Modulation of endothelial cell function by normal polyspecific human intravenous immunoglobulins: a possible mechanism of action in vascular diseases

Multifaceted Tissue-Protective Functions of Polyvalent Immunoglobulin Preparations in Severe Infections-Interactions with Neutrophils, Complement, and Coagulation Pathways

Severe infections induce immune defense mechanisms and initial tissue damage, which produce an inflammatory neutrophil response. Upon dysregulation of these responses, inflammation, further tissue damage, and systemic spread of the pathogen may occur. Subsequent vascular inflammation and activation of coagulation processes may cause microvascular obstruction at sites distal to the primary site of infection. Low immunoglobulin (Ig) M and IgG levels have been detected in patients with severe infections like sCAP and sepsis, associated with increased severity and mortality. Based on Ig's modes of action, supplementation with polyvalent intravenous Ig preparations (standard IVIg or IgM/IgA-enriched Ig preparations) has long been discussed as a treatment option for severe infections. A prerequisite seems to be the timely administration of Ig preparations before excessive tissue damage has occurred and coagulopathy has developed. This review focuses on nonclinical and clinical studies that evaluated tissue-protective activities resulting from interactions of Igs with neutrophils, complement, and the coagulation system. The data indicate that coagulopathy, organ failure, and even death of patients can possibly be prevented by the timely combined interactions of (natural) IgM, IgA, and IgG with neutrophils and complement.

Intravenous Immunoglobulin: Mechanism of Action in Autoimmune and Inflammatory Conditions

Intravenous immunoglobulin (IVIG) is the mainstay of therapy for humoral immune deficiencies and numerous inflammatory disorders. Although the use of IVIG may be supplanted by several targeted therapies to cytokines, the ability of polyclonal normal IgG to act as an effector molecule as well as a regulatory molecule is a clear example of the polyfunctionality of IVIG. This article will address the mechanism of action of IVIG in a number of important conditions that are otherwise resistant to treatment. In this commentary, we will highlight mechanistic studies that shed light on the action of IVIG. This will be approached by identifying effects that are both common and disease-specific, targeting actions that have been demonstrated on cells and processes that represent both innate and adaptive immune responses.

Application of intravenous immunoglobulin (IVIG) to modulate inflammation in critical COVID-19 - A theoretical perspective

COVID-19 is an airway disease that has affected ~125 million people worldwide, caused by a novel coronavirus termed severe acute respiratory syndrome coronavirus 2 (SARS-CoV2), spread through respiratory droplets, direct contact, and aerosol transmission. Although most patients presenting with absent or mild symptoms recover completely, the highest morbidity and mortality rates are seen in the elderly, and patients with comorbidities such as cardiovascular diseases, cancer, immunosuppressive diseases, diabetes, and pre-existing respiratory illnesses. Several therapeutic strategies have been examined, but a wide-ranging therapeutic option for particularly severe cases of COVID-19 remains to be elucidated. Considering the indications presented by COVID-19 patients who present similarly with inflammatory conditions, intravenous immunoglobulin (IVIG) administration has been examined as a possible route to reduce proinflammatory markers such as ESR, CRP and ferritin by reducing inflammation, based on its anti-inflammatory effects as indicated by utilisation of IVIG for numerous other inflammatory conditions. Herein, summarising the recent key clinical evaluations of IVIG administration, we present our hypothesis that administration of IVIG within a specific dosage would be extremely beneficial towards reducing mortality and perhaps even the length of hospitalisation of patients exhibiting severe COVID-19 symptoms.

Risiken und Chancen von Immuntherapien in Zeiten der Coronavirus-2019-Pandemie

Immuntherapien stellen die essenzielle Grundlage der Behandlung von neuroinflammatorischen Erkrankungen dar. In Zeiten der Coronavirus-2019 (COVID-19)-Pandemie ergibt sich im klinischen Alltag jedoch zunehmend die Frage, ob eine Immuntherapie bei neurologischen Patienten aufgrund des potenziellen Infektionsrisikos eingeleitet, intensiviert, pausiert oder gar beendet werden sollte. Unsicherheit besteht v. a. deshalb, weil verschiedene nationale und internationale Fachgesellschaften diesbezüglich unterschiedliche Empfehlungen veröffentlichten. In diesem Artikel soll ein Überblick über die Wirkmechanismen von Immuntherapien und den daraus abzuleitenden Infektionsrisiken in Bezug auf COVID-19 (durch den Coronavirus verursachte Erkrankung) gegeben werden. Potenzielle Chancen und vorteilhafte Effekte einzelner Substrate in der Akuttherapie von COVID-19 werden diskutiert.

Merits and culprits of immunotherapies for neurological diseases in times of COVID-19

Immunosuppression and immunomodulation are valuable therapeutic approaches for managing neuroimmunological diseases. In times of the Coronavirus disease 2019 (COVID-19) pandemic, clinicians must deal with the question of whether immunotherapy should currently be initiated or discontinued in neurological patients. Uncertainty exists especially because different national medical associations publish different recommendations on the extent to which immunotherapies must be continued, monitored, or possibly switched during the current pandemic. Based on the most recently available data both about the novel coronavirus and the approved immunotherapies for neurological diseases, we provide an updated overview that includes current treatment strategies and the associated COVID-19 risk, but also the potential of immunotherapies to treat COVID-19.

