Induction of Regulatory T Cells by Intravenous Immunoglobulin: A Bridge between Adaptive and Innate Immunity

Immunomodulatory and anti-inflammatory properties of immunoglobulin G antibodies

Antibodies provide an essential layer of protection from infection and reinfection with microbial pathogens. An impaired ability to produce antibodies results in immunodeficiency and necessitates the constant substitution with pooled serum antibodies from healthy donors. Among the five antibody isotypes in humans and mice, immunoglobulin G (IgG) antibodies are the most potent anti-microbial antibody isotype due to their long half-life, their ability to penetrate almost all tissues and due to their ability to trigger a wide variety of effector functions. Of note, individuals suffering from IgG deficiency frequently produce self-reactive antibodies, suggesting that a normal serum IgG level also may contribute to maintaining self-tolerance. Indeed, the substitution of immunodeficient patients with pooled serum IgG fractions from healthy donors, also referred to as intravenous immunoglobulin G (IVIg) therapy, not only protects the patient from infection but also diminishes autoantibody induced pathology, providing more direct evidence that IgG antibodies play an active role in maintaining tolerance during the steady state and during resolution of inflammation. The aim of this review is to discuss different conceptual models that may explain how serum IgG or IVIg can contribute to maintaining a balanced immune response. We will focus on pathways depending on the IgG fragment crystallizable (Fc) as pre-clinical data in various mouse model systems as well as human clinical data have demonstrated that the IgG Fc-domain recapitulates the ability of intact IVIg with respect to its ability to trigger resolution of inflammation. We will further discuss how the findings already have or are in the process of being translated to novel therapeutic approaches to substitute IVIg in treating autoimmune inflammation.

Non B Cell-Derived Immunoglobulins in Intestinal Tract

Intestinal epithelium constitutes a barrier to the unrestricted movement of pathogens, and other detrimental substances from the external world (gut lumen) into the interstitial environment. Intestinal epithelial cells obstruct harmful substances passing through the epithelium as a physical and chemical barrier; Moreover, the epithelial cells can express Toll-like receptors (TLRs) and cytokines to exert innate immune function. In addition, high levels of immunoglobulin A (IgA) and other antibodies exist in the intestinal mucosa, maintaining intestinal immune homeostasis in conjunction with intestinal probiotics. Traditionally, these antibodies have been deemed to be secreted by submucosal plasma cells. Nonetheless, in recent years, it has been demonstrated that intestinal epithelial cells produce a substantial amount of Igs, especially IgA or free Ig light chains, which are involved in intestinal immune homeostasis and the survival of normal epithelial cells. Furthermore, mounting evidence affirms that many human carcinoma cells, including colorectal cancer (CRC), can overexpress Igs, particularly IgG. Cancer-derived Igs exhibit a unique V(D)J rearrangement pattern distinct from B cell-derived Ig; moreover, this cancer cell-derived IgG also has a unique sialic acid modification on the 162 site of CH1 domain (SIA-IgG). The SIA-IgG plays a crucial role in promoting cancer initiation, progression, metastasis, and tumour immune escape. Simultaneously, CRC cells can also express free Ig light chains, which promote colitis, colitis-associated colon carcinogenesis, and CRC progression. Therefore, Igs expressed by CRC cells could be a potential target for diagnosing and preventing the transformation of inflammation into cancer, as well as treating CRC.

Role of immune cells in the establishment of implantation and maintenance of pregnancy and immunomodulatory therapies for patients with repeated implantation failure and recurrent pregnancy loss

Background

Immune cells play an important role in the establishment of pregnancy, and abnormalities in the immune system can cause implantation failure and miscarriage.

Methods

Previous papers have been summarized and the role of immune cells in reproduction is reviewed.

Results

The immune environment in the uterus changes drastically from before implantation to after pregnancy to maintain pregnancy. In allogeneic pregnancies, immature dendritic cells (DCs) that induce immune tolerance from outside the uterus flow into the uterus, and mature DCs that remain in the uterus express programmed cell death ligand 2, which suppresses the immune response. Macrophages are classified into M1-macrophages, which induce inflammation, and M2-macrophages, which suppress inflammation; M1-macrophages are required for luteinization, and M2-macrophages induce the differentiation of endometrial epithelial cells to enable implantation. Regulatory T cells, which suppress rejection, are essential for the implantation and maintenance of allogeneic pregnancies. Implantation failure and fetal loss are associated with decreased numbers or qualitative abnormalities of DCs, macrophages, and regulatory T cells. The clinical usefulness of immunomodulatory therapies in patients with repeated implantation failure and recurrent pregnancy loss has been reported.

Conclusion

The provision of individualized medical care in cases of implantation failure or miscarriage may improve clinical outcomes.

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.

