An fc gamma receptor-mediated upregulation of the production of interleukin 10 by intravenous immunoglobulin in bone-marrow-derived mouse dendritic cells stimulated with lipopolysaccharide in vitro

Regulation of dendritic cell function by Fc-γ-receptors and the neonatal Fc receptor

Dendritic cells (DCs) express receptors to sense pathogens and/or tissue damage and to communicate with other immune cells. Among those receptors, Fc receptors (FcRs) are triggered by the Fc region of antibodies produced during adaptive immunity. In this review, the role of FcγR and neonatal Fc receptor (FcRn) in DC immunity will be discussed. Their expression in DC subsets and impact on antigen uptake and presentation, DC maturation and polarisation of T cell responses will be described. Lastly, we will discuss the importance of FcR-mediated DC function in the context of immunity during viral infection, inflammatory disease, cancer and immunotherapy.

Therapeutic normal IgG intravenous immunoglobulin activates Wnt-β-catenin pathway in dendritic cells

Therapeutic normal IgG intravenous immunoglobulin (IVIG) is a well-established first-line immunotherapy for many autoimmune and inflammatory diseases. Though several mechanisms have been proposed for the anti-inflammatory actions of IVIG, associated signaling pathways are not well studied. As β-catenin, the central component of the canonical Wnt pathway, plays an important role in imparting tolerogenic properties to dendritic cells (DCs) and in reducing inflammation, we explored whether IVIG induces the β-catenin pathway to exert anti-inflammatory effects. We show that IVIG in an IgG-sialylation independent manner activates β-catenin in human DCs along with upregulation of Wnt5a secretion. Mechanistically, β-catenin activation by IVIG requires intact IgG and LRP5/6 co-receptors, but FcγRIIA and Syk are not implicated. Despite induction of β-catenin, this pathway is dispensable for anti-inflammatory actions of IVIG in vitro and for mediating the protection against experimental autoimmune encephalomyelitis in vivo in mice, and reciprocal regulation of effector Th17/Th1 and regulatory T cells.

IgG stimulated β2 adrenergic receptor activation is attenuated in patients with ME/CFS

Background

There is emerging evidence of a network of natural autoantibodies against GPCR which is dysregulated in various diseases. β2 adrenergic and M3 and M4 cholinergic receptor (β2 AdR and M3/4 mAChR) antibodies were found to be elevated in a subset of ME/CFS patients.

Methods

We comparatively analyzed the effects of polyclonal IgG on β2 AdR signaling and immune cell function in vitro. 16 IgG fractions were isolated from serum of 5 ME/CFS patients with elevated (CFS AAB_high) and 5 with normal levels (CFS AAB_norm) of β2 AdR autoantibodies, and from 6 healthy controls (HC). The effect of each IgG on β-arrestin recruitment and cAMP production in β2 AdR and M3/4R reporter cell lines was studied. Further effect of each IgG on human monocyte cytokine production and on T cell proliferation in vitro was analyzed. In addition, studies on cytokine production in β2 AdR wild type and knockout mice splenocytes incubated with IgG fractions were performed.

Results

We found that IgGs from HC could stimulate β-arrestin recruitment and cAMP production in β2 AdR reporter cell lines whereas IgGs from CFS AAB_high had no effect. The IgG-mediated activation of β2 AdR was confirmed in β2 AdR wt and ko mice. In accordance with previous studies IgG fractions from HC inhibited LPS-induced TNFα and stimulated LPS-induced IL-10 production of monocytes. Further IgG fractions from HC enhanced proliferation of T-cells stimulated with anti-CD3/CD28. IgG fractions from CFS AAB_high patients had no significant effect on both cytokine production and T cell proliferation, while IgGs from CFS AAB_norm had an intermediate effect. We could also observe that IgG can modulate the signaling of β2 AdR ligands isoprenline and propranolol.

Conclusions

We provide evidence that IgG can activate β2 AdR. The β2 AdR activation by IgG is attenuated in ME/CFS patients. A dysregulation of β2 AdR function could explain many symptoms of ME/CFS.

