IVIg and LPS Co-stimulation Induces IL-10 Production by Human Monocytes, Which Is Compromised by an FcγRIIA Disease-Associated Gene Variant

Effects of Intravenous Immunoglobulins on Human Innate Immune Cells: Collegium Internationale Allergologicum Update 2024

BACKGROUND

Intravenous immunoglobulin (IVIg) has been used for almost 40 years in the treatment of autoimmune and systemic inflammatory diseases. Numerous cells are involved in the innate immune response, including monocytes/macrophages, neutrophils, dendritic cells, mast cells, basophils, eosinophils, natural killer cells, and innate lymphoid cells. Many studies have investigated the mechanisms by which IVIg down-modulates inflammatory and autoimmune processes of innate immune cells. However, questions remain regarding the precise mechanism of action in autoimmune or inflammatory conditions. The aim of this work was to review the immunomodulatory effect of IVIg on only human innate immune cells. A narrative review approach was chosen to summarize key evidence on the immunomodulatory effects of commercially available and unmodified IVIg on human innate immune cells.

SUMMARY

Numerous different immunomodulatory effects of IVIg have been reported, with some very different effects depending on the immune cell type and disease. Several limitations of the different studies were identified. Of the 77 studies identified and reviewed, 29 (37.7%) dealt with autoimmune or inflammatory diseases. Otherwise, the immunomodulatory effects of IVIg were studied only in healthy donors using an in vitro experimental approach. Some of the documented effects showed disease-specific effects, such as in Kawasaki disease. Various methodological limitations have also been identified that may reduce the validity of some studies.

KEY MESSAGE

As further insights have been gained into the various inflammatory cascades activated in immunological diseases, interesting insights have also been gained into the mechanism of action of IVIg. We are still far from discovering all the immunomodulatory mechanisms of IVIg.

Phenotype and oxidative burst of low-density neutrophil subpopulations are altered in common variable immunodeficiency patients

Common variable immunodeficiency disorder (CVID) is the most common form of primary antibody immunodeficiency. Due to low antibody levels, CVID patients receive intravenous or subcutaneous immunoglobulin replacement therapy as treatment. CVID is associated with the chronic activation of granulocytes, including an increased percentage of low-density neutrophils (LDNs). In this study, we examined changes in the percentage of LDNs and the expression of their surface markers in 25 patients with CVID and 27 healthy donors (HD) after in vitro stimulation of whole blood using IVIg. An oxidative burst assay was used to assess the functionality of LDNs. CVID patients had increased both relative and absolute LDN counts with a higher proportion of mLDNs compared to iLDNs, distinguished based on the expression of CD10 and CD16. Immature LDNs in the CVID and HD groups had significantly reduced oxidative burst capacity compared to mature LDNs. Interestingly we observed reduced oxidative burst capacity, reduced expression of CD10 after stimulation of WB, and higher expression of PD-L1 in mature LDNs in CVID patients compared to HD cells. Our data indicate that that the functional characteristics of LDNs are closely linked to their developmental stage. The observed reduction in oxidative burst capacity in mLDNs in CVID patients could contribute to an increased susceptibility to recurrent bacterial infections among CVID patients.

JNK signaling during IL-3-mediated differentiation contributes to the c-kit-potentiated allergic inflammatory capacity of mast cells