T Regulatory Cell-Associated Tolerance Induction by High-Dose Immunoglobulins in an HLA-Transgenic Mouse Model of Pemphigus

Pemphigus vulgaris (PV) is a potentially lethal autoimmune bullous skin disorder caused by IgG autoantibodies against desmoglein 3 (Dsg3) and Dsg1. During the last three decades, high-dose intravenous immunoglobulins (IVIgs) have been applied as an effective and relatively safe treatment regime in severe, therapy-refractory PV. This prompted us to study T- and B- cell polarization by IVIg in a human-Dsg3-dependent mouse model for PV. Using humanized mice transgenic for HLA-DRB1*04:02, which is a highly prevalent haplotype in PV, we employed IVIg in two different experimental approaches: in prevention and quasi-therapeutic settings. Our data show that intraperitoneally applied IVIg was systemically distributed for up to 42 days or longer. IVIg-treated Dsg3-immunized mice exhibited, in contrast to Dsg3-immunized mice without IVIg, significantly less Dsg3-specific IgG, and showed induction of T regulatory cells in lymphatic tissue. Ex vivo splenocyte analysis upon Dsg3-specific stimulation revealed an initial, temporarily reduced antigen-induced cell proliferation, as well as IFN-γ secretion that became less apparent over the course of time. Marginal-zone B cells were initially reduced in the preventive approach but re-expanded over time. In contrast, in the quasi-therapeutic approach, a robust down-regulation in both spleen and lymph nodes was observed. We found a significant down-regulation of the immature transitional 1 (T1) B cells in IVIg-treated mice in the quasi-therapeutic approach, while T2 and T3, representing a healthy stage of B-cell development, appeared to be up-regulated by IVIg. In summary, in two experimental settings employing an active PV mouse model, we demonstrate distinct alterations of T- and B-cell populations upon IVIg treatment, compatible with a tolerance-associated polarization in lymphatic tissue. Our data suggest that the clinical efficacy of IVIg is at least modulated by distinct alterations of T- and B-cell populations compatible with a tolerance-associated polarization in lymphatic tissue.

Immune Cell Functionality during Decidualization and Potential Clinical Application

Due to a vast influx in the secretory phase of the menstrual cycle, leukocytes represent 40-50% of the decidua at the time of implantation. Their importance for the implantation, maintenance of pregnancy, and parturition are known yet not fully understood. Thus, in idiopathic infertility, decidual immune-related factors are speculated to be the cause. In this review, the immune cell functions in the decidua were summarized, and clinical diagnostics, as well as interventions, were discussed. There is a rising number of commercially available diagnostic tools. However, the intervention options are still limited and/or poorly studied. In order for us to make big steps towards the proper use of reproductive immunology findings, we need to understand the mechanisms and especially support translational research.

Leprosy rash precipitated by immunotherapy for suspected inflammatory neuropathy

Leprosy is a chronic granulomatous infection caused by Mycobacterium leprae complex, causing skin and nerve lesions with potential for permanent disability. Leprosy can be overlooked in Western settings, as it is more prevalent in low-income and middle-income countries. We describe a 38-year-old woman with a 4-year history of progressive numbness of the left hand incorrectly diagnosed as multifocal acquired demyelinating sensory and motor neuropathy on the basis of clinical and neurophysiological findings. Treatment with empirical weekly corticosteroid followed by intravenous immunoglobulin resulted in the sudden development of a widespread rash; we then diagnosed borderline lepromatous leprosy on skin biopsy. We postulate that the immune treatments induced a temporary state of immune tolerance followed by a rebound of a T cell-mediated immune response resulting in a type 1 immunological response.

Sialylated IVIg binding to DC-SIGN+ Hofbauer cells induces immune tolerance through the caveolin-1/NF-kB pathway and IL-10 secretion

Although the use of IVIg has increased in various immune-driven diseases and even in pregnancy, the exact action mechanisms of IVIg are not fully understood. Dendritic cell-specific intercellular adhesion molecule-3 grabbing non-integrin (DC-SIGN) is a known receptor for α-2,6-sialylated IgG (sIVIg), which is responsible for the anti-inflammatory effect of IVIg. DC-SIGN is expressed on Hofbauer cells (HBCs) of the fetal villi of the placenta which act as an innate immune modulator at the maternal-fetal interface. Preeclampsia is a major complication in pregnancy and is related to IL-10, a cytokine with an important role in immune tolerance. DC-SIGN interaction with sIVIg in HBCs promoted IL-10 secretion through the activation of the caveolin-1/NF-κB pathway, especially in plasma lipid rafts. Consistent results were obtained for HBCs from patients with preeclampsia. Collectively, the stimulation of DC-SIGN⁺ HBCs with sIVIg enhanced immune tolerance in the feto-maternal environment, suggesting the therapeutic application of sIVIg to prevent preeclampsia.