Phenotypic and Transcriptomic Lymphocytes Changes in Allograft Recipients After Intravenous Immunoglobulin Therapy in Kidney Transplant Recipients

High dose intravenous immunoglobulin (IVIG) are widely used after kidney transplantation and its biological effect on T and B cell phenotype in the context of maintenance immunosuppression was not documented yet. We designed a monocentric prospective cohort study of kidney allograft recipients with anti-HLA donor specific antibodies (DSA) without acute rejection on screening biopsies treated with prophylactic high-dose IVIG (2 g/kg) monthly for 2 months. Any previous treatment with Rituximab was an exclusion criterion. We performed an extensive analysis of phenotypic and transcriptomic T and B lymphocytes changes and serum cytokines after treatment (day 60). Twelve kidney transplant recipients who completed at least two courses of high-dose IVIG (2 g/kg) were included in a median time of 45 (12–132) months after transplant. Anti-HLA DSA characteristics were similar before and after treatment. At D60, PBMC population distribution was similar to the day before the first infusion. CD8⁺ CD45RA⁺ T cells and naïve B-cells (Bm2⁺) decreased (P = 0.03 and P = 0.012, respectively) whereas Bm1 (mature B-cells) increased (P = 0.004). RORγt serum mRNA transcription factor and CD3 serum mRNA increased 60 days after IVIG (P = 0.02 for both). Among the 25 cytokines tested, only IL-18 serum concentration significantly decreased at D60 (P = 0.03). In conclusion, high dose IVIG induced limited B cell and T cell phenotype modifications that could lead to anti-HLA DSA decrease. However, no clinical effect has been isolated and the real benefit of prophylactic use of IVIG after kidney transplantation merits to be questioned.

Mechanisms of Action of Intravenous Immunoglobulin (IVIG)

Therapeutic preparations of pooled normal polyspecific immunoglobulin G for intravenous use (intravenous immunoglobulin, IVIG) have been shown to be effective in the treatment of a number of autoimmune and systemic inflammatory conditions. IVIG prevents the occurrence of experimental autoimmune encephalomyelitis. Increasing evidence suggests that IVIG is of benefit in patients with relapsing-remitting multiple sclerosis. The present review discusses the immunoregulatory properties and mechanisms of action of IVIG in autoimmune disease.

IVIG-mediated effector functions in autoimmune and inflammatory diseases

Intravenous immunoglobulin (IVIG) is a pooled preparation of normal IgG obtained from several thousand healthy donors. It is widely used in the immunotherapy of a large number of autoimmune and inflammatory diseases. The mechanisms of action of IVIG are complex and, as discussed in this review, experimental and clinical data provide an indicator that the therapeutic benefit of IVIG therapy is due to several mutually non-exclusive mechanisms affecting soluble mediators as well as cellular components of the immune system. These mechanisms depend on Fc and/or F(ab')2 fragments. A better understanding of the effector functions of IVIG should help in identification of biomarkers of responses to IVIG in autoimmune patients.

Therapeutic Potential of Intravenous Immunoglobulin in Acute Brain Injury

Acute ischemic and traumatic injury of the central nervous system (CNS) is known to induce a cascade of inflammatory events that lead to secondary tissue damage. In particular, the sterile inflammatory response in stroke has been intensively investigated in the last decade, and numerous experimental studies demonstrated the neuroprotective potential of a targeted modulation of the immune system. Among the investigated immunomodulatory agents, intravenous immunoglobulin (IVIg) stand out due to their beneficial therapeutic potential in experimental stroke as well as several other experimental models of acute brain injuries, which are characterized by a rapidly evolving sterile inflammatory response, e.g., trauma, subarachnoid hemorrhage. IVIg are therapeutic preparations of polyclonal immunoglobulin G, extracted from the plasma of thousands of donors. In clinical practice, IVIg are the treatment of choice for diverse autoimmune diseases and various mechanisms of action have been proposed. Only recently, several experimental studies implicated a therapeutic potential of IVIg even in models of acute CNS injury, and suggested that the immune system as well as neuronal cells can directly be targeted by IVIg. This review gives further insight into the role of secondary inflammation in acute brain injury with an emphasis on stroke and investigates the therapeutic potential of IVIg.

The potential of intravenous immunoglobulins for cancer therapy: a road that is worth taking?

Much has been learned recently about the role of immunoglobulins as effector molecules of the adaptive immunity and as active elements in the maintenance of immune homeostasis. The increasing number of pathologies where intravenous immunoglobulins (IVIg) display a beneficial action illustrates their therapeutic relevance. Considering recent findings on the ability of IVIg to modulate macrophage polarization, herein we review evidences on the antitumoral activity of IVIg. Fragmentary and nonconclusive, available evidences are just suggestive of the potential of IVIg in antitumoral therapy, but encourage for the generation of additional evidences through well-designed clinical trials, and for additional studies to address the molecular effects of IVIg as a means to avoid the extrapolation of data gathered from animal models.

Disruption of Endothelial Cell Homeostasis Plays a Key Role in the Early Pathogenesis of Coronary Artery Abnormalities in Kawasaki Disease

Disruption of endothelial cell homeostasis may be associated with the pathogenesis of coronary artery abnormalities (CAA) in Kawasaki disease (KD). We sought to clarify the poorly understood pathogenic role of endothelial cell survival and death in KD vasculitis. Human umbilical vein endothelial cells (HUVECs) stimulated with sera from KD patients, compared with sera from patients with bacterial infections, exhibited significant increases in cytotoxicity, high mobility group box protein 1 (HMGB-1), and caspase-3/7 and a decrease in phosphorylated Akt/Akt (pAkt/Akt) ratios. HUVECs stimulated with sera from KD patients treated with immunoglobulin (IG) showed significantly decreased cytotoxicity, HMGB-1, and caspase-3/7 levels and increased pAkt/Akt ratios, as compared with results for untreated HUVECs (P < 0.001, P = 0.008, P = 0.040, and P < 0.001, respectively). In HUVECs stimulated with sera from KD patients, the increased cytotoxicity levels and the suppression of increased pAkt/Akt ratios after subsequent IG treatment were closely related to the development of CAA (P = 0.002 and P = 0.035). Our data reveal that shifting the balance toward cell death rather than survival appears to perturb endothelial cell homeostasis and is closely related to the development of CAA. The cytoprotective effects of IG treatment appear to ameliorate endothelial cell homeostasis.

