Alloimmunity and autoimmunity in chronic rejection

Humoral immunity to lung antigens early post-transplant confers risk for chronic lung allograft dysfunction

BACKGROUND

Autoantibodies and de novo donor HLA-specific antibodies (dnDSA) may contribute to chronic lung allograft dysfunction (CLAD). However, the breadth of reactivities against self-antigens and their association with CLAD has been underexamined. In a single-centre study, we screened lung transplant (LTx) recipients for novel autoantibodies at transplant and 6 months post-LTx, assessed dnDSA exposure, and tested their relationship with CLAD-free survival.

METHODS

Serum samples were collected from 89 crossmatch-negative bilateral lung transplant recipients at the time of LTx and 6 months post-LTx, prior to a CLAD diagnosis, for autoantibody screening using a custom antigen microarray optimized for IgM and IgG detection.

RESULTS

Patients who developed CLAD by 5 years post-LTx demonstrated a decrease in average IgG reactivity, but no decrease in IgM reactivity when measured at 6 months post-LTx. IgG anti-tropoelastin, SP-D, and thyroglobulin autoantibodies were significantly elevated 6 months post-LTx in patients who developed CLAD by 5 years, compared to those who remained CLAD-free at 5 years. In contrast, patients who remained CLAD-free at 5 years had elevated levels of IgG anti-CENP-B at both timepoints and PM/SCL100 at 6 months post-LTx, suggesting these may confer protection. Exposure to autoantibodies against lung-enriched targets, as opposed to ubiquitous antigens, and dnDSA conferred increased CLAD risk.

CONCLUSIONS

We have identified novel autoantibodies associated with CLAD-free survival. Our results bolster the independent relationship between autoantibodies and CLAD. We also identified autoantibody signatures that are associated with a marked increase in CLAD risk. Exposure to lung-enriched targets and dnDSA may have a reciprocal amplifying effect that lies on a tissue-specific mechanistic pathway leading to CLAD.

Repeated CXCR4 Blockade by Plerixafor Attenuates Transplant Vasculopathy in Murine Aortic Allografts

Plerixafor, a hematopoietic stem cell mobilization agent, increases the peripheral blood content of effector and regulatory T cells and may have beneficial effects on cardiac allograft vasculopathy. The aim of the current study was to evaluate its effects in a murine aortic allograft model using different application procedures. Allogeneic donor aorta grafts (n = 8/group) from C57BL/6 mice(H2b) were abdominally transplanted into CBA mice (H2k). Plerixafor application was performed either continuously for 14 d using abdominally implanted osmotic pumps (1 mg/kg/d) or i.p. with a single dose (1 and 5 mg/kg) on day 0 or pulsed injections of 1 mg/kg on days 0, 7, 14, and 21. Cell distribution was monitored by FACS. Aortic grafts were evaluated for neointima development by Elastica-van-Gieson on day 30. Immunofluorescence and intragraft gene expression analysis were performed. On day 14, significantly fewer hematopoietic stem cells were found in the bone marrow of all plerixafor-treated mice. In the pulsed application group, significantly more hematopoietic stem cells were found in the peripheral blood on day 14 (0.045 ± 0.002%; p < 0.01 [pulsed]; versus 0.0068 ± 0.002% [control]) and also more regulatory T cells. PCR revealed lower inflammatory cytokines. The luminal occlusion was significantly reduced in the pulsed treated group (33.65 ± 8.84 versus 53.13 ± 12.41) going along with decreased neointimal CD4+ T cell and plasmacytoid dendritic cell infiltration, as well as less smooth muscle cell proliferation. The application of plerixafor attenuates chronic rejection in aortic allografts via immunomodulatory effects. Injection of repeated low-dose plerixafor is the most effective application form in the aortic transplant model.

Perspective view of allogeneic IgG tumor immunotherapy

Allogeneic tumors are eradicated by host immunity; however, it is unknown how it is initiated until the report in Nature by Yaron Carmi et al. in 2015. Currently, we know that allogeneic tumors are eradicated by allogeneic IgG via dendritic cells. AlloIgG combined with the dendritic cell stimuli tumor necrosis factor alpha and CD40L induced tumor eradication via the reported and our proposed potential signaling pathways. AlloIgG triggers systematic immune responses targeting multiple antigens, which is proposed to overcome current immunotherapy limitations. The promising perspectives of alloIgG immunotherapy would have advanced from mouse models to clinical trials; however, there are only 6 published articles thus far. Therefore, we hope this perspective view will provide an initiative to promote future discussion.

