Model Of Allograft Rejection Research Articles

Suppressive Role of Pigment Epithelium-derived Factor in a Rat Model of Corneal Allograft Rejection.

Immunological rejection is the most common reason for corneal transplantation failure. The importance of T cells in corneal allograft rejection is well demonstrated. Recent studies highlight that pigment epithelium-derived factor (PEDF) plays an immunoregulatory role in ocular diseases by enhancing the suppressive phenotype of regulatory T cells besides its other functions in neurotrophy and antiangiogenesis. The effects of PEDF on immune rejection were examined in rat models of corneal transplantation using slit-lamp microscope observation, immunohistochemistry, flow cytometry, and Western blot. In vitro, we demonstrated PEDF reduced alloreactive T-cell activation using real-time polymerase chain reaction, flow cytometry, and Western blot. Topical administration of PEDF provided corneal transplantation rats with an improved graft survival rate of corneal allografts, reduced hemangiogenesis, and infiltration of immune cells in corneas, in particular, type 17 T helper cells while increased regulatory T cells. Moreover, nerve reinnervation within grafts was promoted in PEDF-treated recipient rats. In vitro, PEDF inhibited alloreactive T-cell activation via the c-Jun N-terminal kinase/c-Jun signaling pathway and upregulated the expressions of interleukin-10 and transforming growth factor-β, emphasizing the suppressive role of PEDF on immune responses. Our results underscore the feasibility of PEDF in alleviating corneal allograft rejection and further illustrate its potential in managing immune-related diseases.

The Potential Role of the Leucocyte Immunoglobulin-Like Receptors in Kidney Transplant Rejection: A Mini Review.

Antibody-mediated rejection (ABMR) remains one of the main causes of long-term graft failure after kidney transplantation, despite the development of powerful immunosuppressive therapy. A detailed understanding of the complex interaction between recipient-derived immune cells and the allograft is therefore essential. Until recently, ABMR mechanisms were thought to be solely caused by adaptive immunity, namely, by anti-human leucocyte antigen (HLA) donor-specific antibody. However recent reports support other and/or additive mechanisms, designating monocytes/macrophages as innate immune contributors of ABMR histological lesions. In particular, in mouse models of experimental allograft rejection, monocytes/macrophages are readily able to discriminate non-self via paired immunoglobulin receptors (PIRs) and thus accelerate rejection. The human orthologs of PIRs are leukocyte immunoglobulin-like receptors (LILRs). Among those, LILRB3 has recently been reported as a potential binder of HLA class I molecules, shedding new light on LILRB3 potential as a myeloid mediator of allograft rejection. In this issue, we review the current data on the role of LILRB3 and discuss the potential mechanisms of its biological functions.

Resveratrol regulates macrophage recruitment and M1 macrophage polarization and prevents corneal allograft rejection in rats.

Resveratrol is an immune modulator that can reduce M1 macrophage polarization in vitro. Reducing macrophage recruitment and M1 polarization can prevent corneal allograft rejection (CGR). In this study, rat corneal allograft rejection models were established to explore the effects of resveratrol on CGR and macrophages and the underlying mechanisms after corneal transplantation. Corneal allograft models were established, and 100 mg/kg resveratrol was injected intraperitoneally. The corneal allografts were assessed clinically using the Holland rejection scoring system, anterior segment photography, and anterior segment optical coherence tomography. Corneal macrophages, pro-inflammatory cytokines, and corneal lymphatic vessels were detected using hematoxylin and eosin staining, immunofluorescence staining, and real-time quantitative polymerase chain reaction (qRT-PCR). Dendritic cells (DCs) in cervical lymph nodes were explored using flow cytometry. RNA sequencing experiments were conducted to identify the mechanisms through which resveratrol affected CGR. The results were verified using Simple Western analysis. Pro-inflammatory cytokines by macrophages in vitro were measured using qRT-PCR and enzyme-linked immunosorbent assays. Resveratrol significantly prolonged the survival of corneal grafts and reduced graft edema and central corneal thickness. Corneal macrophage recruitment and M1 macrophage polarization decreased significantly after corneal transplantation in the resveratrol group. Resveratrol also reduced pro-inflammatory cytokines in corneal grafts and suppressed the early generation of cornea lymphatic vessels and the recruitment of cornea inflammatory cells 14 days after surgery. Resveratrol decreased the proportion of DCs in ipsilateral cervical lymph nodes. The effect of resveratrol on CGR was related to the phosphatidylinositol 3-kinase/protein kinase-B (PI3K/Akt) pathway. Resveratrol reduced the secretion of pro-inflammatory cytokines by M1 macrophages in vitro. Our findings suggest that resveratrol can reduce corneal macrophage recruitment and M1 macrophage polarization after corneal transplantation in rats and prevent CGR. The PI3K/Akt pathway may be an important mechanism that warrants further research.