Human IgGs induce synthesis and secretion of IgGs and neonatal Fc receptor in human umbilical vein endothelial cells

Human IgGs are increasingly used in the therapy of many different immune and inflammatory diseases, however their mechanism of action still remains unclear in most diseases. To gain insight into the mechanism by which IgGs might also exert their effects on endothelial cells, we tested human IgGs on human umbilical vein endothelial cells (HUVECs). IgGs induced a time-dependent increase in the synthesis and secretion of IgGs, together with a marked angiogenic-like transformation of HUVECs that was maximal after a 20-h incubation. IgGs stimulated IG gene transcription without affecting the process of gene rearrangement, already present in control HUVECs. The mechanism involved the activation of transcription factors with the increased expression of HSP90, HSP70 and inactive MMP-9 responsible for the phenotypic differentiation associated with the most intense IgG synthesis and secretion. However, even a short incubation with IgGs followed by recovery of cells was sufficient to trigger and sustain in time the synthesis and secretion of new IgGs, independently of the angiogenic-like transformation visible only when cells were continuously exposed to IgGs. Under the stimulus of IgGs, specific secretory pathways were also activated in HUVECs together with the expression of FcRn, which was always associated with IgGs of new synthesis, forming complexes that were also secreted. Our results disclose a so far unknown and unexpected mechanism of IgGs on HUVECs that behave as Ig-producing immune cells. Results might have relevance for the effects that IgGs also exert in vivo in physiological conditions.

IVIG in APS pregnancy

For more than two decades, the intravenous administration of high doses of IgG pooled from the plasma of healthy donors (immune globulin therapy, also known as ‘IVIG’) has benefited patients with a variety of autoimmune disorders. A potential therapeutic role of IVIG in the prevention of thrombosis and of miscarriages in antiphospholipid syndrome (APS) has been postulated. Multicenter randomized controlled trials attempted to define the role of IVIG in preventing pregnancy complications in APS indicate that simple anticoagulation could not be completely satisfactory, and certain patient subgroups might take advantage of IVIG therapy alone or in combination with heparin.

10% liquid human immunoglobulin (KIOVIG®) for immunomodulation in autoimmune disorders

Intravenous immunoglobulins have been used to treat autoimmune disorders (ADs) for over 50 years. The etiologies of various ADs are not fully understood and although intravenous immunoglobulin treatment has proved its immunomodulatory properties, the roles of proposed mechanisms of action also remain a matter of speculation. A systemic search of the literature regarding KIOVIG® (Baxalta US, Inc., MA, USA) use in clinical trials on patients with ADs and a detailed review of retrieved articles revealed eight relevant publications. These articles reported KIOVIG use in multifocal motor neuropathy, chronic inflammatory demyelinating polyneuropathy, idiopathic thrombocytopenic purpura, Kawasaki disease, Guillain–Barré syndrome and other autoimmune and neurologic disorders and showed that KIOVIG is an effective, safe and well-tolerated treatment in the studied populations. Nevertheless, further studies on larger patient cohorts are needed.

Desensitized morphological and cytokine response after stretch-shortening muscle contractions as a feature of aging in rats

Recovery from contraction-induced injury is impaired with aging. At a young age, the secondary response several days following contraction-induced injury consists of edema, inflammatory cell infiltration, and segmental muscle fiber degeneration to aid in the clearance of damaged tissue and repair. This morphological response has not been wholly established at advanced age. Our aim was to characterize muscle fiber morphology 3 and 10 days following stretch-shortening contractions (SSCs) varying in repetition number (i.e. 0, 30, 80, and 150) for young and old rats. For muscles of young rats, muscle fiber degeneration was overt at 3 days exclusively after 80 or 150 SSCs and returned significantly closer to control values by 10 days. For muscles of old rats, no such responses were observed. Transcriptional microarray analysis at 3 days demonstrated that muscles of young rats differentially expressed up to 2144 genes while muscles of old rats differentially expressed 47 genes. Bioinformatic analysis indicated that cellular movement was a major biological process over-represented with genes that were significantly altered by SSCs especially for young rats. Protein levels in muscle for various cytokines and chemokines, key inflammatory factors for cell movement, increased 3- to 50-fold following high-repetition SSCs for young rats with no change for old rats. This age-related differential response was insightful given that for control (i.e. 0 SSCs) conditions, protein levels of circulatory cytokines/chemokines were increased with age. The results demonstrate ongoing systemic low-grade inflammatory signaling and subsequent desensitization of the cytokine/chemokine and morphological response to contraction-induced injury with aging - features which accompany age-related impairment in muscle recovery.

Therapeutic effect of IVIG on inflammatory arthritis in mice is dependent on the Fc portion and independent of sialylation or basophils

High-dose i.v. Ig (IVIG) is used to treat various autoimmune and inflammatory diseases; however, the mechanism of action remains unclear. Based on the K/BxN serum transfer arthritis model in mice, IVIG suppression of inflammation has been attributed to a mechanism involving basophils and the binding of highly sialylated IgG Fc to DC-SIGN-expressing myeloid cells. The requirement for sialylation was examined in the collagen Ab-induced arthritis (CAbIA) and K/BxN serum transfer arthritis models in mice. High-dose IVIG (1-2 g/kg body weight) suppressed inflammatory arthritis when given prophylactically. The same doses were also effective in the CAbIA model when given subsequent to disease induction. In this therapeutic CAbIA model, the anti-inflammatory effect of IVIG was dependent on IgG Fc but not F(ab')2 fragments. Removal of sialic acid residues by neuraminidase had no impact on the anti-inflammatory activity of IVIG or Fc fragments. Treatment of mice with basophil-depleting mAbs did not abrogate the suppression of either CAbIA or K/BxN arthritis by IVIG. Our data confirm the therapeutic benefit of IVIG and IgG Fc in Ab-induced arthritis but fail to support the significance of sialylation and basophil involvement in the mechanism of action of IVIG therapy.