Hashimoto's thyroiditis and renal transplant rejection

PURPOSE

Hashimoto's thyroiditis (HT) is a common autoimmune thyroid disorder that can disrupt thyroid function and homeostasis. As HT results from a dysregulated immune system, we hypothesized that these patients might be more susceptible to transplant failure; however, literature on this association is limited. The purpose of this study is to examine the association of HT with the risk of renal transplant failure.

METHODS

We utilized the United States Renal Database System dataset collected from 2005 to 2014 and compared the time from first renal transplant to transplant failure in end-stage renal disease (ESRD) patients with a HT diagnosis to ESRD patients without a HT diagnosis that underwent renal transplant.

RESULTS

A total of 144 ESRD patients had International Classification of Disease-9 claim codes for HT prior to renal transplant, amongst a total cohort of 90,301 renal transplant patients aged 18-100 and meeting criteria. Patients with HT were significantly more likely to be female, white, and to have a diagnosis of cytomegalovirus compared to patients without. ESRD patients with a HT diagnosis that underwent renal transplant had a significantly increased risk of renal transplant failure compared to those ESRD renal transplant patients without an HT diagnosis. There was a significantly increased adjusted hazard ratio for graft failure in patients with a HT diagnosis compared to those without.

CONCLUSION

Thyroid health and HT may play a significant role in the development of the increased risk of renal transplant failure observed in this study. Additional studies are needed to investigate the underlying mechanisms for this association.

A cofunctional grouping-based approach for non-redundant feature gene selection in unannotated single-cell RNA-seq analysis

Feature gene selection has significant impact on the performance of cell clustering in single-cell RNA sequencing (scRNA-seq) analysis. A well-rounded feature selection (FS) method should consider relevance, redundancy and complementarity of the features. Yet most existing FS methods focus on gene relevance to the cell types but neglect redundancy and complementarity, which undermines the cell clustering performance. We develop a novel computational method GeneClust to select feature genes for scRNA-seq cell clustering. GeneClust groups genes based on their expression profiles, then selects genes with the aim of maximizing relevance, minimizing redundancy and preserving complementarity. It can work as a plug-in tool for FS with any existing cell clustering method. Extensive benchmark results demonstrate that GeneClust significantly improve the clustering performance. Moreover, GeneClust can group cofunctional genes in biological process and pathway into clusters, thus providing a means of investigating gene interactions and identifying potential genes relevant to biological characteristics of the dataset. GeneClust is freely available at https://github.com/ToryDeng/scGeneClust.

Chronic lung allograft pathology lesions in two rat strain combinations

Background

Chronic lung allograft dysfunction remains an obstacle to long-term survival after lung transplantation. Two phenotypes have been described: obliterative bronchiolitis and restrictive allograft syndrome. Preclinical models are essential to analyze chronic lung allograft dysfunction pathophysiology.

Methods

Orthotopic lung transplants from 38 Lewis into Fischer 344 (Lew→F344) and 67 Brown-Norway into Lewis (BN→Lew) rats were performed in our center in the last decade. We carefully reviewed and quantified all grafts with chronic rejection (40 cases) (18 Lew→F344, 22 BN→Lew) with the aim to investigate if histological changes of chronic lung allograft dysfunction could be also detected in rat grafts.

Results

All animals showed human reminiscent histological lesions. Early chronic rejection lesions were detected in BN→Lew. End-stage chronic rejection with features of obliterative bronchiolitis was observed in 33% of Lew→F344; end-stage with restrictive allograft syndrome chronic rejection in 67% and 80% of Lew→F344 and BN→Lew, respectively. BN→Lew showed higher grades of endotheliitis, vascular fibrosis, and lower grades of lymphoid aggregates than Lew→F344 (P=0.007, P=0.043, P=0.004, respectively).

Conclusions

Chronic rejection lesions in rat lung allografts mimic those in humans. The frequent occurrence of restrictive allograft syndrome-like lesions in BN→Lew may be related to a higher degree of mismatch in this strain combination. These animal models could allow future mechanistic studies to better understand chronic lung allograft dysfunction pathogenesis.

Prevalence of red-blood-cell and non-red-blood-cell-targeted autoantibodies in alloimmunized postpartum women

BACKGROUND AND OBJECTIVES

Alloantibodies against red-blood-cell (RBC) antigens often coincide with alloantibodies against leucocytes and platelets and sometimes with autoantibodies towards various antigens. Chimerism may be one of the factors responsible for the combination of allo- and autoantibodies. Women with alloantibodies against RBC antigens causing haemolytic disease of the fetus and neonate may need to receive intrauterine transfusions. These transfusions increase not only maternal antibody formation but also fetomaternal bleeding and may enhance fetal chimerism. We determined the prevalence of and risk factors for autoantibodies against some common clinical target antigens, in alloimmunized women after IUT.