Downregulation of a tumor suppressor gene LKB1 in lung transplantation as a biomarker for chronic murine lung allograft rejection.

We recently demonstrated decreased tumor suppressor gene liver kinase B1 (LKB1) level in lung transplant recipients diagnosed with bronchiolitis obliterans syndrome. STE20-related adaptor alpha (STRADα) functions as a pseudokinase that binds and regulates LKB1 activity. A murine model of chronic lung allograft rejection in which a single lung from a B6D2F1 mouse was orthotopically transplanted into a DBA/2J mouse was employed. We examined the effect of LKB1 knockdown using CRISPR-CAS9 in vitro culture system. Significant downregulation of LKB1 and STRADα expression was found in donor lung compared to recipient lung. STRADα knockdown significantly inhibited LKB1, pAMPK expression but induced phosphorylated mammalian target of rapamycin (mTOR), fibronectin, and Collagen-I, expression in BEAS-2B cells. LKB1 overexpression decreased fibronectin, Collagen-I, and phosphorylated mTOR expression in A549 cells. We demonstrated that downregulation of LKB1-STRADα pathway accompanied with increased fibrosis, results in development of chronic rejection following murine lung transplantation.

IL17A and IL17RA gene polymorphisms in Fanconi anemia.

Fanconi anemia is a rare autosomal recessive disease. In this disease, cytokine pathways can induce the bone marrow failure that is observed in individuals with Fanconi anemia. Interleukin IL-17 exhibits a protective effect in organisms because it induces neutrophil recruitment and shows a pathological role in several models of autoimmune diseases, periodontal disease, cancer, allograft rejection, and graft versus host disease. Polymorphisms in the IL17A and IL17RA genes were evaluated from DNA in saliva, comparing individuals with or without Fanconi anemia, using models of genotypic transmission (additive, dominant, and recessive). Polymorphisms in the IL17A and IL17RA genes (rs2241044 [C allele], rs879577 [C allele], rs9606615 [T allele], and rs2241043 [C allele]) were risk factors for developing Fanconi anemia. We also performed an analysis of gene markers with clinical variables in the Fanconi group. Polymorphisms in the IL17A gene (rs3819025 [A allele] and rs2275913 [G allele], respectively) were associated with an age of less than 20 years (p = 0.026; RP 0.65) and the female sex (p = 0.043; RP 0.88). The IL17RA gene was also associated with age and the presence of leukoplakia (a potentially malignant oral disorder). An age of less than 20 years was associated with rs917864 (T allele; p = 0.036; RP 0.67). The presence of leukoplakia was associated with rs17606615 (T allele; p = 0.042; RP 0.47). To our knowledge, this is the first study that associates IL17A and IL17RA gene polymorphisms with Fanconi anemia and examines rs2241044 polymorphisms in scientific literature thus far.

Low-dose IL-2 prevents murine chronic cardiac allograft rejection: Role for IL-2-induced T regulatory cells and exosomes with PD-L1 and CD73

