Anti-endothelial Cell Autoantibodies Research Articles

Serum of Post-COVID-19 Syndrome Patients with or without ME/CFS Differentially Affects Endothelial Cell Function In Vitro.

A proportion of COVID-19 reconvalescent patients develop post-COVID-19 syndrome (PCS) including a subgroup fulfilling diagnostic criteria of Myalgic encephalomyelitis/Chronic Fatigue Syndrome (PCS/CFS). Recently, endothelial dysfunction (ED) has been demonstrated in these patients, but the mechanisms remain elusive. Therefore, we investigated the effects of patients’ sera on endothelia cells (ECs) in vitro. PCS (n = 17), PCS/CFS (n = 13), and healthy controls (HC, n = 14) were screened for serum anti-endothelial cell autoantibodies (AECAs) and dysregulated cytokines. Serum-treated ECs were analysed for the induction of activation markers and the release of small molecules by flow cytometry. Moreover, the angiogenic potential of sera was measured in a tube formation assay. While only marginal differences between patient groups were observed for serum cytokines, AECA binding to ECs was significantly increased in PCS/CFS patients. Surprisingly, PCS and PCS/CFS sera reduced surface levels of several EC activation markers. PCS sera enhanced the release of molecules associated with vascular remodelling and significantly promoted angiogenesis in vitro compared to the PCS/CFS and HC groups. Additionally, sera from both patient cohorts induced the release of molecules involved in inhibition of nitric oxide-mediated endothelial relaxation. Overall, PCS and PCS/CFS patients′ sera differed in their AECA content and their functional effects on ECs, i.e., secretion profiles and angiogenic potential. We hypothesise a pro-angiogenic effect of PCS sera as a compensatory mechanism to ED which is absent in PCS/CFS patients.

Role of B-Cell in the Pathogenesis of Systemic Sclerosis.

Systemic sclerosis (SSc) is a rare multisystem autoimmune disease, characterized by fibrosis, vasculopathy, and autoimmunity. Recent advances have highlighted the significant implications of B-cells in SSc. B-cells are present in affected organs, their subpopulations are disrupted, and they display an activated phenotype, and the regulatory capacities of B-cells are impaired, as illustrated by the decrease in the IL-10+ producing B-cell subpopulation or the inhibitory membrane co-receptor density. Recent multi-omics evidence highlights the role of B-cells mainly in the early stage of SSc and preferentially during severe organ involvement. This dysregulated homeostasis partly explains the synthesis of anti-endothelial cell autoantibodies (AECAs) or anti-fibroblast autoantibodies (AFAs), proinflammatory or profibrotic cytokines (interleukin-6 and transforming growth factor-β) produced by B and plasma cells. That is associated with cell-to-cell interactions with endothelial cells, fibroblasts, vascular smooth muscle cells, and other immune cells, altogether leading to cell activation and proliferation, cell resistance to apoptosis, the impairment of regulatory mechanisms, and causing fibrosis of several organs encountered in the SSc. Finally, alongside these exploratory data, treatments targeting B-cells, through their depletion by cytotoxicity (anti-CD20 monoclonal antibody), or the cytokines produced by the B-cell, or their costimulation molecules, seem interesting, probably in certain profiles of early patients with severe organic damage.

Cytokine cascade in Kawasaki disease versus Kawasaki-like syndrome.

Kawasaki disease (KD) is a medium vessel systemic vasculitis that predominantly occurs in children below five years of age. It is an acute febrile condition in which coronary artery aneurysms and myocarditis are the most common cardiovascular complications. It is most often characterized by hypercytokinemia. The etiopathogenesis of KD is not fully understood. The present review synthesizes the recent advances in the pathophysiology and treatment options of KD. According to different studies, the genetic, infections and autoimmunity factors play a major role in pathogenesis. Several susceptibility genes (e.g. caspase 3) and cytokines (e.g. IL-2, IL-4, IL-6, IL-10, IFN-gamma and TNF-alpha) have been identified in KD. Patients with high cytokine levels are predisposed to KD shock syndrome. The importance of respiratory viruses in the pathogenesis of the disease is unclear. Coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may induce in children and adults an abnormal systemic inflammatory response. This syndrome shares characteristics with KD. It has been called by many terms like MIS-C (Multisystem Inflammatory Syndrome in Children), PIMS-TS (pediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2), hyperinflammatory shock syndrome, cytokine storm (cytokine release syndrome) or simply, Kawasaki-like syndrome. The cytokine's role in the development of KD or Kawasaki-like syndrome being triggered by COVID-19 is controversial. The presences of the antiendothelial cell autoantibodies (AECAs) together with the newly developed hypothesis of immunothrombosis are considered potential pathogenic mechanisms for KD. In consequence, the diagnosis and treatment of KD and Kawasaki-like syndrome, one of the most common causes of acquired heart disease in developed countries, are challenging without a clearly defined protocol.