MATERIALS AND METHODS

We tested for autoantibodies against RBC, anti-thyroid peroxidase, anti-extractable nuclear antigens, anti-cyclic citrullinated proteins and anti-tissue transglutaminase. Women with and without autoantibodies were compared for age; number of RBC alloantibodies, pregnancies and IUTs, and other factors that may play a role in immunization.

RESULTS

Non-RBC-targeted autoantibodies were present in 40 of 258 tested women (15·5%, with 90% anti-TPO specificity), comparable to the prevalence reported in healthy Dutch women of these ages. Surprisingly, compared with women who had a single RBC alloantibody, a significantly higher proportion of women with multiple RBC alloantibodies had autoantibodies (5·3% and 18·4%, respectively; odds ratio 4·06, 95% CI: 1·20-13·7). Other characteristics of women with and without autoantibodies were not different.

CONCLUSION

Multiple RBC alloantibodies after extensive allogeneic exposure during pregnancy and presumed increased fetomaternal chimerism are not associated with (selected) autoantibodies. Lack of allo-RBC multi-responsiveness seems associated with decreased auto(-TPO) antibody formation.

Breath volatile organic compounds of lung transplant recipients with and without chronic lung allograft dysfunction

INTRODUCTION

Chronic lung allograft dysfunction with its clinical correlative of bronchiolitis obliterans syndrome (BOS) remains the major limiting factor for long-term graft survival. Currently there are no established methods for the early diagnosis or prediction of BOS. To assess the feasibility of breath collection as a non-invasive tool and the potential of breath volatile organic compounds (VOC) for the early detection of BOS, we compared the breath VOC composition between transplant patients without and different stages of BOS.

METHODS

75 outpatients (25 BOS stage 0, 25 BOS stage 1 + 2, 25 BOS stage 3) after bilateral lung transplantation were included. Exclusion criteria were active smoking, oxygen therapy and acute infection. Patients inhaled room air through a VOC and sterile filter and exhaled into an aluminum reservoir tube. Breath was loaded directly onto Tenax^® TA adsorption tubes and was subsequently analyzed by gas-chromatography/mass-spectrometry.

RESULTS

The three groups were age and gender matched, but differed with respect to time since transplantation, the spectrum of underlying disease, and treatment regimes. Relative to patients without BOS, BOS stage 3 patients showed a larger number of different VOCs, and more pronounced differences in the level of VOCs as compared to BOS stage 1 + 2 patients. Logistic regression analysis found no differences between controls and BOS 1 + 2, but four VOCs (heptane, isopropyl-myristate, ethyl-acetate, ionone) with a significant contribution to the discrimination between controls and BOS stage 3. A combination of these four VOCs separated these groups with an area under the curve of 0.87.

CONCLUSION

Breath sample collection using our reservoir sampler in the clinical environment was feasible. Our results suggest that breath VOCs can discriminate severe BOS. However, convincing evidence for VOCs with a potential to detect early onset BOS is lacking.

Autologous subcutaneous adipose tissue transplants improve adipose tissue metabolism and reduce insulin resistance and fatty liver in diet-induced obesity rats

Long‐term dietary and pharmacological treatments for obesity have been questioned, particularly in individuals with severe obesity, so a new approach may involve adipose tissue transplants, particularly autologous transplants. Thus, the aim of this study was to evaluate the metabolic effects of autologous subcutaneous adipose tissue (SAT) transplants into two specific intraabdominal cavity sites (omental and retroperitoneal) after 90 days. The study was performed using two different diet‐induced obesity (DIO) rat models: one using a high‐fat diet (HFD) and the other using a high‐carbohydrate diet (HCHD). Autologous SAT transplant reduced hypertrophic adipocytes, improved insulin sensitivity, reduced hepatic lipid content, and fasting serum‐free fatty acids (FFAs) concentrations in the two DIO models. In addition, the reductions in FFAs and glycerol were accompanied by a greater reduction in lipolysis, assessed via the phosphorylation status of HSL, in the transplanted adipose tissue localized in the omentum compared with that localized in the retroperitoneal compartment. Therefore, the improvement in hepatic lipid content after autologous SAT transplant may be partially attributed to a reduction in lipolysis in the transplanted adipose tissue in the omentum due to the direct drainage of FFAs into the liver. The HCHD resulted in elevated fasting and postprandial serum insulin levels, which were dramatically reduced by the autologous SAT transplant. In conclusion, the specific intraabdominal localization of the autologous SAT transplant improved the carbohydrate and lipid metabolism of adipose tissue in obese rats and selectively corrected the metabolic parameters that are dependent on the type of diet used to generate the DIO model.

