Distinct transcriptional programs activated by interleukin-10 with or without lipopolysaccharide in dendritic cells: induction of the B cell-activating chemokine, CXC chemokine ligand 13

Adipose-derived stem cell modulate tolerogenic dendritic cell-induced T cell regulation is correlated with activation of Notch-NFκB signaling

BACKGROUND

Adipose-derived stem cells (ASCs) are recognized for their potential immunomodulatory properties. In the immune system, tolerogenic dendritic cells (DCs), characterized by an immature phenotype, play a crucial role in inducing regulatory T cells (Tregs) and promoting immune tolerance. Notch1 signaling has been identified as a key regulator in the development and function of DCs. However, the precise involvement of Notch1 pathway in ASC-mediated modulation of tolerogenic DCs and its impact on immune modulation remain to be fully elucidated. This study aims to investigate the interplay between ASCs and DCs, focusing the role of Notch1 signaling and downstream pathways in ASC-modulated tolerogenic DCs.

METHODS

Rat bone marrow-derived myeloid DCs were directly co-cultured with ASCs to generate ASC-treated DCs (ASC-DCs). Notch signaling was inhibited using DAPT, while NFκB pathways were inhibited by NEMO binding domain peptide and si-NIK. Flow cytometry assessed DC phenotypes. Real-time quantitative PCR, Western blotting and immunofluorescence determined the expression of Notch1, Jagged1 and the p52/RelB complex in ASC- DCs.

RESULTS

Notch1 and Jagged1 were highly expressed on both DCs and ASCs. ASC-DCs displayed significantly reduced levels of CD80, CD86 and MHC II compared to mature DCs. Inhibiting the Notch pathway with DAPT reversed the dedifferentiation effects. The percentage of induced CD25+/FOXP3+/CD4+ Tregs decreased when ASC-DCs were treated with DAPT (inhibition of the Notch pathway) and si-NIK (inhibition of the non-canonical NFκB pathway).

CONCLUSIONS

ASCs induce DC tolerogenicity by inhibiting maturation and promoting downstream Treg generation, involving the Notch and NFκB pathways. ASC-induced tolerogenic DCs can be a potential immunomodulatory tool for clinical application.

Status and trends of RGS16 based on data visualization analysis: A review

G-protein signaling regulator 16 (RGS16) has been confirmed that RGS16 is associated with cancer, neurodegenerative diseases, and cardiovascular diseases. Moreover, many studies have shown that RGS16 can be used as a biomarker for cancer diagnosis and prognosis. We used CiteSpace and VOS viewer software to perform a bibliometric analysis of 290 publications in the core collection of Web of Science. All the articles come from 399 institutions, including 618 authors, 179 journals, 40 countries, 115 keywords, 1 language, two types of papers, and reviews. The United States has the largest number of publications. The Research Center of Allergy and Infectious Diseases (NIAID) publishes the most papers, Emory University is the most recent of all institutions with the most recent results in the RGS16 study. Cell biology is the most studied discipline, and the most studied topic is migration. Drury published RGS16-related articles with the most citations (n = 15), and Berman published articles with the most citations (n = 106). The biological applications of RGS16 are currently a hot area of RGS16 research, including inflammation, cancer, ulcerative colitis, metabolic acidosis, platelet activation, and thrombosis. The current scientometrics study provides an overview of RGS16 research from 1995 to 2022. This study provides an overview of current and potential future research hotspots in the field of RGS16 and can be used as a resource for interested researchers.

Functions of regulators of G protein signaling 16 in immunity, inflammation, and other diseases

Regulators of G protein signaling (RGS) act as guanosine triphosphatase activating proteins to accelerate guanosine triphosphate hydrolysis of the G protein α subunit, leading to the termination of the G protein-coupled receptor (GPCR) downstream signaling pathway. RGS16, which is expressed in a number of cells and tissues, belongs to one of the small B/R4 subfamilies of RGS proteins and consists of a conserved RGS structural domain with short, disordered amino- and carboxy-terminal extensions and an α-helix that classically binds and de-activates heterotrimeric G proteins. However, with the deepening of research, it has been revealed that RGS16 protein not only regulates the classical GPCR pathway, but also affects immune, inflammatory, tumor and metabolic processes through other signaling pathways including the mitogen-activated protein kinase, phosphoinositide 3-kinase/protein kinase B, Ras homolog family member A and stromal cell-derived factor 1/C-X-C motif chemokine receptor 4 pathways. Additionally, the RGS16 protein may be involved in the Hepatitis B Virus -induced inflammatory response. Therefore, given the continuous expansion of knowledge regarding its role and mechanism, the structure, characteristics, regulatory mechanisms and known functions of the small RGS proteinRGS16 are reviewed in this paper to prepare for diagnosis, treatment, and prognostic evaluation of different diseases such as inflammation, tumor, and metabolic disorders and to better study its function in other diseases.