Mast cells are leukocytes that mediate various aspects of immunity and drive allergic hypersensitivity pathologies. Mast cells differentiate from hematopoietic progenitor cells in a manner that is largely IL-3 dependent. However, molecular mechanisms, including the signaling pathways that control this process, have yet to be thoroughly investigated. Here, we examine the role of the ubiquitous and critical mitogen-activated protein kinase signaling pathway due to its position downstream of the IL-3 receptor. Hematopoietic progenitor cells were harvested from the bone marrow of C57BL/6 mice and differentiated to bone marrow-derived mast cells in the presence of IL-3 and mitogen-activated protein kinase inhibitors. Inhibition of the JNK node of the mitogen-activated protein kinase pathway induced the most comprehensive changes to the mature mast cell phenotype. Bone marrow-derived mast cells differentiated during impaired JNK signaling expressed impaired c-kit levels on the mast cell surface, first detected at week 3 of differentiation. Following 1 wk of inhibitor withdrawal and subsequent stimulation of IgE-sensitized FcεRI receptors with allergen (TNP-BSA) and c-kit receptors with stem cell factor, JNK-inhibited bone marrow-derived mast cells exhibited impediments in early-phase mediator release through degranulation (80% of control), as well as late-phase secretion of CCL1, CCL2, CCL3, TNF, and IL-6. Experiments with dual stimulation conditions (TNP-BSA + stem cell factor or TNP-BSA alone) showed that impediments in mediator secretion were found to be mechanistically linked to reduced c-kit surface levels. This study is the first to implicate JNK activity in IL-3-mediated mast cell differentiation and also identifies development as a critical and functionally determinative period.

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.

Functional IgG Autoantibodies against Autonomic Nervous System Receptors in Symptomatic Women with Silicone Breast Implants

The association between the clinical picture of symptomatic women with silicone breast implants (SBI) and dysregulated immunity was in dispute for decades. In the current study, we describe for the first time the functional activity of purified IgG antibodies derived from symptomatic women with SBIs (suffering from subjective/autonomic-related symptoms), both in vitro and in vivo. We found that IgGs, derived from symptomatic women with SBIs, dysregulate inflammatory cytokines (TNFα, IL-6) in activated human peripheral blood mononuclear cells, compared to healthy-women-derived IgGs. Importantly, behavioral studies conducted following intracerebroventricular injection of IgGs derived from symptomatic women with SBIs (who have dysregulated circulating level of IgG autoantibodies directed against autonomic nervous system receptors) into mice brains demonstrated a specific and transient significant increment (about 60%) in the time spent at the center of the open field arena compared with mice injected with IgG from healthy women (without SBIs). This effect was accompanied with a strong trend of reduction of the locomotor activity of the SBI-IgG treated mice, indicating an overall apathic-like behavior. Our study is the first to show the potential pathogenic activity of IgG autoantibodies in symptomatic women with SBIs, emphasizing the importance of these antibodies in SBI-related illness.

A subset of antibodies targeting citrullinated proteins confers protection from rheumatoid arthritis

Although elevated levels of anti-citrullinated protein antibodies (ACPAs) are a hallmark of rheumatoid arthritis (RA), the in vivo functions of these antibodies remain unclear. Here, we have expressed monoclonal ACPAs derived from patients with RA, and analyzed their functions in mice, as well as their specificities. None of the ACPAs showed arthritogenicity nor induced pain-associated behavior in mice. However, one of the antibodies, clone E4, protected mice from antibody-induced arthritis. E4 showed a binding pattern restricted to skin, macrophages and dendritic cells in lymphoid tissue, and cartilage derived from mouse and human arthritic joints. Proteomic analysis confirmed that E4 strongly binds to macrophages and certain RA synovial fluid proteins such as α-enolase. The protective effect of E4 was epitope-specific and dependent on the interaction between E4-citrullinated α-enolase immune complexes with FCGR2B on macrophages, resulting in increased IL-10 secretion and reduced osteoclastogenesis. These findings suggest that a subset of ACPAs have therapeutic potential in RA.

Macrophage immunotherapy: overcoming impediments to realize promise

As an essential component of immunity, macrophages have key roles in mammalian host defense, tissue homeostasis, and repair, as well as in disease pathogenesis and pathophysiology. A source of fascination and extensive research, in this Opinion we challenge the utility of the M1-M2 paradigm, and discuss the importance of accurate characterization of human macrophages. We comment on the application of single cell analytics to define macrophage subpopulations and how this could advance therapeutic options. We argue that human macrophage cell therapy can be used to alleviate many diseases, and offer a viewpoint on the knowledge gaps that must be filled to render such a therapeutic approach a reality and, ideally, a common future practice in precision medicine.

