Polyspecific immunoglobulins (IVIg) suppress proliferation of human (auto)antigen-specific T cells without inducing apoptosis

Case Report: Susceptibility to viral infections and secondary hemophagocytic lymphohistiocytosis responsive to intravenous immunoglobulin as primary manifestations of adenosine deaminase 2 deficiency

Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive disease associated with a highly variable clinical presentation, including systemic vasculitis, immunodeficiency, and cytopenia. We report a case of a 16-year-old girl affected by recurrent viral infections [including cytomegalovirus (CMV)-related hepatitis and measles vaccine virus-associated manifestations] and persistent inflammation, which occurred after Parvovirus infection and complicated by secondary hemophagocytic lymphohistiocytosis (HLH). HLH’s first episode presented at 6 years of age and was preceded by persistent fever and arthralgia with evidence of Parvovirus B19 infection. The episode responded to intravenous steroids but relapsed during steroids tapering. High-dose intravenous immunoglobulin (IVIG) helped manage her clinical symptoms and systemic inflammation. The frequency of IVIG administration and the dosage were progressively reduced. At the age of 9, she experienced varicella zoster virus (VZV) reactivation followed by the recurrence of the inflammatory phenotype complicated by HLH with neurological involvement. Again, high-dose steroids and monthly IVIG resulted in a quick response. Targeted next-generation sequencing (NGS) for autoinflammatory diseases and immunodeficiencies revealed the homozygous Leu183Pro ADA2 mutation, which was confirmed by Sanger analysis. ADA2 enzymatic test showed a complete loss of ADA2 activity. For about 3 years, IVIG alone was completely effective in preventing flares of inflammation and neurological manifestations. Anti-TNF treatment was started at the age of 13 for the appearance of recurrent genital ulcers, with a complete response. This case further expands the clinical spectrum of DADA2 and emphasizes the importance of extensive genetic testing in clinical phenotypes characterized by persistent unspecific inflammatory syndromes. The use of high doses of IVIG might represent a possible effective immune modulator, especially in combination with anti-TNF treatment.

Role of HLA-I Structural Variants and the Polyreactive Antibodies They Generate in Immune Homeostasis

Cell-surface HLA-I molecules consisting of β2-microglobulin (β2m) associated heavy chains (HCs), referred to as Face-1, primarily present peptides to CD8+ T-cells. HCs consist of three α-domains, with selected amino acid sequences shared by all alleles of all six isoforms. The cell-surface HLA undergoes changes upon activation by pathological conditions with the expression of β2m-free HCs (Face-2) resulting in exposure of β2m-masked sequences shared by almost all alleles and the generation of HLA-polyreactive antibodies (Abs) against them. Face-2 may homodimerize or heterodimerize with the same (Face-3) or different alleles (Face-4) preventing exposure of shared epitopes. Non-allo immunized males naturally carry HLA-polyreactive Abs. The therapeutic intravenous immunoglobulin (IVIg) purified from plasma of thousands of donors contains HLA-polyreactive Abs, admixed with non-HLA Abs. Purified HLA-polyreactive monoclonal Abs (TFL-006/007) generated in mice after immunizing with Face-2 are documented to be immunoregulatory by suppressing or activating different human lymphocytes, much better than IVIg. Our objectives are (a) to elucidate the complexity of the HLA-I structural variants, and their Abs that bind to both shared and uncommon epitopes on different variants, and (b) to examine the roles of those Abs against HLA-variants in maintaining immune homeostasis. These may enable the development of personalized therapeutic strategies for various pathological conditions.

Pediatric Rheumatologic Effects of COVID-19

A multisystem inflammatory syndrome (MISC) can result from COVID-19 infection in previously healthy children and adolescents. It is potentially life threatening and is treated initially with intravenous immunoglobulin and aspirin but may require anti-inflammatory monoclonal antibody treatment in severe cases. SARS-CoV-2 infection can cause macrophage activation syndrome, chilblains, and flares of existing rheumatologic diseases. The pandemic has led to later presentation of some rheumatologic conditions as parents and patients have avoided health care settings. PubMed and Google scholar have been utilized to review the literature on the rheumatologic conditions resulting from COVID-19 and the current treatment options.

