In vitro inhibition of tumour necrosis factor-alpha and interleukin-6 production by intravenous immunoglobulins

Successful Treatment of Steroid-Refractory Checkpoint Inhibitor Myocarditis with Globulin Derived-Therapy: A case report and literature review

Immune checkpoint inhibitor (ICI) monoclonal antibody drugs are an important interface of immunology and cancer biology with the intended goal to create cancer specific treatments with less systemic toxicity. Recognition of immune-related adverse events is critical and these include significant cardiovascular toxicity and myocarditis. Compared with other immune-related events, ICI associated myocarditis is rare but is associated with high mortality. The majority of cases present early in the course of therapy and patients can rapidly progress to fulminant myocarditis. Initially, the mainstay of treatment in patients with ICI-associated myocarditis is immunosuppressive therapy with glucocorticoids. For those who do not respond to steroids, the optimal treatment is unclear. This review summarizes the potential adjunctive treatment options for patients with steroid-refractory myocarditis by illustrating a case of myocarditis that was treated with Thymoglobulin and immunoglobulin.

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.

Role of Host Immune and Inflammatory Responses in COVID-19 Cases with Underlying Primary Immunodeficiency: A Review

Coronavirus disease 2019 (COVID-19) has spread rapidly and become a pandemic. Caused by a novel human coronavirus called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), severe COVID-19 is characterized by cytokine storm syndromes due to innate immune activation. Primary immunodeficiency (PID) cases represent a special patient population whose impaired immune system might make them susceptible to severe infections, posing a higher risk to COVID-19, but this could also lead to suppressed inflammatory responses and cytokine storm. It remains an open question as to whether the impaired immune system constitutes a predisposing or protective factor for PID patients when facing SARS-CoV-2 infection. After literature review, it was found that, similar to other patient populations with different comorbidities, PID patients may be susceptible to SARS-CoV-2 infection. Their varied immune status, however, may lead to different disease severity and outcomes after SARS-CoV-2 infection. PID patients with deficiency in antiviral innate immune signaling [eg, Toll-like receptor (TLR)3, TLR7, or interferon regulatory factor 7 (IRF7)] or interferon signaling (IFNAR2) may be linked to severe COVID-19. Because of its anti-infection, anti-inflammatory, and immunomodulatory effects, routine intravenous immunoglobulin therapy may provide some protective effects to the PID patients.

The novel polyclonal Ab preparation trimodulin attenuates ex vivo endotoxin-induced immune reactions in early hyperinflammation

Sepsis is a syndrome associated with excessive inflammation. Since mortality from sepsis remains high, more laboratory research is needed to provide insight into more effective ways to use novel, potentially more beneficial agents in sepsis. We investigated the ex vivo immunomodulatory effect of a novel polyclonal Ab preparation, trimodulin, containing IgM (∼23%), IgA (∼21%) and IgG (∼56%). Using whole blood and purified PBMCs from healthy volunteers and patients with sepsis, various ex vivo investigations upon endotoxin challenge and pre- and post-trimodulin treatment were performed. Endotoxin-induced TNF-α secretion was noticeably lower with than without trimodulin, implying attenuation of the hyper-responsive state. Trimodulin also lowered TLR2, TLR4, CD11b and CD64 detection on LPS/lipoteichoic acid-stimulated monocytes. These responses were observed in cells from healthy volunteers only shortly after ex vivo endotoxin stimulation and in whole blood from patients with early-stage sepsis. Furthermore, trimodulin markedly reduced lymphocyte proliferation and release of pro- and anti-inflammatory cytokines, but did not affect phagocytosis or oxidative-burst activities of endoxin-stimulated cells. Thus, trimodulin mitigated monocyte and lymphocyte hyperinflammatory responses early after endotoxin exposure. Determining whether early in vivo administration of trimodulin will elicit similar positive immunomodulatory effects and offer a clinical benefit warrants investigation.