Microfluidic system for immune cell activation and inflammatory cytokine profiling: Application to screening of dietary supplements for anti-inflammatory properties

A versatile and reconfigurable microfluidic chip has been fully in-house fabricated and tested for immune cell culture, activation, and quantification of multi-cytokine secretion. The chip comprises three vertically stacked fluidic layers for perfusion, cell culture and cytokine capture, and quantification, respectively. The perfused media were separated from the cell culture by employing a biomimetic membrane as a model of the intestinal epithelial layer. Time-resolved detection and quantification of several secreted cytokines were enabled by an array of parallel channels, which are interfaced with the cell culture by a porous membrane. Each channel hosts magnetic beads conjugated with a specific antibody against the cytokine of interest. Magnetic bead-assisted agitation enables homogenization of the cell culture supernatant and perfusion of the cytokines through the bottom immune assay channels. As a proof of concept, THP-1 monocytic cells and their induced macrophages were used as a model of immune-responsive cells. The cells were sequentially stimulated by lipopolysaccharides and two dietary supplements, namely, docosahexaenoic acid (DHA) and curcumin, which are known to possess inflammasome-modulating activity. Both DHA and curcumin have shown anti-inflammatory effects by downregulating the secretion of TNFα, IL-6, IL-1β, and IL-10. Treatment of the cells with DHA and curcumin together lowered the TNFα secretion by ∼54%. IL-6 secretion was lowered upon cell treatment with curcumin, DHA, or DHA and curcumin co-treatment by 69%, 78%, or 67%, respectively. IL-1β secretion was lowered by 67% upon curcumin treatment and 70% upon curcumin and DHA co-treatment. IL-10 secretion was also lowered upon treating the cells with DHA, curcumin, or DHA and curcumin together by 7%, 53%, or 54%, respectively. The limit of the detection of the assay was determined as 25 pg/ml. Four cytokine profiling was demonstrated, but the design of the chip can be improved to allow a larger number of cytokines to be simultaneously detected from the same set of cells.

The Functional Role of IgA in the IgM/IgA-Enriched Immunoglobulin Preparation Trimodulin

In comparison to human immunoglobulin (Ig) G, antibodies of IgA class are not well investigated. In line with this, the functional role of the IgA component in IgM/IgA-enriched immunoglobulin preparations is also largely unknown. In recent years, powerful anti-pathogenic and immunomodulatory properties of human serum IgA especially on neutrophil function were unraveled. Therefore, the aim of our work is to investigate functional aspects of the trimodulin IgA component, a new plasma-derived polyvalent immunoglobulin preparation containing ~56% IgG, ~23% IgM and ~21% IgA. The functional role of IgA was investigated by analyzing the interaction of IgA with FcαRI, comparing trimodulin with standard intravenous IgG (IVIG) preparation and investigating Fc receptor (FcR)-dependent functions by excluding IgM-mediated effects. Trimodulin demonstrated potent immunomodulatory, as well as anti-pathogenic effects in our neutrophil model (neutrophil-like HL-60 cells). The IgA component of trimodulin was shown to induce a strong FcαRI-dependent inhibitory immunoreceptor tyrosine-based activation motif (ITAMi) signaling, counteract lipopolysaccharide-induced inflammation and mediate phagocytosis of Staphylococcus aureus. The fine-tuned balance between immunomodulatory and anti-pathogenic effects of trimodulin were shown to be dose-dependent. Summarized, our data demonstrate the functional role of IgA in trimodulin, highlighting the importance of this immunoglobulin class in immunoglobulin therapy.

