Allergen challenge differentially affects the number of circulating monocyte subsets

The adaptor protein TRAF3 is an immune checkpoint that inhibits myeloid-derived suppressor cell expansion

Myeloid-derived suppressor cells (MDSCs) are aberrantly expanded in cancer patients and under other pathological conditions. These cells orchestrate the immunosuppressive and inflammatory network to facilitate cancer metastasis and mediate patient resistance to therapies, and thus are recognized as a prime therapeutic target of human cancers. Here we report the identification of the adaptor protein TRAF3 as a novel immune checkpoint that critically restrains MDSC expansion. We found that myeloid cell-specific Traf3-deficient (M-Traf3 ^-/-) mice exhibited MDSC hyperexpansion during chronic inflammation. Interestingly, MDSC hyperexpansion in M-Traf3 ^-/- mice led to accelerated growth and metastasis of transplanted tumors associated with an altered phenotype of T cells and NK cells. Using mixed bone marrow chimeras, we demonstrated that TRAF3 inhibited MDSC expansion via both cell-intrinsic and cell-extrinsic mechanisms. Furthermore, we elucidated a GM-CSF-STAT3-TRAF3-PTP1B signaling axis in MDSCs and a novel TLR4-TRAF3-CCL22-CCR4-G-CSF axis acting in inflammatory macrophages and monocytes that coordinately control MDSC expansion during chronic inflammation. Taken together, our findings provide novel insights into the complex regulatory mechanisms of MDSC expansion and open up unique perspectives for the design of new therapeutic strategies that aim to target MDSCs in cancer patients.

Effect of Dermatophagoides pteronyssinus extract on the expression of genes involved in inflammation and tissue remodeling by peripheral blood mononuclear cells of allergic asthma patients

PURPOSE

House dust mite allergy constitutes a risk factor for asthma development and is associated with a faster decline of lung function in allergic asthmatics (AAs). To evaluate the effect of Dermatophagoides pteronyssinus (Dp) allergens on the expression of genes involved in inflammation and tissue remodeling by peripheral blood mononuclear cells (PBMCs) isolated from the blood of AAs.

MATERIALS AND METHODS

The cells from AAs, allergic rhinitis without asthma patients (ARs), and healthy controls (HCs) were cultured in the presence of Dp, lipopolysaccharide (LPS), or without any stimulation. The expression of 84 genes was evaluated using a low-density microarray whereas, the quantitative expression analysis of selected genes was performed using a real-time polymerase chain reaction. The concentration of selected proteins in the cell culture supernatants was assessed using ELISA.

RESULTS

Stimulation of PBMCs with Dp and LPS resulted in a significant upregulation of 8 and 15 among 84 studied genes, respectively. The greatest upregulation was observed for CCL2 and CCL3 using Dp and LPS, respectively. In comparison with HCs, in AAs, significantly increased upregulation of CCL2 in response to Dp was found. The secretion of CCL2 and CCL3 by PBMCs reflected the pattern of gene expression at the mRNA level. The mean Dp-stimulated secretion of CCL2 by PBMCs of ARs was less than in AAs (p ​< ​0.01), both being notably greater than in the HCs (p ​< ​0.01).

CONCLUSION

Rapid and potent upregulation of CCL2 expression by PBMCs in response to Dp may constitute an important contribution to the development of allergic asthma.

Systemic corticosteroid therapy augments ex vivo release of sCD163 by peripheral blood monocytes of asthmatic patients

Introduction

The CD163 is exclusively expressed by mononuclear phagocytes as a transmembrane protein, which synthesis is regulated by anti- and pro-inflammatory signals. After shedding from the cell surface it exists in body fluids as a soluble protein (sCD163) which exerts anti-inflammatory effects.

Aim

To evaluate serum concentration and ex vivo production of sCD163 by peripheral blood mononuclear cells (PBMC) in asthmatic patients treated with inhaled (ICS) or oral corticosteroids (OCS).

Material and methods

The study was performed on 35 allergic asthma patients (AAs) including 15 treated with ICS (ICS-AAs), 10 with OCS (OCS-AAs), 10 during asthma exacerbation (EX-AAs) before OCS had been started and 13 non-atopic healthy subjects (HCs) as a control group. PBMC were cultured in vitro for up to 144 h. The concentration of sCD163 in serum and the culture supernatants was evaluated with ELISA.