Therapeutic Potential of HLA-I Polyreactive mAbs Mimicking the HLA-I Polyreactivity and Immunoregulatory Functions of IVIg

HLA class-I (HLA-I) polyreactive monoclonal antibodies (mAbs) reacting to all HLA-I alleles were developed by immunizing mice with HLA-E monomeric, α-heavy chain (αHC) open conformers (OCs). Two mAbs (TFL-006 and TFL-007) were bound to the αHC's coated on a solid matrix. The binding was inhibited by the peptide 117AYDGKDY123, present in all alleles of the six HLA-I isoforms but masked by β2-microglobulin (β2-m) in intact HLA-I trimers (closed conformers, CCs). IVIg preparations administered to lower anti-HLA Abs in pre-and post-transplant patients have also shown HLA-I polyreactivity. We hypothesized that the mAbs that mimic IVIg HLA-I polyreactivity might also possess the immunomodulatory capabilities of IVIg. We tested the relative binding affinities of the mAbs and IVIg for both OCs and CCs and compared their effects on (a) the phytohemagglutinin (PHA)-activation T-cells; (b) the production of anti-HLA-II antibody (Ab) by B-memory cells and anti-HLA-I Ab by immortalized B-cells; and (c) the upregulation of CD4+, CD25+, and Fox P3+ T-regs. The mAbs bound only to OC, whereas IVIg bound to both CC and OC. The mAbs suppressed blastogenesis and proliferation of PHA-activated T-cells and anti-HLA Ab production by B-cells and expanded T-regs better than IVIg. We conclude that a humanized version of the TFL-mAbs could be an ideal, therapeutic IVIg-mimetic.

Plasma exchange therapy for acute necrotizing encephalopathy of childhood

IMPORTANCE

Acute necrotizing encephalopathy (ANE) is a rare disease with high mortality. Plasma exchange (PLEX) has recently been reported to treat ANE of childhood (ANEC), but its efficacy is uncertain.

OBJECTIVE

This study aimed to investigate the effectiveness of PLEX on ANEC.

METHODS

A retrospective study was conducted in four pediatric intensive care units from December 2014 to December 2020. All patients who were diagnosed with ANEC were included; however, these patients were excluded if their length of stay was less than 24 h. Participants were classified into PLEX and non-PLEX groups.

RESULTS

Twenty-nine patients with ANEC were identified, 10 in the PLEX group and 19 in the non-PLEX group. In the PLEX group, C-reactive protein, procalcitonin, alanine aminotransferase, and aspartate aminotransaminase levels were significantly lower after 3 days of treatment than before treatment (13.1 vs. 8.0, P = 0.043; 9.8 vs. 1.5, P = 0.028; 133.4 vs. 31.9, P = 0.028; 282.4 vs. 50.5, P = 0.046, respectively). Nine patients (31.0%, 9/29) died at discharge, and a significantly difference was found between the PLEX group and non-PLEX group [0 vs. 47.4% (9/19), P = 0.011]. The median follow-up period was 27 months, and three patients were lost to follow-up. Thirteen patients (50.0%, 13/26) died at the last follow-up, comprising three (33.3%, 3/9) in the PLEX group and ten (58.8%, 10/17) in the non-PLEX group, but there was no significant difference between the two groups (P = 0.411). Three patients (10.3%, 3/29) fully recovered.

INTERPRETATION

PLEX may reduce serum C-reactive protein and procalcitonin levels and improve liver function in the short term. PLEX may improve the prognosis of ANEC, and further studies are needed.

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.