[SARS-CoV-2 antibody response to the second COVID-19 vaccination in neuromuscular disease patients under immune modulating treatment]

Successful vaccination (adequate elevation of anti-spike protein antibodies) is attributed with sufficient protection against a severe course of coronavirus disease 2019 (COVID-19). For patients with chronic inflammatory diseases (CID) and immunosuppression the success of vaccination is an ongoing scientific discourse. Therefore, we evaluated the antibody titer against the S1 antigen of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) 2 weeks after complete immunization in patients with an underlying neuromuscular disease (NMD), who presented to our neurological day clinic and outpatient department for regular infusions of immunoglobulins. The data show that patients with chronic autoimmune NMD and simultaneous immunosuppressive or immune modulating treatment show an antibody response after vaccination with both mRNA and vector vaccines. In comparison to healthy subjects there is a comparable number of seroconversions due to the vaccination. A correlation between immunoglobulin dose and vaccination response could not be found; however, in contrast, there was a significant reduction of specific antibody synthesis, especially for the combination of mycophenolate mofetil (MMF) and prednisolone.

Systems biology and artificial intelligence analysis highlights the pleiotropic effect of IVIg therapy in autoimmune diseases with a predominant role on B cells and complement system

Intravenous immunoglobulin (IVIg) is used as treatment for several autoimmune and inflammatory conditions, but its specific mechanisms are not fully understood. Herein, we aimed to evaluate, using systems biology and artificial intelligence techniques, the differences in the pathophysiological pathways of autoimmune and inflammatory conditions that show diverse responses to IVIg treatment. We also intended to determine the targets of IVIg involved in the best treatment response of the evaluated diseases. Our selection and classification of diseases was based on a previously published systematic review, and we performed the disease characterization through manual curation of the literature. Furthermore, we undertook the mechanistic evaluation with artificial neural networks and pathway enrichment analyses. A set of 26 diseases was selected, classified, and compared. Our results indicated that diseases clearly benefiting from IVIg treatment were mainly characterized by deregulated processes in B cells and the complement system. Indeed, our results show that proteins related to B-cell and complement system pathways, which are targeted by IVIg, are involved in the clinical response. In addition, targets related to other immune processes may also play an important role in the IVIg response, supporting its wide range of actions through several mechanisms. Although B-cell responses and complement system have a key role in diseases benefiting from IVIg, protein targets involved in such processes are not necessarily the same in those diseases. Therefore, IVIg appeared to have a pleiotropic effect that may involve the collaborative participation of several proteins. This broad spectrum of targets and 'non-specificity' of IVIg could be key to its efficacy in very different diseases.

Intravenous Immunoglobulins Promote an Expansion of Monocytic Myeloid-Derived Suppressor Cells (MDSC) in CVID Patients

Common variable immunodeficiency disorders (CVID), the most common primary immune deficiency, includes heterogeneous syndromes characterized by hypogammaglobulinemia and impaired antibody responses. CVID patients frequently suffer from recurrent infections and inflammatory conditions. Currently, immunoglobulin replacement therapy (IgRT) is the first-line treatment to prevent infections and aminorate immune alterations in CVID patients. Intravenous Immunoglobulin (IVIg), a preparation of highly purified poly-specific IgG, is used for treatment of immunodeficiencies as well as for autoimmune and inflammatory disorders, as IVIg exerts immunoregulatory and anti-inflammatory actions on innate and adaptive immune cells. To determine the mechanism of action of IVIg in CVID in vivo, we determined the effect of IVIg infusion on the transcriptome of peripheral blood mononuclear cells from CVID patients, and found that peripheral blood monocytes are primary targets of IVIg in vivo, and that IVIg triggers the acquisition of an anti-inflammatory gene profile in human monocytes. Moreover, IVIg altered the relative proportions of peripheral blood monocyte subsets and enhanced the proportion of CD14⁺ cells with a transcriptional, phenotypic, and functional profile that resembles that of monocytic myeloid-derived suppressor cells (MDSC). Therefore, our results indicate that CD14 + MDSC-like cells might contribute to the immunoregulatory effects of IVIg in CVID and other inflammatory disorders.

Intravenous immunoglobulins in patients with COVID-19-associated moderate-to-severe acute respiratory distress syndrome (ICAR): multicentre, double-blind, placebo-controlled, phase 3 trial

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a major complication of COVID-19 and is associated with high mortality and morbidity. We aimed to assess whether intravenous immunoglobulins (IVIG) could improve outcomes by reducing inflammation-mediated lung injury.

METHODS

In this multicentre, double-blind, placebo-controlled trial, done at 43 centres in France, we randomly assigned patients (1:1) receiving invasive mechanical ventilation for up to 72 h with PCR confirmed COVID-19 and associated moderate-to-severe ARDS to receive either IVIG (2 g/kg over 4 days) or placebo. Random assignment was done with a web-based system and was stratified according to the participating centre and the duration of invasive mechanical ventilation before inclusion in the trial (<12 h, 12-24 h, and >24-72 h), and treatment was administered within the first 96 h of invasive mechanical ventilation. To minimise the risk of adverse events, the IVIG administration was divided into four perfusions of 0·5 g/kg each administered over at least 8 hours. Patients in the placebo group received an equivalent volume of sodium chloride 0·9% (10 mL/kg) over the same period. The primary outcome was the number of ventilation-free days by day 28, assessed according to the intention-to-treat principle. This trial was registered on ClinicalTrials.gov, NCT04350580.