TBA225, a fusion toxoid vaccine for protection and broad neutralization of staphylococcal superantigens

Superantigens (SAgs) play a major role in the pathogenesis of Staphylococcus aureus and are associated with several diseases, including food poisoning, bacterial arthritis, and toxic shock syndrome. Monoclonal antibodies to these SAgs, primarily TSST-1, SEB and SEA have been shown to provide protection in animal studies and to reduce clinical severity in bacteremic patients. Here we quantify the pre-existing antibodies against SAgs in many human plasma and IVIG samples and demonstrate that in a major portion of the population these antibody titers are suboptimal and IVIG therapy only incrementally elevates the anti-SAg titers. Our in vitro neutralization studies show that a combination of antibodies against SEA, SEB,and TSST-1 can provide broad neutralization of staphylococcal SAgs. We report a single fusion protein (TBA₂₂₅) consisting of the toxoid versions of TSST-1, SEB and SEA and demonstrate its immunogenicity and protective efficacy in a mouse model of toxic shock. Antibodies raised against this fusion vaccine provide broad neutralization of purified SAgs and culture supernatants of multiple clinically relevant S. aureus strains. Our data strongly supports the use of this fusion protein as a component of an anti-virulence based multivalent toxoid vaccine against S. aureus disease.

Intravenous immunoglobulin preparation prevents the production of pro-inflammatory cytokines by modulating NFκB and MAPKs pathways in the human monocytic THP-1 cells stimulated with procalcitonin

OBJECTIVE

In the previous investigations, we showed that intravenous immunoglobulin (IVIG) prevented cytokine release in procalcitonin (PCT)-stimulated monocytic cells. The aim of the present study was to investigate the underlying mechanisms of inhibition of IVIG on cytokine production in PCT-stimulated THP-1 cells.

METHODS

THP-1 cells treated with phorbol myristate acetate were stimulated with PCT. The protein levels of pro-inflammatory cytokines [tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and high-mobility group box 1 (HMGB1)] in the culture supernatants were determined using enzyme-linked immunosorbent assay kits. The mRNA level of TNF-α was determined by reverse transcription-polymerase chain reaction. The phosphorylations of nuclear factor kappa B (NFκB) and the mitogen-activated protein kinases (MAPKs) were determined by Western blotting.

RESULTS

IVIG reduced mRNA expression and protein production of TNF-α in PCT-stimulated THP-1 cells. Not only IVIG but also both the Fc fragment and the F(ab')2 fragment inhibited PCT-induced TNF-α, IL-6, and HMGB1 production. Furthermore, IVIG and its fragments suppressed PCT-induced phosphorylations of NFκB, p38 MAPK, and c-Jun N-terminal kinase.

CONCLUSIONS

Our results indicate that IVIG prevents PCT-induced cytokine production mediated by not only the Fab region but also the Fc region. The activity of IVIG and its fragments might be regulated by inhibiting NFκB and MAPKs pathways in THP-1 cells.

Role of immunoglobulin in neuronal apoptosis in a neonatal rat model of hypoxic ischemic brain injury

The objective of the present study was to evaluate the neuroprotective effects of immunoglobulin (Ig) in a neonatal hypoxic ischemic (HI) rat model. Seven-day-old rat pups were randomly assigned to control, hypoxia and hypoxia + Ig groups. The rats in the hypoxia +Ig group were intraperitoneally administered 1 g/kg Ig once, immediately after hypoxia. Saline was administered to the rats in the hypoxia group at the same time point. Eight rats from each of the Ig + hypoxia and hypoxia groups were sacrificed by decapitation 4 and 24 h following the administration of Ig or saline. The rats of the control group were sacrificed at the 4 h time-point. Caspase-3 activity, as well as IL-1β, IL-6 and TNF-α mRNA expression levels, were studied in the left ischemic hemispheres. Induction of cerebral ischemia increased the TNF-α, IL-6 and IL-1β mRNA expression levels significantly at 4 and 24 h in the left ischemic hemispheres in the hypoxia group compared with those in the control group. The systemic administration of Ig following HI encephalopathy significantly reduced the TNF-α, IL-6 and IL-1β mRNA expression levels in the ischemic tissue in the Ig + hypoxia group compared with those in the hypoxia group. In the hypoxia group, caspase-3 activity in the left half of the brain was found to be significantly increased compared with that in the control group. Caspase-3 activity in the Ig + hypoxia group was significantly lower than that in the hypoxia group. The observations of the present study indicate that Ig administration may be an efficient treatment approach for reducing cerebral apoptosis associated with hypoxic ischemia.