Targeted Therapies for Autoimmune Bullous Diseases: Current Status

Autoimmune bullous skin disorders are rare but meaningful chronic inflammatory diseases, many of which had a poor or devastating prognosis prior to the advent of immunosuppressive drugs such as systemic corticosteroids, which down-regulate the immune pathogenesis in these disorders. Glucocorticoids and adjuvant immunosuppressive drugs have been of major benefit for the fast control of most of these disorders, but their long-term use is limited by major side effects such as blood cytopenia, osteoporosis, diabetes mellitus, hypertension, and gastrointestinal ulcers. In recent years, major efforts were made to identify key elements in the pathogenesis of autoimmune bullous disorders, leading to the identification of their autoantigens, which are mainly located in desmosomes (pemphigus) and the basement membrane zone (pemphigoids). In the majority of cases, immunoglobulin G, and to a lesser extent, immunoglobulin A autoantibodies directed against distinct cutaneous adhesion molecules are directly responsible for the loss of cell-cell and cell-basement membrane adhesion, which is clinically related to the formation of blisters and/or erosions of the skin and mucous membranes. We describe and discuss novel therapeutic strategies that directly interfere with the production and regulation of pathogenic autoantibodies (rituximab), their catabolism (intravenous immunoglobulins), and their presence in the circulation and extravascular tissues such as the skin (immunoadsorption), leading to a significant amelioration of disease. Moreover, we show that these novel therapies have pleiotropic effects on various proinflammatory cells and cytokines. Recent studies in bullous pemphigoid suggest that targeting of immunoglobulin E autoantibodies (omalizumab) may be also beneficial. In summary, the introduction of targeted therapies in pemphigus and pemphigoid holds major promise because of the high efficacy and fewer side effects compared with conventional global immunosuppressive therapy.

HLA Class Ia and Ib Polyreactive Anti-HLA-E IgG2a Monoclonal Antibodies (TFL-006 and TFL-007) Suppress Anti-HLA IgG Production by CD19+ B Cells and Proliferation of CD4+ T Cells While Upregulating Tregs

The anti-HLA-E IgG2a mAbs, TFL-006 and TFL-007, reacted with all HLA-I antigens, similar to the therapeutic preparations of IVIg. Indeed, IVIg lost its HLA reactivity, when its HLA-E reactivity was adsorbed out. US-FDA approved IVIg to reduce antibodies in autoimmune diseases. But the mechanism underlying IVIg-mediated antibody reduction could not be ascertained due to the presence of other polyclonal antibodies. In spite of it, the cost prohibitive high or low IVIg is administered to patients waiting for donor organ and for allograft recipients for lowering antiallograft antibodies. A mAb that could mimic IVIg in lowering Abs, with defined mechanism of action, would be highly beneficial for patients. Demonstrably, the anti-HLA-E mAbs mimicked several functions of IVIg relevant to suppressing the antiallograft Abs. The mAbs suppressed activated T cells and anti-HLA antibody production by activated B cells, which were dose-wise superior to IVIg. The anti-HLA-E mAb expanded CD4+, CD25+, and Foxp3+ Tregs, which are known to suppress T and B cells involved in antibody production. These defined functions of the anti-HLA-E IgG2a mAbs at a level superior to IVIg encourage developing their humanized version to lower antibodies in allograft recipients, to promote graft survival, and to control autoimmune diseases.

Dose-dependent inhibition of demyelination and microglia activation by IVIG

Objective

Intravenous immunoglobulin (IVIG) is an established treatment for numerous autoimmune conditions. Clinical trials of IVIG for multiple sclerosis, using diverse dose regimens, yielded controversial results. The aim of this study is to dissect IVIG effector mechanisms on demyelination in an ex vivo model of the central nervous system (CNS)‐immune interface.

Methods

Using organotypic cerebellar slice cultures (OSC) from transgenic mice expressing green fluorescent protein (GFP) in oligodendrocytes/myelin, we induced extensive immune‐mediated demyelination and oligodendrocyte loss with an antibody specific for myelin oligodendrocyte glycoprotein (MOG) and complement. Protective IVIG effects were assessed by live imaging of GFP expression, confocal microscopy, immunohistochemistry, gene expression analysis and flow cytometry.

Results

IVIG protected OSC from demyelination in a dose‐dependent manner, which was at least partly attributed to interference with complement‐mediated oligodendroglia damage, while binding of the anti‐MOG antibody was not prevented. Staining with anti‐CD68 antibodies and flow cytometry confirmed that IVIG prevented microglia activation and oligodendrocyte death, respectively. Equimolar IVIG‐derived Fab fragments or monoclonal IgG did not protect OSC, while Fc fragments derived from a polyclonal mixture of human IgG were at least as potent as intact IVIG.

Interpretation

Both intact IVIG and Fc fragments exert a dose‐dependent protective effect on antibody‐mediated CNS demyelination and microglia activation by interfering with the complement cascade and, presumably, interacting with local immune cells. Although this experimental model lacks blood–brain barrier and peripheral immune components, our findings warrant further studies on optimal dose finding and alternative modes of application to enhance local IVIG concentrations at the site of tissue damage.

