Anti-ETAR and anti-AT1R autoantibodies are elevated in patients with endstage cystic fibrosis

Bariatric surgery modulates plasma levels of antibodies against angiotensin II type 1 and endothelin 1 type A receptor in severe obesity

PURPOSE

The contribution of endothelial-targeted autoantibodies against the angiotensin II type 1 receptor (anti-AT1R) and the anti-endothelin 1 type A receptor (anti-ETAR1) has been proposed in the development of cardiovascular diseases. However, no data have been reported yet in obesity. In this observational study we evaluated the relationship between anthropometric and metabolic parameters and anti-AT1R and anti-ETAR1 concentrations in a cohort of patients with severe obesity and associated comorbidities undergoing bariatric surgery.

METHODS

Clinical evaluation and metabolic assessment were performed in 36 subjects referring to our Center for the Study and Integrated Treatment of Obesity at the University Hospital of Padova. Circulating inflammatory adipocytokines and the endothelial dysfunction marker asymmetric dimethylarginine (ADMA) were evaluated; plasma levels of anti-AT1R and anti-ETAR1 were also determined. 10 normal-weight subjects were considered as a control group. 29 patients out of 36 were re-evaluated after surgery.

RESULTS

With respect to normal-weight controls patients showed significantly higher plasma levels of anti-AT1R (28 ± 20.4 vs 13.5 ± 2.8 U/mL, p < 0.005) and ADMA (0.8 ± 0.1 vs 0.54 ± 0.08 uM/L, p < 0.0001) but not anti-ETAR1 (14.2 ± 1.3 vs 13.3 ± 2 U/mL, p = 0.1). Anti-AT1R concentration showed an increasing trend with the worsening of glycemic status, while the presence of arterial hypertension among the patients did not affect autoantibodies levels. One year after surgery, a significant improvement in body weight and metabolic and inflammatory parameters was observed, along with a significant reduction of anti-AT1R (28.1 ± 20.4 U/mL vs 22.6 ± 16 U/mL, p < 0.05) and anti-ETAR1 (14.2 ± 1.3 U/L vs 13 ± 1.6 U/L, p < 0.01).

CONCLUSIONS

Subjects with obesity present higher plasma levels of anti-AT1R which are more related to glycemic profile than blood pressure levels, and are reduced by bariatric surgery. Considering the detrimental effects of these autoantibodies on vascular health, they should be assessed as potential biomarkers in obesity and metabolic diseases.

The role of lung-restricted autoantibodies in the development of primary and chronic graft dysfunction

Lung transplantation is a life-saving treatment for both chronic end-stage lung diseases and acute respiratory distress syndrome, including those caused by infectious agents like COVID-19. Despite its increasing utilization, outcomes post-lung transplantation are worse than other solid organ transplants. Primary graft dysfunction (PGD)-a condition affecting more than half of the recipients post-transplantation-is the chief risk factor for post-operative mortality, transplant-associated multi-organ dysfunction, and long-term graft loss due to chronic rejection. While donor-specific antibodies targeting allogenic human leukocyte antigens have been linked to transplant rejection, the role of recipient's pre-existing immunoglobulin G autoantibodies against lung-restricted self-antigens (LRA), like collagen type V and k-alpha1 tubulin, is less understood in the context of lung transplantation. Recent studies have found an increased risk of PGD development in lung transplant recipients with LRA. This review will synthesize past and ongoing research-utilizing both mouse models and human subjects-aimed at unraveling the mechanisms by which LRA heightens the risk of PGD. Furthermore, it will explore prospective approaches designed to mitigate the impact of LRA on lung transplant patients.

Extracellular Vesicles Mediate Immune Responses to Tissue-Associated Self-Antigens: Role in Solid Organ Transplantations