FINDINGS

Between April 3, and October 20, 2020, 146 patients (43 [29%] women) were eligible for inclusion and randomly assigned: 69 (47%) patients to the IVIG group and 77 (53%) to the placebo group. The intention-to-treat analysis showed no statistical difference in the median number of ventilation-free days at day 28 between the IVIG group (0·0 [IQR 0·0-8·0]) and the placebo group (0·0 [0·0-6·0]; difference estimate 0·0 [0·0-0·0]; p=0·21). Serious adverse events were more frequent in the IVIG group (78 events in 22 [32%] patients) than in the placebo group (47 events in 15 [20%] patients; p=0·089).

INTERPRETATION

In patients with COVID-19 who received invasive mechanical ventilation for moderate-to-severe ARDS, IVIG did not improve clinical outcomes at day 28 and tended to be associated with an increased frequency of serious adverse events, although not significant. The effect of IVIGs on earlier disease stages of COVID-19 should be assessed in future trials.

FUNDING

Programme Hospitalier de Recherche Clinique.

Neuropathophysiology of coronavirus disease 2019: neuroinflammation and blood brain barrier disruption are critical pathophysiological processes that contribute to the clinical symptoms of SARS-CoV-2 infection

Coronavirus disease 2019 (COVID-19) is caused by the novel SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) first discovered in Wuhan, Hubei province, China in December 2019. SARS-CoV-2 has infected several millions of people, resulting in a huge socioeconomic cost and over 2.5 million deaths worldwide. Though the pathogenesis of COVID-19 is not fully understood, data have consistently shown that SARS-CoV-2 mainly affects the respiratory and gastrointestinal tracts. Nevertheless, accumulating evidence has implicated the central nervous system in the pathogenesis of SARS-CoV-2 infection. Unfortunately, however, the mechanisms of SARS-CoV-2 induced impairment of the central nervous system are not completely known. Here, we review the literature on possible neuropathogenic mechanisms of SARS-CoV-2 induced cerebral damage. The results suggest that downregulation of angiotensin converting enzyme 2 (ACE2) with increased activity of the transmembrane protease serine 2 (TMPRSS2) and cathepsin L in SARS-CoV-2 neuroinvasion may result in upregulation of proinflammatory mediators and reactive species that trigger neuroinflammatory response and blood brain barrier disruption. Furthermore, dysregulation of hormone and neurotransmitter signalling may constitute a fundamental mechanism involved in the neuropathogenic sequelae of SARS-CoV-2 infection. The viral RNA or antigenic peptides also activate or interact with molecular signalling pathways mediated by pattern recognition receptors (e.g., toll-like receptors), nuclear factor kappa B, Janus kinase/signal transducer and activator of transcription, complement cascades, and cell suicide molecules. Potential molecular targets and therapeutics of SARS-CoV-2 induced neurologic damage are also discussed.

New insights into IVIg mechanisms and alternatives in autoimmune and inflammatory diseases

PURPOSE OF REVIEW

Intravenous immunoglobulin (IVIg) is an effective treatment for an increasing number of autoimmune and inflammatory conditions. However, IVIg continues to be limited by problems of potential shortages and cost. A number of mechanisms have been described for IVIg, which have been captured in newly emergent IVIg mimetic and IVIg alternative therapies. This review discusses the recent developments in IVIg mimetics and alternatives.

RECENT FINDINGS

Newly emergent IVIg mimetics and alternatives capture major proposed mechanisms of IVIg, including FcγR blockade, FcRn inhibition, complement inhibition, immune complex mimetics and sialylated IgG. Many of these emergent therapies have promising preclinical and clinical trial results.

SUMMARY

Significant research has been undertaken into the mechanism of IVIg in the treatment of autoimmune and inflammatory disease. Understanding the major IVIg mechanisms has allowed for rational development of IVIg mimetics and alternatives for several IVIg-treatable diseases.

Case Report: Successful Response to Intravenous Immunoglobulin and Steroid Pulses in a Renal Transplant Recipient With Severe Covid-19 Disease and Associated Acute Allograft Failure

The impact of Covid-19 pneumonia caused by SARS-CoV-2 on transplanted populations under chronic immunosuppression seems to be greater than in normal population. Clinical management of the disease, particularly in those patients worsening after a cytokine storm, with or without allograft impairment and using available therapeutic approaches in the absence of specific drugs to fight against the virus, involves a major challenge for physicians. We herein provide evidence of the usefulness of high-dose intravenous immunoglobulin (IVIG) combined with steroid pulses to successfully treat a case of Covid-19 pneumonia in a single-kidney transplanted patient with mechanical ventilation and hemodialysis requirements in the setting of a cytokine storm. A rapid decrease in the serum level of inflammatory cytokines, particularly IL-6, IL-8, TNF-α, MCP-1 and IL-10, as well as of acute-phase reactants such as ferritin, D-dimer and C-reactive protein was observed after the IVIG infusion and methylprednisolone bolus administration with a parallel clinical improvement and progressive allograft function recovery, allowing the patient’s final discharge 40 days after the treatment onset. The immunomodulatory effect of IVIG together with the anti-inflammatory and immunosuppressive potential of steroids could be an alternative strategy to treat severe cases of Covid-19 pneumonia associated with an uncontrolled inflammatory response in transplanted populations.