B in TB: B Cells as Mediators of Clinically Relevant Immune Responses in Tuberculosis

The protective role of B cells and humoral immune responses in tuberculosis infection has been regarded as inferior to cellular immunity directed to the intracellular pathogen Mycobacterium tuberculosis. However, B-cell–mediated immune responses in tuberculosis have recently been revisited in the context of B-cell physiology and antigen presentation. We discuss in this review the diverse functions of B cells in tuberculosis, with a focus on their biological and clinical relevance to progression of active disease. We also present the peptide microarray platform as a promising strategy to discover unknown antigenic targets of M. tuberculosis that could contribute to the better understanding of epitope focus of the humoral immune system against M. tuberculosis.

Protection from experimental autoimmune encephalomyelitis by polyclonal IgG requires adjuvant-induced inflammation

Background

Intravenous immunoglobulin (IVIG) proved to be an efficient anti-inflammatory treatment for a growing number of neuroinflammatory diseases and protects against the development of experimental autoimmune encephalomyelitis (EAE), a widely used animal model for multiple sclerosis (MS).

Methods

The clinical efficacy of IVIG and IVIG-derived F(ab’)₂ fragments, generated using the streptococcal cysteine proteinase Ide-S, was evaluated in EAE induced by active immunization and by adoptive transfer of myelin-specific T cells. Frequency, phenotype, and functional characteristics of T cell subsets and myeloid cells were determined by flow cytometry. Antibody binding to microbial antigen and cytokine production by innate immune cells was assessed by ELISA.

Results

We report that the protective effect of IVIG is lost in the adoptive transfer model of EAE and requires prophylactic administration during disease induction. IVIG-derived Fc fragments are not required for protection against EAE, since administration of F(ab’)₂ fragments fully recapitulated the clinical efficacy of IVIG. F(ab’)₂-treated mice showed a substantial decrease in splenic effector T cell expansion and cytokine production (GM-CSF, IFN-γ, IL-17A) 9 days after immunization. Inhibition of effector T cell responses was not associated with an increase in total numbers of Tregs but with decreased activation of innate myeloid cells such as neutrophils, monocytes, and dendritic cells. Therapeutically effective IVIG-derived F(ab’)₂ fragments inhibited adjuvant-induced innate immune cell activation as determined by IL-12/23 p40 production and recognized mycobacterial antigens contained in Freund’s complete adjuvant which is required for induction of active EAE.

Conclusions

Our data indicate that F(ab’)₂-mediated neutralization of adjuvant contributes to the therapeutic efficacy of anti-inflammatory IgG. These findings might partly explain the discrepancy of IVIG efficacy in EAE and MS.

Intravenous immunoglobulin treatment in chronic neurological diseases: do we have maintenance dose right?

Objectives. We tried to define, on individual basis, minimal effective maintenance dose of intravenous immunoglobulins (IVIG) in 26 patients with chronic neurological conditions requiring long-term IVIG treatment. Methods. Clinical criteria were reviewed in individual cases (Phase 1) followed by titration phase (Phase 2, 12 months) and posttitration/follow-up phase (Phase 3, 3 months). Objective neurological examination and patient self-reports were used for clinical follow-up. Results. 69.2% of patients reported condition as stable, 26.9% as better, and 3.9% as mildly worse. Original mean monthly dose was 1 g/kg; over the period of 12 months we reduced dose of IVIG to mean dose 0.67 g/kg (range 0.3–2.5 g/kg, P < 0.0001) which meant reduction by 36.4%. We identified 4 nonresponders and diagnosis in one case was reclassified to degenerative disease. In follow-up phase we reduced dose further to 0.60 g/kg. Cumulative monthly dose dropped from 2040 g to 1298 g and to 991 g, respectively. Financial expenses were reduced significantly (by −36.4% during titration phase and by −51.4% during follow-up phase) (comparing with baseline) (P < 0.0001). Conclusion. Individual dose titration leads to significant maintenance IVIG dose reduction with preserved clinical efficacy. Maintenance dose below 1 g/kg (in our study around 0.7 g/kg) has acceptable risk/benefit ratio.