Transplantation is a treatment option for patients diagnosed with end-stage organ diseases; however, long-term graft survival is affected by rejection of the transplanted organ by immune and nonimmune responses. Several studies have demonstrated that both acute and chronic rejection can occur after transplantation of kidney, heart, and lungs. A strong correlation has been reported between de novo synthesis of donor-specific antibodies (HLA-DSAs) and development of both acute and chronic rejection; however, some transplant recipients with chronic rejection do not have detectable HLA-DSAs. Studies of sera from such patients demonstrate that immune responses to tissue-associated antigens (TaAgs) may also play an important role in the development of chronic rejection, either alone or in combination with HLA-DSAs. The synergistic effect between HLA-DSAs and antibodies to TaAgs is being established, but the underlying mechanism is yet to be defined. We hypothesize that HLA-DSAs damage the transplanted donor organ resulting in stress and leading to the release of extracellular vesicles, which contribute to chronic rejection. These vesicles express both donor human leukocyte antigen (HLA) and non-HLA TaAgs, which can activate antigen-presenting cells and lead to immune responses and development of antibodies to both donor HLA and non-HLA tissue-associated Ags. Extracellular vesicles (EVs) are released by cells under many circumstances due to both physiological and pathological conditions. Primarily employing clinical specimens obtained from human lung transplant recipients undergoing acute or chronic rejection, our group has demonstrated that circulating extracellular vesicles display both mismatched donor HLA molecules and lung-associated Ags (collagen-V and K-alpha 1 tubulin). This review focuses on recent studies demonstrating an important role of antibodies to tissue-associated Ags in the rejection of transplanted organs, particularly chronic rejection. We will also discuss the important role of extracellular vesicles released from transplanted organs in cross-talk between alloimmunity and autoimmunity to tissue-associated Ags after solid organ transplantation.

Antibodies against Angiotensin II Type 1 and Endothelin 1 Type A Receptors in Cardiovascular Pathologies

Angiotensin II receptor type 1 (AT1R) and endothelin-1 receptor type A (ETAR) are G-protein-coupled receptors (GPCRs) expressed on the surface of a great variety of cells: immune cells, vascular smooth cells, endothelial cells, and fibroblasts express ETAR and AT1R, which are activated by endothelin 1 (ET1) and angiotensin II (AngII), respectively. Certain autoantibodies are specific for these receptors and can regulate their function, thus being known as functional autoantibodies. The function of these antibodies is similar to that of natural ligands, and it involves not only vasoconstriction, but also the secretion of proinflammatory cytokines (such as interleukin-6 (IL6), IL8 and TNF-α), collagen production by fibroblasts, and reactive oxygen species (ROS) release by fibroblasts and neutrophils. The role of autoantibodies against AT1R and ETAR (AT1R-AAs and ETAR-AAs, respectively) is well described in the pathogenesis of many medical conditions (e.g., systemic sclerosis (SSc) and SSc-associated pulmonary hypertension, cystic fibrosis, and allograft dysfunction), but their implications in cardiovascular diseases are still unclear. This review summarizes the current evidence regarding the effects of AT1R-AAs and ETAR-AAs in cardiovascular pathologies, highlighting their roles in heart transplantation and mechanical circulatory support, preeclampsia, and acute coronary syndromes.

Anti-AT1R autoantibodies and prediction of the severity of Covid-19

The stimulation of AT1R (Angiotensin II Receptor Type 1) by Angiotensin II has, in addition to the effects on the renin-angiotensin system, also pro-inflammatory effects through stimulation of ADAM17 and subsequent production of INF-gamma and Interleukin-6. This pro-inflammatory action stimulate the cytokine storm that characterizes the most severe forms of SARS-CoV-2 infection. We studied the effect of AT1Rab on the AT1R on 74 subjects with SARS-CoV-2 infection with respiratory symptoms requiring hospitalization. We divided the patients into 2 groups: 34 with moderate and 40 with severe symptoms that required ICU admission. Hospitalized subjects showed a 50% reduction in the frequency of AT1Rab compared to healthy reference population. Of the ICU patients, 33/40 (82.5%) were AT1Rab negative and 16/33 of them (48.5%) died. All 7 patients positive for AT1Rab survived. These preliminary data seem to indicate a protective role played by AT1R autoantibodies on inflammatory activation in SARS-CoV-2 infection pathology.

Set Up for Failure: Pre-Existing Autoantibodies in Lung Transplant

Lung transplant patients have the lowest long-term survival rates compared to other solid organ transplants. The complications after lung transplantation such as primary graft dysfunction (PGD) and ultimately chronic lung allograft dysfunction (CLAD) are the main reasons for this limited survival. In recent years, lung-specific autoantibodies that recognize non-HLA antigens have been hypothesized to contribute to graft injury and have been correlated with PGD, CLAD, and survival. Mounting evidence suggests that autoantibodies can develop during pulmonary disease progression before lung transplant, termed pre-existing autoantibodies, and may participate in allograft injury after transplantation. In this review, we summarize what is known about pulmonary disease autoantibodies, the relationship between pre-existing autoantibodies and lung transplantation, and potential mechanisms through which pre-existing autoantibodies contribute to graft injury and rejection.