The Role of Anti-Endothelial Cell Autoantibodies and Immune Response in Acute Low-Tone Hearing Loss.

Immunity is associated with acute low tone hearing loss. However, the exact pathophysiology of immunity-mediated acute low tone hearing loss remains unknown. In this study, we evaluated the presence, therapeutic effectiveness, and immunopathological mechanisms of anti-endothelial cell autoantibodies (AECEs) in patients with acute low-frequency hearing loss. Forty-nine patients who were treated as inpatients having acute low-frequency hearing loss and additional symptoms, such as ear fullness, tinnitus, dizziness, or hyperacusis, were enrolled in this study. Serum samples from these patients were collected for laboratory serum autoimmunity detection, including AECAs, antinuclear antibodies, immunoglobulin, and circular immune complex. Therapeutic responses to combination therapy in short-term outcome and serum cytokine levels were compared between AECA-positive and AECA-negative patients. Anti-endothelial cell autoantibodies-positive patients tended to show significantly less response to standard therapy compared with AECAs controls (P < .05). Moreover, some serum cytokine levels elevated in both AECAs- and AECAs+ groups. Positive ratio of interleukin-8 and concentrations of macrophage inflammatory protein-1α were found higher in AECAs+ groups (P < .05). The results supported that AECAs might wield influence on the short-term outcome of acute low-tone hearing loss (ALHL) treatment. Furthermore, AECA-mediated acute low-frequency hearing loss possibly involved dysregulation of inflammation process and release of cytokines.

Autoimmune Aspects of Kawasaki Disease.

Kawasaki disease (KD) is a vasculitis that is part of systemic vasculitis syndrome. It affects medium-sized vessels and is characterized by hypercytokinemia. Although the etiology of KD remains unidentified, epidemiological features point to the role of infection and genetic predisposition. Recent studies on KD revealed endothelial damage and resultant thrombin generation, as well as B-cell activation during the acute phase. Several antiendothelial cell autoantibodies (AECAs) have been identified in KD patients. Analysis of this phenomenon together with the recently developed concept of immunothrombosis reveals a potential pathogenic mechanism for KD. First, polyclonal antibodies generated against invading microorganisms would exhibit cross-reactivity toward endothelial cell components and become dominant during affinity maturation. Binding of AECAs to endothelial cells would cause endothelial activation or damage, with proinflammatory cytokine release, thus fostering a hypercoagulable state resulting from leukocyte activation by proinflammatory cytokines. This, in turn, would lead to coronary artery lesions. KD vasculitis might be initiated upon binding of AECAs to the vasa vasorum and progress to panvasculitis and a vulnerable vessel wall, resulting in an aneurysm. The aneurysm would cause flow recirculation and alteration of wall shear stress. Consequently, platelets activated by shear stress, along with ultralarge von Willebrand factor (VWF) released by endothelial cells, would cause platelet-driven arterial thrombosis. Autoimmunity-associated thrombosis initiated by binding of AECAs to endothelial cells might play a major role in the pathogenesis of certain subtypes of KD. The notion of KD consisting of subtypes, the major one of which is AECA-associated vasculitis, will help improve our understanding of KD and further promote early and accurate diagnosis, which remains challenging.

Circulating plasmablasts are elevated and produce pathogenic anti-endothelial cell autoantibodies in idiopathic pulmonary arterial hypertension.