Zbtb7a induction in alveolar macrophages is implicated in anti-HLA-mediated lung allograft rejection

Chronic rejection significantly limits long-term success of solid organ transplantation. De novo donor-specific antibodies (DSAs) to mismatched donor human leukocyte antigen after human lung transplantation predispose lung grafts to chronic rejection. We sought to delineate mediators and mechanisms of DSA pathogenesis and to define early inflammatory events that trigger chronic rejection in lung transplant recipients and obliterative airway disease, a correlate of human chronic rejection, in mouse. Induction of transcription factor zinc finger and BTB domain containing protein 7a (Zbtb7a) was an early response critical in the DSA-induced chronic rejection. A cohort of human lung transplant recipients who developed DSA and chronic rejection demonstrated greater Zbtb7a expression long before clinical diagnosis of chronic rejection compared to nonrejecting lung transplant recipients with stable pulmonary function. Expression of DSA-induced Zbtb7a was restricted to alveolar macrophages (AMs), and selective disruption of Zbtb7a in AMs resulted in less bronchiolar occlusion, low immune responses to lung-restricted self-antigens, and high protection from chronic rejection in mice. Additionally, in an allogeneic cell transfer protocol, antigen presentation by AMs was Zbtb7a-dependent where AMs deficient in Zbtb7a failed to induce antibody and T cell responses. Collectively, we demonstrate that AMs play an essential role in antibody-induced pathogenesis of chronic rejection by regulating early inflammation and lung-restricted humoral and cellular autoimmunity.

Autologous and Allogenous Antibodies in Lung and Islet Cell Transplantation

The field of organ transplantation has undoubtedly made great strides in recent years. Despite the advances in donor-recipient histocompatibility testing, improvement in transplantation procedures, and development of aggressive immunosuppressive regimens, graft-directed immune responses still pose a major problem to the long-term success of organ transplantation. Elicitation of immune responses detected as antibodies to mismatched donor antigens (alloantibodies) and tissue-restricted self-antigens (autoantibodies) are two major risk factors for the development of graft rejection that ultimately lead to graft failure. In this review, we describe current understanding on genesis and pathogenesis of antibodies in two important clinical scenarios: lung transplantation and transplantation of islet of Langerhans. It is evident that when compared to any other clinical solid organ or cellular transplant, lung and islet transplants are more susceptible to rejection by combination of allo- and autoimmune responses.

"Mouse Clone Model" for evaluating the immunogenicity and tumorigenicity of pluripotent stem cells

To investigate the immune-rejection and tumor-formation potentials of induced pluripotent stem cells and other stem cells, we devised a model—designated the “Mouse Clone Model”—which combined the theory of somatic animal cloning, tetraploid complementation, and induced pluripotent stem cells to demonstrate the applicability of stem cells for transplantation therapy.

Decellularized matrices for cardiovascular tissue engineering

Cardiovascular disease (CVD) is one of the leading causes of death in the Western world. The replacement of damaged vessels and valves has been practiced since the 1950's. Synthetic grafts, usually made of bio-inert materials, are long-lasting and mechanically relevant, but fail when it comes to "biointegration". Decellularized matrices, instead, can be considered biological grafts capable of stimulating in vivo migration and proliferation of endothelial cells (ECs), recruitment and differentiation of mural cells, finally, culminating in the formation of a biointegrated tissue. Decellularization protocols employ osmotic shock, ionic and non-ionic detergents, proteolitic digestions and DNase/RNase treatments; most of them effectively eliminate the cellular component, but show limitations in preserving the native structure of the extracellular matrix (ECM). In this review, we examine the current state of the art relative to decellularization techniques and biological performance of decellularized heart, valves and big vessels. Furthermore, we focus on the relevance of ECM components, native and resulting from decellularization, in mediating in vivo host response and determining repair and regeneration, as opposed to graft corruption.

Facial and hand allotransplantation

Vascularized composite allotransplantation (VCA) is a novel therapeutic option for treatment of patients suffering from limb loss or severe facial disfigurement. To date, 72 hand and 19 facial transplantations have been performed worldwide. VCA in hand and facial transplantation is a complex procedure requiring a multidisciplinary team approach and extensive surgical planning. Despite good functional outcome, courses after hand and facial transplantation have been complicated by skin rejection. Long-term immunosuppression remains a necessity in VCA for allograft survival. To widen the scope of these quality-of-life-improving procedures, minimization of immunosuppression to limit risks and side effects is needed.

Immunology of liver transplantation

In comparison with other solid-organ transplants, liver allografts are immunologically privileged. Allografts are rejected by immune reactions of the host, and clinical therapy for liver allografts includes immunosuppression to prevent rejection. Orthotopic liver transplant causes systemic donor-specific T-cell tolerance. In addition, antigens introduced into hepatocytes or the portal vein cause tolerance. The basic mechanism in liver tolerance may include continuous exposure of diverse liver cell types to endotoxin derived from intestinal bacteria. This exposure promotes the expression of cytokines, antigen-presenting molecules, and costimulatory signals that inactivate T cells, partly by effects on liver antigen-presenting cells. A simple, reliable, noninvasive assay to evaluate antidonor alloreactivity may be important in implementing these approaches in the laboratory and clinic.