Results

The greatest serum sCD163 concentration was demonstrated in EX-AAs, which was significantly greater than that in other studied subgroups. The concentration of sCD163 in PBMC culture supernatants was greater in AAs than in HCs (p = 0.006). Among individual asthma subgroups the greatest concentration of sCD163 was demonstrated in PBMC culture supernatants of OCS-AAs, which was significantly greater than in ICS-AAs (p < 0.001) and EX-AAs (p < 0.001), both being significantly greater than in HCs (p < 0.001).

Conclusions

In AAs, enhanced capability of PBMCs to release sCD163 may be at least partially responsible for the anti-inflammatory effects of systemic corticosteroid therapy.

Asthmatic Bronchial Smooth Muscle Increases CCL5-Dependent Monocyte Migration in Response to Rhinovirus-Infected Epithelium

Asthma exacerbations, a major concern in therapeutic strategies, are most commonly triggered by viral respiratory infections, particularly with human rhinovirus (HRV). Infection of bronchial epithelial (BE) cells by HRV triggers inflammation, notably monocyte recruitment. The increase of bronchial smooth muscle (BSM) mass in asthma, a hallmark of bronchial remodeling, is associated with the annual rate of exacerbations. The aim of the present study was to assess whether or not BSM could increase monocyte migration induced by HRV-infected BE. We used an advanced in vitro model of co-culture of human BE cells in air-liquid interface with human BSM cells from control and asthmatic patients. Inflammation triggered by HRV infection (HRV-16, MOI 0.1, 1 h) was assessed at 24 h with transcriptomic analysis and multiplex ELISA. In vitro CD14⁺ monocyte migration was evaluated with modified Boyden chamber. Results showed that HRV-induced monocyte migration was substantially increased in the co-culture model with asthmatic BSM, compared with control BSM. Furthermore, the well-known monocyte migration chemokine, CCL2, was not involved in this increased migration. However, we demonstrated that CCL5 was further increased in the asthmatic BSM co-culture and that anti-CCL5 blocking antibody significantly decreased monocyte migration induced by HRV-infected BE. Taken together, our findings highlight a new role of BSM cells in HRV-induced inflammation and provide new insights in mucosal immunology which may open new opportunities for prevention and/or treatment of asthma exacerbation.

Current Concepts on 6-sulfo LacNAc Expressing Monocytes (slanMo)

The human mononuclear phagocytes system consists of dendritic cells (DCs), monocytes, and macrophages having different functions in bridging innate and adaptive immunity. Among the heterogeneous population of monocytes the cell surface marker slan (6-sulfo LacNAc) identifies a specific subset of human CD14^- CD16⁺ non-classical monocytes, called slan⁺ monocytes (slanMo). In this review we discuss the identity and functions of slanMo, their contributions to immune surveillance by pro-inflammatory cytokine production, and cross talk with T cells and NK cells. We also consider the role of slanMo in the regulation of chronic inflammatory diseases and cancer. Finally, we highlight unresolved questions that should be the focus of future research.

Subcutaneous immunotherapy induces alterations in monocytes and dendritic cells homeostasis in allergic rhinitis patients

Background

Specific subcutaneous immunotherapy (SCIT) can achieve long-term remission in patients with allergic rhinitis (AR) through complex and still unknown mechanisms. The aim of this study is to evaluate the effect of SCIT over CD16⁺ and CD16⁻ monocytes, myeloid (mDCs) and plasmacytoid dendritic cells (pDCs) in patients with AR, comparatively to pharmacological standard treatment (non-SIT).

Methods

The relative frequency and absolute number of monocytes and DC subsets, the frequency of these cells producing TNFα after in vitro stimulation with Dermatophagoides pteronyssinus (Dpt) extract, and the expression levels of receptor-bound IgE or IgG were assessed by flow cytometry, in peripheral blood samples from 23 healthy individuals (HG) and 43 participants with AR mono-sensitized to Dpt; 10 with non-SIT treatment and 33 under SCIT, just before (SCIT-T0) and 4 h after administration (SCIT-T4). Moreover, IFNα mRNA expression was evaluated in purified pDCs, by qRT-PCR.