Polyclonal and monoclonal antibodies in clinic

Immunoglobulins (Ig) or antibodies are heavy plasma proteins, with sugar chains added to amino-acid residues by N-linked glycosylation and occasionally by O-linked glycosylation. The versatility of antibodies is demonstrated by the various functions that they mediate such as neutralization, agglutination, fixation with activation of complement and activation of effector cells. Naturally occurring antibodies protect the organism against harmful pathogens, viruses and infections. In addition, almost any organic chemical induces antibody production of antibodies that would bind specifically to the chemical. These antibodies are often produced from multiple B cell clones and referred to as polyclonal antibodies. In recent years, scientists have exploited the highly evolved machinery of the immune system to produce structurally and functionally complex molecules such as antibodies from a single B clone, heralding the era of monoclonal antibodies. Most of the antibodies currently in the clinic, target components of the immune system, are not curative and seek to alleviate symptoms rather than cure disease. Our group used a novel strategy to identify reparative human monoclonal antibodies distinct from conventional antibodies. In this chapter, we discuss the therapeutic relevance of both polyclonal and monoclonal antibodies in clinic.

Polyclonal immunoglobulin G for autoimmune demyelinating nervous system disorders

Demyelinating diseases with presumed autoimmune pathogenesis are characterised by direct or indirect immune-mediated damage to myelin sheaths, which normally surround nerve fibres to ensure proper electrical nerve conduction. Parenteral administration of polyclonal IgG purified from multi-donor human plasma pools may beneficially modulate these misguided immune reactions via several mechanisms that are outlined in this review. Convincing therapeutic evidence from controlled trials now exists for certain disorders of the peripheral nervous system, including Guillain-Barré syndrome, chronic inflammatory demyelinating polyradiculoneuropathy, and multifocal motor neuropathy. In addition, there is evidence for potential therapeutic benefits of IgG in patients with chronic inflammatory demyelinating diseases of the central nervous system, including multiple sclerosis and neuromyelitis optica. This review introduces these disorders, briefly summarises the established treatment options, and discusses therapeutic evidence for the use of polyclonal immunoglobulins with a particular emphasis on recent clinical trials and meta-analyses.

Bench-to-bedside review: Immunoglobulin therapy for sepsis - biological plausibility from a critical care perspective

Sepsis represents a dysregulated host response to infection, the extent of which determines the severity of organ dysfunction and subsequent outcome. All trialled immunomodulatory strategies to date have resulted in either outright failure or inconsistent degrees of success. Intravenous immunoglobulin (IVIg) therapy falls into the latter category with opinion still divided as to its utility. This article provides a narrative review of the biological rationale for using IVIg in sepsis. A literature search was conducted using the PubMed database (1966 to February 2011). The strategy included the following text terms and combinations of these: IVIg, intravenous immune globulin, intravenous immunoglobulin, immunoglobulin, immunoglobulin therapy, pentaglobin, sepsis, inflammation, immune modulation, apoptosis. Preclinical and extrapolated clinical data of IVIg therapy in sepsis suggests improved bacterial clearance, inhibitory effects upon upstream mediators of the host response (for example, the nuclear factor kappa B (NF-κB) transcription factor), scavenging of downstream inflammatory mediators (for example, cytokines), direct anti-inflammatory effects mediated via Fcγ receptors, and a potential ability to attenuate lymphocyte apoptosis and thus sepsis-related immunosuppression. Characterizing the trajectory of change in immunoglobulin levels during sepsis, understanding mechanisms contributing to these changes, and undertaking IVIg dose-finding studies should be performed prior to further large-scale interventional trials to enhance the likelihood of a successful outcome.

Anti-inflammatory effects of high-dose IgG on TNF-α-activated human coronary artery endothelial cells

High-dose infusion of IgG (IVIG) is used to treat autoimmune and inflammatory diseases, including Kawasaki disease (KD). Although the immunomodulatory effects of IVIG on blood cells such as macrophages have been well studied, its effects on tissue cells remain unclear. Here, we show that high-dose IgG specifically and completely inhibited TNF-α-induced, but not IL-1β-induced, secretion of proinflammatory cytokines such as G-CSF and IL-6 by cultured human coronary artery endothelial cells (HCAECs). High-dose IgG did not inhibit TNF-α-mediated early signaling events of the NF-κB and MAPK pathways but it potently inhibited gene expression of G-CSF and IL-6 12 h after TNF-α-stimulation. Interestingly, suppression of the G-CSF and IL-6 gene expression correlated closely with functional inhibition of a transcription factor, C/EBPδ, whose binding sites in the promoters of G-CSF and IL-6 have been shown to be critical for their transcriptional activation. Furthermore, the inhibitory effect of intact IgG on HCAECs was exerted mainly via its F(ab')(2) fragment, and not its Fc fragment. These findings suggest that the clinical effects of IVIG on KD patients are at least in part due to its direct anti-inflammatory effects on the coronary endothelium, which is a major lesion site in the pathogenesis of KD.

Current proposed mechanisms of action of intravenous immunoglobulins in inflammatory neuropathies

Intravenous immunoglobulins (IVIg) have been shown in a number of trials, to be an effective treatment for the three main types of inflammatory neuropathies: Guillain-Barré Syndrome (GBS), chronic inflammatory demyelinating polyneuropathy (CIDP), and multifocal motor neuropathy (MMN). IVIg is thought to exert its immunomodulatory effects by affecting several components of the immune system including B-cells, T-cells, macrophages, complement, cytokines and cellular adhesion molecules. This article reviews the published evidence and the principal postulated mechanisms of action of intravenous immunoglobulins with special emphasis on inflammatory neuropathies.

Immunoglobulin g (IgG) expression in human umbilical cord endothelial cells

Traditional views hold that immunoglobulin G (IgG) in the human umbilical cord is internalized by human umbilical endothelial cells for passive immunity. In this study, the protein and mRNA transcripts of IgG were found in the cytoplasm of human umbilical endothelial cells by immunohistochemistry, in situ hybridization, and reverse transcription PCR (RT-PCR). The essential enzymes for IgG synthesis and assembling, RAG1 (recombination activating gene 1), RAG2, and variable (V), diversity (D), and joining (J) segments for recombination of IgG, were also found in these cells by RT-PCR and real-time PCR. These results indicate that umbilical endothelial cells are capable of synthesizing IgG with properties similar to those of immune cells and that they may play additional roles besides lining the vessels and transporting IgG.

