimumab and telitacicept on B-cell activation, differentiation and antibody production in vitro were determined. A chronic rejection model in mouse was established by allogeneic cardiac transplantation with CTLA4-Ig treatment. Allograft survival, histology, DSA levels, and B-cell responses were analyzed to evaluate the chronic rejection-preventive effects of belimumab and telitacicept. RESULTSIn vitro experiments confirmed that belimumab and telitacicept inhibited B-cell activation and differentiation and reduced antibody production. In vivo experiments indicated that they significantly prolonged allograft survival, attenuated chronic rejection through significant suppression of myocardial ischemic necrosis and interstitial fibrosis, and reduced DSA-IgG levels, C4d deposition, and inflammatory cell infiltration. Furthermore, the frequencies of B cells, plasma cells and IgG producing cells in the recipients’ spleen, lymph nodes, bone marrow, and blood were decreased after BLyS inhibitors treatment. CONCLUSIONSThis study demonstrated that belimumab and telitacicept inhibit B-cell responses and antibody production and alleviate chronic transplant rejection. Therefore, BLyS inhibitors are expected to be used for the prevention of chronic rejection in clinical practice.

Targeting TFH cells is a novel approach for donor-specific antibody desensitization of allograft candidates: an in vitro and in vivo study.

The presence of donor-specific antibodies (DSA) are associated with graft failure either following human leukocyte antigen (HLA)-mismatched allogeneic stem cell transplantation or after organ transplantation. Although targeting B cells and plasma cells have been used for desensitization, there have been reports of failure. T-follicular helper (Tfh) cells assist B cells in differentiating into antibody-secreting plasma cells. We used haploidentical allograft as a platform to investigate the possibility of targeting Tfh cells to desensitize DSA. The quantities of circulating Tfh (cTfh) cell subsets in allograft candidates were abnormal, and these cells, including the cTfh2 and cTfhem cell subsets, were positively related to the production of anti-HLA antibodies. Ex vivo experiments showed that the cTfh cells of anti-HLA antibody-positive allograft candidates could induce B cells to differentiate into DSA-producing plasmablasts. The immune synapse could be involved in the assistance of cTfh cells to B cells in antibody production. In vitro experiments and in vivo clinical pilot studies indicated that targeting cTfh cells with sirolimus can inhibit their auxiliary function in assisting B cells. Ex vivo and in vivo studies demonstrated the effect of sirolimus and rituximab on DSA desensitization compared with either sirolimus or rituximab alone (60%, 43.75%, and 30%, respectively). Our findings provide new insight into the role of Tfh cells in the pathogenesis of DSA production in HLA-mismatched transplant candidates. Our data also indicate that targeting Tfh cells is a novel strategy for DSA desensitization and combination of sirolimus and rituximab might be a potential therapy. The prospective cohort of this study is registered at http://www.chictr.org.cn as #ChiCTR-OPC-15006672.

Single-Cell Heterogeneity Restorative Chimeric Engineering Nanoparticles for Alleviating Antibody-Mediated Allograft Injury.

Disturbance of single-cell transcriptional heterogeneity is an inevitable consequence of persistent donor-specific antibody (DSA) production and allosensitization. However, identifying and efficiently clearing allospecific antibody repertoires to restore single-cell transcriptional profiles remain challenging. Here, inspired by the high affinity of natural bacterial proteins for antibodies, a genetic engineered membrane-coated nanoparticle termed as DSA trapper by the engineering chimeric gene of protein A/G with phosphatidylserine ligands for macrophage phagocytosis was reported. It has been shown that DSA trappers adsorbed alloreactive antibodies with high saturation and activated the heterophagic clearance of antibody complexes, alleviating IgG deposition and complement activation. Remarkably, DSA trappers increased the endothelial protective lineages by 8.39-fold, reversed the highly biased cytotoxicity, and promoted the proliferative profiles of Treg cells, directly providing an obligate immune tolerant niche for single-cell heterogeneity restoration. In the mice of allogeneic transplantation, the DSA trapper spared endothelial from inflammatory degenerative rosette, improved the glomerular filtration rate, and prolonged the survival of allogeneic mice from 23.6 to 78.3 days. In general, by identifying the lineage characteristics of rejection-related antibodies, the chimeric engineered DSA trapper realized immunoadsorption and further phagocytosis of alloantibody complexes to restore the single-cell genetic architecture of the allograft, offering a promising prospect for the treatment of alloantibody-mediated immune injury.