Results

After SCIT administration we observed a strong decrease of circulating pDCs, although accompanied by higher levels of IFNα mRNA expression, and an increase of circulating CD16⁺ monocytes. AR participants under SCIT exhibited a higher expression of receptor-bound IgE in all cell populations that expressed the high affinity receptor for IgE (FcεRI) and a higher frequency of CD16⁺ monocytes producing TNFα. Conversely, we observed a decrease in the frequency of mDCs producing TNFα in AR under SCIT, similar to the observed in the control group.

Conclusions

SCIT seems to induce numeric, phenotypic, and functional changes in circulating monocytes and dendritic cells, contributing at least in part to the well described immunological alterations induced by this type of immunotherapy.

The CD14 (-159 C/T) SNP is associated with sCD14 levels and allergic asthma, but not with CD14 expression on monocytes

LPS-ligation to CD14/TLR-4 on monocytes/macrophages triggers the production of IL-12-family cytokines. IL12/18 promote TH₁-differentiation, counteracting the TH₂-driven asthma. Therefore, CD14 modulation could alter the TH₂-differentiation and should be taken into account when studying asthma. To analyse the alteration in CD14 levels and its association with CD14 (−159 C/T) SNP (rs2569190) in Caucasian adults with stable allergic asthma, we performed a cross-sectional study (277 healthy subjects vs. 277 patients) where clinical parameters, CD14 values and the CD14 (−159 C/T) SNP were studied. Apart from typical biomarkers, we found an increment of neuron-specific enolase (NSE) in allergic asthma, probably linked to monocyte activity. Indeed, we evidenced increased monocyte numbers, but lower CD14 expression and normalised sCD14 values in patients. Moreover, we noticed an association of the T allele (P = 0.0162) and TT genotype (P = 0.0196) of the CD14 SNP with a decreased risk of allergic asthma and augmented sCD14 levels. In conclusion, monocyte CD14 expression and normalized sCD14 values were reduced in stable state asthmatics, and this could be related to the presence of an expanded CD14^low monocyte subset. This study also demonstrates that the CD14 (−159 C/T) polymorphism is a risk factor for moderate-severe allergic asthma in adult Caucasians.

Tissue factor variants induce monocyte transformation and transdifferentiation into endothelial cell-like cells

Essentials Monocytes (Mo) transdifferentiate into endothelial cell-like (ECL) cells. Mo induce tissue factor (TF) expression and secretion in microvascular endothelial cells (mECs). TF interacts with Mo in a paracrine fashion, inducing their transdifferentiation into ECL cells. TF generates a positive feedback crosstalk between Mo and mECs that promotes angiogenesis.

SUMMARY

Background Monocytes (Mo) increase neovascularization by releasing proangiogenic mediators and/or transdifferentiating into endothelial cell-like (ECL) cells. Recently, we have reported that Mo-microvascular endothelial cells (mECs) crosstalk induces mEC-tissue factor (TF) expression and promotes angiogenesis. However, the effect of TF on Mo remains unknown. Objective Here, we analyzed whether TF might exert angiogenic effects by inducing transdifferentiation of Mo. Methods Full-length TF (flTF) and alternatively spliced TF (asTF) were overexpressed in mECs, and their supernatants were added to Mo cultures. CD16 positivity and expression of vascular endothelial cell (VEC) markers in Mo were analyzed by fluorescence activated cell sorting. The capacity to form tube-like structures were visualized in three-dimensional cultures. Results In mECs flTF and asTF expression and release were increased in cultures with Mo-conditioned media. TF variants induced expansion of a CD16+ Mo subset and Mo transdifferentiation into ECL-cells expressing VEC markers that can form new microvessels. CD16+ Mo exposed to TF showed an increased expression of VE-cadherin, von Willebrand factor (VWF) and eNOS. Mo cultured with supernatants obtained from TF-silenced mECs did not transdifferentiate to ECL-cells or expressed VEC markers. Blocking β1-integrin in Mo significantly blocked the effects of the TF variants. Conclusions Mo induce mECs to express and release TF, which drives CD16- Mo to transform into CD16+ Mo and to transdifferentiate into ECL-cells that can form new microvessels. Our results reveal a TF-mediated positive feedback between mECs and Mo that stimulates Mo differentiation and induces angiogenesis.

