Human Lung Transplantation Research Articles

(218) - Down Regulation of microRNA-21 Is Significantly Associated with Signaling and Activation of the Toll-Like Receptor in Human Lung Transplant Recipients with Primary Graft Dysfunction

(218) - Down Regulation of microRNA-21 Is Significantly Associated with Signaling and Activation of the Toll-Like Receptor in Human Lung Transplant Recipients with Primary Graft Dysfunction

B Cell-Activating Transcription Factor Plays a Critical Role in the Pathogenesis of Anti-Major Histocompatibility Complex-Induced Obliterative Airway Disease.

Antibodies (Abs) against major histocompatibility complex (MHC) results in T helper-17 (Th17)-mediated immunity against lung self-antigens (SAgs), K-α1 tubulin and collagen V and obliterative airway disease (OAD). Because B cell-activating transcription factor (BATF) controls Th17 and autoimmunity, we proposed that BATF may play a critical role in OAD. Anti-H2K(b) was administered intrabronchially into Batf (-/-) and C57BL/6 mice. Histopathology of the lungs on days 30 and 45 after Ab administration to Batf (-/-) mice resulted in decreased cellular infiltration, epithelial metaplasia, fibrosis, and obstruction. There was lack of Abs to SAgs, reduction of Sag-specific interleukin (IL)-17 T cells, IL-6, IL-23, IL-17, IL-1β, fibroblast growth factor-6, and CXCL12 and decreased Janus kinase 2, signal transducer and activator of transcription 3 (STAT3), and retinoid-related orphan receptor γT. Further, micro-RNA (miR)-301a, a regulator of Th17, was reduced in Batf (-/-) mice in contrast to upregulation of miR-301a and downregulation of protein inhibitor of activated STAT3 (PIAS3) in anti-MHC-induced OAD animals. We also demonstrate an increase in miR-301a in the bronchoalveolar lavage cells from lung transplant recipients with Abs to human leukocyte antigen. This was accompanied by reduction in PIAS3 mRNA. Therefore, we conclude that BATF plays a critical role in the immune responses to SAgs and pathogenesis of anti-MHC-induced rejection. Targeting BATF should be considered for preventing chronic rejection after human lung transplantation.

Inhibiting Integrin αvβ5 Reduces Ischemia-Reperfusion Injury in an Orthotopic Lung Transplant Model in Mice.

Primary graft dysfunction after lung transplantation is the leading cause of morbidity and mortality in the immediate posttransplant period and is characterized by endothelial and epithelial barrier disruption and the leakage of protein-rich edema fluid. Integrins are cell surface receptors that have an important role in maintenance of the cell barrier, and inhibition of integrins, such as αvβ5, can diminish alveolar flooding in lung injury models. We hypothesized that inhibition of αvβ5 during donor lung cold ischemia would reduce endothelial permeability during reperfusion. Using an orthotopic single lung transplantation model with and without cold ischemia, donor lungs were perfused with αvβ5-blocking antibody (ALULA) or control antibody at the time of collection, followed by transplantation, 8 h of reperfusion, and the measurement of lung injury parameters. Prolonged cold ischemia (18 h) produced increases in extravascular lung water, protein permeability, and neutrophilic alveolitis and decreased oxygenation compared with lungs without cold ischemia. Perfusion of lungs with αvβ5 antibody versus control antibody protected donor lungs from injury and significantly improved oxygenation. In summary, αvβ5 integrin blockade protects from the development of ischemia-reperfusion lung injury and is a promising approach to preventing primary graft dysfunction in human lung transplant procedures.

Therapeutic lymphangiogenesis ameliorates established acute lung allograft rejection.

Lung transplantation is the only viable option for patients suffering from otherwise incurable end-stage pulmonary diseases such as chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis. Despite aggressive immunosuppression, acute rejection of the lung allograft occurs in over half of transplant recipients, and the factors that promote lung acceptance are poorly understood. The contribution of lymphatic vessels to transplant pathophysiology remains controversial, and data that directly address the exact roles of lymphatic vessels in lung allograft function and survival are limited. Here, we have shown that there is a marked decline in the density of lymphatic vessels, accompanied by accumulation of low-MW hyaluronan (HA) in mouse orthotopic allografts undergoing rejection. We found that stimulation of lymphangiogenesis with VEGF-C156S, a mutant form of VEGF-C with selective VEGFR-3 binding, alleviates an established rejection response and improves clearance of HA from the lung allograft. Longitudinal analysis of transbronchial biopsies from human lung transplant recipients demonstrated an association between resolution of acute lung rejection and decreased HA in the graft tissue. Taken together, these results indicate that lymphatic vessel formation after lung transplantation mediates HA drainage and suggest that treatments to stimulate lymphangiogenesis have promise for improving graft outcomes.