Intravenous immunoglobulin preparation attenuates LPS-induced production of pro-inflammatory cytokines in human monocytic cells by modulating TLR4-mediated signaling pathways

Intravenous immunoglobulin (IVIG) has been used for the treatment of inflammatory and autoimmune diseases. The ability to modulate cytokine production has been formerly described as one of the mechanisms of its action. This study aimed to investigate the effect of IVIG on the production of pro-inflammatory cytokines in lipopolysaccharide (LPS)-stimulated monocytic cells. Peripheral blood mononuclear cells (PBMCs) or THP-1 cells treated with phorbol myristate acetate (PMA) were stimulated with LPS. The protein levels of pro-inflammatory cytokines [tumor necrosis factor (TNF)-α, interleukin (IL)-6, and high-mobility group box 1 (HMGB1)] in the culture supernatants were determined using appropriate enzyme-linked immunosorbent assay kits. The mRNA of TNF-α was determined by reverse transcription-polymerase chain reaction. The phosphorylation of nuclear factor kappa B (NF-κB) and the mitogen-activated protein kinases was examined by Western blot analyses. IVIG suppressed the production of pro-inflammatory cytokines such as TNF-α and IL-6 in LPS-stimulated PBMCs. Furthermore, IVIG inhibited TNF-α, IL-6, and HMGB1 production from LPS-stimulated THP-1 cells treated with PMA. In addition, Fc fragment prepared from the IVIG inhibited production of these cytokines from the cells to the same degree as IVIG, whereas Fab and F(ab')(2) fragments inhibited this only partially. We showed that IVIG and Fc fragments suppressed LPS-induced signal transduction pathways involving phosphorylation of NF-κB, p38, and c-Jun N-terminal kinase (JNK). Taken together, our results suggest that IVIG attenuates LPS-induced cytokine production predominantly mediated by its Fc region. The activity might be regulated by inhibiting NF-κB, p38, and JNK pathways in human monocytic cells.

Effects of human intravenous immunoglobulin on amyloid pathology and neuroinflammation in a mouse model of Alzheimer's disease

BACKGROUND

Human intravenous immunoglobulin (hIVIG) preparation is indicated for treating primary immunodeficiency disorders associated with impaired humoral immunity. hIVIG is known for its anti-inflammatory properties and a decent safety profile. Therefore, by virtue of its constituent natural anti-amyloid beta antibodies and anti-inflammatory effects, hIVIG is deemed to mediate beneficial effects to patients of Alzheimer's disease (AD). Here, we set out to explore the effects of hIVIG in a mouse model of AD.

METHODS

We treated APP/PS1dE9 transgenic and wild-type mice with weekly injections of a high hIVIG dose (1 g/kg) or saline for 3 or 8 months. Treatment effect on brain amyloid pathology and microglial reactivity was assessed by ELISA, immunohistochemistry, RT-PCR, and confocal microscopy.

RESULTS

We found no evidence for reduction in Aβ pathology; instead 8 months of hIVIG treatment significantly increased soluble levels of Aβ40 and Aβ42. In addition, we noticed a significant reduction in CD45 and elevation of Iba-1 markers in specific sub-populations of microglial cells. Long-term hIVIG treatment also resulted in significant suppression of TNF-α and increase in doublecortin positive adult-born neurons in the dentate gyrus.

CONCLUSIONS

Our data indicate limited ability of hIVIG to impact amyloid burden but shows changes in microglia, pro-inflammatory gene expression, and neurogenic effects. Immunomodulation by hIVIG may account for its beneficial effect in AD patients.

Intravenous immunoglobulin prevents release of proinflammatory cytokines in human monocytic cells stimulated with procalcitonin

OBJECTIVE

The aim of this study was to investigate whether the stimulation of monocytic cells with procalcitonin (PCT) results in the release of proinflammatory cytokines. The effects of intravenous immunoglobulin (IVIG) on the production of cytokines from the cells stimulated with PCT were also studied.

MATERIALS AND METHODS

Cultured monocytic cells [THP-1 cells treated with phorbol myristate acetate or peripheral blood mononuclear cells (PBMCs)] were stimulated with PCT. The protein levels of proinflammatory cytokines [tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and high mobility group box-1] in the culture supernatants were determined by ELISA kits. The concentration of PCT-specific IgG antibody in IVIG was measured using a specific ELISA.