B-lymphocyte lineage cells and the respiratory system

Adaptive humoral immune responses in the airways are mediated by B cells and plasma cells that express highly evolved and specific receptors and produce immunoglobulins of most isotypes. In some cases, such as autoimmune diseases or inflammatory diseases caused by excessive exposure to foreign antigens, these same immune cells can cause disease by virtue of overly vigorous responses. This review discusses the generation, differentiation, signaling, activation, and recruitment pathways of B cells and plasma cells, with special emphasis on unique characteristics of subsets of these cells functioning within the respiratory system. The primary sensitization events that generate B cells responsible for effector responses throughout the airways usually occur in the upper airways, tonsils, and adenoid structures that make up the Waldeyer ring. On secondary exposure to antigen in the airways, antigen-processing dendritic cells migrate into secondary lymphoid organs, such as lymph nodes, that drain the upper and lower airways, and further B-cell expansion takes place at those sites. Antigen exposure in the upper or lower airways can also drive expansion of B-lineage cells in the airway mucosal tissue and lead to the formation of inducible lymphoid follicles or aggregates that can mediate local immunity or disease.

Chronic rejection: a significant role for Th17-mediated autoimmune responses to self-antigens

Despite progress in the field of organ transplantation for improvement in graft survival and function, long-term graft function is still limited by the development of chronic allograft rejection. Various immune-mediated and nonimmune-mediated processes have been postulated in the pathogenesis of chronic rejection. In this review, the authors discuss the important role of alloimmune responses to donor-specific antigens and autoimmune responses to tissue restricted self-antigens in the immunopathogenesis of chronic rejection following solid organ transplantation. In particular, the authors discuss the role of induction of Th17-type autoimmune responses and the crosstalk between autoimmune and alloimmune responses. These self-perpetuate each other leading to activation of profibrotic and proinflammatory cascades that ultimately result in the development of chronic rejection.

Anti-major histocompatibility complex-induced obliterative airway disease: selective role for CD4 and CD8 T cells in inducing immune responses to self-antigens

BACKGROUND

The goal of this study was to define the role of T-cell sub-sets in the pathogenesis of autoimmunity-induced obliterative airway disease by passive transfer of CD8+ or CD4+ T cells.

METHODS

Antibodies to major histocompatibility complex (MHC) class I were administered intrabronchially into C57BL/6 animals. Lungs were analyzed by histopathology and immunohistochemistry. The CD8+ and CD4+ T-cell sub-sets were purified from the lung-infiltrating cells and intrabronchially transferred. Frequency of cells secreting interleukin-17, interferon-γ, or interleukin-10 to self-antigens was enumerated by enzyme-linked immunospot assay. Myeloperoxidase and antibodies to self-antigens were determined by enzyme-linked immunosorbent assay. Cytokine and growth factor expression was determined by quantitative reverse-transcription polymerase chain reaction.

RESULTS

Passive transfer of lung-infiltrating CD8 T cells isolated after anti-MHC class I administration, along with sub-optimal dose, induced significantly higher cellular infiltration (89.3% ± 7.9% vs 62.8% ± 10.1%, p < 0.05) vs the CD4 transfer group. Further, passive transfer of CD8 cells resulted in infiltration of neutrophils and macrophages, suggesting early injury response. In contrast, passive transfer of CD4+ T cells induced a significantly higher degree of luminal occlusion (29.3% ± 5.6% vs 8.6 ± 2.5%, p < 0.05) and fibrosis (54.4% ± 9.3% vs 10.2% ± 2.4%, p < 0.05) vs the CD8 group and B-cell infiltration, leading to immune responses to lung-associated self-antigens and fibrosis.

CONCLUSION

Ligation of MHC molecules by its specific antibodies induced early injury with neutrophils, macrophages, and CD8 T cells, which leads to exposure of cryptic self-antigens and their presentation by the infiltrating CD4+ T cells and B cells, leading to the development of immune responses to self-antigens and culminating in obliterative airway disease.

Endothelium and Regulatory Inflammatory Mechanisms During Organ Rejection

Endothelial integrity is mandatory for physiologic organ function; however, endothelium dysfunction can be caused by systemic inflammation, occurring during sepsis or organ rejection after transplantation. This article will address our current understanding of endothelial involvement in organ transplantation and rejection. Overall, more detailed studies focusing on the endothelial modulation after organ transplantation would be necessary to investigate the role of endothelium activation during organ rejection.