To determine the effects and immunological mechanisms of low-dose interleukin-2 (IL-2) in a murine model of chronic cardiac allograft rejection (BALB/c to C57BL/6) after costimulatory blockade consisting of MR1 (250 μg/ip day 0) and CTLA4-Ig (200 μg/ip day 2), we administered low-dose IL-2 (2000 IU/day) starting on posttransplant day 14 for 3 weeks. T regulatory (Treg) cell infiltration of the grafts was determined by immunohistochemistry; circulating exosomes by western blot and aldehyde bead flow cytometry; antibodies to donor MHC by immunofluorescent staining of donor cells; and antibodies to cardiac self-antigens (myosin, vimentin) by ELISA. We demonstrated that costimulation blockade after allogeneic heart transplantation induced circulating exosomes containing cardiac self-antigens and antibodies to both donor MHC and self-antigens, leading to chronic rejection by day 45. Treatment with low-dose IL-2 prolonged allograft survival (>100 days), prevented chronic rejection, and induced splenic and graft-infiltrating CD4+ CD25+ Foxp3 Treg cells by day 45 and circulating exosomes (Foxp3+) with PD-L1 and CD73. MicroRNA 142, associated with the TGFβ pathway, was significantly downregulated in exosomes from IL-2-treated mice. In conclusion, low-dose IL-2 delays rejection in a murine model of chronic cardiac allograft rejection and also induces graft-infiltrating Tregs and circulating exosomes with immunoregulatory molecules.

404.5: The Role of LAG3 in Antibody Responses to Kidney Transplantation

The functions of coinhibitory receptor lymphocyte activation gene-3 (LAG3) in T cells are well studied, however its role in humoral immune responses remains poorly characterized. The goal of this study was to test the role of recipient LAG3 in a mouse model of renal allograft rejection. Murine kidney transplant surgeries were performed from C3H (H-2Dk) donors to B6 WT, LAG3-/-, CD4CreLAG3fl/fl & CD19CreLAG3fl/fl recipients (H-2Db) after bilateral nephrectomy. Grafts were evaluated by immunistochemistry. WT recipients were treated with anti-mCD20 or anti-CD8 mAbs to deplete B cells or CD8 T cells, respectively. Immune responses were assessed by flow cytometry, ELISPOT assay, and serum levels of MHC-I and MHC-II-reactive IgG donor specific antibody (DSA) were determined by ELISA. Compared to WT animals, naïve B6.LAG3-/- mice have elevated numbers of CD44hi memory T cells, CXCR5hi follicular T cells, and B220+CD138+ plasma cells, and increased frequencies of memory T cells reactive to H-2Dd, H-2Ds, H-2Dq and H-2Dk (Figure 1A) and increased levels of serum IgG antibodies against H-2Dd, H-2Dk, I-Ad and I-Ak alloantigens (Figure 1B). All C3H kidney allografts survived for > 60d (n=5) in WT recipients, whereas recipient LAG3 deficiency led to rapid allograft rejection (MST of 14d, n=5) (Figure 2A) and elevated serum creatinine levels at d14 posttransplant. Compared to WT, LAG3-/- recipients had elevated frequencies of anti-donor IFNγ producing T cells and increased levels of DSA against MHC-I and MHC-II (Figure 2B). Graft histology at rejection revealed minimal T cell infiltration, diffuse C4d staining, atrophic peritubular capillaries, endothelial swelling and edema characteristic of antibody mediated rejection (AMR) (Figure 2C). Recipient CD8 T cell depletion did not alter rejection kinetics in LAG3-/- recipients (MST of 16d) (Figure 3A&B), and graft histological findings (Figure 3C) mirrored those of unmanipulated LAG3 deficient recipients (Figure 2C), demonstrating hallmark characterstics of AMR. B cell depletion significantly extended C3H kidney allograft survival (MST of >30d) (Figure 3D&E), suggesting the predominant role of alloantibody rather than T cell mediated rejection in these mice. However, neither T nor B cell conditional knockout recipients rejected the allograft demonstrating LAG3 expression on both cell types is necessary to mediate rejection.These findings demonstrate that LAG3 regulates both T and B cell functions in response to kidney allografts, and is an attractive therapeutic target for the prevention of AMR.

Role for exosomes with self-antigens and immune regulatory molecules in allo- and auto-immunity leading to chronic immune injury following murine kidney transplantation