Immunoglobulin G of systemic sclerosis patients programs a pro-inflammatory and profibrotic phenotype in monocyte-like THP-1 cells

OBJECTIVES

Functional IgG autoantibodies against diverse G protein-coupled receptors, i.e. antibodies with agonistic or antagonistic activity at these receptors, are abundant in human serum. Their levels are altered in patients with SSc, and autoantibodies against angiotensin II receptor 1 (ATR1) and endothelin receptor A (ETA) have been suggested to drive SSc by inducing the chemokines CXCL8 and CCL18 in the blood. The objective of our study is to profile the effect of IgG in SSc (SSc-IgG) on the production of soluble mediators in monocytic cells.

METHODS

Monocyte-like THP-1 cells were stimulated with SSc-IgG and their secretome was analysed. Furthermore, the significance of major pro-inflammatory pathways for the induction of CXCL8 and CCL18 in response to SSc-IgG was assessed by a pharmacological approach.

RESULTS

Stimulation with SSc-IgG significantly alters the secretome of THP-1 cells towards a general pro-inflammatory and profibrotic phenotype, which includes an increase of CCL18 and CXCL8. The consequent expression profiles vary depending on the individual donor of the SSc-IgG. CCL18 and CXCL8 expression is thus regulated differentially, with AP-1 driving the induction of both CCL18 and CXCL8 and the TAK/IKK-β/NF-κB pathway and ERK1/2 driving that of CXCL8.

CONCLUSIONS

Our results suggest that SSc-IgG contributes to the generation of the pro-inflammatory/profibrotic tissue milieu characteristic of SSc by its induction of a respective phenotype in monocytes. Furthermore, our results highlight AP-1 as a critical regulator of gene transcription of CCL18 in monocytic cells and as a promising pharmacological therapeutic target for the treatment of SSc.

Non-HLA Autoantibodies at 1 Year Negatively Affect 5-Year Native Renal Function in Liver Transplant Recipients

BACKGROUND

Angiotensin II type-1 receptor (AT₁R) and endothelin-1 type A receptor (ET_AR) autoantibodies, in addition to allograft injury, can bind native endothelial cells and cause vascular vasoconstriction and fibrosis progression in nontransplanted organs. Therefore, we investigated long-term native renal function in liver transplant (LT) recipients with and without anti-AT₁R-Abs and/or anti-ET_AR-Abs present in serum.

METHODS

Primary LT recipients at our single center from January 2000 to April 2009 had their prospectively collected pre-LT (1269 patients) and year 1 post-LT (795 patients) serum tested retrospectively for anti-AT₁R-Abs and/or anti-ET_AR-Abs. Anti-AT₁R-Abs and anti-ET_AR-Abs testing was accomplished with a standardized solid phase assay in which >10 U was considered positive.

RESULTS

Pretransplant anti-AT₁R-Abs and/or anti-ET_AR-Abs did not change the median delta creatinine from pretransplant to 1 year post-transplant. In multivariable analysis controlling for diabetes (DM) and calcineurin inhibitor (CNI) use, anti-AT₁R-Abs and/or anti-ET_AR-Abs at 1-year remained statistically significantly associated with a decline in GFR (measured by Modification of Diet in Renal Disease-6) from years 1-5 post-LT (P = .04). In diabetic patients the association with a decline in renal function was more pronounced with (-9.29 mL/min) vs without (-2.28 mL/min) anti-AT₁R-Abs and/or anti-ET_AR-Abs at year 1, respectively (P = .004).

CONCLUSION

At 1-year post-LT, the autoantibodies anti-AT₁R-Abs and/or anti-ET_AR-Abs are associated in multivariable analysis with an increased risk of native renal function decline especially in diabetic patients.