De novo development of dsa and autoantibodies to lung associated self-antigens is associated with upregulation of transcription factor Zbtb7a: Role in chronic rejection following human lung transplantation

Aim Administration of anti-MHC class I (H-2Kb) leads to induction of transcription factor Zinc finger and BTB domain containing 7A (Zbtb7a) leading to inflammatory cascade and chronic rejection in a murine obliterative airway disease model. Development of DSA and Abs to lung-associated self-antigens (K-alpla-1 Tubulin (K α 1T) and Collagen V (Col-V) are significant risk factors in development of bronchiolitis obliterans syndrome (BOS) following human lung transplantation (LTx). The current study focused on the role of Zbtb7a in development of BOS following human LTx. Methods We analyzed 25 LTx patients that developed BOS years after LTx as well as 10 stable LTx performed at Barnes-Jewish Washington University. Kinetics of Zbtb7a expression was studied in bronchoalveolar lavage (BAL) cells. Quantitative PCR analysis was performed to evaluate mRNA levels and data was compared with the DSA, autoantibody and immunosuppression. Results Increases in the Zbtb7a expression was observed in BAL cells collected at visits immediately prior to clinical BOS diagnosis compared with earlier visits. Zbtb7a expression was significantly (p 0.01) increased (150%) in pre-BOS BAL cells. On the contrary, stable patients did not demonstrate any change in Zbtb7a levels. All of the BOS+ patients had developed DSA and Abs to K α 1T and Col-V. Zbtb7a expression in 13 patients who received Ab directed therapy following DSA demonstrated significant reduction along with decrease in DSA and Abs to lung self-antigens. Therefore, Zbtb7a activation is an important inducer of the DSA and autoantibody. Conclusions Up regulation of Zbtb7a was positively associated with de novo DSA and Abs to lung-associated self-antigens. Ab directed therapy significantly reduced Zbtb7a expression. We propose that Zbtb7a may be used as a prognostic marker in evaluating Ab-induced inflammation in the lung as well as efficacy of Ab directed therapy following development of DSA.

Detection of donor cell-free dna using digital PCR in lung transplant recipients with graft rejection and infection

Aim Bronchoscopy and transbronchial lung biopsy are currently the gold standard for detection of acute rejection and chronic dysfunction (bronchiolitis obliterans syndrome [BOS]) following human lung transplantation (LTx). However, these procedures are expensive and invasive. Up to now, few new methods have demonstrated clinical utility, therefore development of noninvasive biomarkers of rejection are needed. Methods We developed, optimized and validated a novel method to rapidly quantify donor-derived circulating cell free DNA (DcfDNA) as a potential non-invasive biomarker for lung allograft rejection. The method involves the development of a panel of probes that specifically target a unique sequence on human leucocyte antigen (HLA) alleles. After Tx, donor/recipient probes are chosen based on the mismatched HLA loci, followed by droplet digital PCR used as a quantitative assay to accurately track the trace amount of DcfDNA in a 100–1000 fold excess of recipient background DNA. Result With as low as 30pg genomic DNA, we are able to provide an absolute measurement of the copy numbers of target DNA molecule. Each probe was specific as the average false positive rate was about 1 per 100,000 reads. With constant level of background cfDNA mimicking recipient cfDNA, another serially diluted cfDNA was used as donor cfDNA were spiked in. The fraction of spiked cfDNA was measured and calculated. A quantitative linearity was observed spanning all dilutions. The fraction of spiked cfDNA was accurately measured down to 0.2% of total cfDNA. We applied this method to a pilot set of sixty sera from nineteen LTx recipients grouped into biopsy-proven acute rejection, BOS or stable. The level of DcfDNA was significantly elevated in patients with acute rejection (7.9 ± 2.2%, n = 16), compared to stable (2.76 ± 1.4%, n = 22) or BOS (1.70 ± 0.35, n = 22). We also demonstrate significant elevations of DcfDNA in the stable or BOS patients undergoing severe lung infection (4.6 ± 1.82, n = 16), suggesting a higher level of turnover rate in the grafted organ during infection. Conclusions We developed and validated a clinically feasible application of digital PCR to quantify DcfDNA, which can be used as a non-invasive biomarker for acute lung allograft rejection and infection.