Suppression of blastogenesis and proliferation of activated CD4(+) T cells: intravenous immunoglobulin (IVIg) versus novel anti-human leucocyte antigen (HLA)-E monoclonal antibodies mimicking HLA-I reactivity of IVIg

Activated CD4(+) T cells undergo blastogenesis and proliferation and they express several surface receptors, including β2-microglobulin-free human leucocyte antigen (HLA) heavy chains (open conformers). Intravenous immunoglobulin (IVIg) suppresses activated T cells, but the mechanism is unclear. IVIg reacts with HLA-Ia/Ib antigens but its reactivity is lost when the anti-HLA-E Ab is adsorbed out. Anti-HLA-E antibodies may bind to the peptides shared by HLA-E and the HLA-I alleles. These shared peptides are cryptic in intact HLA, but exposed in open conformers. The hypothesis that anti-HLA-E monoclonal antibodies (mAbs) that mimic HLA-I reactivity of IVIg may suppress activated T cells by binding to the shared peptides of the open conformers on the T cell surface was tested by examining the relative binding affinity of those mAbs for open conformers coated on regular beads and for intact HLA coated on iBeads, and by comparing the effects on the suppression of phytohaemagglutinin (PHA)-activated T cells of three entities: IVIg, anti-HLA-E mAbs that mimic IVIg [Terasaki Foundation Laboratory (TFL)-006 and (TFL)-007]; and anti-HLA-E antibodies that do not mimic IVIg (TFL-033 and TFL-037). Suppression of blastogenesis and proliferation of those T cells by both IVIg and the anti-HLA-E mAbs was dose-dependent, the dose required with mAbs 50-150-fold lower than with IVIg. TFL-006 and TFL-007 significantly suppressed blastogenesis and proliferation of activated CD4(+) T cells, but neither the non-IVIg-mimicking mAbs nor control antibodies did so. The suppression may be mediated by Fab-binding of TFL-006/TFL-007 to the exposed shared peptides. The mAb binding to the open conformer may signal T cell deactivation because the open conformers have an elongated cytoplasmic tail with phosphorylation sites (tryosine(320)/serine(335)).

Intravenous immunoglobulin for the treatment of Alzheimer's disease: current evidence and considerations

Alzheimer's disease (AD) is a devastating neurodegenerative form of dementia with increasing incidence rates in most countries. AD is characterized by amyloid plaques and neurofibrillary tangles in the brains of AD individuals accompanied by global neuronal loss. The peptide amyloid-β (Aβ) aggregates to amyloid plaques in AD brains. As a result, many therapeutic approaches target Aβ. Human plasma and the plasma product intravenous immunoglobulin (IVIG) contain naturally-occurring anti-Aβ antibodies (Nabs-Aβ) that appear to reduce risks of developing AD. IVIG sequesters Aβ and thus interferes with AD progression. This study reviews the role of different Aβ species, Nabs-Aβ, preclinical data, and clinical studies of IVIG as potential AD treatments. The focus of this study is the outcomes of a recent Gammaglobulin Alzheimer's Partnership Phase III trial that did not reach primary endpoints, as well as efforts to compare IVIG with current anti-Aβ monoclonals such as bapineuzumab, solanezumab, and BIIB037. Moreover, this study critically examines current market and ethical consequences of potential off-label uses of IVIG, limits in IVIG supply, and subsequent challenges.

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.

Use of immunoglobulins in the prevention of GvHD in a xenogeneic NOD/SCID/γc- mouse model

The efficacy of IVIG in preventing GvHD has not been definitely demonstrated clinically. Using a xenogeneic model of GvHD in NOD/SCID/γc- (NSG) mice, we showed that weekly administration of IVIG significantly reduced the incidence and associated mortality of GvHD to a degree similar to CsA. Unlike CsA and OKT3, IVIG were not associated with inhibition of human T-cell proliferation in mice. Instead, IVIG significantly inhibited the secretion of human IL-17, IL-2, IFN-γ and IL-15 suggesting that IVIG prevented GvHD by immunomodulation. Furthermore, the pattern of modification of the human cytokine storm differed from that observed with CsA and OKT3. Finally, in a humanized mouse model of immune reconstitution, in which NSG mice were engrafted with human CD34(+) stem cells, IVIG transiently inhibited B-cell reconstitution, whereas peripheral T-cell reconstitution and thymopoiesis were unaffected. Together these in vivo data raise debate related to the appropriateness of IVIG in GvHD prophylaxis. In addition, this model provides an opportunity to further elucidate the precise mechanism(s) by which IVIG inhibit GvHD.