Intravenous immunoglobulin as an important adjunct in the prevention and therapy of coronavirus 2019 disease

The coronavirus disease-19 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) challenged globally with its morbidity and mortality. A small percentage of affected patients (20%) progress into the second stage of the disease clinically presenting with severe or fatal involvement of lung, heart and vascular system, all contributing to multiple-organ failure. The so-called 'cytokines storm' is considered the pathogenic basis of severe disease and it is a target for treatment with corticosteroids, immunotherapies and intravenous immunoglobulin (IVIg). We provide an overview of the role of IVIg in the therapy of adult patients with COVID-19 disease. After discussing the possible underlying mechanisms of IVIg immunomodulation in COVID-19 disease, we review the studies in which IVIg was employed. Considering the latest evidence that show a link between new coronavirus and autoimmunity, we also discuss the use of IVIg in COVID-19 and anti-SARS-CoV-2 vaccination related autoimmune diseases and the post-COVID-19 syndrome. The benefit of high-dose IVIg is evident in almost all studies with a rapid response, a reduction in mortality and improved pulmonary function in critically ill COVID-19 patients. It seems that an early administration of IVIg is crucial for a successful outcome. Studies' limitations are represented by the small number of patients, the lack of control groups in some and the heterogeneity of included patients. IVIg treatment can reduce the stay in ICU and the demand for mechanical ventilation, thus contributing to attenuate the burden of the disease.

A monocyte/dendritic cell molecular signature of SARS-CoV-2-related multisystem inflammatory syndrome in children with severe myocarditis

Background

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in children is generally milder than in adults, but a proportion of cases result in hyperinflammatory conditions often including myocarditis.

Methods

To better understand these cases, we applied a multiparametric approach to the study of blood cells of 56 children hospitalized with suspicion of SARS-CoV-2 infection. Plasma cytokine and chemokine levels and blood cellular composition were measured, alongside gene expression at the bulk and single-cell levels.

Findings

The most severe forms of multisystem inflammatory syndrome in children (MIS-C) related to SARS-CoV-2 that resulted in myocarditis were characterized by elevated levels of pro-angiogenesis cytokines and several chemokines. Single-cell transcriptomics analyses identified a unique monocyte/dendritic cell gene signature that correlated with the occurrence of severe myocarditis characterized by sustained nuclear factor κB (NF-κB) activity and tumor necrosis factor alpha (TNF-α) signaling and associated with decreased gene expression of NF-κB inhibitors. We also found a weak response to type I and type II interferons, hyperinflammation, and response to oxidative stress related to increased HIF-1α and Vascular endothelial growth factor (VEGF) signaling.

Conclusions

These results provide potential for a better understanding of disease pathophysiology.

Funding

Agence National de la Recherche (Institut Hospitalo-Universitaire Imagine, grant ANR-10-IAHU-01; Recherche Hospitalo-Universitaire, grant ANR-18-RHUS-0010; Laboratoire d’Excellence ‘‘Milieu Intérieur,” grant ANR-10-LABX-69-01; ANR-flash Covid19 “AIROCovid” and “CoVarImm”), Institut National de la Santé et de la Recherche Médicale (INSERM), and the “URGENCE COVID-19” fundraising campaign of Institut Pasteur.

Children with SARS-CoV-2 infection were initially thought to have only mild COVID-19 symptoms. However, several weeks into the first wave of SARS-CoV-2 infections, there was a surge of a postacute pathology called multisystem inflammatory syndrome in children (MIS-C). The authors recruited a cohort of children with suspicion of SARS-CoV-2 infection and uncovered hyperinflammation, hypoxic conditions, exacerbation of TNF-α signaling via NF-κB, and absence of responses to type I and type II IFN secretion in the most severe forms of MIS-C with severe myocarditis. This work led the authors to identify in monocytes and validate in peripheral blood mononuclear cells a molecular signature of 25 genes that allows discrimination of the most severe forms of MIS-C with myocarditis.