Idiopathic pulmonary arterial hypertension (IPAH) is a devastating pulmonary vascular disease in which autoimmune and inflammatory phenomena are implicated. B cells and autoantibodies have been associated with IPAH and identified as potential therapeutic targets. However, the specific populations of B cells involved and their roles in disease pathogenesis are not clearly defined. We aimed to assess the levels of activated B cells (plasmablasts) in IPAH, and to characterize recombinant antibodies derived from these plasmablasts. Blood plasmablasts are elevated in IPAH, remain elevated over time, and produce IgA autoantibodies. Single-cell sequencing of plasmablasts in IPAH revealed repertoires of affinity-matured antibodies with small clonal expansions, consistent with an ongoing autoimmune response. Recombinant antibodies representative of these clonal lineages bound known autoantigen targets and displayed an unexpectedly high degree of polyreactivity. Representative IPAH plasmablast recombinant antibodies stimulated human umbilical vein endothelial cells to produce cytokines and overexpress the adhesion molecule ICAM-1. Together, our results demonstrate an ongoing adaptive autoimmune response involving IgA plasmablasts that produce anti-endothelial cell autoantibodies in IPAH. These antibodies stimulate endothelial cell production of cytokines and adhesion molecules, which may contribute to disease pathogenesis. These findings suggest a role for mucosally-driven autoimmunity and autoimmune injury in the pathogenesis of IPAH.

Endothelial cell autoantibodies in predicting declining renal function, end-stage renal disease, or death in adult type 2 diabetic nephropathy.

Albuminuria is a strong predictor of diabetic nephropathy chronic kidney disease outcomes. Yet, therapeutic albuminuria-lowering has not consistently translated into a reduction in clinical events suggesting the involvement of additional pathogenic factors. Our hypothesis is that anti-endothelial cell autoantibodies play a role in development and progression in diabetic nephropathy. We determined anti-endothelial cell antibody (AECA) bioactivity in protein A-elutes of baseline plasma in 305 participants in the VA NEPHRON-D study, a randomized trial of angiotensin receptor blocker (ARB) or dual ARB plus angiotensin-converting enzyme inhibitor therapy in type 2 diabetes with proteinuric nephropathy. Thirty-eight percent (117/305) of participants had significantly reduced endothelial cell survival ( ≤80%) in the IgG fraction of plasma. A VA NEPHRON-D primary endpoint [end-stage renal disease (ESRD), significant reduction in estimated glomerular filtration rate, or death] was experienced by 58 individuals. In adjusted Cox regression analysis, there was a significant interaction effect of baseline anti-endothelial cell-mediated cell survival and albuminuria on the hazard rate (HR) for primary composite endpoint (P = 0.017). Participants lacking strongly inhibitory antibodies with albuminuria ≥1 g/g creatinine had a significantly increased primary event hazard ratio, 3.41 – 95% confidence intervals (CI 1.84–6.33; P < 0.001) compared to those lacking strongly inhibitory antibodies with lower baseline albuminuria ( <1 g/g creatinine). These results suggest that anti-endothelial cell antibodies interact significantly with albuminuria in predicting the composite endpoint of death, ESRD, or substantial decline in renal function in older, adult type 2 diabetic nephropathy.