ObjectiveAntibodies against donor human leukocyte antigen are a risk factor for chronic immune injury (CII) following renal transplantation; however, it is often not detectable. The main goal of this study is to gain new insights into the kinetics of exosome release and content in sensitized vs non-sensitized recipients. Towards this, we investigated the role for circulating exosomes with allo and self-antigens as well as immunoregulatory molecules in the development of CII and acute rejection. MethodsUsing murine kidney allograft rejection models, we investigated the role of exosomes on immune responses leading to allo- and auto-immunity to self-antigens resulting in rejection. Exosomes were analyzed for kidney self-antigens (Collagen-IV, fibronectin, angiotensin II receptor type 1), and immune-regulatory molecules (PD-L1, CD73) using western blot. Antibodies to donor MHC in serum samples were detected by immunofluorescence, self-antigens by enzyme-linked immunosorbent assay and kidney tissue infiltrating cells were determined by immunohistochemistry. ResultsBALB/c; H2d to C57BL/6; H2b renal transplantation (BALB/c), resulted in tubulitis and cellular infiltration by day 14, suggestive of acute inflammation, that was self-limiting with functioning graft. This contributed to CII on post-transplant day >100, which was preceded by induction of exosomes with donor and self-antigens leading to antibodies and immune-regulatory molecules. The absence of acute rejection in this allogenic transplant model is likely due to the induction of splenic and, graft-infiltrating CD4 + FoxP3+ T regulatory cells. In contrast, prior sensitization by skin graft followed by kidney transplantation induced antibodies to MHC and self-antigens leading to acute rejection. ConclusionWe demonstrate a pivotal role for induction of exosomes with immune-regulatory molecules, allo- and auto-immunity to self-antigens leading to chronic immune injury following murine kidney transplantation.

Therapeutic effect of multiple functional minicircle vector encoding anti-CD25/IL-10/CXCR3 in allograft rejection model.

Background/AimsWe previously proposed minicircle vector technology as the potential platform for the development and production of new biologics. In this study, we have designed a novel target molecule for the treatment of allograft rejection and evaluated its feasibility as the therapeutic agent in this disease using the minicircle vector system.MethodsWe engineered vectors to carry cassette sequences for anti-CD25, interleukin-10 (IL-10), and C-X-C motif chemokine receptor 3 (CXCR3) fusion protein, and then isolated minicircle vectors from the parent vectors. We verified the substantial production of anti-CD25/IL-10/CXCR3 fusion protein from minicircles and their duration in HEK293T cells and mice models. We also evaluated whether minicircle-derived anti-CD25/IL-10/CXCR3 has therapeutic effects in a skin allograft in mice model.ResultsWe confirmed the production of anti-CD25/IL-10/CXCR3 from minicircle by its significant availability in cells transfected with the minicircle and in its conditioned media. After a single injection of minicircle by hydrodynamic injection via mouse tail vein, luminescence or red fluorescence was maintained until 40 days in the liver tissue, suggesting the production of anti-CD25/IL-10/CXCR3 protein from minicircles via protein synthesis machinery in the liver. Mice treated with the minicircle encoding anti-CD25/IL-10/CXCR3 showed prolonged skin allograft survival times accompanied by improved immunologic regulation e.g., reduction of the lymphocyte population of Th1, Th2, and Th17 and an induction of regulatory T cells.ConclusionsThese findings implied that self-generated anti-CD25/IL-10/CXCR3 protein drug by minicircle technology is functionally active and relevant for reducing allograft rejection. The minicircle vector system may be useful for developing new biological drugs, avoiding manufacturing or practical problems.

Bringing Clarity to the Murky Problem of Cardiac Allograft Vasculopathy

Although most published studies involving preclinical mouse models of cardiac allograft rejection tend to center on the issues of acute rejection and tolerance induction, arguably the more pressing need in the field of clinical transplantation is better understanding of chronic allograft injury. That is, chronic graft injury is a far greater current clinical problem than is early graft loss due to acute rejection. In heart transplantation, cardiac allograft vasculopathy (CAV) is a form of pronounced coronary artery disease that occurs over time after transplant1 and remains the major source of transplant loss and recipient mortality.