Development of antibody-tagged nanoparticles for detection of transplant rejection using biomagnetic sensors

Organ transplantation is a life-saving procedure and the preferred method of treatment for a growing number of disease states. The advent of new immunosuppressants and improved care has led to great advances in both patient and graft survival. However, acute T-cell-mediated graft rejection occurs in a significant quantity of recipients and remains a life-threatening condition. Acute rejection is associated with decrease in long-term graft survival, demonstrating a need to carefully monitor transplant patients. Current diagnostic criteria for transplant rejection rely on invasive tissue biopsies or relatively nonspecific clinical features. A noninvasive way is needed to detect, localize, and monitor transplant rejection. Capitalizing on advances in targeted contrast agents and magnetic-based detection technology, we developed anti-CD3 antibody-tagged nanoparticles. T cells were found to bind preferentially to antibody-tagged nanoparticles, as identified through light microscopy, transmission electron microscopy, and confocal microscopy. Using mouse skin graft models, we were also able to demonstrate in vivo vascular delivery of T-cell targeted nanoparticles. We conclude that targeting lymphocytes with magnetic nanoparticles is conducive to developing a novel, noninvasive strategy for identifying transplant rejection.

T regulatory cells play a significant role in modulating MHC class I antibody-induced obliterative airway disease

The molecular mechanisms leading to the development of chronic lung allograft dysfunction following de novo development of antibodies to mismatched donor MHC remain undefined. We demonstrated that intrabronchial administration of antibodies to MHC class I resulted in induction of both innate and adaptive cellular immune responses characterized by a predominance of Th17 specific to lung associated self-antigens Kα1-tubulin and Collagen-V leading to the development of obliterative airway lesions (OAD), correlate of chronic rejection following human lung transplantation. To determine the role of regulatory T cells (Treg) in the pathogenesis of OAD, we administered anti-MHC class I to mice, in which Treg were depleted by conditional ablation of FoxP3+cells. Under this condition, we observed a threefold increase in pulmonary cellular infiltration, luminal occlusion and fibrous deposition when compared anti-MHC class I Ab administered mice maintaining FoxP3. OAD lesions were accompanied with enhanced accumulation of neutrophils along with self-antigen-specific Th17 and humoral responses. However, IL-17-blockade or adoptive transfer of Treg abrogated OAD. We conclude that Treg exerts a suppressive effect on anti-MHC induced IL-8-mediated neutrophil infiltration and innate immune responses that leads to inhibition of Th17 immune responses to lung associated self-antigens which is critical for development of OAD.

Complement activation is not required for obliterative airway disease induced by antibodies to major histocompatibility complex class I: Implications for chronic lung rejection

BACKGROUND

The role of non-complement activating antibodies (ncAbs) to mismatched donor human leukocyte antigen (HLA) in the pathogenesis of chronic lung rejection is not known. We used a murine model of obliterative airway disease (OAD) induced by Abs to major histocompatibility major histocompatibility complex (MHC) class I and serum from donor-specific Abs developed in human lung transplant (LTx) recipients to test the role of ncAbs in the development of OAD and bronchiolitis obliterans syndrome (BOS).

METHODS

Anti-MHC ncAbs were administered intrabronchially in B.10 mice or in C3 knockout (C3KO) mice. Lungs were analyzed by histopathology. Lymphocytes secreting interleukin (IL)-17, interferon-γ, or IL-10 to collagen V and K-α1 tubulin (Kα1T) were enumerated by enzyme-linked immunospot assay. Serum antibodies to collagen V and Kα1T were determined by enzyme-linked immunosorbent assay. Cytokine and growth factor expression in lungs was determined by real-time polymerase chain reaction. Donor-specific Abs from patients with BOS and control BOS-negative LTx recipients were analyzed by C1q assay.

RESULTS

Administration of ncAbs in B.10 mice or C3KO resulted in OAD lesions. There were significant increases in IL-17- and interferon-γ-secreting cells to collagen V and Kα1T, along with serum Abs to these antigens. There was also augmented expression of monocyte chemotactic protein-1, IL-6, IL-1β, vascular endothelial growth factor, transforming growth factor-β, and fibroblastic growth factor in mice administered ncAbs by Day 3. Among 5 LTx recipients with BOS, only 1 had C1q binding donor-specific Abs.

CONCLUSION

Complement activation by Abs to MHC class I is not required for development of OAD and human BOS. Therefore, anti-MHC binding to epithelial and endothelial cells can directly activate pro-fibrotic and pro-inflammatory cascades leading to immune response to self-antigens and chronic rejection.