RESULTS

PCT induced the release of cytokines from THP-1 cells in a time- and dose-dependent manner. IVIG inhibited the release of cytokines from the cells stimulated with PCT. It was confirmed that IVIG also inhibited TNF-α release in the same dose range for PBMCs stimulated with PCT. The presence of PCT-specific IgG antibody was detected in the tested IVIG, which might be one of the mechanisms.

CONCLUSIONS

PCT induced the release of proinflammatory cytokines from THP-1 cells and PBMCs. The function of PCT was prevented by the presence of IVIG.

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.

Overview of the pathogenesis and treatment of chronic inflammatory demyelinating polyneuropathy with intravenous immunoglobulins

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired heterogeneous disorder of immune origin affecting the peripheral nerves, causing motor weakness and sensory symptoms and signs. The precise pathophysiology of CIDP remains uncertain although B and T cell mechanisms are believed to be implicated. Intravenous immunoglobulins (IVIg) have been shown in a number of trials to be an effective treatment for CIDP. IVIg is thought to exert its immunomodulatory effects by affecting several components of the immune system including B-cells, T-cells, macrophages and complement. This article provides an overview of the pathogenesis of CIDP and of its treatment with IVIg.

Beneficial effect of triple treatment plus immunoglobulin in experimental nephrotic syndrome

Combinations of antiproteinurics, including angiotensin I-converting enzyme inhibitors + angiotensin II receptor antagonist + statins, are promising choices in the treatment of steroid-resistant nephrotic syndrome. We aimed to investigate the effects of high doses of immunoglobulin in addition to these combinations in rats with adriamycin-induced nephrosis. The study included 40 rats allocated into five groups: control, nephrotic syndrome without treatment, dual therapy (DT) with enalapril + losartan, triple therapy (TT) with enalapril + losartan + simvastatin, and quadruple therapy (QT) with enalapril + losartan + simvastatin + a high dose of immunoglobulin. The proteinuria levels were not statistically different between DT, TT and QT groups at weeks 5, 8, 12 and 16. At week 16, serum creatinine levels in the QT group were significantly lower than those in the control, DT and TT groups. The glomerulosclerosis index in the DT group was significantly lower than in the TT and QT groups. The scores for interstitial fibrosis and TGF-beta staining were similar among treatment groups. In conclusion, we showed that quadruple therapy including immunoglobulin had a beneficial effect on renal function in the late phase, but it had no additional effects in reducing proteinuria or in glomerulosclerosis score in experimental nephrotic syndrome. Further studies with angiotensin I-converting enzyme inhibitors (ACEIs), angiotensin II receptor antagonists (AIIRAs) and immunoglobulin combinations would offer some benefits in the treatment of nephrotic syndrome.

Neuroprotection in stroke by complement inhibition and immunoglobulin therapy

Activation of the complement system occurs in a variety of neuroinflammatory diseases and neurodegenerative processes of the CNS. Studies in the last decade have demonstrated that essentially all of the activation components and receptors of the complement system are produced by astrocytes, microglia, and neurons. There is also rapidly growing evidence to indicate an active role of the complement system in cerebral ischemic injury. In addition to direct cell damage, regional cerebral ischemia and reperfusion (I/R) induces an inflammatory response involving complement activation and generation of active fragments, such as C3a and C5a anaphylatoxins, C3b, C4b, and iC3b. The use of specific inhibitors to block complement activation or their mediators such as C5a, can reduce local tissue injury after I/R. Consistent with therapeutic approaches that have been successful in models of autoimmune disorders, many of the same complement inhibition strategies are proving effective in animal models of cerebral I/R injury. One new form of therapy, which is less specific in its targeting of complement than monodrug administration, is the use of immunoglobulins. Intravenous immunoglobulin (IVIG) has the potential to inhibit multiple components of inflammation, including complement fragments, pro-inflammatory cytokine production and leukocyte cell adhesion. Thus, IVIG may directly protect neurons, reduce activation of intrinsic inflammatory cells (microglia) and inhibit transendothelial infiltration of leukocytes into the brain parenchyma following an ischemic stroke. The striking neuroprotective actions of IVIG in animal models of ischemic stroke suggest a potential therapeutic potential that merits consideration for clinical trials in stroke patients.