MNK/eIF4E Ser209 Inhibitor eFT-508 Prevents and Therapeutically Treats Fibrosis in a Murine Model of Restrictive Chronic Lung Allograft Rejection

<h3>Purpose</h3> Lung transplant is limited by poor outcomes due to chronic lung allograft dysfunction, CLAD. A fulminant CLAD phenotype, restrictive allograft syndrome (RAS), with limited therapies underscores the need to understand underlying mechanisms. MNK1 kinase is a key translational regulator of cellular functions via eIF4E serine 209 phosphorylation. Here we investigate the role of MNK/eIF4E Ser209 in mesenchymal cell activation and the therapeutic effectiveness of eFT-508 in a murine model of RAS. <h3>Methods</h3> Human lung allograft derived MCs treated with eFT-508 (10uM x 24h) were immunoblotted for collagen I, alpha smooth muscle actin, CD44, autotaxin. A modified boyden chamber assay was utilized for migration. We recently reported a murine RAS model, B6D2F1/J into C57BL6/J. Mice were administered eFT-508 5mg/kg/daily/gavage in a preventive group days 7-28, or therapeutic group days 14-28. <h3>Results</h3> Human allograft derived MCs from CLAD patients demonstrated 4-fold increase in MNK1 (Thr197/202) and eIF4E Ser209 compared to non-fibrotic MCs. Upon eFT-508 treatment, we observed reduced eIF4E Ser209, collagen I, alpha smooth muscle actin and SPARC expression, and migration (n=7; p<0.05). CD44 and autotaxin protein expression was decreased upon eFT-508 treatment, along with secreted autotaxin activity (n=9; p=0.0005). <i>In vivo</i> preventive treatment with eFT-508 decreased airway fibrosis upon histological examination utilizing trichrome staining. Pleural thickness measurements were also reduced compared to vehicle treated controls. A significant reduction in hydroxyproline content, autotaxin secretion, and activity were also noted in eFT-508 treated transplant lung homogenates (n=7; p<0.001). Therapeutic treatment with eFT-508 reduced hydroxyproline content compared to vehicle treated allografts (n=4; p=0.0252). <h3>Conclusion</h3> MNK/eIF4E Ser209 inhibition reduced fibrotic protein expression and migration, demonstrating a role for this pathway in MC activation. <i>In vivo</i> MNK/eIF4E Ser209 inhibition reduced graft fibrosis by preventive and therapeutic treatment regimens in a murine model of RAS. This data highlights a novel therapeutic option for preventing development and progression of RAS.

Mesenchymal stem cell derived exosomes-based immunological signature in a rat model of corneal allograft rejection therapy.

Mesenchymal stem cells (MSCs) are promising candidates for immunomodulatory therapy that are currently being tested in corneal allograft rejection. In this study, we tested the effects of Mesenchymal stem cells derived exosomes in the corneal allograft rejection model. Mesenchymal stem cells derived exosomes (MSC-exo) were collected and characterized. Wistar-Lewis rat corneal allograft rejection models were established. PKH26 labeled exosomes were used for track experiment. Models were randomly separated into four groups and treated with graded doses of exosomes or same volumn of PBS. Corneal grafts were assessed for rejection degree using slit-lamp biomicroscopy. Grafts were examined histologically using hematoxylin-eosin (H-E) staining and immunohistochemically using antibodies against CD4, CD8 and CD25. A comprehensive graft mRNA gene expression array analysis was conducted and checked by real-time polymerase chain reaction (PCR). The nanovesicles obtained were expressing exosome specific protein markers CD9, CD63, CD81. The labeled exosomes could be detected in both cornea and anterior chamber two hours after injection.The 10 μg exosomes subconjunctival injection can effectively prolong graft survival time (MST 16.3 ± 2.5 days). 10 μg exosomes-treated group can inhibit the infiltration of CD4+ and CD25+ T cells. IFN-γ and CXCL11 levels were significantly decreased in grafts obtained from postoperative exosomes-treated rats when compared with controls. MSC-exo can cross biological barrier and play better role directly towards target tissue. MSC-exo can effectively prolong grafts survival time. Th1 signaling pathway was significantly inhibited in the exosomes treated group.

T cell fat catabolism: A novel target for kynurenine?

T cell fat catabolism: A novel target for kynurenine?

Blocking hyaluronan synthesis alleviates acute lung allograft rejection.