OR7 Antibodies to MHC class I induce transcription factor Zbtb7a and regulate development of autoimmunity leading to chronic rejection

Aim Chronic rejection, bronchiolitis obliterans syndrome (BOS), is a major hurdle following human lung transplantation. Antibodies (Ab) to HLA (DSA) and lung-associated antigens (Collagen V (Col-V) and K-alpha-1 Tubulin (K α 1T) have been associated with development of BOS. Our goal was to demonstrate early events (genes and their role in inflammation) associated with administration of anti-MHC class I (H-2 Kb) into murine (C57BL/6) lungs that precede cellular and humoral autoimmunity and chronic rejection. Methods We analyzed molecular signatures arising from anti-MHC administration by genechip microarray. Zbtb7a was selected for functional analysis. siRNA-Lentivirus was used to knockdown Zbtb7a in lungs to study its role in Ab induced chronic rejection. Kinetics of Ab development and T cell responses was tested by ELISA and ELISPOT. Changes in leukocyte profile were analyzed by flow cytometry and gene expression levels by real-time PCR. Results In genechip assay, 12 genes including Zbtb7a were significantly ( p 1.5-fold) at 4 h post Ab administration. Use of siRNA-Lentivirus knocked down Zbtb7a expression. Following anti-MHC I, Zbtb7a knockdown demonstrated significant ( p α 1T and anti-Col-V, and remained free from inflammation and fibrosis. Further, anti-MHC elicited lower K α 1T and Col-V specific Th17 and Th1 cells. Moreover, less infiltration of neutrophil and B cell were seen in lungs and decreased levels of B cell (CXCL13) and neutrophil (CXCL15) chemoattractants were observed. Conclusions We demonstrate that DSA activates unique molecular signature involved in lung autoimmunity. Zbtb7a, as a transcription factor induced by DSA, is a “master regulator” of B and T cell development and has novel inflammatory functions leading to chronic rejection. By targeted knockdown, we established that Zbtb7a has an obligatory role in the amplification of inflammatory circuits where its loss rendered protection from Ab induced obliterative airway disease.

OR15 De novo development of DSA following human lung transplantation is associated with changes on circulating micro-RNA involved in T and B cell regulation and fibrogenesis

Aim Chronic rejection (bronchiolitis obliterans syndrome (BOS)) is the major limitation for long-term survival after lung transplantation (LTx). Its pathogenesis, however, is poorly understood and no effective predictive biomarkers have been identified. Several studies have shown that de novo development of antibodies to donor mismatched HLA (DSA) is a significant risk factor for the development of BOS. Methods Thirty LTx recipients from Barnes Jewish Hospital/Washington University School of Medicine (10 stable DSA− and BOS−, 10 DSA+ BOS− and 10 DSA+ and BOS+) were analyzed for circulating microRNAs (miRNAs). MiRNAs expression in the recipients’ serum was detected using RNA extraction and quantitative PCR analysis. Results We identified eight miRNAs which were selectively expressed on lung allograft recipients with de novo developed DSA and diagnosed with BOS in comparison to stable LTx without DSA and BOS: miR-369-5p, miR-144, miR-134, miR-10a, miR-195 miR-142-5p, miR-133b, and miR-155 (p Conclusion Our results, for the first time, demonstrated differential expression of circulating miRNAs in lung allograft recipients with de novo development of DSA and BOS. These dysregulated miRNAs are involved in T and B cell regulation and fibrogenesis, indicating their role in the development of DSA leading to chronic lung allograft rejection.

2. Challenge of organ shortage is enormous, but we’re heading towards a future where we have time and ability to improve and augment organs before more and better transplants