Inhibition of TNFR1 Attenuates LPS Induced Apoptosis and Inflammation in Human Nucleus Pulposus Cells by Regulating the NF-KB and MAPK Signalling Pathway

Intervertebral disc degeneration (IDD) is accompanied by nucleus pulposus (NP) cell apoptosis, inflammation, and extracellular matrix degradation. Tumour necrosis factor receptor 1 (TNFR1) is a receptor of TNF-α, and is deeply involved in the processes of IDD. However, the effect of TNFR1 inhibition on IDD is not clear. Herein, we report that TNFR1 was increased in LPS-treated HNPCs. The aim of this study was to investigate the potential therapeutic effect of TNFR1 siRNA and selective antagonists of TNFR1 (GSK1995057) on HNPC damage. The results showed that the blockade of TNFR1 by TNFR1 siRNA and GSK1995057 effectively suppressed the cell viability loss, apoptosis, and inflammation induced by LPS in HNPCs. Furthermore, we found that TNFR1 siRNA and GSK1995057 inhibited activation of the NF-KB and MAPK signalling pathways in LPS-stimulated HNPCs. In summary, the blockade of TNFR1 effectively suppressed LPS-induced apoptosis and inflammation in HNPCs through the NF-KB and MAPK signalling pathways. This revealed that the blockade of TNFR1 may provide a potential therapeutic treatment for IDD.

FcRn is a CD32a coreceptor that determines susceptibility to IgG immune complex-driven autoimmunity

IgG immune complexes (ICs) promote autoimmunity through binding fragment crystallizable (Fc) γ-receptors (FcγRs). Of these, the highly prevalent FcγRIIa (CD32a) histidine (H)-131 variant (CD32a^H) is strongly linked to human autoimmune diseases through unclear mechanisms. We show that, relative to the CD32a arginine (R)-131 (CD32a^R) variant, CD32a^H more avidly bound human (h) IgG1 IC and formed a ternary complex with the neonatal Fc receptor (FcRn) under acidic conditions. In primary human and mouse cells, both CD32a variants required FcRn to induce innate and adaptive immune responses to hIgG1 ICs, which were augmented in the setting of CD32a^H. Conversely, FcRn induced responses to IgG IC independently of classical FcγR, but optimal responses required FcRn and FcγR. Finally, FcRn blockade decreased inflammation in a rheumatoid arthritis model without reducing circulating autoantibody levels, providing support for FcRn’s direct role in IgG IC-associated inflammation. Thus, CD32a and FcRn coregulate IgG IC-mediated immunity in a manner favoring the CD32a^H variant, providing a novel mechanism for its disease association.

High-Dose Intravenous Immunoglobulins in the Treatment of Severe Acute Viral Pneumonia: The Known Mechanisms and Clinical Effects

The current outbreak of viral pneumonia, caused by novel coronavirus SARS-CoV-2, is the focus of worldwide attention. The WHO declared the COVID-19 outbreak a pandemic event on Mar 12, 2020, and the number of confirmed cases is still on the rise worldwide. While most infected individuals only experience mild symptoms or may even be asymptomatic, some patients rapidly progress to severe acute respiratory failure with substantial mortality, making it imperative to develop an efficient treatment for severe SARS-CoV-2 pneumonia alongside supportive care. So far, the optimal treatment strategy for severe COVID-19 remains unknown. Intravenous immunoglobulin (IVIg) is a blood product pooled from healthy donors with high concentrations of immunoglobulin G (IgG) and has been used in patients with autoimmune and inflammatory diseases for more than 30 years. In this review, we aim to highlight the known mechanisms of immunomodulatory effects of high-dose IVIg therapy, the immunopathological hypothesis of viral pneumonia, and the clinical evidence of IVIg therapy in viral pneumonia. We then make cautious therapeutic inferences about high-dose IVIg therapy in treating severe COVID-19. These inferences may provide relevant and useful insights in order to aid treatment for COVID-19.

The spinal microglial IL-10/β-endorphin pathway accounts for cinobufagin-induced mechanical antiallodynia in bone cancer pain following activation of α7-nicotinic acetylcholine receptors

Background

Cinobufagin is the major bufadienolide of Bufonis venenum (Chansu), which has been traditionally used for the treatment of chronic pain especially cancer pain. The current study aimed to evaluate its antinociceptive effects in bone cancer pain and explore the underlying mechanisms.

Methods

Rat bone cancer model was used in this study. The withdrawal threshold evoked by stimulation of the hindpaw was determined using a 2290 CE electrical von Frey hair. The β-endorphin and IL-10 levels were measured in the spinal cord and cultured primary microglia, astrocytes, and neurons.