Lung allograft rejection results in the accumulation of low–molecular weight hyaluronic acid (LMW-HA), which further propagates inflammation and tissue injury. We have previously shown that therapeutic lymphangiogenesis in a murine model of lung allograft rejection reduced tissue LMW-HA and was associated with improved transplant outcomes. Herein, we investigated the use of 4-Methylumbelliferone (4MU), a known inhibitor of HA synthesis, to alleviate acute allograft rejection in a murine model of lung transplantation. We found that treating mice with 4MU from days 20 to 30 after transplant was sufficient to significantly improve outcomes, characterized by a reduction in T cell–mediated lung inflammation and LMW-HA content and in improved pathology scores. In vitro, 4MU directly attenuated activation, proliferation, and differentiation of naive CD4+ T cells into Th1 cells. As 4MU has already been demonstrated to be safe for human use, we believe examining 4MU for the treatment of acute lung allograft rejection may be of clinical significance.

Adipose-Derived Stem/Stromal Cells in Kidney Transplantation: Status Quo and Future Perspectives.

Kidney transplantation (KT) is the gold standard treatment of end-stage renal disease. Despite progressive advances in organ preservation, surgical technique, intensive care, and immunosuppression, long-term allograft survival has not significantly improved. Among the many peri-operative complications that can jeopardize transplant outcomes, ischemia–reperfusion injury (IRI) deserves special consideration as it is associated with delayed graft function, acute rejection, and premature transplant loss. Over the years, several strategies have been proposed to mitigate the impact of IRI and favor tolerance, with rather disappointing results. There is mounting evidence that adipose stem/stromal cells (ASCs) possess specific characteristics that could help prevent, reduce, or reverse IRI. Immunomodulating and tolerogenic properties have also been suggested, thus leading to the development of ASC-based prophylactic and therapeutic strategies in pre-clinical and clinical models of renal IRI and allograft rejection. ASCs are copious, easy to harvest, and readily expandable in culture. Furthermore, ASCs can secrete extracellular vesicles (EV) which may act as powerful mediators of tissue repair and tolerance. In the present review, we discuss the current knowledge on the mechanisms of action and therapeutic opportunities offered by ASCs and ASC-derived EVs in the KT setting. Most relevant pre-clinical and clinical studies as well as actual limitations and future perspective are highlighted.

Diffusion-Weighted Imaging and Mapping of T1 and T2 Relaxation Time for Evaluation of Chronic Renal Allograft Rejection in a Translational Mouse Model.

We hypothesized that multiparametric MRI is able to non-invasively assess, characterize and monitor renal allograft pathology in a translational mouse model of chronic allograft rejection. Chronic rejection was induced by allogenic kidney transplantation (ktx) of BALB/c-kidneys into C57BL/6-mice (n = 23). Animals after isogenic ktx (n = 18) and non-transplanted healthy animals (n = 22) served as controls. MRI sequences (7T) were acquired 3 and 6 weeks after ktx and quantitative T1, T2 and apparent diffusion coefficient (ADC) maps were calculated. In addition, in a subset of animals, histological changes after ktx were evaluated. Chronic rejection was associated with a significant prolongation of T1 time compared to isogenic ktx 3 (1965 ± 53 vs. 1457 ± 52 ms, p < 0.001) and 6 weeks after surgery (1899 ± 79 vs. 1393 ± 51 ms, p < 0.001). While mean T2 times and ADC were not significantly different between allogenic and isogenic kidney grafts, histogram-based analysis of ADC revealed significantly increased tissue heterogeneity in allografts at both time points (standard derivation/entropy/interquartile range, p < 0.05). Correspondingly, histological analysis showed severe inflammation, graft fibrosis and tissue heterogeneity in allogenic but not in isogenic kidney grafts. In conclusion, renal diffusion weighted imaging and mapping of T2 and T1 relaxation times enable detection of chronic renal allograft rejection in mice. The combined quantitative assessment of mean values and histograms provides non-invasive information of chronic changes in renal grafts and allows longitudinal monitoring.

Ablation of Survivin in T Cells Attenuates Acute Allograft Rejection after Murine Heterotopic Heart Transplantation by Inducing Apoptosis.