Pathogenic roles of autoantibodies in systemic sclerosis: Current understandings in pathogenesis

The potential pathogenic role for autoantibodies in systemic sclerosis has captivated researchers for the past 40 years. This review answers the question whether there is yet sufficient knowledge to conclude that certain serum autoantibodies associated with systemic sclerosis contribute to its pathogenesis. Definitions for pathogenic, pathogenetic and functional autoantibodies are formulated, and the need to differentiate these autoantibodies from natural autoantibodies is emphasized. In addition, seven criteria for the identification of pathogenic autoantibodies are proposed. Experimental evidence is reviewed relevant to the classic systemic sclerosis antinuclear autoantibodies, anti-topoisomerase I and anticentromere, and to functional autoantibodies to endothelin 1 type A receptor, angiotensin II type 1 receptor, muscarinic receptor 3, platelet-derived growth factor receptor, chemokine receptors CXCR3 and CXCR4, estrogen receptor α, and CD22. Pathogenic evidence is also reviewed for anti-matrix metalloproteinases 1 and 3, anti-fibrillin 1, anti-IFI16, anti-eIF2B, anti-ICAM-1, and anti-RuvBL1/RuvBL2 autoantibodies. For each autoantibody, objective evidence for a pathogenic role is scored qualitatively according to the seven pathogenicity criteria. It is concluded that anti-topoisomerase I is the single autoantibody specificity with the most evidence in favor of a pathogenic role in systemic sclerosis, followed by anticentromere. However, these autoantibodies have not been demonstrated yet to fulfill completely the seven proposed criteria for pathogenicity. Their contributory roles to the pathogenesis of systemic sclerosis remain possible but not yet conclusively demonstrated. With respect to functional autoantibodies and other autoantibodies, only a few criteria for pathogenicity are fulfilled. Their common presence in healthy and disease controls suggests that major subsets of these immunoglobulins are natural autoantibodies. While some of these autoantibodies may be pathogenetic in systemic sclerosis, establishing that they are truly pathogenic is a work in progress. Experimental data are difficult to interpret because high serum autoantibody levels may be due to polyclonal B-cell activation. Other limitations in experimental design are the use of total serum immunoglobulin G rather than affinity-purified autoantibodies, the confounding effect of other systemic sclerosis autoantibodies present in total immunoglobulin G and the lack of longitudinal studies to determine if autoantibody titers fluctuate with systemic sclerosis activity and severity. These intriguing new specificities expand the spectrum of autoantibodies observed in systemic sclerosis. Continuing elucidation of their potential mechanistic roles raises hope of a better understanding of systemic sclerosis pathogenesis leading to improved therapies.

Immunotherapy of Endothelin-1 Receptor Type A for Pulmonary Arterial Hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a chronic fatal disease. The treatment of PAH is less than ideal and the control is far from satisfactory worldwide. Vaccination provides a promising approach for treatment of PAH.

OBJECTIVES

This study sought to find a vaccine against endothelin-1 (ET-1) receptor type A (ETAR) for treating PAH.

METHODS

The ETRQβ-002 vaccine was screened and the specific antibodies against epitope ETR-002 belonging to the second extracellular loop of ETAR (including the polyclonal and monoclonal antibody) were produced. The effect of the antibodies on Ca²⁺-dependent signal transduction events was investigated. In vivo, ETRQβ-002 vaccine was used to vaccinate monocrotaline (MCT)- and Sugen/hypoxia-induced pulmonary hypertension animals. The monoclonal antibody (mAb) against ETR-002 was also injected into the PAH animals. The effect of ETRQβ-002 vaccine on pulmonary hypertension and remodeling of pulmonary arterioles and right ventricle (RV) was carefully evaluated. Further, the possible immune-mediated damage was detected in normal vaccinated animals.

RESULTS

ETR-002 peptide has perfect immunogenicity and ETRQβ-002 vaccine could induce strong antibody production. In vitro, the anti-ETR-002 antibody bound to ETAR and inhibited Ca²⁺-dependent signal transduction events, including extracellular signal-regulated kinase phosphorylation and elevation of intracellular Ca²⁺ concentration induced by ET-1. In vivo, both ETRQβ-002 vaccine and the mAb significantly decreased the RV systolic pressure up to 20 mm Hg and 10 mm Hg in MCT-exposed rats and Sugen/hypoxia-exposed mice, respectively. Also, ETRQβ-002 vaccine/mAb obviously ameliorated pathological remodeling of pulmonary arterioles and hypertrophy of the RV in PAH animals. Additionally, no significant immune-mediated damage was detected in vaccinated animals.

CONCLUSIONS

ETRQβ-002 vaccine/mAb attenuated remodeling of pulmonary arterioles and RV in MCT- and Sugen/hypoxia-induced PAH animals and decreased RV systolic pressure effectively through diminishing the pressure response and inhibiting signal transduction initiated by ET-1. ETRQβ-002 vaccine/mAb may provide a novel and promising method for PAH treatment.