Kawasaki disease: aetiopathogenesis and therapeutic utility of intravenous immunoglobulin

Kawasaki disease (KD) is an acute febrile childhood vasculitis, associated with the development of coronary artery abnormalities in 25–30% of untreated patients. The aetiopathogenesis is not well known but it is accepted that an undefined infectious trigger in genetically predisposed individuals results in the disease. KD is characterized by an endothelial cell injury, which could be due to abnormal cytokine production and to generation of cytotoxic antibodies against the endothelial cells. Intravenous immunoglobulin IVIG is an effective treatment in preventing the occurrence of coronary artery abnormalities in KD. Several mechanisms may explain the anti-inflammatory effects of IVIG in this disease. They include modification of the cytokine balance, and alteration on both the differentiation and the function of monocytes/macrophages, neutrophils and lymphocytes.

Involvement of innate and adaptive immunity in a murine model of coronary arteritis mimicking Kawasaki disease

Kawasaki disease (KD) is the most common cause of acquired cardiac disease and acute vasculitis in children in the developed world. Injection of a cell wall extract isolated from Lactobacillus casei (LCCWE) into mice causes a focal coronary arteritis that histopathologically mimics the coronary lesions observed in KD patients. In this study we used this model to investigate the participation of T cells, B cells, and dendritic cells (DC) in the development of coronary arteritis. RAG1(-/-), B cell(null), and wild-type (WT) mice were injected with a single dose of LCCWE (500 microg/mouse i.p.). None of the RAG1(-/-) mice developed coronary arteritis, whereas 70% of WT and 100% of B cell(null) mice developed coronary lesions, indicating that T cells were required for lesion formation. When splenocytes isolated from LCCWE-treated mice were restimulated with LCCWE, we observed significant IFN-gamma secretion in WT but not in RAG1(-/-) mice. Immunohistochemical staining showed F4/80(+) macrophages, activated MIDC-8(+) myeloid DCs (mDC), plasmacytoid DCs, and colocalization of CD3(+) T cells with mDCs in coronary artery lesions, suggesting an Ag-driven process. T cells but not B cells are required for LCCWE-induced coronary arteritis. Similar to human lesions, the coronary lesions contain macrophages, activated mDCs, and plaslmacytoid DCs all in close proximity to T cells, further strengthening the relevance of this mouse model to the immunopathology of coronary disease in KD. These studies are consistent with the interpretation that macrophages and DCs may collaborate with T cells in the pathological mechanisms of coronary arteritis.

Anti-vascular endothelial growth factor (VEGF) specific activity of intravenous immunoglobulin (IVIg)

Intravenous immunoglobulins (IVIg) preparations can be beneficial therapeutic agents for the treatment of tumor metastases as has been shown in both human and animal studies. Operating mechanisms have not yet been completely elucidated. Some of the mechanisms proposed entail the stimulation of the production of IL-12, a cytokine that exhibits anti-angiogenic activities, as well as inhibition of endothelial cells proliferation and vascular endothelial growth factor (VEGF) secretion. The aim of the present study was to investigate whether in an IVIg preparation there are natural antibodies directed against VEGF with the potential to affect angiogenesis. Using both sandwich and direct ELISA assays, IVIg was found to specifically recognize and bind VEGF in a dose-dependent manner. The binding specificity was confirmed by inhibition of IVIg binding to VEGF by VEGF as an inhibitor, as shown by ELISA and immunoblot. A mouse hind limb ischemia model was employed to evaluate the in vivo IVIg-induced inhibition of angiogenesis. IVIg was found to exhibit inhibitory effect on VEGF-mediated blood perfusion in the ischemic limb. The present study shows a presence of anti-VEGF fraction in IVIg preparation.

VASCULAR INFLAMMATION AND ATHEROGENESIS ARE ACTIVATED VIA RECEPTORS FOR PAMPs AND SUPPRESSED BY REGULATORY T CELLS

Despite significant advances in identifying the risk factors and elucidating atherosclerotic pathology, atherosclerosis remains the leading cause of morbidity and mortality in industrialized society. These risk factors independently or synergistically lead to chronic vascular inflammation, which is an essential requirement for the progression of atherosclerosis in patients. However, the mechanisms underlying the pathogenic link between the risk factors and atherosclerotic inflammation remain poorly defined. Significant progress has been made in two major areas, which are determination of the roles of the receptors for pathogen-associated molecular patterns (PAMPs) in initiation of vascular inflammation and atherosclerosis, and characterization of the roles of regulatory T cells in suppression of vascular inflammation and atherosclerosis. In this review, we focus on three related issues: (1) examining the recent progress in endothelial cell pathology, inflammation and their roles in atherosclerosis; (2) analyzing the roles of the receptors for pathogen-associated molecular patterns (PAMPs) in initiation of vascular inflammation and atherosclerosis; and (3) analyzing the advances in our understanding of suppression of vascular inflammation and atherosclerosis by regulatory T cells. Continuous improvement of our understanding of the risk factors involved in initiation and promotion of artherogenesis, will lead to the development of novel therapeutics for ischemic stroke and cardiovascular diseases.

What is the contents of the magic draft IVIg?

Intravenous immunoglobulins (IVIg) consist of IgG concentrated from pooled plasma of numerous donors. Their contents is variable, depending in part on the method of preparation. Natural antibodies and natural autoantibodies are prominent in these preparations and their function. Among these, are the idiotype (Id)/anti-Id dimers. Attention has recently been paid to Fc-gamma receptors and sialylation of the IgG from IVIg.