Although studies in oncology have well explored the pharmacological effects of Birc5, little is known about its role in allogeneic T-cell responses. Therefore, the present study used a mouse model of acute heart allograft rejection to investigate the protective effect and mechanism of conditional knockout of Birc5 in T cells. Survivin (encoded by Birc5) was up-regulated in T cells activated in vivo and in vitro. Deletion of Birc5 in T cells attenuated acute heart allograft rejection by reducing the ratio of effector to naive T cells and Th1 to Tregs. In addition, deletion of Birc5 had no noticeable effect on proliferation but on apoptosis and the secretion of IFN-γ. The results revealed a significant increase in the percentage of Annexin V positive CD4+ T cells in the Birc5-/- group, compared to the WT. Moreover, there was significant increase in early apoptotic alloreactive T cells in Birc5 -/- mice and this was partly mediated by caspase-3. Furthermore, treatment with YM155 inhibited acute heart allograft rejection in vivo and increased T-cell apoptosis in healthy human PBMCs in vitro. The results highlight a potential therapeutic target for the prevention and treatment of acute transplant rejection.

Single-Cell RNA Sequencing Reveals the Immunological Profiles of Renal Allograft Rejection in Mice.

Allograft rejection is a common immunological feature in renal transplantation and is associated with reduced graft survival. A mouse renal allograft rejection model was induced and single-cell RNA sequencing (scRNA-seq) data of CD45+ leukocytes in kidney allografts on days 7 (D7) and 15 (D15) after operation was analyzed to reveal a full immunological profiling. We identified 20 immune cell types among 10,921 leukocytes. Macrophages and CD8+ T cells constituted the main populations on both timepoints. In the process from acute rejection (AR) towards chronic rejection (CR), the proportion of proliferating and naïve CD8+ T cells dropped significantly. Both B cells and neutrophils decreased by about 3 folds. On the contrary, the proportion of macrophages and dendritic cells (DCs) increased significantly, especially by about a 4.5-fold increase in Ly6cloMrc1+ macrophages and 2.6 folds increase in Ly6cloEar2+ macrophages. Moreover, myeloid cells harbored the richest ligand and receptor (LR) pairs with other cells, particularly for chemokine ligands such as Cxcl9, Cxcl10, Cxcl16 and Yars. However, macrophages with weak response to interferon gamma (IFNg) contributed to rejection chronicization. To conclude, reduction in CD8 T cells, B cells and neutrophils while increasing in Ly6cloMrc1+ macrophages and Ly6cloEar2+ macrophages, may contribute significantly to the progress from AR towards CR.

Novel Correlation between B Cell Survival Cytokines and Inhibitors in Hemophilia A