Effect of early treatment with polyvalent immunoglobulin on acute respiratory distress syndrome associated with SARS-CoV-2 infections (ICAR trial): study protocol for a randomized controlled trial

BACKGROUND

As of mid-June 2020, 7,500,000 people were infected with SARS-CoV-2 worldwide and 420,000 people died, mainly from coronavirus disease 2019 (COVID-19)-related acute respiratory distress syndrome (ARDS). COVID-19-related ARDS is subject to a mortality rate of 50% and prolonged period of mechanical ventilation, with no specific pharmacological treatment currently available (Infection au nouveau Coronavirus (SARS-CoV-2), COVID-19, France et Monde. https://www.santepubliquefrance.fr/dossiers/coronavirus-covid-19 ). Because of its immunomodulatory action, we propose to evaluate the efficacy and safety of intravenous immunoglobulin (IVIG) administration in patients developing COVID-19-related ARDS.

METHODS

The trial is a phase III double-blind, randomized, multicenter, parallel group, concurrent, controlled study in hospitalized participants with COVID-19 requiring mechanical ventilation using a sequential design. Participants in the treatment group will receive infusions of polyvalent immunoglobulin for 4 consecutive days, and the placebo group will receive an equivalent volume of sodium chloride 0.9% for the same duration. The primary outcome is the number of ventilator-free days up to the 28th day. Secondary objectives are to evaluate the effect of IVIG on (1) organ failure according to the Sequential Organ Failure Assessment (SOFA) score at 14 and 28 days, (2) lung injury score at 14 and 28 days, (3) the occurrence of grade 3 or 4 adverse events of IVIG, (4) length of intensive care unit (ICU) stay, (5) length of hospital stay, (6) functional outcomes at day 90 defined by the activities of daily living and instrumental activities of the daily living scales, and (7) 90-day survival. One hundred thirty-eight subjects will be randomized in a 1:1 ratio to IVIG or placebo groups (69 in each group), considering 90% power, alpha level 0.05 (two sides), and 0.67 effect size level.

DISCUSSION

The ICAR trial investigates the effect of IVIG in COVID-19-related ARDS. We expect an increase in the survival rate and a reduction in the duration of mechanical ventilation, which is associated with significant morbidity.

TRIAL REGISTRATION

EudraCT 2020-001570-30. ClinicalTrials.gov NCT04350580 . Registered on 17 April 2020.

Normalization of electroretinogram and symptom resolution of melanoma-associated retinopathy with negative autoantibodies after treatment with programmed death-1 (PD-1) inhibitors for metastatic melanoma

Melanoma-associated retinopathy (MAR) is a paraneoplastic syndrome that involves the production of autoantibodies which can cross-react with retinal epitopes leading to visual symptoms. Autoantibodies can target intracellular proteins, and only a few are directed against membrane proteins. This discrepancy in autoantibody-protein target can translate into different immune responses (T-cell mediated vs B-cell mediated). Historically, treatment of MAR has focused on surgical reduction or immunosuppressive medication, mainly glucocorticoids. However, tumor resection is not relevant in metastatic melanoma in which MAR is mostly encountered. Moreover, the use of glucocorticoids can reduce the efficacy of immunotherapy. We report the first case to our knowledge with subjective resolution of visual symptoms and objective evidence of normalization of electroretinogram of MAR with undetectable autoantibodies after administration of programmed death-1 (PD-1) inhibitor (pembrolizumab) without the use of surgical reduction or systemic immunosuppression. This case highlights the potential improvement and resolution of negative autoantibody MAR with the use of PD-1 inhibitors and emphasizes the importance of multidisciplinary approach and team discussion to avoid interventions that can decrease immunotherapy-mediated anti-tumor effect.