Basic principles of intravenous immunoglobulin (IVIg) treatment

The original rationale for the therapeutic application of immunoglobulins was prevention and treatment of infectious diseases. With the description of agammaglobulinemia, substitution therapy became the primary indication for the use of immunoglobulins. Limitations and side effects of the intramuscular administration of immunoglobulins led to the development of preparations for intravenous use (IVIg). In the early 1980s an immunomodulatory effect of IVIg was described. Since then, the efficacy of IVIg has been established in controlled trials for diseases like idiopathic thrombocytopenic purpura, Kawasaki disease, Guillain-Barré syndrome, dermatomyositis, and many others. There is a large body of evidence that IVIg can modulate an immune reaction at the level of T cells, B cells, and macrophages, interferes with antibody production and degradation, modulates the complement cascade, and has effects on the cytokine network. However, the precise mechanism of action is not yet clear.

Kawasaki disease

Kawasaki disease is an acute febrile, systemic vasculitic syndrome of an unknown etiology that primarily occurs in children younger than five years of age. The principal presentations of Kawasaki disease include fever, bilateral nonexudative conjunctivitis, erythema of the lips and oral mucosa, changes in the extremities, rash, and cervical lymphadenopathy. Coronary artery aneurysms or ectasia develops in 15% to 25% of untreated children with the disease, which may later lead to myocardial infarction, sudden death, or ischemic heart disease. Treatment with intravenous gamma globulin (IVIG) is effective, but the mode of action is still unclear. The development of a diagnostic test, a more specific therapy, and ultimately the prevention of this potentially fatal illness in children are all dependent upon the continued advances in determining the etiopathogenesis of this fascinating disorder.

Comparative study of the anti-inflammatory effect of two intravenous immunoglobulin preparations manufactured by different processes

Intravenous immunoglobulin (IVIG) is increasingly used in the treatment of diverse immune-mediated disorders. Since several preparations of IVIG are available for therapy, it is possible that different manufacturing processes might influence clinical efficacy of IVIG. An insight into the mechanisms of action of such different IVIG preparations is therefore necessary that will provide further guidelines for the utility of IVIG preparations in autoimmune and inflammatory diseases. Since endothelial cells (EC) influence the inflammatory process via production of cytokines, chemokines and expression of adhesive molecules, we analyzed the anti-inflammatory effect on EC of two IVIG preparations: caprylated IVIG (IVIG-C) versus solvent/detergent-treated IVIG (IVIG-SD) preparation. We found that both IVIG preparations inhibit in an equivalent manner, the expression of different pro-inflammatory factors such as IL-6, IL-8, GM-CSF, IL-1beta and TNF-alpha and the adhesion molecules ICAM-1 and VCAM-1. Our results thus suggest that the caprylate while inactivating the virus and enhancing the yield of IgG during IVIG formulation, does not modulate the immunomodulatory properties of IVIG at EC level and that the two preparations show similar anti-inflammatory effects.

Effects of intravenous immunoglobulin and methylprednisolone on human umbilical vein endothelial cells in vitro

Endothelial cells (ECs) do more than just play a role in distinguishing blood and tissues. These cells are also influenced by various chemical mediators present in the blood and tissues. In addition, they produce diverse cytokines, chemokines, adhesion molecules, and growth factors. Therefore, ECs are actively involved in the inflammatory and immune response. We investigated the effects of intravenous immunoglobulin (IVIG) and methylprednisolone (MP) on activated human ECs, by examining the individual and combined effects of the drugs. Human umbilical vein ECs (HUVECs) obtained from the umbilical cords of healthy newborns were cultured. After the HUVECs were treated with interleukin (IL)-1beta, the effects of IVIG and/or MP on the activated HUVECs were assessed by cell proliferation, mRNA expression, and the production of vascular cell adhesion molecule (VCAM)-1, IL-1beta, and vascular EC growth factor (VEGF). IVIG and MP inhibited HUVEC proliferation. IVIG and MP significantly down regulated mRNA expression and the production of VCAM-1, IL-1beta, and VEGF. The combination of IVIG and MP generally showed a greater suppressive effect on mRNA expression and on the production of VCAM-1, IL-1beta, and VEGF. Our results suggest that some of the corticosteroid-sparing effects of IVIG observed in patients with severe asthma could be related to a decreased ability of ECs to proliferate, and to a down regulation of the expression of molecules involved in the onset and progression of airway inflammation.

Comparative Analysis of Antigen Specificities in the Monomeric and Dimeric Fractions of Intravenous Immunoglobulin

Intravenous immunoglobulin (IVIG) preparations are derived from the pooled plasma of thousands of healthy donors and contain a complex mix of antibodies. Depending on the formulation, IVIG preparations contain variable amounts of monomeric and dimeric IgG. The biological and therapeutic significance of these IVIG fractions is still ill defined. Kinetic analysis of monomeric and dimeric IgG isolated by size-exclusion chromatography revealed a stable monomeric versus an unstable dimeric IgG fraction tending to dissociation. Biochemical analysis by 2D gel electrophoresis and isotype analysis showed no significant differences between the fractions. In contrast, comparative analysis by immunodot, ELISA, FACS, and immunohistology of monomeric and dimeric IgG fractions showed a preferential reactivity of the dimeric IgG on a variety of both self-antigens and exoantigens.

Intravenous Immunoglobulin and Plasmapheresis in Acute Humoral Rejection: Experience in Renal Allograft Transplantation

Acute humoral rejection (AHR) in kidney transplantation is associated with higher rates of allograft loss when compared with acute cellular rejection (ACR). Treatment with intravenous immunoglobulin (IVIG) combined with plasmapheresis (PP) has been used recently in many centers. We report the incidence, clinical characteristics, and outcome of patients with AHR treated with IVIG and PP. All patients (n=519) at our institution who underwent kidney transplantation between January 1999 and August 2003 were retrospectively analyzed and classified according to biopsy results into three groups: AHR, ACR, and no rejection. AHR was diagnosed in 23 patients (4.5%) and ACR in 75 patients (15%). Mean follow-up was 844+/-23 days. Female sex, black race, and high panel-reactive antibody were risk factors for AHR. Most AHR patients (22 of 23) were treated with IVIG and PP. Two-year graft survival was numerically worse in patients with AHR versus ACR (78% vs. 85%, p=0.5) but the difference was not statistically significant. Graft survival after AHR treated with IVIG and PP is much better than it has been historically. IVIG in combination with PP is an effective treatment for AHR. Graft survival in this setting is similar to graft survival in patients with ACR.