Antibodies to MHC class II molecules induce autoimmunity: critical role for macrophages in the immunopathogenesis of obliterative airway disease

Previous studies have shown that intrabronchial administration of antibodies (Abs) to MHC class I resulted in development of obliterative airway disease (OAD), a correlate of chronic human lung allograft rejection. Since development of Abs specific to mismatched donor HLA class II have also been associated with chronic human lung allograft rejection, we analyzed the role of Abs to MHC class II in inducing OAD. Administration of MHC class II Abs (M5/114) to C57BL/6 mice induced the classical features of OAD even though MHC class II expression is absent de novo on murine lung epithelial and endothelial cells. The induction of OAD was accompanied by enhanced cellular and humoral immune responses to self-antigens (Collagen V and K- α1Tubulin). Further, lung-infiltrating macrophages demonstrated a switch in their phenotype predominance from MΦ1 (F4/80⁺CD11c⁺) to MΦ2 (F4/80⁺CD206⁺) following administration of Abs and prior to development of OAD. Passive administration of macrophages harvested from animals with OAD but not from naïve animals induced OAD lesions. We conclude that MHC class II Abs induces a phenotype switch of lung infiltrating macrophages from MΦ1 (F4/80⁺CD11c⁺) to MΦ2 (F4/80⁺CD206⁺) resulting in the breakdown of self-tolerance along with an increase in autoimmune Th17 response leading to OAD.

IDO-competent-DCs induced by IFN-γ attenuate acute rejection in rat liver transplantation

PURPOSE

We established a stable rat model of liver transplantation using Sprague-Dawley rats and Wistar rats in order to investigate the role of the IDO gene in acute rejection after rat liver transplantation.

METHODS

IDO gene expression and IDO enzyme activity were quantified in liver syngeneic grafts and allografts using microdialysis-HPLC. Liver allografts were evaluated for IDO expression by histopathology. We measured liver function-related biomarkers in liver allografts which were re-infused with untreated or IFN-γ-treated dendritic cells (DCs).

RESULTS

We found a significant increase in IDO gene expression and IDO enzyme activity in liver allografts compared the sham and syngeneic graft groups. There was a significant correlation between the number of IDO-positive cells and severity of acute rejection. IDO gene expression and enzyme activity was upregulated in the IFN-γ-treated DC group within 7 days after transplantation compared to the untreated DC group and survival rates were significantly improved.

CONCLUSIONS

Our results suggested that IDO gene expression correlates with the severity of acute rejection and that IFN-γ-induced IDO-positive DCs may attenuate acute rejection and catalyze local tryptophan metabolism via IDO enzyme expression, leading to immune tolerance after liver transplantation.

Inhibition of renin angiotensin aldosterone system causes abrogation of obliterative airways disease through inhibition of tumor necrosis factor-α-dependant interleukin-17

BACKGROUND

Alloimmune-induced immune responses to self-antigens are involved in the development of chronic lung allograft rejection. Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) have been shown to modulate autoimmune diseases. This study investigated the effect of modulation of the renin angiotensin aldosterone system (RAAS) a murine model of obliterative airways disease (OAD).

METHODS

Major histocompatibility complex (MHC) class I antibodies were administered intrabronchially to C57Bl/6 mice on Days 1, 2, 3, and 6, and weekly thereafter. ACEI/ARB (10 mg/kg/day) were administered in water 5 days before antibody administration. Antibodies were analyzed by enzyme-linked immunosorbent assay, cytokines by Luminex, Th-frequency by enzyme-linked immunosorbent spot, and transcription factors by Western blotting and real-time polymerase chain reaction.

RESULTS

Significant decreases (50%-70%) in airway lesions and fibrous deposition were noted in lungs at Day 30 in the animals administered ACEI and ARB vs controls. Antibody concentrations to self-antigens also decreased from 14 ± 21 to 62 ± 18 μg/ml for collagen V and from 263 ± 43 to 84 ± 28 μg/ml for K-α1 tubulin. Th-precursor frequency and cytokine analysis showed increased interleukin (IL)-10 (3-fold increase) and decreased levels of IL-6 (3.4-fold) and IL-17 (4-fold decrease; p < 0.05) in ACEI and ARB groups. There was also messenger RNA level downregulation of tumor necrosis factor-α (8.6-fold) and p38/mitogen-activated protein (MAP)kinase (3.1-fold) in the treatment groups.

CONCLUSIONS

Our results demonstrate that modulation of RAAS leads to downregulation of IL-17 through tumor necrosis factor-α-dependant IL-6 through p38/MAPKinase pathway and thus abrogation of anti-MHC-induced OAD.