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.

Antibody therapy (IVIG): evaluation of the use of genomics and proteomics for the study of immunomodulation therapeutics

BACKGROUND AND OBJECTIVES

Intravenous immunoglobulin (IVIG) is used for an increasingly diverse number of therapeutic applications as an immunomodulation drug. Although it has demonstrated therapeutic effectiveness, the mechanism of action of IVIG in these disorders is poorly understood; this lack of understanding complicates rational clinical application and reimbursement for 'off-label' use.

MATERIALS AND METHODS

Selected literature on the clinical use of IVIG as an immunomodulation drug is reviewed. We present a brief description of DNA microarray and protein microarray technology and the application of such technologies to the study of immune system cells. The several studies on the application of DNA microarray technology to study gene expression in response to IVIG are presented.

RESULTS

There is increasing data on the use of DNA microarray and protein microarray technology to study gene expression in immune system cells including T cells, B cells, macrophages, and leucocytes. There is less information on the effect of IVIG on gene expression in immune system cells. However, there is sufficient information available to suggest that this is a practical approach with the caveat that such work will require careful experimental design and clear definition of the normal population.

CONCLUSIONS

DNA and protein microarray assays can be used to (i) provide rational indications for the clinical use of IVIG, (ii) provide for specific analysis of raw material and end product IVIG in screening for content related to immunomodulation, and (iii) accelerate the development of next generation products which would be more focused and/or targeted therapeutics.

The efficiency of intraperitoneal high-dose immunoglobulin in experimental nephrotic syndrome

Although it has been reported that high-dose immunoglobulin has beneficial effects in chronic glomerulonephritis, it is not known whether it is effective in the treatment of idiopathic nephrotic syndrome. We have investigated the effects of intraperitoneal immunoglobulin in adriamycin-induced nephrotic syndrome. Adriamycin (2 mg kg(-1) per dose) was given intravenously to sixteen Wistar albino rats (eight control and eight treatment rats) on day 1 and at week 3. At week 5 intraperitoneal immunoglobulin (1 g kg(-1) per dose) was given to the treatment group on two consecutive days whereas the control group received intraperitoneal saline solution. In both treatment and control groups urinary protein excretion was significantly elevated after administration of adriamycin (P=0.018). Urinary protein excretion, serum albumin, and triglyceride levels in the two groups were not significantly different after 5, 8, 12, and 16 weeks. Serum creatinine levels were higher and creatinine clearance was significantly lower in the control group in week 16 (P=0.001 and P=0.049, respectively). Glomerular sclerosis index was significantly lower in the treatment group (P=0.012). Although intraperitoneal high-dose immunoglobulin did not reverse biochemical results, it is encouraging that glomerular sclerosis index was significantly lower in the treatment group.

Intravenous immunoglobulin inhibits NF-kappaB activation and affects Fcgamma receptor expression in monocytes/macrophages

High-dose intravenous immunoglobulin (IVIG) therapy is well established as a standard therapy for Kawasaki disease (KD) that reduces the risk of developing coronary artery aneurysms. Activation of monocytes/macrophages and tumor necrosis factor-alpha (TNF-alpha) activity are responsible for severe vascular injury in acute KD. We examined whether or not IVIG inhibits TNF-alpha-induced activation of transcription factor NF-kappaB, a factor that is essential for the expression of proinflammatory cytokines, in human monocytic U-937 cells. The inhibitory effect of IVIG on NF-kappaB activation induced by TNF-alpha was evaluated by Western blotting and flow cytometry. In addition, we examined the effect of IVIG on the expression of FcgammaIII (CD16) and FcgammaRIIb (CD32b) in U-937 cells and peripheral blood CD14+ monocytes/macrophages by flow cytometry. Western blotting demonstrated that IVIG inhibits NF-kappaB activation in U-937 cells, and flow cytometry that IVIG inhibits NF-kappaB activation in U-937 cells in a dose-related manner. Western blotting of cytoplasmic extracts of U-937 cells revealed that IVIG inhibited degradation of the IkappaBalpha protein. Moreover, flow cytometry demonstrated that IVIG decreased the expression of FcgammaRIII in U-937 cells and peripheral blood CD14+ monocytes/macrophages. However, Western blotting revealed that IVIG did not affect the quantity of FcgammaRIII protein, and PCR that IVIG did not affect the quantity of FcgammaRIII mRNA in the cells. These findings suggest that IVIG inhibits TNF-alpha-induced NF-kappaB activation in monocytes/macrophages, and blocks FcgammaRIII on the membranes of monocytes/macrophages.