Responsiveness to i.v. immunoglobulin therapy in patients with toxic epidermal necrolysis: A novel pharmaco-immunogenetic concept

Toxic epidermal necrolysis (TEN) represents a rare drug-induced autoimmune reaction with delayed-type hypersensitivity that initiates the process of developing massive keratinocyte apoptosis, dominantly in the dermoepidermal junction. Although the etiopathophysiology has not yet been fully elucidated, the binding of Fas ligand (FasL, CD95L) to the Fas receptor (CD95) was shown to play a key role in the induction of apoptosis in this syndrome. The knowledge of the role of immunoglobulin G (IgG) in inhibition of Fas-mediated apoptosis contributed to the introduction of i.v. Ig (IVIg) in the therapy of TEN patients. Despite great enthusiasm for this therapy at the end of the 1990s, subsequent studies in various populations and meta-analyses could not unequivocally confirm the efficacy of the IVIg-based treatment concept. Today, therefore, we are faced with the dilemmas of how to adjust therapy of TEN patients most effectively, which patients could benefit from IVIg therapy and what dose of the preparation should be administrated. The ground-breaking question is: do the host genetic profiles influence the responsiveness and side-effects of IVIg therapy in TEN patients? Based on recent pharmacological, immunological and genetic findings, we suggest that the variability of IVIg therapy outcomes in TEN patients may be related to functional variants in Fas, FasL and Fc-γ receptor genes. This novel concept could lead to improved quality of care for patients with TEN, facilitating personalized therapy to reduce mortality.

Mechanisms of action and historical facts on the use of intravenous immunoglobulins in systemic lupus erythematosus

The current existing therapies for severe cases of systemic lupus erythematosus (SLE) patients are still limited. Intravenous immunoglobulin (IVIGs), which are purified from the plasma of thousands of healthy human donors, have been profiled as efficacious and life-saving options for SLE patients refractory to conventional therapy. The specific mechanism of action by which IVIGs generate immunomodulation in SLE is not currently understood. In this manuscript, we reviewed some of the hypothesis that have been postulated to explain the IVIG effects, including those on T and B cell intracellular signalling and activation, as well as the interferon signalling pathways involved in the detection of nucleic acids and the defective removal of immune complexes and debris.

Immunoglobulin G Enhances Generation of Inducible T Regulatory Cells and Increases Their Regulatory Function

Intravenous immunoglobulin (IVIg) has been shown to be effective in the treatment of a variety of autoimmune diseases. To clarify the role of T regulatory cells (Tregs) in the immunoregulatory effect of IVIg, we focused on human inducible T regulatory cells (iTregs) and investigated the mechanism of action of IVIg. When immunoglobulin G (IgG) was added to a culture system that differentiates iTregs from anti-CD3 antibody activated CD4+CD25- T cells in the presence of syngeneic immature dendritic cells, interleukin (IL)-2 and transforming growth factor-β (TGF-β), the expression of forkhead box P3 (FoxP3), which is the master transcription factor for Tregs in CD4+CD25+ T cells, increased in an IgG concentration-dependent manner. The expression of FoxP3 in iTregs in the 20 mg/mL IgG group was twice as high as that in the saline group. iTregs that highly expressed FoxP3 not only partially suppressed the polyclonal proliferative response of T cells derived from the same individual but also produced significantly more inhibitory cytokines IL-10 and TGF-β. The ability of IgG to enhance iTregs differentiation was also observed in the Fc fragment, but not in the F(ab')₂ fragment. These results suggest the clinical regulation of immune responses by IVIg administration may contribute at least to enhancing the differentiation of iTregs and partial immunosuppressive functions.

Reversing Autoimmunity Combination of Rituximab and Intravenous Immunoglobulin

In this concept paper, the authors present a unique and novel protocol to treat autoimmune diseases that may have the potential to reverse autoimmunity. It uses a combination of B cell depletion therapy (BDT), specifically rituximab (RTX) and intravenous immunoglobulin (IVIg), based on a specifically designed protocol (Ahmed Protocol). Twelve infusions of RTX are given in 6–14 months. Once the CD20⁺ B cells are depleted from the peripheral blood, IVIg is given monthly until B cells repopulation occurs. Six additional cycles are given to end the protocol. During the stages of B cell depletion, repopulation and after clinical recovery, IVIg is continued. Along with clinical recovery, significant reduction and eventual disappearance of pathogenic autoantibody occurs. Administration of IVIg in the post-clinical period is a crucial part of this protocol. This combination reduces and may eventually significantly eliminates inflammation in the microenvironment and facilitates restoring immune balance. Consequently, the process of autoimmunity and the phenomenon that lead to autoimmune disease are arrested, and a sustained and prolonged disease and drug-free remission is achieved. Data from seven published studies, in which this combination protocol was used, are presented. It is known that BDT does not affect check points. IVIg has functions that mimic checkpoints. Hence, when inflammation is reduced and the microenvironment is favorable, IVIg may restore tolerance. The authors provide relevant information, molecular mechanism of action of BDT, IVIg, autoimmunity, and autoimmune diseases. The focus of the manuscript is providing an explanation, using the current literature, to demonstrate possible pathways, used by the combination of BDT and IVIg in providing sustained, long-term, drug-free remissions of autoimmune diseases, and thus reversing autoimmunity, albeit for the duration of the observation.