Can we face the challenge of expanding use of intravenous immunoglobulin in neurology?

The use of high-dose polyclonal intravenous immunoglobulin (IVIG) in the treatment of autoimmune neurological diseases has expanded over the last decade. Based on controlled clinical trials IVIG can be considered currently as the first-line treatment in Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy and multifocal motor neuropathy, and it may be used as a rescue therapy in worsening myasthenia gravis. IVIG is a second-line therapy in dermatomyositis, stiff-person syndrome and pregnancy-associated or postpartum relapses of multiple sclerosis. Although the biological efficacy of IVIG is due to multiple effects on the immune system, many mechanisms are still unknown. The awareness of risks and complications of IVIG therapy has increased, but severe side effects are still considered rare. Due to increasing costs of this treatment, careful selection of patients who will benefit from IVIG is extremely important.

In vivo modulation of the expressions of Fas and CD25 by intravenous immunoglobulin in common variable immunodeficiency

Although the presence of physiologic anti-CD95 (Fas, APO-1) autoantibodies in intravenous immunoglobulin (IVIG) preparations is known, the effects of these antibodies in patients with common variable immunodeficiency are unclear (CVID). The aim of the study was to assess the effects of IVIG in Fas expression, activation markers and the subsets of T cells in patients with CVID. We studied 15 cases with CVID and 10 healthy controls with no signs of immunodeficiency. The Fas expression of T cells, activation markers (CD25, CD69 and HLA-DR) and T-cell subsets were analyzed by four-color flow cytometry. We found that the Fas expression of CD3+ T cells in patients was significantly higher than in controls. In addition, there was a significant increase in the Fas expression of CD3+ T cells and CD4+ T cells, and the CD25 expression of CD3+ and CD4+ T cells after IVIG supplementation (P < 0.05). The CD69 and HLA-DR expressions of T cells and CD8+ T cells were not affected by IVIG infusion. Our observation showed that IVIG replacement causes an increase in the Fas and CD25 expressions in patients with CVID. These data suggest that the Fas protein may have an important role in the effects of IVIG for the control of autoimmunity in patients with CVID, as well as in the generation of autoimmune disease.

Indirect inhibition of in vivo and in vitro T-cell responses by intravenous immunoglobulins due to impaired antigen presentation

Several clinical studies done with intravenous immunoglobulin (IVIg)-treated autoimmune patients as well as several in vitro studies have revealed that IVIg can reduce polyclonal T-cell activation and modify their cytokine secretion pattern. However, their effect on (auto)antigen-specific T-cell responses has never been addressed directly. In the present work, we used an in vivo model of induction of antigen-specific T-cell responses and an in vitro antigen presentation system to study the effects of IVIg on T-cell responses. The results obtained showed that IVIg inhibited both the in vivo and in vitro antigen-specific T-cell responses but that this effect was the indirect consequence of a reduction in the antigen presentation ability of antigen-presenting cells. The inhibitory effect of IVIg was FcgammaRIIb-independent, suggesting that IVIg must interfere with activating FcgammaRs expressed on antigen-presenting cells to reduce their ability to present antigens. Such inhibition of T-cell responses by reducing antigen presentation may therefore contribute to the well-known anti-inflammatory effects of IVIg in autoimmune diseases.

Therapeutic activities of intravenous immunoglobulins in multiple sclerosis involve modulation of chemokine expression

The objective of this study was to identify genes that are differentially expressed in peripheral T cells of patients with MS exacerbation receiving treatment with IVIG. Using microarray analysis, we identified 360 genes that were at least two-fold up- or down-regulated. The expression of four representative genes (PTGER4, CXCL5, IL11 and CASP2) was confirmed by quantitative PCR. Four of the differentially expressed genes encode chemokines (CXCL3, CXCL5, CCL13 and XCL2) that are involved in directing leukocyte migration. We suggest that the modulation of chemokine expression in peripheral T cells contributes to the beneficial activity of IVIG in patients with MS exacerbation.