Unilateral hearing loss due to pegylated interferon-α2b and ribavirin therapy

Combination of pegylated interferon and ribavirin is the standard of care in patients with chronic hepatitis C virus infection. However this therapy has many side effects, including flu-like symptoms, neuropsychiatric symptoms and cytopenias. Auditory symptoms like tinnitus and hearing loss have only rarely been reported. A 40-year-old man, incidentally detected to have hepatitis C virus (HCV) infection a year ago, was referred to our hospital for further management. He was asymptomatic and physical examination was unremarkable. Investigations revealed normal complete blood counts, renal function tests, glucose and bilirubin, and elevated alanine aminotransferase (ALT 126 U/L). Anti-HCV was positive, HCV viral load was 4.2×10 IU/mL and genotype was 3. Ultrasonography abdomen revealed normal size and echotexture of liver. He was diagnosed to have chronic HCV infection and was started on pegylated interferon α2b 80 μg subcutaneously per week (body weight 62 kg) plus oral ribavirin 800 mg/ day. He used to have fever and flu-like symptoms lasting for 2–3 days after each dose of interferon. Hemoglobin declined by 3 gm/dL by week 12 and he lost 5 kg of weight. His viral load had become negative by week 4 (rapid virological response) and remained negative at week 12 (early virological response). In the 19th week of antiviral therapy, he started having pain in left ear associated with some hearing loss. He denied any history of hearing loss or exposure to any ototoxic drugs in the past. Tympanic membrane did not reveal any abnormality. MRI of the middle ear was normal. Pure tone audiometry showed a profound sensorineural hearing loss of 70/120 dB in his left ear and normal hearing of 18/18 dB in the right ear. The patient decided to discontinue further therapy. At the end of treatment his ALT values were normal and HCV RNA was undetectable. He was prescribed multivitamins and anti-inflammatory drugs. Pain in the left ear decreased but hearing loss showed no improvement over a 6-month follow up. HCV RNA was undetectable indicating sustained virological response. This case illustrates a rare adverse reaction of sudden unilateral sensorineural hearing loss in a patient receiving pegIFNα2b and ribavirin combination therapy for chronic HCV infection. MRI ruled out other causes for such acute unilateral hearing loss such as temporal bone fracture, rupture of round or oval window membranes or vestibular schwannoma. Both unilateral and bilateral acute sensorineural hearing loss with interferon therapy have been rarely reported in literature, unilateral being more common [1–6, 9, 10]. In a prospective study, 32 (44%) of 73 patients receiving interferon developed abnormalities on audiometry [1]. These resolved completely within 7–14 days after discontinuation of therapy. In another prospective study, 9 of 27 patients with chronic hepatitis B receiving interferon-alpha developed sensorineural hearing loss [2]. They further observed that this loss increased gradually with subsequent doses but recovered completely after discontinuation of treatment. Various hypothesis for ototoxicity associated with interferon therapy are autoimmune (detection of anti-endothelial cell autoantibodies and response to prednisolone) [1, 3–5], direct S. Jain :V. Midha Department of Medicine, Dayanand Medical College and Hospital, Ludhiana, Punjab 1410 01, India

Anti‐Endothelial Cell Antibodies in Dogs with Immune‐Mediated Hemolytic Anemia and Other Diseases Associated with High Risk of Thromboembolism

Dogs with immune-mediated hemolytic anemia (IMHA) and certain inflammatory diseases are at high risk of developing thromboembolic disease. The presence of anti-endothelial cell autoantibodies (AECA) has been associated with an increased risk of thromboembolism in humans. AECA will be detected more often in dogs at risk of thromboembolism than in healthy control animals or dogs with diseases not associated with a higher risk of thromboembolism. Ninety-one sick dogs and 22 healthy control dogs. Retrospective case-controlled study. Serum was screened for the presence of AECA. Dogs were identified for the study based on the risk of thromboembolism as determined by clinical impression and the underlying disease process. Flow cytometry and normal canine endothelial cells were used to screen serum samples from sick and healthy control dogs for the presence of AECA. In addition, serum from dogs with confirmed thromboemboli was also screened for the presence of AECA by immunohistochemistry. AECA were detected in 2/91 sick dogs, both with infectious diseases, but were not found in healthy dogs. Anti-endothelial antibodies were not detected in 21 dogs with IMHA and 20 dogs with systemic inflammatory response syndrome, sepsis, or both. We conclude that AECA are rarely detectable in dogs considered at high risk of thromboembolism. These findings suggest that AECA may not play an important role in the pathogenesis of thromboembolism in dogs with IMHA and other inflammatory diseases.

Low plasma basic fibroblast growth factor is associated with laser photocoagulation treatment in adult type 2 diabetes mellitus from the Veterans Affairs Diabetes Trial