Over the past four decades, Lung transplant has evolved to a successful modality for treating end stage lung disease in selected patients. However, lung transplant is not problem-free. Primary graft dysfunction is the most severe form of post transplant lung ischemia and reperfusion injury and is correlated with early and late mortality after lung transplantation. Many studies have been performed to optimize the donor lung preservation in order to minimize ischemic injury to the donor lung. However, no major breakthrough has been made in donor lung preservation. Cold flush and storage has been accepted as a standard preservation of donor lungs in clinical lung transplantation. With the concept of living organ transplant, that is, heart beating, lung breathing, kidney making urine and liver producing bile, Transmedics developed a portable ex-vivo warm perfusion system that allows the donor lungs functioning and “breathing” in a near-physiologic state outside the body during transport, thus minimizing the donor lung ischemic time. Gregor Warnecke and his colleagues reported first-in-man experience of the portable OCS lung device for concomitant preservation, assessment and transport of donor lungs. It demonstrated that lungs can be safely preserved with the OCS lung, resulting in complete organ use and successful transplantation in their high-risk recipients. As one of the major lung transplant centers participating in the INSPIRE trial, the lung transplant team at Ronald Reagan UCLA medical center successfully performed the nation’s first “breathing lung” transplant in November, 2012. The INSPIRE trial has been conducted in leading lung transplant centers in Europe, the United States, Australia, and Canada. The interim results from the INSPIRE trial are suggesting significant improvement in post lung transplant clinical outcomes using the TransMedics OCS lung portable perfusion and ventilation system. In addition, other important clinical parameters such as in-hospital mortality, 6-month survival, rate of lung-related complications, time on mechanical ventilation and ICU stay may be better in the OCS group as compared to cold storage. With OCS, surgeons may accept suboptimal organs or those obtained from non-heart-beating donors through assessment of donor lung function at donor site, thus expending the donor pool without compromising patient outcome. The OCS lung enables surgeons to continuously monitor and assess the lung function and quality until transplantation. By doing so, it makes the recipient transplant team coordinate with the procure team easier, the timing of recipient incision more flexible. It allows two separate single lung transplantation that share lungs from one donor proceeding one after the other. OCS lung also allows surgeons to procure lungs over longer distance, leading to development of an international organ sharing system. We believe that this OCS lung technology has a potential of bringing human lung transplantation to a new cornerstone.

(344) - The Impact of Cell Death Signals on Short and Long Term Outcome in Human Lung Transplantation

(344) - The Impact of Cell Death Signals on Short and Long Term Outcome in Human Lung Transplantation

MicroRNA-144 dysregulates the transforming growth factor-β signaling cascade and contributes to the development of bronchiolitis obliterans syndrome after human lung transplantation

Bronchiolitis obliterans syndrome (BOS), chronic lung allograft rejection, remains an impediment for the function of the transplanted organ. In this study, we defined the role of the microRNA (miRNA) miR-144 in fibroproliferation leading to BOS. Biopsy specimens were obtained from 20 lung transplant recipients with BOS((+)) and 19 without BOS((-)). Expression of miR-144 and its target, transforming growth factor-β (TGF-β)-induced factor homeobox 1(TGIF1), were analyzed by real-time polymerase chain reaction and Western blot. Overexpression of miR-144 and luciferase reporter genes were performed to elucidate miRNA-target interactions. The function of miR-144 was evaluated by transfecting fibroblasts and determining the response to TGF-β by analyzing Sma- and Mad-related family (Smads), fibroblast growth factor, TGF-β, and vascular endothelial growth factor.Smooth muscle actin-α-positive stress fibers and F-actin filaments in lung fibroblasts were analyzed by immunofluorescence. Analysis of miR-144 in the biopsy specimens demonstrated 4.1 ± 0.8-fold increases in BOS(+) compared with BOS(-) patients, with a significant reduction in TGIF1 (3.6 ± 1.2-fold), a corepressor of Smads. In vitro transfection confirmed that over-expression of miR-144 results in a reduction in TGIF1 and an increase in SMAD2, SMAD4, fibroblast growth factor-6, TGF-β, and vascular endothelial growth factor. Increasing miR-144 by transfecting, increased smooth muscle actin-α and fibronectin, and knockdown of miR-144 diminished fibrogenesis in MRC-5 fibroblasts. miR-144 is a critical regulator of the TGF-β signaling cascade and is over-expressed in lungs with BOS. Therefore, miR-144 is a potential target toward preventing fibrosis leading to BOS after lung transplant.