Modulatory effect of intravenous immunoglobulin on Th17/Treg cell balance in women with unexplained recurrent spontaneous abortion

Recurrent spontaneous abortion (RSA) is a growing problem worldwide. In a majority of cases, the cause remains unknown but there is increasing evidence that immunologic factors play an important role. Intravenous immunoglobulin (IVIg) therapy has been proposed to have immune modulatory effects and therefore been applicable for the treatment of patients with RSA. Although its efficacy is still controversial, several recent studies suggest that IVIg treatment may improve pregnancy outcomes. CD4⁺ T cells and their related cytokines play an important role in maternal-fetal immune regulation, and an imbalance of Th17/Treg cell ratio has been proposed as a cause for RSA. We review the scientific evidence supporting a modulatory effect of IVIg on Th17/Treg cell balance and discuss the potential mechanisms how IVIg might enhance Treg cells function. We propose that correction of Th17/Treg cell dysregulation could be one of the mechanisms that can explain the positive therapeutic effects of IVIg therapy. Consequently, selecting patients with abnormal Th17/Treg cell ratios could increase the success of IVIg therapy.

High-dose of intravenous immunoglobulin modulates immune tolerance in premature infants

BACKGROUND

Intravenous immunoglobulin (IVIG) is commonly used to improve the immunomodulatory effects, although its regulatory effect on premature Treg cells is unclear. The purpose of this study is to study the effect of high dose of IVIG (HD-IVIG) on Treg cells expression and cytokine profile in premature birth.

METHODS

Fifty-two premature infants were enrolled in this study and thirty-one premature infants who were suspected to have intrauterine infection received HD-IVIG (1-2 g/kg) at the first day of birth; the remaining 21 premature infants were assigned as the control group. The peripheral blood CD4 + T and foxp3+ Treg cells were checked by flow cytometry, and cytokine concentrations were detected by cytometric bead array.

RESULTS

With the gestational age growth, peripheral blood CD4 + T and foxp3+ Treg cells of prematurity gradually declined from 50% to 35% and from 8% to 6%, respectively. Meanwhile, HD-IVIG increased the percentage of CD4 + T and foxp3+ Treg cells compared with their baseline levels (p < 0.001). HD-IVIG demonstrated different regulating effects on cytokines secretion, increased IL-17 and TGF-β, and inhibited IL-6 secretion.

CONCLUSION

Our results demonstrated that HD-IVIG not only enhanced the premature immune tolerance, but also suppressed the excessive inflammation response mediated by IL-6.

TRIAL REGISTRATION

This study was under the clinical study registration (ChiCTR-ORC-16008872, date of registration, 2016-07-21).

Innovative Approaches to Improve Anti-Infective Vaccine Efficacy

Safe and efficacious vaccines are arguably the most successful medical interventions of all time. Yet the ongoing discovery of new pathogens, along with emergence of antibiotic-resistant pathogens and a burgeoning population at risk of such infections, imposes unprecedented public health challenges. To meet these challenges, innovative strategies to discover and develop new or improved anti-infective vaccines are necessary. These approaches must intersect the most meaningful insights into protective immunity and advanced technologies with capabilities to deliver immunogens for optimal immune protection. This goal is considered through several recent advances in host-pathogen relationships, conceptual strides in vaccinology, and emerging technologies. Given a clear and growing risk of pandemic disease should the threat of infection go unmet, developing vaccines that optimize protective immunity against high-priority and antibiotic-resistant pathogens represents an urgent and unifying imperative.

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.

Tregitopes and impaired antigen presentation: Drivers of the immunomodulatory effects of IVIg?

Introduction

Although intravenous immunoglobulin (IVIg) is commonly used in the clinic to treat various autoimmune and severe inflammatory diseases, the mode of action is not fully elucidated. This work investigates two proposed mechanisms: (1) the potential role of regulatory T‐cell epitopes (Tregitopes) from the constant domain of IgG in the immunosuppressive function of IVIg; and (2) a potential impact of IVIg on the ability of antigen presenting cells (APCs) to present peptides.

Methods and Results

Investigation of the HLA class II peptide repertoire from IVIg‐loaded dendritic cells (DCs) via MHC‐associated peptide proteomics (MAPPs) revealed that numerous IgG‐derived peptides were strongly presented along the antibody sequence. Surprisingly, Tregitopes 167 and 289 did not show efficient natural presentation although they both bound to HLA class II when directly loaded as “naked” peptides on human DCs. In addition, both Tregitopes could not reproduce the inhibitory effect of IVIg in a human in vitro T‐cell proliferation assay as well as in vivo in mice. MAPPs data demonstrate that presentation of peptides from several antigens remained unchanged even when competed with high doses of IVIg, in both human and mouse.

Conclusion

These data suggest that the effects mediated by IVIg are not caused by Tregitopes nor by impaired antigen presentation.

Effect of intravenous immunoglobulin on the function of Treg cells derived from immunosuppressed mice with Pseudomonas aeruginosa pneumonia

AIM

The present study aimed to investigate the effect of intravenous immunoglobulin (IVIG) on regulatory T (Treg) cells derived from immunosuppressed mice with Pseudomonas aeruginosa (PA) pneumonia.