Basic fibroblast growth factor (bFGF) is a potent endothelial cell mitogen that does not normally circulate. Yet plasma bFGF-like bioactivity was increased in association with persistent microalbuminuria and retinopathy in adult type 2 diabetes mellitus. In the present study, we tested whether plasma bFGF immunoreactivity (IR) could predict the need for laser treatment of diabetic retinopathy in a baseline subset of advanced type 2 diabetes mellitus from the Veterans Affairs Diabetes Trial (mean: age, 59 years; diabetes duration, 11 years; baseline glycosylated hemoglobin, 9.5%). Plasma bFGF-IR was determined with a sensitive and specific 2-site enzyme-linked immunoassay in 172 patients at the baseline visit. Results were dichotomized at 4.5 pg/mL, the upper limit in healthy men. There was an unexpected significant association between low baseline plasma bFGF-IR level and the interim (4 years) need for laser treatment. First laser treatment was significantly more likely to be required in patients with low compared with high baseline bFGF (19% vs 6%, P = .03 for the difference). After adjusting for clinical risk factors, low vs high bFGF (hazard ratio [HR], 5.01; P = .012), duration of diabetes (HR, 1.05; P = .050), and low-density lipoprotein cholesterol concentration (HR, 0.98; P = .027) were all significantly associated with time to first laser occurrence. These and our prior results suggest that low plasma bFGF-IR may be a marker for the presence of anti–endothelial cell autoantibodies that may contribute to the need for laser photocoagulation treatment in adult men with advanced type 2 diabetes mellitus.

Autoantibodies against glomerular endothelial cells in anti‐neutrophil cytoplasmic autoantibody‐associated systemic vasculitis

The prevalence of anti-endothelial cell autoantibodies (AECA) in patients with anti-neutrophil cytoplasmic autoantibody-associated systemic vasculitis (ASV) has been reported by several groups with conflicting results ranging from 8% to 100%. Types of substrate cells used for AECA testing partially explain this variation. Endothelial cells from kidney origin have been reported to be predominant in AECA binding. Therefore, we investigated AECA prevalence using a human glomerular endothelial cell line compared with primary human umbilical vein endothelial cells, which have frequently been used for AECA detection. Sera from 43 ASV patients (29 Wegener's granulomatosis (WG), 14 microscopic polyangiitis (MPA)) with active disease were assessed for AECA positivity using cell-based enzyme-linked immunosorbent assay. Forty serum samples from healthy controls were tested in parallel. To evaluate endothelial activation levels, soluble intercellular cell adhesion molecule-1 and vascular cell adhesion molecule-1 were measured with capture enzyme-linked immunosorbent assay. The AECA were detected in 4 of 29 WG patients (14%), but none of 14 MPA patients was positive for AECA using glomerular endothelial cell as a substrate, whereas AECA were positive in 10% of WG patients and 14% of MPA patients on human umbilical vein endothelial cells. No significant differences were found between ASV patients and controls in AECA test. Serum levels of vascular cell adhesion molecule-1 and soluble intercellular cell adhesion molecule-1 in ASV patients were significantly higher than in controls. However, there were no differences between AECA-positive and -negative patients for both of the activation markers. The AECA, directed against glomerular endothelial cells, have a low prevalence in ASV patients with active disease and are not correlated with endothelial activation.

Anti-Platelet and Anti-Endothelial Cell Autoantibodies in Vietnamese Infants and Children with Dengue Hemorrhagic Fever

Dengue hemorrhagic fever (DHF) is a serious public health problem. Increased vascular permeability and thrombocytopenia are the hallmarks of DHF. The mechanisms involved in DHF/Dengue shock syndrome (DSS) pathogenesis is not fully understood. This study gives evidence of the presence of antibodies which cross-reacted with platelets, and endothelial cells in the sera of Vietnamese infants and children with DHF/DSS. The anti-platelet, anti-endothelial cell IgM levels were higher in the sera of DHF/DSS infants and children, compared with controls. However, the levels of these autoantibodies were not correlated with the severity of DHF (non-shock DHF vs DSS). The antiplatelet, and anti-endothelial cell autoantibodies may play a role in the pathogenesis of DHF/DSS in infants and children with predominantly primary, and secondary dengue infections, respectively. The epitopes shared by surface molecules of platelets and endothelial cells and dengue virus antigens need to be identified and avoided in designing the safe candidate vaccines.

Could diabetic retinopathy be an autoimmune disease?