Human antibodies to bacterial superantigens and their ability to inhibit T-cell activation and lethality

Bacterial superantigens (BSAgs) cause massive stimulation of the immune system and are associated with various pathologies and diseases. To address the role of antibodies in protection against BSAgs, we screened the sera of 29 human volunteers for antibodies to the SAgs staphylococcal enterotoxin A (SEA), SEB, SEC1, and toxic shock syndrome toxin 1 (TSST-1). Although all volunteers had detectable levels of antibodies against SEB and SEC1, many (9 out of 29 volunteers) lacked detectable antibody to SEA or had minimal titers. Antibody titers to TSST-1 were well below those to SEB and SEC1, and three volunteers lacked detectable antibody to this BSAg. In addition, pooled immunoglobulin preparations obtained from different companies had antibody titers against SEs and TSST-1. There was a good correlation between antibody titers and inhibition of superantigenic effects of these toxins. Transfer of SEB-specific antibodies, obtained from pooled sera, suppressed in vitro T-cell proliferation and totally protected mice against SEB. These data suggest that the inhibitory activity of human sera was specific to antibodies directed against the toxins. Thus, it may be possible to counteract with specific antibodies BSAg-associated pathologies caused by stimulation of the immune system.

Polyclonal immunoglobulins (IVIg) modulate nitric oxide production and microglial functions in vitro via Fc receptors

Controlled trials in multiple sclerosis (MS) and case reports in acute demyelinating encephalomyelitis (ADEM) have shown that intravenous immunoglobulins (IVIg) are of therapeutic benefit in central nervous system (CNS) inflammatory diseases. Studies in experimental autoimmune encephalomyelitis (EAE) have suggested these effects are mediated by modulation of the cytokine network and T cell responses. However, there are no data on the influence of IVIg on the local immune reaction in the CNS, the site of inflammation in EAE. We have therefore studied the effect of IVIg on cultured rat microglia, the main immune cell in the CNS. IVIg increased nitric oxide (NO) production in a dose-dependent manner in microglia stimulated with IFNgamma. The increase was only marginal in LPS-treated cells, and no effect was seen in untreated microglia or after stimulation with TNFalpha or PMA. This enhancement of NO production depended on the Fc portion of IVIg and could be abrogated by the pharmacological inhibition of Syk and phosphatidylinositol 3-kinase, two enzymes involved in the signalling cascade of Fc receptors. TNFalpha secretion was dose-dependently stimulated by IVIg in both untreated microglia and after stimulation with LPS or IFNgamma. Again, this effect was mediated through the Fc portion. Finally, we showed that Fc receptor-mediated phagocytosis was inhibited by IVIg, presumably by blockade of the Fc receptor. These different effects may protect oligodendrocytes from antibody mediated phagocytosis and on the other hand could terminate the immune reaction by induction of apoptosis in infiltrating T cells via NO and TNFalpha. We propose that IVIg, in addition to known effects on the peripheral immune system, may also modulate the local immune reaction in CNS inflammatory disease.

Monocyte-macrophage system as targets for immunomodulation by intravenous immunoglobulin

Pooled human intravenous immunoglobulin (IVIg) has been used successfully to treat or ameliorate the clinical manifestations of humoral immune deficiencies, haematological disorders, HIV infection and many other diseases states. However, the mechanism of action of IVIg remains unclear. Several mechanisms of action of IVIg have been proposed. These include Fcy receptor blockade, accelerated clearance of endogenous pathogenic auto-antibodies, inhibition of components of the complement cascade, neutralization of super-antigens and bacterial toxins as well as anti-cytokine and anti-idiotype effects. A major contributor to host immunity and immune surveillance against infection, tissue or cell damage and malignancy is the monocyte/macrophage system. Monocyte-directed inflammation is a desirable consequence of microbiological or malignant challenge. However, monocyte hyperactivity may contribute to certain pathological conditions. These include the systemic inflammatory response syndrome (SIRS), septic shock, other dysregulated inflammatory disorders and auto-immunity. Novel therapies that can suppress the hyperactive state or correct monocyte/macrophage dysfunction without compromising normal host cell-mediated immunity are desirable. In this review, we discuss the immunomodulatory effects of IVIg focussing particularly upon the monocyte/macrophage system in pertinent disease states.