On the modelling and analysis of the regulatory network of dengue virus pathogenesis and clearance

Dengue virus can ignite both protective and pathogenic responses in human. The pathogenesis is related with modified functioning of our immune system during infection. Pattern recognition receptors like Toll like receptor 3 is vital for the induction of innate immunity in case of Dengue infection. Toll like receptor 3 induces TRIF mediated activation of Type 1 interferons and Fc receptor mediated induction of cytokines. Interferons have been related with clearance of Dengue virus but it has adopted modified regulatory mechanisms to counter this effect. SOCS protein is also induced due to the interferon and cytokine mediated signalling which can subsequently play its part in the regulation of interferon and cytokine production. Our hypothesis in this study relates the pathogenesis of Dengue virus with the SOCS mediated inhibition of our innate immunity. We used the qualitative formalism of René Thomas to model the biological regulatory network of Toll like receptor 3 mediated signalling pathway in an association with pathogenesis of dengue. Logical parameters for the qualitative modelling were inferred using a model checking approach implemented in SMBioNet. A linear hybrid model, parametric linear hybrid automaton, was constructed to incorporate the activation and inhibition time delays in the qualitative model. The qualitative model captured all the possible expression dynamics of the proteins in the form of paths, some of which were observed as abstract cycles (representing homoeostasis) and diverging paths towards stable states. The analysis of the qualitative model highlighted the importance of SOCS protein in elevating propagation of dengue virus through inhibition of type 1 interferons. Detailed qualitative analysis of regulatory network endorses our hypothesis that elevated levels of cytokine subsequently induce SOCS expression which in turn results into the continuous down-regulation of Toll like receptor 3 and interferon. This may result into the Dengue pathogenesis during the stage of immunosuppression. Further analysis with HyTech (HYbrid TECHnology) tool provided us with the real-time constraints (delay constraints) of the proteins involved in the cyclic paths of the regulatory network backing the evidence provided by the qualitative analysis. The HyTech results also suggest that the role of SOCS is vital in homoeostasis.

Prevention of immunoglobulin G immobilization eliminates artifactual stimulation of dendritic cell maturation by intravenous immunoglobulin in vitro

Intravenous immunoglobulin (IVIg), a therapeutic preparation containing pooled human immunoglobulin (Ig) G, has been suggested to inhibit differentiation and maturation of dendritic cells (DCs); however, controversies exist on this issue. We aimed to reinvestigate the effects of IVIg on human DC maturation and cytokine production, and to determine whether an artifactual determinant is involved in the observed effects. Human monocyte-derived DCs or freshly isolated blood myeloid DCs were cultured in the presence of IVIg in vitro, and the expression of maturation markers CD80, CD86, CD83, and Human Leukocyte Antigen-DR were determined by flow cytometry, whereas production of interleukin (IL)-12 and IL-10 was measured by enzyme-linked immunosorbent assay, and T-cell stimulatory capacity was determined in cocultures with allogeneic CD4(+) T cells. Interestingly, we observed that IVIg did not inhibit, but instead stimulated, spontaneous maturation and T-cell stimulatory ability of human DCs, while leaving lipopolysaccharide-induced DC maturation and cytokine production unaffected. Strikingly, prevention of IVIg binding to culture plate surface, or blocking of the activating Fcγ receptor IIa on DC, abrogated the stimulatory effect of IVIg on costimulatory molecule expression and on T-cell stimulatory capacity of DCs, suggesting that IVIg activates DCs on IgG adsorption to the plastic surface. This study warrants for careful study design when performing cell culture studies with IVIg to prevent artifactual effects, and shows that IVIg does not modulate directly costimulatory molecule expression, cytokine production, or allogeneic T-cell stimulatory capacity of human DCs.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Characterisation of interleukin-10 expression on different vascular structures in allergic nasal mucosa

BACKGROUND

Interleukin-10 (IL-10) is a negative regulator of immune responses and was previously shown to be expressed by human nasal endothelial cells, while the adhesion molecule MECA-79 plays a role in trans-endothelial migration of immune competent cells. In this study we investigate the relationship between endothelial IL-10 and MECA-79 expression to address the question whether immune competent cells could be affected at the mucosal entry site.

METHODS

Nasal turbinate biopsies were taken from house dust mite allergic patients, before and after nasal allergen provocation. Subsequent slides of biopsies were stained for IL10, MECA-79, CD34, and IL10-Receptor. Capillaries, arteries/veins, and sinusoids were evaluated separately.

RESULTS

90% of sinusoids are IL-10 positive and all sinusoids are negative for MECA-79, while 4.8% of capillaries are positive for IL-10, and 2.2% are positive for MECA-79. Although about 47% of arteries/veins are positive for IL-10 and 57.1% are positive for MECA-79, only about 20% are positive for both markers. Furthermore, we showed that the myo-fibroblasts surrounding all sinusoids stain positive for IL10R.

CONCLUSIONS

IL10 expression on vascular structures is not related to MECA expression for sinusoids and capillaries and only partly related on arteries/veins, however sinusoidal endothelial IL10 expression is always seen in combination with IL-10R expression of sinusoidal myo-fibroblasts.