Diabetic retinopathy is a common and progressive complication of diabetes mellitus. It is characterized by the loss of pericytes, hypertrophy of basement membrane, microaneurysms formation, increased vascular permeability, capillary occlusions, neovascularisation and fibrovascular proliferation. The pathogenesis of diabetic retinopathy is still insufficiently understood, although some reports have implicated the role of the immune system. We hypothesize that, according to some current data diabetic retinopathy could also be considered as an autoimmune disease. The finding of antipericyte and antiendothelial cell autoantibodies in the circulation of diabetic patients strongly suggests that some autoimmune activity has been involved in the early pathophysiology of diabetic retinopathy. There is even more evidence that implicates the presence of autoimmune mechanisms in the proliferative stage of this disease: elevated levels of tumor necrosis factor-alpha, interleukin-8 and soluble interleukin-2 receptor in the serum of diabetic patients, increased vitreous concentration of the interleukin-6 and interleukin-8 in patients with proliferative retinopathy. Furthermore, preretinal membranes in diabetic patients contain deposits of immunoglobulins, activated complement components, monocytes, T and B lymphocytes, fibroblastes and lymphokynes. In diabetic patients human leukocyte antigen DR and DQ expression on the retinal vascular endothelial cells as well as on pigment and nonpigment epithelial cells was found. These antigens are normally restricted to immunocompetent cells and play an important regulatory role in the immune response. Their aberrant expression has been found on nonlymphoid cells in various autoimmune diseases whilst abnormal expression of DR and DQ antigens at sites where they do not normally exist would result in autoimmunity by converting the target cell into a functional antigen-presenting cell. In conclusion, although the pathogenesis of diabetic retinopathy is not completely understood it is known that the immune system is certainly involved in its development. However, there is increasing evidence of the presence of some autoimmune processes in the early stages of diabetic retinopathy and particularly in its proliferative phases. Consequently, diabetic retinopathy could also be considered as an autoimmune disease.

New developments in the pathogenesis of systemic sclerosis

Systemic sclerosis (SSc) is characterized by extensive fibrosis, vasculopathy and activation of the immune system. Fibrosis can be caused by profibrotic cytokines, such as transforming growth factor-β (TGFβ), interleukin-4 (IL-4), platelet-derived growth factor (PDGF), and connective tissue growth factor. Vasculopathy can be caused by TGFβ, PDGF, while paucity of vessels in skin lesions can be attributed to anti-endothelial cell autoantibodies. Recent studies have suggested that the activation of the immune system is of paramount importance in the pathogenesis of SSc. T Cells are activated by antigen, infiltrate early the skin lesions in SSc, and produce the profibrotic cytokine IL-4. They are also required for autoantibody production. B cells may contribute to fibrosis, as deficiency of CD19, a B cell transduction molecule, results in decreased fibrosis in animal models of fibrosis. These new developments have direct impact on the treatment of SSc. Medications directed against immune cells or harmful soluble factors in small trials in SSc are encouraging.

Induction of endothelial cell apoptosis by heat-shock protein 60-reactive antibodies from anti-endothelial cell autoantibody-positive systemic lupus erythematosus patients.

To determine whether anti-endothelial cell autoantibodies (AECAs) from systemic lupus erythematosus (SLE) patients with the antiphospholipid syndrome are involved in the initial endothelial cell (EC) membrane perturbation effect that is postulated to provide a target for antiphospholipid antibody (aPL) binding and, hence, to trigger the thrombotic cascade. To identify the AECA antigenic target on ECs and to determine the mechanism whereby the EC membrane is disrupted. AECAs from SLE patients were assayed for binding to ECs by flow cytometry. Positive AECAs were assayed by immunoblotting, and a consensus antigen was identified by mass spectrometry. This candidate antigen was tested in recombinant form for AECA recognition. AECAs were affinity-purified on this antigen and incubated with ECs to determine their physiologic effects. Anti-Hsp60 antibody titers were determined by enzyme-linked immunosorbent assay. The relationship of anti-Hsp60 status and lupus anticoagulant (LAC) status to thrombotic manifestations between disease onset and the last followup visit were analyzed. Most of the SLE sera (73%) possessed IgG that bound to the surface of ECs. These positive IgG shared reactivity against a 60-kd EC surface polypeptide that was identified as human Hsp60. The presence of Hsp60 at the EC surface was established using anti-Hsp60 antibodies from commercial sources or affinity-purified from SLE sera that bound ECs. Incubation of ECs with these anti-Hsp60 antibodies induced apoptosis in a time- and dose-dependent manner, as determined by Hoechst 33342 dye staining of condensed nuclei and by annexin V binding to surface phosphatidylserine. Anti-Hsp60 antibodies were not restricted to SLE patients, but were found in patients with other autoimmune diseases. However, anti-Hsp60 antibodies were significantly associated with an increased frequency of thrombosis when present in combination with LAC in the SLE patients. The presence of Hsp60 at the surface of ECs serves as a target for the anti-Hsp60 antibodies in SLE sera. These anti-Hsp60 antibodies bind to ECs and induce apoptosis, particularly phosphatidylserine exposure, thus providing a target for the binding of aPL and inducing the subsequent thrombotic cascade.