In vivo modulation of cytokine synthesis by intravenous immunoglobulin

We examined the effects of intravenous immunoglobulin (IVIG) on cytokine regulation in vivo using samples taken before and after replacement-dose (200-400 mg/kg) IVIG in a group of patients with common variable immunodeficiency (CVID) and X-linked agammaglobulinaemia (XLA). The intracellular cytokine content of CD4+ and CD8+ lymphocytes, and their CD28+/- subsets, were measured following in vitro activation with phorbol myristate acetate (PMA) and ionomycin. The cytokines IL-2, interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha), and the early activation marker CD69, were assessed by four-colour flow cytometry of whole blood cultures taken before and after IVIG infusion. There was a significant increase in IL-2 expression in CD4+ (and CD4+28-) cells and an increase in TNF-alpha expression in CD8+28- cells following IVIG in CVID, but not in XLA patients. IFN-gamma and CD69 expression were not affected by IVIG infusion. This increase in TNF-alpha and IL-2, combined with unchanged IFN-gamma expression, is evidence against the putative 'anti-inflammatory' role of IVIG, and may explain the failure of resolution of granulomata in CVID patients treated with IVIG alone.

Rapidly deteriorating polyneuropathy associated with osteosclerotic myeloma responsive to intravenous immunoglobulin and radiotherapy

Osteosclerotic myeloma is a plasma-cell dyscrasia characterized by osteosclerotic bone lesions, which may be associated with progressive demyelinating polyneuropathy. We describe a 49-year-old patient with rapidly deteriorating polyneuropathy associated with osteosclerotic myeloma, who responded favorably to a combination of intravenous immunoglobulin and radiotherapy.

The growth arresting effect of human immunoglobulin for intravenous use is mediated by antibodies recognizing membrane glycolipids

Intravenous human IgG (IVIg) given to patients with autoimmune disorders can result in significant clinical improvement in some patients. The mechanism(s) by which IVIg induces these improvements is(are) not known. We have previously shown that IVIg inhibited the proliferation of peripheral blood lymphocytes in allogeneic mixed lymphocyte reactions and of autonomously growing human and mouse cell lines. In an effort to identify the antigen(s) to which the human IgG binds, the human B cell line JY, whose proliferation was inhibited by IVIg, was incubated with IVIg, washed extensively with PBS, and lysed. Human IgG from these lysates was purified by protein A-Sepharose (IVIgJY). IVIgJY binds to and inhibits the proliferation of JY cells and of peripheral blood lymphocytes stimulated in a MLR at a 1000- to 10,000-fold lower concentration compared to IVIg. IVIgJY was analyzed on a 5-15% gradient SDS/PAGE and only immunoglobulin heavy- and light-chain (run under reducing conditions) proteins were detected. Immunoprecipitation experiments from JY cell lysates with IVIgJY indicated that this IgG did not bind to a protein epitope. Thin-layer immunoblot experiments showed that the IVIgJY binds to glycolipids expressed by JY cells and lymphocytes. Furthermore, evidence is presented indicating that antiglycolipid antibodies are involved in IVIg-induced growth inhibition.

A recombinant tumor necrosis factor-alpha p80 receptor:Fc fusion protein decreases circulating bioactive tumor necrosis factor-alpha but not lung injury or mortality during immunosuppression-related gram-negative bacteremia

PURPOSE

During gram-negative bacteremia (GNB), tumor necrosis factor-alpha (TNF-alpha) is a critical early mediator of host defense, whose overexpression can initiate acute lung injury, multiple organ failure, and death. In this study we evaluated the ability of a chimeric fusion protein containing two extracellular domains of the human p80 TNF-alpha receptor and the Fc region of human IgG1 (TNFR:Fc) to reduce circulating TNF-alpha, and to ameliorate organ injury and improve survival in a rodent model of GNB during immunosuppression-related neutropenia.