Monocyte subpopulations study in patients with plaque psoriasis

Psoriasis is a chronic and systemic, immune-mediated, inflammatory disease, mainly manifested by skin and / or joints lesions, presenting with a wide degree of clinical severity, but generally with great impact on patients' quality of life. Despite advances in the understanding of its pathogenesis, especially regarding the participation of T-lymphocytes and the key role of TNF, the triggering factor of the disease at the molecular level remains unknown, as well as the function of other cell populations. By presenting antigens to T-lymphocytes, monocytes assume an important role in both innate and adaptive immune response. In the last two decades, by using flow cytometry with antibodies against CD14 (receptor for lipopolysaccharide) and CD16 (low affinity receptor for IgG), human blood monocytes were classified into three subpopulations: classical (CD14++CD16-), intermediate (CD14++CD16+), and non-classical (CD14+CD16++). Under normal conditions the population of classical monocytes corresponds to about 85%, while intermediate to 5.4%, and nonclassical to 9.2%. However, intermediate and nonclassical subsets are increased in various inflammatory situations, such as moderate to severe asthma, colorectal cancer, and rheumatoid arthritis. Despite psoriasis being considered a disease of inflammatory nature, scarce studies evaluating the frequency of subpopulations of monocytes in psoriatic patients are found on current medical literature, and they are restricted to peripheral blood analysis. This study aims to identify the frequency of monocyte subpopulations in blood levels as well as lesional skin of plaque psoriasis patients, and to evaluate their association to cytokines, and clinical disease severity.

Soluble CD163 modulates cytokine production by peripheral blood mononuclear cells stimulated by Dermatophagoides pteronyssinus allergens in vitro

PURPOSE

The CD163 is a scavenger receptor expressed exclusively on monocytes/macrophages which has been shown to exert anti-inflammatory effects. The aim of this study was to evaluate the effect of exogenous sCD163 on production of selected cytokines by peripheral blood mononuclear cells (PBMC) of house dust mite allergic patients (AAPs) stimulated in vitro with Dermatophagoides pteronyssinus (Dp) allergens.

PATIENTS AND METHODS

The study was performed in 24 AAPs and 12 healthy control subjects (HCs). Peripheral blood mononuclear cells were cultured for up to 144h (T₁₄₄) in the presence of Dp extract with or without sCD163. Concentration of interleukin (IL) - 10, IL-13 and transforming growth factor beta (TGF-β) was evaluated in the cell culture supernatants using ELISA. Expression of the selected cytokines was evaluated in cell culture lysates using Taqman-based real time polymerase chain reaction (RT-PCR).

RESULTS

Dp-stimulated PBMC from AAPs released more IL-10 and IL-13 than those from HCs. The greatest up-regulation of IL-10 expression was seen at T₆, while that of IL-13 was delayed. Soluble CD163 augmented production of IL-10 in response to Dp stimulation. No significant effect of sCD163 on production of IL-13 and IL-10 by PBMC of HCs could be demonstrated.

CONCLUSIONS

In AAPs sCD163 modulates the immune response to Dp allergens potentiating anti-inflammatory, homeostatic mechanisms.

Development of asthmatic response upon bronchial allergen challenge is associated with dynamic changes of interleukin-10-producing and interleukin-10-responding CD4+ T cells

The role of adaptive immune system in regulation of asthmatic responses remains elusive. Here, we performed a comprehensive time-course analysis of mutual relationships between development of asthmatic response following allergen challenge and changes in several CD4+ T cell subsets which we characterized as either releasing interleukin-10 (CD4+CD25−CD127− and CD4+CD25+CD127+ T cells) or responding to IL-10 (CD4+ T cell subsets expressing CD210). Patients that developed asthmatic reaction were described as responders (R) whereas the others were named non-responders (NR). In R, in contrast to NR, at 6 h, we demonstrated significant expansion of CD4+CD25−CD127− T cells which was followed by drop to baseline values at 24 h. In contrast, in R, we observed decrease in numbers of CD4+CD25+CD127+ and CD4+CD25−CD127+ T cells at 24 h. Interestingly, at baseline, despite comparable IL-10 levels, R presented with lower levels of all CD4+ T cell subsets expressing CD210. In R, the numbers of CD4+CD210+ T cell subsets were further decreased following bronchial challenge which was paralleled by decrease in IL-10 serum levels. Altogether, our data suggest that dynamic interactions between IL-10-producing and IL-10-responding CD4+ T cells could contribute to pathogenesis of asthmatic responses in atopic individuals.