The most significant complication of factor VIII (FVIII) replacement in hemophilia A (HA) is the development of neutralizing antibodies (inhibitors) in 20-30% of severe HA patients. While several studies have investigated links between polymorphisms in cytokine regulatory elements and inhibitors, very few have measured patients' serum cytokine levels to understand their contribution. As an antibody-mediated process, inhibitor development must rely on the maturation and proliferation of FVIII-specific B cells, but details of this response remain poorly understood. One of the principal mechanisms of B cell tolerance is regulated at the transitional (TR) B cell stage when newly emerging B cells from the bone marrow remain susceptible to clonal deletion. TR B cell survival is highly dependent upon the abundance of the cytokine BAFF whereas BCMA, another member of the same family, is key to plasma cell survival (Parsons et al, Transplant Rev 2010). Inherited elevated levels of BAFF increase the risk of multiple sclerosis and lupus, where levels of 2 ng/mL (~2x normal) are associated with poor outcome (Steri et al, NEJM 2017, Cheema et al, Arthritis Rheum 2001). BAFF is expressed by dendritic cells, monocytes and macrophages and stimulates B cell proliferation, differentiation and survival (Litinskiy et al, Nature Immunology 2002). High levels of BAFF have been observed during immune reconstitution after rituximab therapy in allograft transplant recipients and may potentiate alloreactive B-cell immunity to promote rejection (Rickert et al, Transplant Rev 2010). We hypothesized that BAFF and/or BCMA may contribute to 1) the development of inhibitors in HA and 2) persistence of inhibitors in refractory patients. Here we analyze correlation of BAFF, BCMA, and 10 other cytokines with inhibitors in human HA samples and BAFF levels in murine inhibitor models.Samples from HA patients were collected longitudinally on an IRB approved protocol. Plasma BAFF and BCMA levels were measured by multiplex ELISA (R&D Systems). Nijmegen-modified Bethesda assays for inhibitor titer and anti-FVIII IgG subclasses were measured as described previously (Hofbauer et al, Blood 2015). A cohort of samples was analyzed for additional cytokines (IL2, IL4, IL5, IL6, IL10, IL12p70, IL17A, IL21, IFNγ, and TNFα) via a customized Luminex based multiplex microbead array (Millipore). C57Bl/6 HA mice were immunized with human FVIII 1 mcg weekly for 4 weeks and Bethesda assays tested at 8 weeks. Plasma from mice with high titer inhibitors (BU > 5, n=8) and non-inhibitor controls (n=2) was analyzed for murine BAFF via ELISA (R&D Systems). Data was analyzed with Prism using ANOVA, χ2 for categorical or t-test for continuous variables and are reported as mean ± SEM.Fifty-seven HA patients, 24 with and 33 without inhibitors, were enrolled with no difference in age, disease severity, or race (p = 0.13, 0.08 and 0.39, respectively by χ2); 2 were treated with rituximab. Patients with inhibitors had a higher frequency of large deletions or inversions. Excluding rituximab patients, BAFF levels were higher in patients undergoing immune tolerance induction (ITI) (1.53 ± 0.16) versus non-inhibitor patients (1.11 ± 0.09), and normalized in those who tolerized (0.98 ± 0.14 ng/mL, p = 0.024). BCMA levels were higher in patients with inhibitors (22.56 ± 1.95 vs 17.59 ± 0.59 ng/mL, p = 0.005) and correlated with Bethesda titer (r = 0.202, p = 0.024). Notably, none of the additional cytokines tested were associated with inhibitors. Consistent with allograft rejection models, BAFF levels rose 4-5 fold from baseline post-rituximab and did not normalize until anti-FVIII IgG was undetectable in rituximab-exposed patients. Consistent with human data, HA mice with inhibitors had higher BAFF levels than non-inhibitor mice (6.96 ± 0.37 vs 5.76 ± 0.08 ng/mL, p = 0.015, Welch's t-test).Here we uncover a novel underlying mechanism for modulation of inhibitor formation. BAFF may allow for the persistence of anti-FVIII antibodies during ITI and after rituximab therapy in HA inhibitor patients. Soluble BCMA levels correlate with inhibitor titer, suggesting it plays a role in anti-FVIII plasma cell survival. BAFF levels also increase in HA mice with inhibitor formation. Preclinical testing of antibody or cellular therapies against these cytokines may facilitate translational studies with FDA approved anti-BAFF therapies and enhance tolerance induction in HA. DisclosuresLacey:Novartis: Research Funding; Genentech: Honoraria. Chen:Novartis: Research Funding. Raffini:CSL Behring: Consultancy; Genetech: Consultancy; Green Cross Inc: Consultancy; Bayer: Consultancy.

Noncytotoxic Inhibition of the Immunoproteasome Regulates Human Immune Cells In Vitro and Suppresses Cutaneous Inflammation in the Mouse.

Inhibitors of the immunoproteasome (i-20S) have shown promise in mouse models of autoimmune diseases and allograft rejection. In this study, we used a novel inhibitor of the immunoproteasome, PKS3053, that is reversible, noncovalent, tight-binding, and highly selective for the β5i subunit of the i-20S to evaluate the role that i-20S plays in regulating immune responses in vitro and in vivo. In contrast to irreversible, less-selective inhibitors, PKS3053 did not kill any of the primary human cell types tested, including plasmacytoid dendritic cells, conventional dendritic cells, macrophages, and T cells, all of which expressed genes encoding both the constitutive proteasome (c-20S) and i-20S. PKS3053 reduced TLR-dependent activation of plasmacytoid dendritic cells, decreasing their maturation and IFN-α response and reducing their ability to activate allogenic T cells. In addition, PKS3053 reduced T cell proliferation directly and inhibited TLR-mediated activation of conventional dendritic cells and macrophages. In a mouse model of skin injury that shares some features of cutaneous lupus erythematosus, blocking i-20S decreased inflammation, cellular infiltration, and tissue damage. We conclude that the immunoproteasome is involved in the activation of innate and adaptive immune cells, that their activation can be suppressed with an i-20S inhibitor without killing them, and that selective inhibition of β5i holds promise as a potential therapy for inflammatory skin diseases such as psoriasis, cutaneous lupus erythematosus, and systemic sclerosis.