Effects of Intravenous Immunoglobulins on Peripheral Blood Mononuclear Cell Activation in Vitro

The therapeutic effects of intravenous immunoglobulins (IVIGs) on different chronic inflammatory and autoimmune diseases is well appreciated, though clinical studies with high-evidence levels are largely missing. Similar to the broad spectrum of diseases and their underlying etiopathogenic background, the mechanisms of action seem heterogenous and multifold. Several studies addressing in vitro and in vivo effects of IVIG on various immunological parameters have been described with partly contradictory results. In this study immunoglobulins and stabilizers present in commercial IVIG preparations were studied in regard to the in vitro proliferation and cytokine production of peripheral blood mononuclear cells when stimulated with phytohemagglutinin (PHA), interleukin 2, and tetanus toxoid. Whereas the immunoglobulins stimulate the proliferation of PBMCs and decrease IFNgamma secretion, stabilizers of IVIG seem to inhibit the proliferation of PBMCs while increasing the secretion of IFN gamma. These effects have to be taken into account when balancing the impact of IVIG dosage and infusion intervals and relating them to clinical side effects and therapeutic efficacy.

IVIG enters the central nervous system during treatment of experimental autoimmune encephalomyelitis and is localised to inflammatory lesions

Intravenous immunoglobulin (IVIG) treatment reduces the relapse rate in relapsing-remitting multiple sclerosis (MS) and may interfere with MS pathology through its various anti-inflammatory and immunomodulatory properties. It is presently unknown whether IVIG enters the central nervous system (CNS) in sufficient amounts to influence the local immune response within the brain and spinal cord, or if the treatment effects are entirely due to peripheral actions of IVIG. The purpose of the present study was to evaluate if IVIG radiolabeled with 99mTc enters the CNS during treatment of experimental autoimmune encephalomyelitis (EAE) in the susceptible rat strain Dark Agouti. After in vivo administration of 99mTc-IVIG we observed significantly increased accumulation in the brain and spinal cord from rats with EAE. Accumulation of 99mTc-IVIG was not detectable in CNS tissue from control animals. In peripheral tissue samples minor increases in 99mTc-IVIG organ binding were observed in the liver and kidney during EAE. Localisation of 99mTc-IVIG in the brain tissue was visualised by autoradiography and revealed significant accumulation of IVIG only in areas also affected by perivascular inflammation and leakage of serum proteins. In conclusion, the results indicate that significant extravasation of IVIG to the CNS only occurs when blood-brain barrier function is compromised during EAE.

IVIg attenuates T cell-mediated killing of human neurons

Beneficial effects of intravenous immunoglobulin (IVIg) in relapsing-remitting multiple sclerosis (MS) have been described, including a decrease of brain atrophy. We have previously shown that activated T cells kill neurons in culture. In this manuscript, we show that the pretreatment of activated T cells with IVIg attenuates T cell neurotoxicity. This is attributed to the ability of IVIg to decrease the adhesion of T cells onto neurons, possibly through an effect on LFA-1, and by lowering the levels of Fas and FasL on T cells. Our results are relevant to understanding how therapies affect the MS disease process.

Intravenous immunoglobulin ameliorates experimental autoimmune encephalomyelitis and reduces neuropathological abnormalities when administered prophylactically

BACKGROUND AND METHODS

Immunomodulation with intravenous immunoglobulin (IVIG) represents a way of interfering with the disease process in multiple sclerosis (MS). In this study, the effects of IVIG on neurological symptoms and central nervous system (CNS) pathology were evaluated in experimental autoimmune encephalomyelitis (EAE), an MS animal model. EAE was induced in susceptible Dark Agouti rats by active immunization with a spinal cord homogenate, and infusions of 1 g/kg IVIG were given prophylactically or therapeutically.

RESULTS

The administration of IVIG at the time of immunization significantly suppressed the development of neurological symptoms compared with infusions of placebo (mean EAE score 0.6+/-0.3 versus 2.3+/-0.4). Moreover, the prophylactic IVIG administration resulted in a significant inhibition of the inflammatory response in CNS tissue (inflammation score 1.1+/-0.2 versus 1.8+/-0.2 after placebo). No beneficial effects were obtained by therapeutic IVIG infusions as the EAE disease course and the degree of inflammation and demyelination in the CNS were not different from animals receiving treatment with placebo.

CONCLUSIONS

The present study indicates that IVIG reduces the symptoms of EAE by suppression of the CNS inflammation that characterizes CNS pathology in these animals. Taking into account data from clinical trials of IVIG in MS, the results further suggest that IVIG acts primarily during the induction phase of the immune response thus preventing the development of relapses in MS.