#6011 VIRAL INFECTION AND DE NOVO PRODUCTION OF DONOR SPECIFIC ANTIBODIES IN KIDNEY TRANSPLANTATION: DCD VS DBD

Abstract Background and Aims Viruses are among the most common causes of opportunistic infection after transplantation and an accurate screening and follow-up is needed in order to prevent related complication as systemic damages and worsening of kidney function. On the other hand, in the first years after transplantation, antibody-mediated rejection (ABMR) is one of the first cause of graft lost and de novo production of donor specific antibody (dnDSAs) is the main source. In this monocentric study we analysed data of 255 patient transplanted from January 2016 to February 2022. We studied the incidence of viral infection and dnDSAs in the first one year after transplantation in different sub-groups of patients. Method Data was obtained from our monocentric registry, from January 2016 to February 2022. Starting from 299 kidney transplantation we obtained 255 patients with a complete annual follow-up for viral infection and DSA monitoring. We compared the incidence of viral infection and dnDSAs in different sub-group: transplanted from donation after brain-death treated with Basiliximab as induction therapy (DBDb), transplanted from donation after brain-death treated with rabbit anti-human thymocyte immunoglobulin (rATG) as induction therapy (DBDt), transplanted from donation after circulatory death treated with rATG as induction therapy (DCD) and transplanted treated with rATG as induction (DBDt+DCD). Results Global incidence of viral infection was 73% and dnDSAs formation was present in 12,5% of all patients. DBDs showed an incidence of 69% of viral infection and 10% of dnDSAs while in DBDt these values were 77,4% and 25%, respectively. In DCD data of viral infection was higher (96,7%) whereas dnDSAs was 14%. rATG (DBDt+DCD) displayed 87,1% of viral infection and 19% of dnDSAs. Conclusion Viral infection and dsDNAs are two paramount aspects in kidney transplantation and demonstrate different incidences depending on donation profile and immunosuppressive induction therapy. Specifically rATG seems to be associated to an higher rate of viral infection and DCD is the more relevant sub-group. Furthermore, rATG was associated with higher dsDNAs rate, especially in DBD treated with rATG. On the best of our knowledge, this data was never observed before. These data, due to the low number of cases, need to be confirmed from larger cohorts. Moreover our study underlines how significant is to develop a personalized approach in order to reduce complications associated to immunosuppressive therapies.

Maternal dendritic cells influence fetal allograft response following murine in-utero hematopoietic stem cell transplantation

BackgroundIntrauterine hematopoietic stem cell transplantation (IUT), potentially curative in congenital haematological disease, is often inhibited by deleterious immune responses to donor cells resulting in subtherapeutic donor cell chimerism (DCC). Microchimerism of maternal immune cells (MMc) trafficked into transplanted recipients across the placenta may directly influence donor-specific alloresponsiveness, limiting DCC. We hypothesized that dendritic cells (DC) among trafficked MMc influence the development of tolerogenic or immunogenic responses towards donor cells, and investigated if maternal DC-depletion reduced recipient alloresponsiveness and enhanced DCC.MethodsUsing transgenic CD11c.DTR (C57BL/6) female mice enabled transient maternal DC-depletion with a single dose of diphtheria toxin (DT). CD11c.DTR females and BALB/c males were cross-mated, producing hybrid pups. IUT was performed at E14 following maternal DT administration 24 h prior. Bone marrow-derived mononuclear cells were transplanted, obtained from semi-allogenic BALB/c (paternal-derived; pIUT), C57BL/6 (maternal-derived; mIUT), or fully allogenic (aIUT) C3H donor mice. Recipient F1 pups were analyzed for DCC, while maternal and IUT-recipient immune cell profile and reactivity were examined via mixed lymphocyte reactivity functional assays. T- and B-cell receptor repertoire diversity in maternal and recipient cells were examined following donor cell exposure.ResultsDCC was highest and MMc was lowest following pIUT. In contrast, aIUT recipients had the lowest DCC and the highest MMc. In groups that were not DC-depleted, maternal cells trafficked post-IUT displayed reduced TCR & BCR clonotype diversity, while clonotype diversity was restored when dams were DC-depleted. Additionally, recipients displayed increased expression of regulatory T-cells and immune-inhibitory proteins, with reduced proinflammatory cytokine and donor-specific antibody production. DC-depletion did not impact initial donor chimerism. Postnatal transplantation without immunosuppression of paternal donor cells did not increase DCC in pIUT recipients; however there were no donor-specific antibody production or immune cell changes.ConclusionsThough maternal DC depletion did not improve DCC, we show for the first time that MMc influences donor-specific alloresponsiveness, possibly by expanding alloreactive clonotypes, and depleting maternal DC promotes and maintains acquired tolerance to donor cells independent of DCC, presenting a novel approach to enhancing donor cell tolerance following IUT. This may have value when planning repeat HSC transplantations to treat haemoglobinopathies.