Molecular basis for downregulation of C5a-mediated inflammation by IgG1 immune complexes in allergy and asthma

Allergy and asthma are triggered primarily by the binding of allergen-specific immunoglobulin E (IgE)-allergen complexes to their receptors, recognition of the allergens by antigen-presenting cells, and allergen presentation to the T cells. These events lead to mucus secretions, runny nose, itchy eyes, sneezing, airway hyperresponsiveness, and nasal congestion. Complement 5a (C5a) has emerged as a central molecule that mediates these allergic reactions. Many allergens and allergen-specific IgG immune complexes (IgG-ICs) cause complement activation and C5a generation. C5a interaction with its receptor (C5aR) leads to the infiltration and activation of several immunologic cell types and the secretion of pathogenic inflammatory and proinflammatory mediators. However, IgG1-IC binding to the IgG inhibitory Fc gamma receptor (FcγRIIB) suppresses C5aR-mediated inflammatory signaling and, hence, may reduce the inflammatory immune responses through this FcγRIIB-mediated pathway. Reviews of the IgG1-IC interactions with C5a-mediated inflammatory immune responses suggest that IgG1-IC-C5a inhibitory therapy may reduce inflammation in allergic diseases.

IL-4/IL-13-dependent and independent expression of miR-124 and its contribution to M2 phenotype of monocytic cells in normal conditions and during allergic inflammation

Monocytic cells exhibit a high level of heterogeneity and have two distinct modes of their activation: 1) classical M1 path associated with inflammation and tissue damage, and 2) alternative M2 path. Although it has been demonstrated that M2 macrophages play an important role in the regulation of the allergic immune responses, tissue maintenance and repair, little is known about the mechanisms that determine the M2 phenotype. We have previously shown that miR-124 is expressed in microglia that exhibit the M2 phenotype and overexpression of miR-124 in macrophages resulted in downregulation of a number of M1 markers (MHC class II, CD86) and up-regulation of several M2 markers (Fizz1, Arg1). We further investigated whether the polarization of macrophages towards the M2 phenotype induced miR-124 expression. We found that exposure of cells to IL-4 and IL-13 resulted in the upregulation of miR-124 in macrophages. We also demonstrated that IL-4 induced expression of three miR-124 precursor transcripts with predominant expression of pri-miR-124.3, suggesting regulation of miR-124 expression by IL-4 on a transcriptional level. Expression of miR-124 in microglia did not depend on IL-4 and/or IL-13, whereas expression of miR-124 in lung resident macrophages was IL-4 and IL-13-dependent and was upregulated by systemic administration of IL-4 or during allergic inflammation. Upregulation of several M2 markers (CD206, Ym1) and downregulation of the M1 markers (CD86, iNOS, TNF) in M2-polarized macrophages was abrogated by a miR-124 inhibitor, suggesting that this microRNA contributed to the M2 phenotype development and maintenance. Finally we showed that human CD14(+)CD16(+) intermediate monocytes, which are found in increased numbers in patients with allergies and bronchial asthma, expressed high levels of miR-124 and exhibited other properties of M2-like cells. Thus, our study suggests that miR-124 serves as a regulator of the M2 polarization in various subsets of monocytic cells both in vitro and in vivo.

Toward a refined definition of monocyte subsets

In a nomenclature proposal published in 2010 monocytes were subdivided into classical and non-classical cells and in addition an intermediate monocyte subset was proposed. Over the last couple of years many studies have analyzed these intermediate cells, their characteristics have been described, and their expansion has been documented in many clinical settings. While these cells appear to be in transition from classical to non-classical monocytes and hence may not form a distinct cell population in a strict sense, their separate analysis and enumeration is warranted in health and disease.

The contribution of allergen-specific IgG to the development of th2-mediated airway inflammation

In both human asthmatics and animal models of allergy, allergen-specific IgG can contribute to Th2-mediated allergic inflammation. Mouse models have elucidated an important role for IgG and Fc-gamma receptor (FcγR) signaling on antigen presenting cells (APC) for the induction of airway inflammation. These studies suggest a positive feedback loop between IgG produced by the adaptive B cell response and FcγR signaling on innate immune cells. Studies of IgG and FcγRs in humans with asthma or allergic lung disease have been more controversial. Some reports have identified associations between allergen-specific IgG and severity of allergic responses, while other studies have found associations of IgG subclass IgG4 with allergic tolerance. In this paper, we review the literature to help define the nature of IgG and FcγR signaling on innate immune cells and how it contributes to the development of allergic immune responses.