Intravenous immunoglobulin treatment of multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis

Intravenous immunoglobulin (IVIG) is an established treatment of immune-mediated demyelinating neuropathy. Since IVIG possesses multiple immunomodulatory and anti-inflammatory properties, IVIG therapy may represent a way of interfering with the disease process in multiple sclerosis (MS). In the MS animal model experimental autoimmune encephalomyelitis (EAE), infusions of IVIG significantly reduced disease symptoms as well as the underlying CNS pathology. IVIG was only effective in EAE when administered in a prophylactic treatment protocol, since IVIG infusions during the established phase of EAE did not alter the disease course or the degree of inflammation found in the central nervous system. IVIG also has the potential to act through myelin repair mechanisms as evidenced by work done in the Theilers murine encephalomyelitis virus model of demyelination. Together these observations have led to certain expectations for IVIG as a treatment for MS, and have resulted in various clinical trials. Several controlled trials report beneficial effects of IVIG on relapse rate, new MRI lesions, and disease progression in relapsing-remitting MS, while a remyelinating effect of IVIG has not been documented. IVIG is, therefore, presently regarded as a second-line therapy of MS.

Fas polymorphisms are associated with the presence of anti-ganglioside antibodies in Guillain–Barré syndrome

Polymorphisms in genes involved in regulation of immune homeostasis may be a susceptibility factor in the induction of cross-reactive anti-ganglioside antibodies after infection in patients with Guillain-Barre syndrome (GBS). In this study we assessed whether polymorphisms in the promoter region of Fas and FasL and sFas and sFasL are related to GBS or its distinct clinical or serological subgroups. We show that the A(-670)G SNP in the promoter region of Fas and high levels of sFas are associated with the presence of anti-ganglioside antibodies, suggesting that Fas-FasL interaction is involved in the production of cross-reactive antibodies in GBS.

Theiler's virus infection: a model for multiple sclerosis

Both genetic background and environmental factors, very probably viruses, appear to play a role in the etiology of multiple sclerosis (MS). Lessons from viral experimental models suggest that many different viruses may trigger inflammatory demyelinating diseases resembling MS. Theiler's virus, a picornavirus, induces in susceptible strains of mice early acute disease resembling encephalomyelitis followed by late chronic demyelinating disease, which is one of the best, if not the best, animal model for MS. During early acute disease the virus replicates in gray matter of the central nervous system but is eliminated to very low titers 2 weeks postinfection. Late chronic demyelinating disease becomes clinically apparent approximately 2 weeks later and is characterized by extensive demyelinating lesions and mononuclear cell infiltrates, progressive spinal cord atrophy, and axonal loss. Myelin damage is immunologically mediated, but it is not clear whether it is due to molecular mimicry or epitope spreading. Cytokines, nitric oxide/reactive nitrogen species, and costimulatory molecules are involved in the pathogenesis of both diseases. Close similarities between Theiler's virus-induced demyelinating disease in mice and MS in humans, include the following: major histocompatibility complex-dependent susceptibility; substantial similarities in neuropathology, including axonal damage and remyelination; and paucity of T-cell apoptosis in demyelinating disease. Both diseases are immunologically mediated. These common features emphasize the close similarities of Theiler's virus-induced demyelinating disease in mice and MS in humans.

Mechanisms of intravenous immunoglobulin action in the treatment of autoimmune disorders

Intravenous immunoglobulins (IVIg) are therapeutic preparations of normal human immunoglobulin (Ig) G obtained from pools of blood from more than 1000 healthy donors, and exert immunomodulatory effects in autoantibody-mediated and T-cell-mediated autoimmune disorders and systemic inflammatory diseases. IVIg mechanisms of action in autoimmune diseases have been extensively analysed during the last 15 years and include the following: (i) interaction of the IgG Fc fragment with Fc receptors on leucocytes and endothelial cells; (ii) interaction of infused IgG with complement proteins; (iii) monocyte and lymphocyte modulation of synthesis and release of cytokines and cytokine antagonists; (iv) modulation of cell proliferation and reparation; (v) neutralisation of circulating autoantibodies; (vi) selection of immune repertoires; and (vii) interaction with other cell-surface molecules on T and B lymphocytes.