A shift in the collagen V antigenic epitope leads to T helper phenotype switch and immune response to self-antigen leading to chronic lung allograft rejection

Immune responses to human leucocyte antigen (HLA) and self-antigen collagen V (Col-V) have been proposed in the pathogenesis of chronic rejection (bronchiolitis obliterans syndrome, BOS) following human lung transplantation (LTx). In this study, we defined the role for the shift in immunodominant epitopes of Col-V in inducing T helper phenotype switch leading to immunity to Col-V and BOS. Sera and lavage from BOS(+) LTx recipients with antibodies to Col-V were analysed. Two years prior to BOS, patients developed antibodies to both Col-V,α1(V) and α2(V) chains. However, at clinical diagnosis of BOS, antibodies became restricted to α1(V). Further, lung biopsy from BOS(+) patients bound to antibodies to α1(V), indicating that these epitopes are exposed. Fourteen Col-V peptides [pep1-14, pep1-4 specific to α1(V), pep5-8 to α1,2(V) and pep9-14 to α2(V)] which bind to HLA-DR4 and -DR7, demonstrated that prior to BOS, pep 6, 7, 9, 11 and 14 were immunodominant and induced interleukin (IL)-10. However, at BOS, the response switched to pep1, 4 and 5 and induced interferon (IFN)-γ and IL-17 responses, but not IL-10. The T helper (Th) phenotype switch is accompanied by decreased frequency of regulatory T cells (T(regs) ) in the lavage. LTx recipients with antibodies to α1(V) also demonstrated increased matrix metalloproteinase (MMP) activation with decreased MMP inhibitor, tissue inhibitor of metalloproteinase (TIMP), suggesting that MMP activation may play a role in the exposure of new Col-V antigenic epitopes. We conclude that a shift in immunodominance of self-antigenic determinants of Col-V results in induction of IFN-γ and IL-17 with loss of tolerance leading to autoimmunity to Col-V, which leads to chronic lung allograft rejection.

Profiling of differentially expressed genes in haemophilia A with inhibitor

Inhibitor development is the most significant complication in the therapy of haemophilia A (HA) patients. In spite of many studies, not much is known regarding the mechanism underlying inhibitor development. To understand the mechanism, we analysed profiles of differentially expressed genes (DEGs) between inhibitor and non-inhibitor HA via a microarray technique. Twenty unrelated Korean HAs were studied: 11 were non-inhibitor and nine were HA with inhibitor (≥5 BU mL(-1)). Microarray analysis was conducted using a Human Ref-8 expression Beadchip system (Illumina) and the data were analysed using Beadstudio software. We identified 545 DEGs in inhibitor HA as compared with the non-inhibitor patients; 384 genes were up-regulated and 161 genes were down-regulated. Among them, 75 genes whose expressions were altered by at least two-fold (>+2 or <-2) were selected and classified via the PANTHER classification method. The expressions of signal transduction and immunity-related genes differed significantly in the two groups. For validation of the DEGs, semi-quantitative RT-PCR (semi-qRT-PCR) was conducted with the six selected DEGs. The results corresponded to the microarray data, with the exception of one gene. We also examined the expression of the genes associated with the antigen presentation process via real-time PCR. The average levels of IL10, CTLA4 and TNFα slightly reduced, whereas that of IFNγ increased in the inhibitor HA group. We are currently unable to explain whether this phenomenon is a function of the inhibitor-inducing factor or is an epiphenomenon of antibody production. Nevertheless, our results provide a possible explanation for inhibitor development.

Immunologic basis of graft rejection and tolerance following transplantation of liver or other solid organs

Transplantation of organs between genetically different individuals of the same species causes a T cell-mediated immune response that, if left unchecked, results in rejection and graft destruction. The potency of the alloimmune response is determined by the antigenic disparity that usually exists between donors and recipients and by intragraft expression of proinflammatory cytokines in the early period after transplantation. Studies in animal models have identified many molecules that, when targeted, inhibit T-cell activation. In addition, some of these studies have shown that certain immunologic interventions induce transplantation tolerance, a state in which the allograft is specifically accepted without the need for chronic immunosuppression. Tolerance is an important aspect of liver transplantation, because livers have a unique microenvironment that promotes tolerance rather than immunity. In contrast to the progress achieved in inducing tolerance in animal models, patients who receive transplanted organs still require nonspecific immunosuppressant drugs. The development of calcineurin inhibitors has reduced the acute rejection rate and improved short-term, but not long-term, graft survival. However, long-term use of immunosuppressive drugs leads to nephrotoxicity and metabolic disorders, as well as manifestations of overimmunosuppression such as opportunistic infections and cancers. The status of pharmacologic immunosuppression in the clinic is therefore not ideal. We review recently developed therapeutic strategies to promote tolerance to transplanted livers and other organs and diagnostic tools that might be used to identify patients most likely to accept or reject allografts.