The diagnosis and management of Kawasaki disease

Kawasaki disease (KD) is a systemic vasculitis of childhood with a predilection for the coronary arteries. It is the predominant cause of paediatric acquired heart disease in developed countries. The aetiology of KD remains unknown and consequently there is no diagnostic test. The diagnosis is made using a constellation of clinical criteria that in isolation have poor sensitivity and specificity. Early treatment prevents overt coronary artery damage in the majority of children. The long-term effects of childhood KD on later cardiovascular health remain unknown. A recent study showed that treatment of KD in Australia is suboptimal, with late diagnosis occurring in approximately half of the cases and an unacceptably high incidence of acute cardiac involvement. These guidelines highlight the difficulties in the diagnosis of KD and offer some clues that may assist early recognition of this important paediatric disease. They also detail current treatment recommendations and the evidence on which they are based. Increased awareness of the epidemiology and spectrum of the clinical presentation of KD is essential for early recognition and optimal management.

Intravenous immunoglobulin g attenuates pulmonary hypertension but induces local neutrophil influx in meconium aspiration in piglets

BACKGROUND

Pulmonary hypertension and inflammation are well-identified pathogenetic features in meconium aspiration syndrome of newborns, but current approaches to their treatment or prevention are still often unsatisfactory.

OBJECTIVES

To investigate the possible protective effects of human intravenous immunoglobulin G (IVIG) on the hypertensive and inflammatory lung injury in severe neonatal meconium aspiration.

METHODS

Eleven newborn (10-12 days old) ventilated and catheterized piglets that received an intratracheal bolus (3 ml/kg) of a 65-mg/ml mixture of human meconium were studied for 6 h. IVIG was infused in 5 piglets 30 min before meconium administration, and 6 piglets served as controls and received the vehicle only.

RESULTS

Meconium instillation induced a biphasic pulmonary hypertensive response, which was significantly diminished by IVIG pretreatment. Similarly, IVIG improved the oxygenation of the piglets, but the intrapulmonary shunt fraction or systemic hemodynamic parameters did not differ between the study groups, except of a minor decrease in the mean arterial blood pressure caused by IVIG. The blood leukocyte count was comparable in the 2 groups. The lung tissue ultrastructural and histological changes, number of apoptotic cells and phospholipase A2 activity were similar in the 2 groups. The amount of neutrophil accumulation, assessed by myeloperoxidase activity, was however significantly increased in macroscopically damaged lung tissue after IVIG administration.

CONCLUSIONS

Our results thus indicate that IVIG treatment of newborns with severe meconium aspiration significantly diminishes the pulmonary hypertensive response and improves oxygenation, but the effects do not extend to protection of lung cellular injury.

Effets immunomodulateurs des immunoglobulines intraveineuses

Intravenous immunoglobulins (IVIg) are therapeutic preparations of normal human IgG obtained from pools of more than 1000 healthy blood donors. They are currently used in the treatment of a wide range of auto-immune diseases, whether associated with auto-antibodies or auto-reactive T lymphocytes, as well as in the treatment of systemic inflammatory diseases. Several mechanisms of action have been identified during the last 20 years, including: (i) modulation of Fc receptors expression on leukocytes and endothelial cells; (ii) interaction with complement proteins; (iii) modulation of cytokines and chemokines synthesis and release; (iv) modulation of cell proliferation and apoptosis; (v) remyelinisation; (vi) neutralisation of circulating autoantibodies; (vii) selection of repertoires of B and T lymphocytes; (viii) interaction with other cell-surface molecules on lymphocytes and monocytes; (ix) corticosteroid sparing. These mechanisms of action are multiple and often intricate. However, they are still little known and further investigations are warranted.

Effect of maternal anti-HPA-1a antibodies and polyclonal IVIG on the activation status of vascular endothelial cells

Maternal anti-HPA-1a antibodies can cause severe fetal and neonatal alloimmune thrombocytopenia (FNAIT), complicated by intracranial haemorrhage (ICH). Antenatal treatment with maternal intravenous immunoglobulin (IVIG) seems to protect against ICH even when thrombocytopenia persists. The aim of this study was to investigate if anti-HPA-1a antibodies and IVIG potentially affect vascular endothelial cells (ECs) in order to identify susceptibility for ICH. Human umbilical cord endothelial cells (HUVEC) were incubated with anti-HPA-1a antibodies with or without polyclonal IVIG and evaluated for EC activation. Maternal sera with anti-HPA-1a antibodies affected neither the EC expression of intracellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1) and tissue factor (TF) nor the release of van Willebrand factor (vWF) or interleukin (IL)-8 nor the integrity of ECs. Maternal sera obtained after IVIG treatment and polyclonal IVIG decrease constitutive and cytokine-induced ICAM-1 and VCAM-1 expression on ECs. The results show that maternal anti-HPA-1a antibodies cause no activation or damage of ECs in this model. The clinical relevance of the de-activating properties of IVIG on EC activation with respect to ICH deserves further investigation.

Kawasaki syndrome

Kawasaki syndrome is an acute, self-limited vasculitis that occurs in children of all ages and presents a challenge for the clinician: the disorder can be difficult to recognise; there is no diagnostic laboratory test; there is an extremely effective therapy; and there is a 25% chance of serious cardiovascular damage if the treatment is not given early in the course of the disease. This review includes discussion of the history of the syndrome, the diagnostic challenges, epidemiology, aetiology, pathology, immunopathogenesis, therapy, genetic influences, and the long-term cardiovascular sequelae.