Antibodies against Angiotensin II Type 1 and Endothelin A Receptors: Relevance and pathogenicity

Antibodies against two G-protein coupled receptors (GPCRs), angiotensin II type 1 receptor (AT1R) and endothelin A receptor (ETAR) are among a growing number of autoantibodies that are found to be associated with allograft dysfunction. AT1R antibodies (AT1Rabs) and ETAR antibodies (ETARabs) have been shown to activate their target receptors and affect signaling pathways. Multiple single center reports have shown an association between presence of these antibodies and acute or chronic rejection and graft loss in kidney, heart, liver, lung and composite tissue transplantations. However, the characteristics of patients that are most likely to develop adverse outcomes, the phenotypes associated with graft damage solely due to these antibodies, and the antibody titer required to cause dysfunction are areas that remain controversial. This review compiles existing knowledge on the effect of antibodies against GPCRs in other diseases in order to bridge the gap in knowledge within transplantation biology. Future areas for research are highlighted and include the need for functional assays and treatment protocols for transplant patients who present with AT1Rabs and ETARabs. Understanding how antibodies that activate GPCRs influence transplantation outcome will have direct clinical implications for preemptive evaluation of transplant candidates as well as the post-transplant care of organ recipients.

The impact of non-HLA antibodies on outcomes after lung transplantation and implications for therapeutic approaches

The role of donor-specific antibodies (DSA) to mismatched human leukocyte antigens (HLA) in lung allograft rejection has been recognized over the past 20 years. During this time, there has been growing experience and recognition of an important role for non-HLA antibodies in lung allograft rejection. Multiple self-antigens have been identified that elicit autoimmune responses including collagen V, K-α 1 tubulin, angiotensin type 1 receptor, and endothelin type A receptor, but it is likely that other antigens elicit similar responses. The paradigm for the pathogenesis of these autoimmune responses consists of exposure of sequestered self-antigens followed by loss of peripheral tolerance, which then promotes allograft rejection. Studies have focused mainly on the impact of autoimmune responses on the development of Bronchiolitis Obliterans Syndrome or its mouse model surrogate. However, there are emerging data that illustrate that non-HLA antibodies can induce acute antibody-mediated rejection (AMR) after lung transplantation. Treatment has focused on antibody-depletion protocols, but experience is limited to cohort studies and appropriate controlled trials have not been conducted. It is noteworthy that depletion of non-HLA antibodies has been associated with favorable clinical outcomes. Clearly, additional studies are needed to identify the optimal therapeutic approaches to non-HLA antibodies in clinical practice.

The Autoimmune-Associated Single Nucleotide Polymorphism Within PTPN22 Correlates With Clinical Outcome After Lung Transplantation

Obstructive chronic lung allograft dysfunction (BOS) is the major limiting factor for lung transplantation (LTx) outcome. PTPN22 is described as the hallmark autoimmunity gene, and one specific single nucleotide polymorphism (SNP), rs2476601, is associated with multiple autoimmune diseases, impaired T cell regulation, and autoantibody formation. Taking into consideration the contribution of autoimmunity to LTx outcome, we hypothesized that polymorphisms in the PTPN22 gene could be associated with BOS incidence. We selected six SNPs within PTPN22 and analyzed both patient and donor genotypes on BOS development post-LTx. A total of 144 patients and matched donors were included, and individual SNPs and haplotype configurations were analyzed. We found a significant association between patients carrying the heterozygous configuration of rs2476601 and a higher risk for BOS development (p = 0.005, OR: 4.400, 95%CI: 1.563–12.390). Kaplan-Meier analysis showed that heterozygous patients exhibit a lower BOS-free survival compared to patients homozygous for rs2476601 (p = 0.0047). One haplotype, which solely contained the heterozygous risk variant, was associated with BOS development (p = 0.015, OR: 7.029, 95%CI: 1.352–36.543). Our results show that LTx patients heterozygous for rs2476601 are more susceptible for BOS development and indicate a deleterious effect of the autoimmune-related risk factor of PTPN22 in patients on LTx outcome.