Raised anti-endothelial cell autoantibodies (AECA), but not anti-neutrophil cytoplasmic autoantibodies (ANCA), in recurrent oral ulceration: modulation of AECA binding by tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma).

Recurrent oral ulceration (ROU) is a common oral mucosal condition of unknown etiology. However, there is evidence to suggest that vasculitis may play a role. Here we investigate the presence in ROU of two autoantibodies associated with vasculitis, AECA and ANCA. AECA target as yet unidentified antigens on the endothelial cell surface and have been identified in patients with vasculitic disorders and inflammatory conditions with a vasculitic component. ANCA target specific neutrophil-associated proteins and are detected in specific vasculitic and chronic inflammatory disorders. AECA and ANCA levels were studied in 20 ROU patients and 20 controls. IgG AECA to the endothelial cell line ECV 304 were detected in 19 ROU patients and four controls. Levels were significantly raised in ROU both to ECV 304 (P < 0.000 05) and to human umbilical vein endothelial cells (HUVEC) (P < 0.005). Although levels were highest during episodes of ulceration, they were also raised between episodes. Stimulation of endothelial cells with TNF-alpha significantly increased AECA binding of both ROU (P < 0.005) and control samples (P < 0.0001), while IFN-gamma decreased binding (ROU P < 0.0001; controls P < 0.05). In contrast, ANCA were detected in only one patient and none of the controls. The presence of raised levels of AECA lends support to the hypothesis that a vasculitic process may underlie ROU. Moreover, these findings suggest that endothelial cell expression of AECA target antigens is increased by TNF-alpha and decreased by IFN-gamma stimulation.

Vitronectin- and Fibronectin-containing Immune Complexes in Primary Systemic Vasculitis

In primary systemic vasculitis anti endothelial cell autoantibodies (AECA) have been described frequently. They represent a heterogeneous group of autoantibodies whose target antigens are mostly unknown. We tried to find AECA-antigens by a co-operative binding assay with a panel of monoclonal antibodies (mAb) directed to human umbilical vein endothelial cells (HUVEC) and extracellular matrix proteins. The mAb were used to bind antigens from lysate of endothelial cells, and binding of human antibodies to these antigens was measured. mAb directed to Vitronectin (VN) and Fibronectin (FN) resulted in enhanced binding of antibodies in sera from patients with Churg Strauss Syndrome (CSS) and Wegener's Granulomatosis (WG) compared to normal sera. Neither free autoantibodies against VN or FN could be detected nor did the addition of endothelial cell lysate influence the binding activity from the patients' sera. This suggests that preformed VN and FN-containing immune complexes (IC) are present in the patient sera. The amount of IC was decreased by incubation with HUVEC, demonstrating that these IC can bind to endothelial cells. However, their involvement in the pathogenesis of the disease is not clearly defined. Our data suggest that there are preformed IC present in sera of patients with CSS and WG that contain VN and FN and bind to endothelial cells.

Autoimmunity in Sudden Sensorineural Hearing Loss: Possible Role of Anti-endothelial Cell Autoantibodies