The endothelium and early immune activation: New perspective and interactions

Far from being just a membrane for the passive transport of cells, molecules, and water between blood vessels and their interstitium or a passive target for humoral immunological reactions, the endothelium is now being viewed as an active modulator of both normal physiological homeostasis and the early inflammatory response. The repertoire of receptors and mediators produced by endothelial cells overlap those traditionally assigned to the immune system. This new paradigm together with the changes caused by brain death in the cadaver donor have far-reaching repercussions on how rejection is conceived, while opening new venues for its prevention. The respective theoretical roles of the neuro-endocrine-immunological axis and of syndecans are highlighted.

Modification of cord blood IL-6 production with IgM enriched human immunoglobulin in term and preterm infants

Pro-inflammatory cytokines contribute significantly to the morbidity of premature infants. IL-6 and IL-8 are involved in the pathogenesis of pulmonary and cerebral tissue injury. The effect of human immunoglobulin preparations on cytokine production in preterm infants has not been studied. We investigated the influence of immunoglobulin on LPS stimulated IL-6 and IL-8 production in cord blood of healthy preterm neonates. Ten non-infected preterm infants delivered by cesarean section and 5 healthy term neonates were included. In the preterm infants, significant IL-6 production was observed in the absence of immunoglobulin after 4 h [median 113 (39-725) pg/ml], 8 h [375 (234-1795) pg/ml] and 12 h [360 (248-2765) pg/ml] of LPS incubation. IL-6 concentrations were significantly lower after incubation with LPS+immunoglobulin after 4 h [median 38 (5-568) pg/ml; p=0.005], 8 h [178 (10-1830) pg/ml; p=0.001] and 12 h [182 (29-2530) pg/ml; p=0.002]. Cultures from term infants produced IL-6 levels approx. 4 times of those from premature infants unaffected by immunoglobulin. IL-8 production also correlated to gestational age and was not affected by immunoglobulin in both groups. Human immunoglobulin preparation may modify IL-6 production in cord blood cultures from premature infants.

Cytokines, chemokines, and cell adhesion molecules in inflammatory myopathies

The inflammatory myopathies include dermatomyositis (DM), polymyositis (PM), and sporadic inclusion-body myositis (s-IBM). In DM, the main immune effector response appears to be humoral and directed against the microvasculature, whereas in both PM and s-IBM, cytotoxic CD8+ T cells and macrophages invade and eventually destroy nonnecrotic muscle fibers expressing major histocompatibility complex class I. The need for more specific and safer therapies in inflammatory myopathies has prompted researchers to better decipher the molecular events associated with inflammation and muscle fiber loss in these diseases. The complex specific migration of leukocyte subsets to target tissues requires a coordinated series of events, namely activation of leukocytes, adhesion to the vascular endothelium, and migration. Cell adhesion molecules (CAM) and chemokines play a major role in this multistep process. In addition, cytokines by stimulating CAM expression and orchestrating T-cell differentiation also influence the immune response. This review focuses on recent advances in defining the molecular events involved in leukocyte trafficking in inflammatory myopathies. Specific topics include a concise summary of clinical features, pathological findings and immunopathology observed in inflammatory myopathies, background information about cytokines, chemokines and cell adhesion molecules, and the expression of these molecules in inflammatory myopathies.

Normal human IgG prevents endothelial cell activation induced by TNFalpha and oxidized low-density lipoprotein atherogenic stimuli

Normal human immunoglobulin G (IgG) has anti-inflammatory and immuno-regulatory properties, which are exploited in the therapy of selected diseases. A putative mechanisms of action is the direct regulation of endothelial cell function by natural antiendothelial cell antibodies. Endothelium activation is a critical event in atherosclerosis. We have verified the ability of normal human IgG to modulate endothelial responses to the atherogenic stimuli tumour necrosis factor-alpha (TNFalpha) and oxidized low-density lipoproteins (oxLDL) in vitro. Confocal microscopy was used to visualize vascular cell adhesion molecule-1 (CD106) expression on endothelial cells, cytoplasmic free calcium ([Ca++]i) modifications and fluorescein-coupled oxLDL internalization. Cytokine secretion was measured by ELISA on cell supernatants. IgG prevented TNFalpha induced CD106 membrane expression and an increase in [Ca++]i, and inhibited the secretion of interleukin-6 (IL-6) and macrophage-colony-stimulating factor (M-CSF). IgG also inhibited CD106 expression induced by oxLDL and one pathway of their internalization, but were ineffective on oxLDL induced [Ca++]i rise and apoptosis. F(ab)'2 fragments from IgG, but not monoclonal IgG, reproduce IgG effects. These findings point to a regulatory role for specific antibodies included in circulating normal IgG towards proinflammatory responses of endothelial cells in atherogenesis and suggest possible development of new therapeutic strategies.

Mechanisms of action of intravenous immunoglobulin in autoimmune and inflammatory diseases

Therapeutic polyclonal intravenous immunoglobulin (IVIg) consists of normal IgG obtained from the pools of plasma of several thousand healthy blood donors. IVIg is used as substitutive treatment of primary and secondary immunodeficiences. Since the first study of Paul Imbach who demonstrated the beneficial effect in idiopathic thrombocytopenic purpura, IVIg is also used in a number of autoimmune and inflammatory diseases. The immunoregulatory effects of IVIg in autoimmune diseases depend on the interaction of Fc portion of immunoglobulins with Fc receptors and on the selection of lymphocyte repertoires of patients through variable regions of infused immunoglobulins. IVIg modulates the activation and effector functions of B and T lymphocytes, neutralizes pathogenic autoantibodies, interferes with antigen presentation and has a strong anti-inflammatory effect which depends on its interaction with the complement system, cytokines and endothelial cells. The immunomodulatory potential of IVIg in patients is thus a result of a variety of complex mechanisms that act in a synergy.