Banff Lung Report: Current knowledge and future research perspectives for diagnosis and treatment of pulmonary antibody-mediated rejection (AMR)

The Lung session of the 2017 14th Banff Foundation for Allograft Pathology Conference, Barcelona focused on the multiple aspects of antibody-mediated rejection (AMR) in lung transplantation. Multidimensional approaches for AMR diagnosis, including classification, histological and immunohistochemical analysis, and donor- specific antibody (DSA) characterization with their current strengths and limitations were reviewed in view of recent research. The group also discussed the role of tissue gene expression analysis in the context of unmet needs in lung transplantation. The current best practice for monitoring of AMR and the therapeutic approach are summarized and highlighted in this report. The working group reached consensus of the major gaps in current knowledge and focused on the unanswered questions regarding pulmonary AMR. An important outcome of the meeting was agreement on the need for future collaborative research projects to address these gaps in the field of lung transplantation.

Mechanisms of Autoantibody-Induced Pathology

Autoantibodies are frequently observed in healthy individuals. In a minority of these individuals, they lead to manifestation of autoimmune diseases, such as rheumatoid arthritis or Graves' disease. Overall, more than 2.5% of the population is affected by autoantibody-driven autoimmune disease. Pathways leading to autoantibody-induced pathology greatly differ among different diseases, and autoantibodies directed against the same antigen, depending on the targeted epitope, can have diverse effects. To foster knowledge in autoantibody-induced pathology and to encourage development of urgently needed novel therapeutic strategies, we here categorized autoantibodies according to their effects. According to our algorithm, autoantibodies can be classified into the following categories: (1) mimic receptor stimulation, (2) blocking of neural transmission, (3) induction of altered signaling, triggering uncontrolled (4) microthrombosis, (5) cell lysis, (6) neutrophil activation, and (7) induction of inflammation. These mechanisms in relation to disease, as well as principles of autoantibody generation and detection, are reviewed herein.

Antibodies against Apoptotic Cells Present in End-stage Lung Disease Patients Do Not Correlate with Clinical Outcome after Lung Transplantation

Antibodies against HLA and non-HLA are associated with transplantation outcome. Recently, pretransplant serum IgG antibody levels against apoptotic cells were found to correlate with kidney allograft loss. We investigated the presence of these antibodies in lung transplantation (LTx) patients and evaluated the correlation of pre-LTx serum levels of IgG antibodies against apoptotic cells with LTx outcome. These cells included donor lung endothelial cells (ECs) obtained from lung perfusion fluid collected during LTx procedure. Cells were isolated, expanded in vitro, and analyzed as targets for antiapoptotic cell reactivity. Cultured cells exhibited EC morphology and were CD31+, CD13+, and vWF+. End-stage lung disease patients showed elevated serum IgG levels against apoptotic lung EC (p = 0.0018) compared to healthy controls. Interestingly, the levels of circulating antibodies directed against either apoptotic Jurkat cells or apoptotic lung ECs did not correlate, suggesting a target cell specificity. We observed no correlation between chronic or acute rejection and pre-LTx serum levels of antiapoptotic antibodies. Also, these levels did not differ between matched patients developing chronic rejection or not during follow-up or at the time of diagnosis, as they remained as high as prior to transplantation. Thus, circulating levels of antiapoptotic cell antibodies are elevated in end-stage lung disease patients, but our data do not correlate with outcome after LTx.

Not All Antibodies Are Created Equal: Factors That Influence Antibody Mediated Rejection

Consistent with Dr. Paul Terasaki's "humoral theory of rejection" numerous studies have shown that HLA antibodies can cause acute and chronic antibody mediated rejection (AMR) and decreased graft survival. New evidence also supports a role for antibodies to non-HLA antigens in AMR and allograft injury. Despite the remarkable efforts by leaders in the field who pioneered single antigen bead technology for detection of donor specific antibodies, a considerable amount of work is still needed to better define the antibody attributes that are associated with AMR pathology. This review highlights what is currently known about the clinical context of pre and posttransplant antibodies, antibody characteristics that influence AMR, and the paths after donor specific antibody production (no rejection, subclinical rejection, and clinical dysfunction with AMR).