Method of Isolated <em>Ex Vivo</em> Lung Perfusion in a Rat Model: Lessons Learned from Developing a Rat EVLP Program

The number of acceptable donor lungs available for lung transplantation is severely limited due to poor quality. Ex-Vivo Lung Perfusion (EVLP) has allowed lung transplantation in humans to become more readily available by enabling the ability to assess organs and expand the donor pool. As this technology expands and improves, the ability to potentially evaluate and improve the quality of substandard lungs prior to transplant is a critical need. In order to more rigorously evaluate these approaches, a reproducible animal model needs to be established that would allow for testing of improved techniques and management of the donated lungs as well as to the lung-transplant recipient. In addition, an EVLP animal model of associated pathologies, e.g., ventilation induced lung injury (VILI), would provide a novel method to evaluate treatments for these pathologies. Here, we describe the development of a rat EVLP lung program and refinements to this method that allow for a reproducible model for future expansion. We also describe the application of this EVLP system to model VILI in rat lungs. The goal is to provide the research community with key information and “pearls of wisdom”/techniques that arose from trial and error and are critical to establishing an EVLP system that is robust and reproducible.

Method of isolated ex vivo lung perfusion in a rat model: lessons learned from developing a rat EVLP program.

The number of acceptable donor lungs available for lung transplantation is severely limited due to poor quality. Ex-Vivo Lung Perfusion (EVLP) has allowed lung transplantation in humans to become more readily available by enabling the ability to assess organs and expand the donor pool. As this technology expands and improves, the ability to potentially evaluate and improve the quality of substandard lungs prior to transplant is a critical need. In order to more rigorously evaluate these approaches, a reproducible animal model needs to be established that would allow for testing of improved techniques and management of the donated lungs as well as to the lung-transplant recipient. In addition, an EVLP animal model of associated pathologies, e.g., ventilation induced lung injury (VILI), would provide a novel method to evaluate treatments for these pathologies. Here, we describe the development of a rat EVLP lung program and refinements to this method that allow for a reproducible model for future expansion. We also describe the application of this EVLP system to model VILI in rat lungs. The goal is to provide the research community with key information and “pearls of wisdom”/techniques that arose from trial and error and are critical to establishing an EVLP system that is robust and reproducible.

Neutrophil extracellular traps are pathogenic in primary graft dysfunction after lung transplantation.

Primary graft dysfunction (PGD) causes early mortality after lung transplantation and may contribute to late graft failure. No effective treatments exist. The pathogenesis of PGD is unclear, although both neutrophils and activated platelets have been implicated. We hypothesized that neutrophil extracellular traps (NETs) contribute to lung injury in PGD in a platelet-dependent manner. To study NETs in experimental models of PGD and in lung transplant patients. Two experimental murine PGD models were studied: hilar clamp and orthotopic lung transplantation after prolonged cold ischemia (OLT-PCI). NETs were assessed by immunofluorescence microscopy and ELISA. Platelet activation was inhibited with aspirin, and NETs were disrupted with DNaseI. NETs were also measured in bronchoalveolar lavage fluid and plasma from lung transplant patients with and without PGD. NETs were increased after either hilar clamp or OLT-PCI compared with surgical control subjects. Activation and intrapulmonary accumulation of platelets were increased in OLT-PCI, and platelet inhibition reduced NETs and lung injury, and improved oxygenation. Disruption of NETs by intrabronchial administration of DNaseI also reduced lung injury and improved oxygenation. In bronchoalveolar lavage fluid from human lung transplant recipients, NETs were more abundant in patients with PGD. NETs accumulate in the lung in both experimental and clinical PGD. In experimental PGD, NET formation is platelet-dependent, and disruption of NETs with DNaseI reduces lung injury. These data are the first description of a pathogenic role for NETs in solid organ transplantation and suggest that NETs are a promising therapeutic target in PGD.

Human recombinant apyrase therapy protects against canine pulmonary ischemia-reperfusion injury

There is accumulating evidence that extracellular adenosine triphosphate (eATP) promotes many of the underlying mechanisms that exacerbate acute lung injury. However, much of these data are from inbred rodent models, indicating the need for further investigation in higher vertebrates to better establish clinical relevance. To this end we evaluated a human recombinant apyrase therapy in a canine warm pulmonary ischemia-reperfusion injury (IRI) model and measured eATP levels in human lung recipients with or without primary lung graft dysfunction (PGD). Warm ischemia was induced for 90 minutes in the left lung of 14 mongrel dogs. Seven minutes after reperfusion, the apyrase APT102 (1 mg/kg, n = 7) or saline vehicle (n = 7) was injected into the pulmonary artery. Arterial blood gases were obtained every 30 minutes up to 180 minutes after reperfusion. Bronchioalveolar lavage fluid (BALF) was analyzed for eATP concentration, cellularity, and inflammatory mediator accumulation. Thirty bilateral human lung transplant recipients were graded for immediate early PGD and assessed for BALF eATP levels. APT102-treated dogs had progressively better lung function and less pulmonary edema during the 3-hour reperfusion period compared with vehicle-treated controls. Protection from IRI was observed, with lower BALF eATP levels, fewer airway leukocytes, and blunted inflammatory mediator expression. Human lung recipients with moderate to severe PGD had significantly higher eATP levels compared with recipients without this injury. Extracellular ATP accumulates in acutely injured canine and human lungs. Strategies that target eATP reduction may help protect lung recipients from IRI.