MATERIALS AND METHODS

Conscious catheterized male rats (n = 37) with stable cyclophosphamide-induced neutropenia were infected intravenously (i.v.) with 5 x 10(9) live Escherichia coli (EC, serotype O55:B5) ending at t = 0. All animals received antibiotics (penicillin/ amikacin sulfate) at t = 0.5 and t = 8 hours, and 0.9% sodium chloride (normal saline solution (NS), 1 mL/h) from t = 0 to 8 hours. Subgroups were post-treated at t = 0.5 hours with a 1.0 mL i.v. dose of TNFR:Fc (60, 600, or 1,200 micrograms; Immunex), 600 micrograms of human IgG1-kappa or IgG1-lambda (Sigma), or NS alone (controls). A separate TNFR:Fc pretreatment subgroup received 600 micrograms/rat of the fusion protein 5 minutes before starting EC infusion. Hemodynamics were monitored continuously through t = 24 hours, and arterial samples were collected at baseline and at t = 1.5, 4.5, 8, and 24 hours after EC were analyzed for blood gases, quantitative culture, serum endotoxin, bioactive and antigenic TNF-alpha, and formed elements. Postmortem tissues were examined for histopathologic changes.

RESULTS

Compared with antibiotic-treated and fluid-supported controls, TNFR:Fc dose-dependently reduced bioactive but not antigenic TNF-alpha without altering bacterial clearance, serum endotoxin, or 24-hour survival. Of note, 600 micrograms of IgG1-kappa or IgG1-lambda attenuated peak bioactive TNF-alpha to a similar degree as 1,200 micrograms TNFR:Fc, and also significantly reduced serum endotoxin levels. Nevertheless, by t = 8 hours all bacteremic rats were hypothermic with tachypnea-related hypocarbia and hyperoxemia and were thrombocytopenic. At death, all subgroups showed similar hepatic glycogen depletion and pulmonary congestion with perivascular edema and alveolar hemorrhage.

CONCLUSIONS

Although TNFR:Fc and its idiotypic control IgG1 reduced circulating bioactive TNF-alpha, neither treatment prevented progression of lethal shock with attendant organ injury in this conscious, antibiotic-treated and fluid-resuscitated model of immunosuppression-related GNB.

Blockade of proliferation and tumor necrosis factor-alpha production occurring during mixed lymphocyte reaction by interferon-gamma-specific natural antibodies contained in intravenous immunoglobulins

The mechanism of action of intravenous immunoglobulins (IVIg) for prevention of graft rejection and graft-versus-host disease (GVHD) is poorly understood. Recently, it has been shown that these preparations contain natural antibodies directed toward interferon (IFN)-gamma. During mixed lymphocyte reaction (MLR), which constitutes an in vitro model of allograft rejection and GVHD, T cell recognition of HLA differences induces IFN-gamma release. This cytokine promotes T cell proliferation and acts as a macrophage-activating factor to provoke tumor necrosis factor-alpha secretion. The aim of the present work is to investigate the influence of IVIg on IFN-gamma production occurring during MLR and its subsequent impact on T cell proliferation and tumor necrosis factor (TNF)-alpha secretion. We tested IVIg preparations for the presence of anti-IFN-gamma and anti-TNF-alpha antibodies. High amounts of anti-IFN-gamma, but not anti-TNF-alpha antibodies, were found. IVIg addition at the initiation of culture resulted in IFN-gamma secretion blockade. Likewise, lymphocyte proliferation and TNF-alpha secretion were inhibited. This inhibition was reversed by the addition of recombinant human IFN-gamma. Furthermore, the inhibitory properties of IVIg were mimicked by an IFN-gamma-specific neutralizing monoclonal antibody. We conclude that the capacity of IVIg to inhibit proliferation and TNF-alpha release during MLR is due to IFN-gamma blockade by natural antibodies. This immunosuppressive mechanism could contribute to the effect of IVIg on prophylaxis of organ graft rejection and GVHD after allogeneic bone marrow transplantation.

Clinical immunology

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