Results

Cinobufagin, given intrathecally, dose-dependently attenuated mechanical allodynia in bone cancer pain rats, with the projected E_max of 90% MPE and ED₅₀ of 6.4 μg. Intrathecal cinobufagin also stimulated the gene and protein expression of IL-10 and β-endorphin (but not dynorphin A) in the spinal cords of bone cancer pain rats. In addition, treatment with cinobufagin in cultured primary spinal microglia but not astrocytes or neurons stimulated the mRNA and protein expression of IL-10 and β-endorphin, which was prevented by the pretreatment with the IL-10 antibody but not β-endorphin antiserum. Furthermore, spinal cinobufagin-induced mechanical antiallodynia was inhibited by the pretreatment with intrathecal injection of the microglial inhibitor minocycline, IL-10 antibody, β-endorphin antiserum and specific μ-opioid receptor antagonist CTAP. Lastly, cinobufagin- and the specific α-7 nicotinic acetylcholine receptor (α7-nAChR) agonist PHA-543613-induced microglial gene expression of IL-10/β-endorphin and mechanical antiallodynia in bone cancer pain were blocked by the pretreatment with the specific α7-nAChR antagonist methyllycaconitine.

Conclusions

Our results illustrate that cinobufagin produces mechanical antiallodynia in bone cancer pain through spinal microglial expression of IL-10 and subsequent β-endorphin following activation of α7-nAChRs. Our results also highlight the broad significance of the recently uncovered spinal microglial IL-10/β-endorphin pathway in antinociception.

Intravenous immunoglobulin (IVIg) or IVIg-treated macrophages reduce DSS-induced colitis by inducing macrophage IL-10 production

Intravenous immunoglobulin (IVIg) is used to treat immune-mediated diseases but its mechanism of action is poorly understood. We have reported that co-treatment with IVIg and lipopolysaccharide activates macrophages to produce large amounts of anti-inflammatory IL-10 in vitro. Thus, we asked whether IVIg-treated macrophages or IVIg could reduce intestinal inflammation in mice during dextran sulfate sodium (DSS)-induced colitis by inducing macrophage IL-10 production in vivo. Adoptive transfer of IVIg-treated macrophages reduces intestinal inflammation in mice and collagen accumulation post-DSS. IVIg treatment also reduces DSS-induced intestinal inflammation and its activity is dependent on the Fc portion of the antibody. Ex vivo, IVIg induces IL-10 production and reduces IL-12/23p40 and IL-1β production in colon explant cultures. Co-staining tissues for mRNA, we demonstrate that macrophages are the source of IL-10 in IVIg-treated mice; and using IL-10-GFP reporter mice, we demonstrate that IVIg induces IL-10 production by intestinal macrophages. Finally, IVIg-mediated protection is lost in mice deficient in macrophage IL-10 production (LysMcre^+/- IL-10^fl/fl mice). Together, our data demonstrate a novel, in vivo mechanism of action for IVIg. IVIg-treated macrophages or IVIg could be used to treat people with intestinal inflammation and may be particularly useful for people with inflammatory bowel disease, who are refractory to therapy.

Intravenous immunoglobulin suppresses the polarization of both classically and alternatively activated macrophages

Intravenous immunoglobulin (IVIG) is one of the widely used immunotherapeutic molecules in the therapy of autoimmune and inflammatory diseases. Previous reports demonstrate that one of the anti-inflammatory actions of IVIG implicates suppression of macrophage activation and release of their inflammatory mediators. However, macrophages are highly plastic and depending on the microenvironmental signals, macrophages can be polarized into pro-inflammatory classic (M1) or anti-inflammatory alternative (M2) type. This plasticity of macrophages raised additional questions on the role of IVIG towards macrophage polarization. In the present report, we show that IVIG affects the polarization of both classically and alternatively activated macrophages and this process is F(ab')₂-independent. Our data thus indicate the lack of reciprocal regulation of inflammatory and non-inflammatory macrophages by IVIG.