MicroRNA, miR144 Dysregulates TGf-b Signaling Cascade and Contributes to Development of BOS Following Human Lung Transplantation.

Aim: Bronchiolitis Obliterans Syndrome (BOS) is characterized by a fibroproliferative cascade that is not amenable to current treatment regimens and remains the major impediment for the long term function of the transplanted organ. MicroRNAs have been shown to significantly impact several biological processes through their ability to regulate gene expression. The objective of the current study was to define the role of miR144 in the development of fibroproliferative cascade in lung transplant recipients. Methods: Lung biopsies were obtained from transplant recipients with and without BOS (n=10 each). Expression levels of miR144 and its gene target TGIF1 were analyzed by quantitative real-time PCR using specific primers. The functional role of the miR144 was evaluated by transfecting human fibroblasts and evaluating their response to TGF-b by analyzing the expression level of SMAD and fibrogenic growth factors by quantitative real time PCR. Results: Analysis of the miR144 in the lung biopsies demonstrated that there was 4.1±0.8 fold increases in the levels of miR144 in the BOS+ when compared to BOS-samples. Similarly, the level of TGIF1 was 3.6±1.2 fold lower in the BOS+ when compared to BOS- samples. These results strongly suggest that overexpression of miR144 in the lungs of BOS+ samples results in a significant reduction in the levels of TGIF1, a transcription factor that acts as a corepressor of SMAD and an inhibitor of the retinoic acid responsive element. These two pathways are implicated in the development of fibrosis and Th17 responses. To confirm we performed In vitro transfection analysis which demonstrated that overexpression of miR144 results in significant reduction in the expression of TGIF1 (4.6±0.7 fold) and significant increases in the expression of SMAD (5.3±1.4 folds), and FGF (4.1±0.9 fold) when compared to nontransfected fibroblasts. Conclusion: We conclude that miR144 is a critical regulator of the TGF-b signaling cascade and is overexpressed in lungs of patients diagnosed with BOS and therefore can be a potential target for therapeutic intervention towards preventing the development of fibrosis and BOS development following human lung transplantation.

(422) - De Novo Development of Donor Specific Antibodies To HLA Is Associated With Dysregulation of microRNA Expression Profile Affecting Immune Responses Resulting in Bronchiolitis Obliterans Syndrome Following Human Lung Transplantation

(422) - De Novo Development of Donor Specific Antibodies To HLA Is Associated With Dysregulation of microRNA Expression Profile Affecting Immune Responses Resulting in Bronchiolitis Obliterans Syndrome Following Human Lung Transplantation

(690) - The Duration of Donor CD4 T Cell Chimerism Following Human Lung Transplantation Is Not Affected By Human Leukocyte Antigen and Natural Killer Cell Alloreactivity

Graft passenger lymphocytes are known to influence auto- and allo-immune responses following transplantation. The fate of the donor passenger CD4 T cells is unclear and maybe influenced by the degree of Human Leukocyte Antigen (HLA) disparities and the natural killer (NK) cell alloreactivity. Thus, we investigated the relationship between the duration of donor CD4 T cell chimerism; the degree of HLA mismatches and NK cell alloreactivity in lung transplant recipients.

(208) - Novel Two-Hit Hypothesis for the Development of De Novo Autoimmunity Following Lung Transplantation

De novo donor-specific HLA alloantibodies precede development of autoantibodies to lung-specific self-antigens following human lung transplantation and both strongly predispose to lung allograft rejection (LAR). The immunological link between allo- and auto- antibodies (Abs) remains unknown. Respiratory viral infections (RVI) are known risk factors of LAR and can lead to apoptosis of local CD4+CD25+foxp3+ regulatory T cells (Tregs). We hypothesize that anti-MHC Abs cause initial injury leading to the exposure of sequestered lung-specific antigens.

(207) - Humoral Allo and Auto Immunity in Human Lung Transplant Recipients

(207) - Humoral Allo and Auto Immunity in Human Lung Transplant Recipients