In order to verify whether anti-endothelial cell autoantibodies (AECAs) can be used as serological markers of inner ear vasculitis in sudden sensorineural hearing loss (SSHL), 32 patients affected by idiopathic SSHL were investigated. All patients underwent a routine general physical examination and extensive audiovestibular, microbiological and immunological investigations. Fourteen normal subjects without a history of HL, autoimmune or metabolic disease served as controls. Detection of AECAs was performed using an indirect immunofluorescence technique. AECA-positive patients were treated with methylprednisone, while AECA-negative patients were treated with a combined regimen of steroids, plasma expander and aspirin. The average hearing recovery for 5 frequencies (0.25-4 kHz) was analyzed in each subject 1 month after treatment and every 3 months thereafter; median follow-up was 12 months (range 9-18 months). A total of 15/32 patients (46.8%; 11/19 females, 4/13 males) were AECA-positive and thus differed significantly from the normal population in whom only 2/14 tested cases were positive ( p =0.03). Severe hearing loss was associated with being AECA-positive in 8/11 cases. During follow-up, 25/32 patients improved their hearing and 17 of these patients were AECA-negative. The seven cases without hearing improvement were all AECA-positive. In patients with SSHL, immune-mediated vascular damage may have a pathogenetic role and AECAs may represent a serological marker of vasculitis even if they are not inner ear-specific and even if they represent an epi-phenomenon rather than the only cause of SSHL.

Autoantibody appearance in cytomegalovirus‐infected liver transplant recipients: Correlation with antigenemia

The presence of anti-endothelial cells (AECA), smooth muscle (SMA), antinuclear (ANA) and antimitochondrial (AMA) autoantibodies, and liver/kidney microsomal antibody type 1 (LKM1) was investigated retrospectively in sera of liver transplant patients and correlated with cytomegalovirus (CMV) infection as determined by the antigenemia test and with the appearance of acute or chronic allograft rejection. Indirect immunofluorescence analysis was carried out in sequential sera from 40 liver transplant patients. Ten out of 23 antigenemia-positive and none of the antigenemia-negative patients developed serum autoantibodies (P = 0.002, Fisher's exact test). Anti-endothelial cell autoantibodies were found in nine cases and SMA in four patients. Antinuclear antibodies were detected in one otherwise autoantibody-negative patient. All but one case of autoantibody positivity were observed in the high antigenemia group (P < 0.0001, Fisher's exact test). In all but one case, autoantibodies were detected in blood during the antigenemia phase and in most cases in coincidence with or after the antigenemia peak. Even though a statistically significant correlation was not found between autoantibody production and the development of acute or chronic allograft rejection, proportionally more acute rejection cases were observed in the autoantibody-positive than in the autoantibody-negative group. It has been speculated that CMV-induced endothelial damage may be a potent antigenic stimulus, which leads to the production of anti-endothelial cells autoantibodies. Anti-endothelial cell autoantibodies may represent not only a marker of cell injury but also contribute to the progression of the inflammatory response leading to the exposure of tissue-privileged self antigens and the induction of other autoantibodies such as SMA.

Immunopathogenesis of dengue virus infection.

Dengue virus infection causes dengue fever (DF), dengue hemorrhagic fever (DHF), and dengue shock syndrome (DSS), whose pathogeneses are not clearly understood. Current hypotheses of antibody-dependent enhancement, virus virulence, and IFN-gamma/TNFalpha-mediated immunopathogenesis are insufficient to explain clinical manifestations of DHF/DSS such as thrombocytopenia and hemoconcentration. Dengue virus infection induces transient immune aberrant activation of CD4/CD8 ratio inversion and cytokine overproduction, and infection of endothelial cells and hepatocytes causes apoptosis and dysfunction of these cells. The coagulation and fibrinolysis systems are also activated after dengue virus infection. We propose a new hypothesis for the immunopathogenesis for dengue virus infection. The aberrant immune responses not only impair the immune response to clear the virus, but also result in overproduction of cytokines that affect monocytes, endothelial cells, and hepatocytes. Platelets are destroyed by crossreactive anti-platelet autoantibodies. Dengue-virus-induced vasculopathy and coagulopathy must be involved in the pathogenesis of hemorrhage, and the unbalance between coagulation and fibrinolysis activation increases the likelihood of severe hemorrhage in DHF/DSS. Hemostasis is maintained unless the dysregulation of coagulation and fibrinolysis persists. The overproduced IL-6 might play a crucial role in the enhanced production of anti-platelet or anti-endothelial cell autoantibodies, elevated levels of tPA, as well as a deficiency in coagulation. Capillary leakage is triggered by the dengue virus itself or by antibodies to its antigens. This immunopathogenesis of DHF/DSS can account for specific characteristics of clinical, pathologic, and epidemiological observations in dengue virus infection.