METHODS

A total of 108 BALB/c mice were randomly divided into the following groups: control group (Control), immunosuppressed group (IS), PA pneumonia group (PA), PA pneumonia in immunosuppressed group (IS + PA), PA pneumonia with IVIG treatment in immunocompetent group (PA + IVIG) and PA pneumonia with IVIG treatment in immunosuppressed group (IS + PA + IVIG). Each group comprised 18 mice. The combined PA pneumonia in immunosuppressed model and the treatment models were established. The mice in each group were sacrificed at 4, 8, and 24 h time points. The general condition and pathological changes in the lung tissues of the mice were monitored. Reverse transcription-polymerase chain reaction was used to detect the forkhead box P3 (FOXP3) mRNA relative expression level in the lung tissues. The enzyme-linked immunosorbent assay was used to detect the serum concentration of active transforming growth factor beta (TGF-β).

RESULTS

No inflammatory response were exhibited in the lung tissues of the mice in Control group and IS group, while varying degrees of acute lung injury were revealed in the mice in PA group, IS + PA group, PA + IVIG group and IS + PA + IVIG group. Lung tissue injury was most apparent at the 8 h time point, and it indicated the greatest effect in IS + PA group. Whereas tissue damages were alleviated in PA + IVIG group and IS + PA + IVIG group compared with IS + PA group. In addition, tissue damage lessened in PA + IVIG group compared with PA group and IS + PA + IVIG group. FOXP3 mRNA expression levels in the lung tissues and the serum concentration of TGF-β were lower in IS group, PA group, IS + PA group and IS + PA + IVIG group at the 4, 8 and 24 h time points, respectively compared with Control group. FOXP3 mRNA expression levels decreased in PA + IVIG group at the 4h time point and TGF-β serum concentrations decreased at the 4 and 8h time points compared with Control group, and subsequently increased.

CONCLUSIONS

In the immunosuppred model with PA pneumonia, the immune system was greatly compromised. IVIG partially restored the immunosuppressed functions of Treg cells, suppressed the overactivated immune system and ameliorated the development of the disease.

Peripherally Generated Foxp3+ Regulatory T Cells Mediate the Immunomodulatory Effects of IVIg in Allergic Airways Disease

IVIg is widely used as an immunomodulatory therapy. We have recently demonstrated that IVIg protects against airway hyperresponsiveness (AHR) and inflammation in mouse models of allergic airways disease (AAD), associated with induction of Foxp3⁺ regulatory T cells (Treg). Using mice carrying a DTR/EGFP transgene under the control of the Foxp3 promoter (DEREG mice), we demonstrate in this study that IVIg generates a de novo population of peripheral Treg (pTreg) in the absence of endogenous Treg. IVIg-generated pTreg were sufficient for inhibition of OVA-induced AHR in an Ag-driven murine model of AAD. In the absence of endogenous Treg, IVIg failed to confer protection against AHR and airway inflammation. Adoptive transfer of purified IVIg-generated pTreg prior to Ag challenge effectively prevented airway inflammation and AHR in an Ag-specific manner. Microarray gene expression profiling of IVIg-generated pTreg revealed upregulation of genes associated with cell cycle, chromatin, cytoskeleton/motility, immunity, and apoptosis. These data demonstrate the importance of Treg in regulating AAD and show that IVIg-generated pTreg are necessary and sufficient for inhibition of allergen-induced AAD. The ability of IVIg to generate pure populations of highly Ag-specific pTreg represents a new avenue to study pTreg, the cross-talk between humoral and cellular immunity, and regulation of the inflammatory response to Ags.

Intravenous immunoglobulin: pharmacological properties and use in polyneuropathies

INTRODUCTION

Intravenous immunoglobulin (IVIg) is increasingly used for the treatment of autoimmune and systemic inflammatory diseases with both licensed and off-label indications. The mechanism of action is complex and not fully understood, involving the neutralization of pathological antibodies, Fc receptor blockade, complement inhibition, immunoregulation of dendritic cells, B cells and T cells and the modulation of apoptosis. Areas covered: First, this review describes the pharmacological properties of IVIg, including the composition, mechanism of action, and adverse events. The second part gives an overview of some of the immune-mediated polyneuropathies, with special focus on the pathomechanism and clinical trials assessing the efficacy of IVIg. A literature search on PubMed was performed using the terms IVIg, IVIg preparations, side effects, mechanism of action, clinical trials, GBS, CIDP. Expert opinion: Challenges associated with IVIg therapy and the treatment possibilities for immune-mediated polyneuropathies are discussed. The availability of IVIg is limited, the expenses are high, and, in several diseases, a chronic therapy is necessary to maintain the immunomodulatory effect. The better understanding of the mechanism of action of IVIg could open the possibility of the development of disease-specific, targeted immune therapies.