Immediate and Catastrophic Antibody-Mediated Rejection in a Lung Transplant Recipient With Anti-Angiotensin II Receptor Type 1 and Anti-Endothelin-1 Receptor Type A Antibodies

Preexisting donor-specific anti-HLA antibodies (DSAs) have been associated with reduced survival of lung allografts. However, antibodies with specificities other than HLA may have a detrimental role on the lung transplant outcome. A young man with cystic fibrosis underwent lung transplantation with organs from a suitable deceased donor. At the time of transplantation, there were no anti-HLA DSAs. During surgery, the patient developed a severe and intractable pulmonary hypertension associated with right ventriular dysfunction, which required arteriovenous extracorporeal membrane oxygenation. After a brief period of clinical improvement, a rapid deterioration in hemodynamics led to the patient's death on postoperative day 5. Postmortem studies showed that lung specimens taken at the end of surgery were compatible with antibody-mediated rejection (AMR), while terminal samples evidenced diffuse capillaritis, blood extravasation, edema, and microthrombi, with foci of acute cellular rejection (A3). Immunological investigations demonstrated the presence of preexisting antibodies against the endothelin-1 receptor type A (ET_A R) and the angiotensin II receptor type 1 (AT₁ R), two of the most potent vasoconstrictors reported to date, whose levels slightly rose after transplantation. These data suggest that preexisting anti-ET_A R and anti-AT₁ R antibodies may have contributed to the onset of AMR and to the catastrophic clinical course of this patient.

Anti-angiotensin II type 1 receptor autoantibodies (AT1R-AAs) in patients with systemic sclerosis: lack of association with disease manifestations

Angiotensin II type 1 receptor autoantibodies (AT₁R-AAs) are known to be associated with malignant hypertension, preeclampsia, and vascular rejection in kidney transplantation. They were also suspected to have pathogenetic role in vasculopathic changes in systemic sclerosis (SSc). Clinical data regarding AT₁R-AAs in SSc are scarce. In this work, we will examine the relationship between serum levels of AT₁R-AAs and disease manifestations. Serum samples from SSc patients and healthy controls were analyzed for AT₁R-AAs by using a commercial ELISA kit. We examined the association of serum levels of AT₁R-AA with disease duration, systolic pulmonary artery pressure (sPAP) measurements, and disease manifestations like cutaneous, lung and esophageal involvements, and the presence of digital ulcers in a cross-sectional manner. There was no statistically significant difference in levels of AT₁R-AAs between SSc (n = 93) patients and healthy controls (n = 66) (p = 0.23). Serum levels of AT₁R-AAs were not correlated with disease duration, sPAP measurements, and showed no association with disease manifestations like lung involvement, esophageal involvement, digital ulcers, and cutaneous fibrosis. In our SSc cohort, AT₁R-AA serum levels were not different from healthy subjects and higher levels were not associated with any disease manifestation neither.

Non-HLA antibodies against endothelial targets bridging allo- and autoimmunity

Detrimental actions of donor-specific antibodies (DSAs) directed against both major histocompatibility antigens (human leukocyte antigen [HLA]) and specific non-HLA antigens expressed on the allograft endothelium are a flourishing research area in kidney transplantation. Newly developed solid-phase assays enabling detection of functional non-HLA antibodies targeting G protein-coupled receptors such as angiotensin type I receptor and endothelin type A receptor were instrumental in providing long-awaited confirmation of their broad clinical relevance. Numerous recent clinical studies implicate angiotensin type I receptor and endothelin type A receptor antibodies as prognostic biomarkers for earlier occurrence and severity of acute and chronic immunologic complications in solid organ transplantation, stem cell transplantation, and systemic autoimmune vascular disease. Angiotensin type 1 receptor and endothelin type A receptor antibodies exert their pathophysiologic effects alone and in synergy with HLA-DSA. Recently identified antiperlecan antibodies are also implicated in accelerated allograft vascular pathology. In parallel, protein array technology platforms enabled recognition of new endothelial surface antigens implicated in endothelial cell activation. Upon target antigen recognition, non-HLA antibodies act as powerful inducers of phenotypic perturbations in endothelial cells via activation of distinct intracellular cell-signaling cascades. Comprehensive diagnostic assessment strategies focusing on both HLA-DSA and non-HLA antibody responses could substantially improve immunologic risk stratification before transplantation, help to better define subphenotypes of antibody-mediated rejection, and lead to timely initiation of targeted therapies. Better understanding of similarities and dissimilarities in HLA-DSA and distinct non-HLA antibody-related mechanisms of endothelial damage should facilitate discovery of common downstream signaling targets and pave the way for the development of endothelium-centered therapeutic strategies to accompany intensified immunosuppression and/or mechanical removal of antibodies.