Unexpected enhancement of FVIII immunogenicity by endothelial expression in lentivirus-transduced and transgenic mice

Factor VIII (FVIII) replacement therapy for hemophilia A is complicated by development of inhibitory antibodies (inhibitors) in ∼30% of patients. Because endothelial cells (ECs) are the primary physiologic expression site, we probed the therapeutic potential of genetically restoring FVIII expression selectively in ECs in hemophilia A mice (FVIIInull). Expression of FVIII was driven by the Tie2 promoter in the context of lentivirus (LV)-mediated in situ transduction (T2F8LV) or embryonic stem cell-mediated transgenesis (T2F8Tg). Both endothelial expression approaches were associated with a strikingly robust immune response. Following in situ T2F8LV-mediated EC transduction, all FVIIInull mice developed inhibitors but had no detectable plasma FVIII. In the transgenic approach, the T2F8Tg mice had normalized plasma FVIII levels, but showed strong sensitivity to developing an FVIII immune response upon FVIII immunization. A single injection of FVIII with incomplete Freund adjuvant led to high titers of inhibitors and reduction of plasma FVIII to undetectable levels. Because ECs are putative major histocompatibility complex class II (MHCII)-expressing nonhematopoietic, "semiprofessional" antigen-presenting cells (APCs), we asked whether they might directly influence the FVIII immune responses. Imaging and flow cytometric studies confirmed that both murine and human ECs express MHCII and efficiently bind and take up FVIII protein in vitro. Moreover, microvascular ECs preconditioned ex vivo with inflammatory cytokines could functionally present exogenously taken-up FVIII to previously primed CD4+/CXCR5+ T follicular helper (Tfh) cells to drive FVIII-specific proliferation. Our results show an unanticipated immunogenicity of EC-expressed FVIII and suggest a context-dependent role for ECs in the regulation of inhibitors as auxiliary APCs for Tfh cells.

Current Paradigms of Tolerogenic Dendritic Cells and Clinical Implications for Systemic Lupus Erythematosus

Tolerogenic dendritic cells (tolDCs) are central players in the initiation and maintenance of immune tolerance and subsequent prevention of autoimmunity. Recent advances in treatment of autoimmune diseases including systemic lupus erythematosus (SLE) have focused on inducing specific tolerance to avoid long-term use of immunosuppressive drugs. Therefore, DC-targeted therapies to either suppress DC immunogenicity or to promote DC tolerogenicity are of high interest. This review describes details of the typical characteristics of in vivo and ex vivo tolDC, which will help to select a protocol that can generate tolDC with high functional quality for clinical treatment of autoimmune disease in individual patients. In addition, we discuss the recent studies uncovering metabolic pathways and their interrelation intertwined with DC tolerogenicity. This review also highlights the clinical implications of tolDC-based therapy for SLE treatment, examines the current clinical therapeutics in patients with SLE, which can generate tolDC in vivo, and further discusses on possibility and limitation on each strategy. This synthesis provides new perspectives on development of novel therapeutic approaches for SLE and other autoimmune diseases.

Δccr5 Genotype Is Associated with Mild Form of Nephropathia Epidemica

Nephropathia Epidemica (NE), a mild form of hemorrhagic fever with renal syndrome (HFRS) and linked to hantavirus infection, is endemic in the Republic of Tatarstan. Several genetic markers of HFRS severity have been identified previously, including human leukocyte antigen (HLA) complexes and nucleotide polymorphism in the tumor necrosis factor alpha (TNFα) gene. Still, our understanding of the genetic markers of NE severity remains incomplete. The frequency of the C-C chemokine receptor type 5 (CCR5) gene wild type and gene with 32-base-pair deletion (Δ32CCR5) genotypes in 98 NE samples and 592 controls was analyzed using PCR. Along with the serum levels of 94 analytes, a lack of differences in the CCR5 genotype distribution between NE cases and the general population suggests that the CCR5 genotype does not affect susceptibility to hantavirus infection. However, in NE cases, significant variation in the serum levels of the host matrix metalloproteases between functional CCR5 homozygous and Δ32CCR5 heterozygous patients was detected. Also, the oliguric phase was longer, while thrombocyte counts were lower in functional CCR5 homozygous as compared to heterozygous NE cases. Our data, for the first time, presents the potential role of the CCR5 receptor genotype in NE pathogenesis. Our data suggests that NE pathogenesis in functional CCR5 homozygous and heterozygous NE patients differs, where homozygous cases may have more disintegration of the extracellular matrix and potentially more severe disease.

The Role of Metabolic Remodeling in Macrophage Polarization and Its Effect on Skeletal Muscle Regeneration

Significance: Macrophages are crucial for tissue homeostasis. Based on their activation, they might display classical/M1 or alternative/M2 phenotypes. M1 macrophages produce pro-inflammatory cytokines, reactive oxygen species (ROS), and nitric oxide (NO). M2 macrophages upregulate arginase-1 and reduce NO and ROS levels; they also release anti-inflammatory cytokines, growth factors, and polyamines, thus promoting angiogenesis and tissue healing. Moreover, M1 and M2 display key metabolic differences; M1 polarization is characterized by an enhancement in glycolysis and in the pentose phosphate pathway (PPP) along with a decreased oxidative phosphorylation (OxPhos), whereas M2 are characterized by an efficient OxPhos and reduced PPP. Recent Advances: The glutamine-related metabolism has been discovered as crucial for M2 polarization. Vice versa, flux discontinuities in the Krebs cycle are considered additional M1 features; they lead to increased levels of immunoresponsive gene 1 and itaconic acid, to isocitrate dehydrogenase 1-downregulation and to succinate, citrate, and isocitrate over-expression. Critical Issues: A macrophage classification problem, particularly in vivo, originating from a gap in the knowledge of the several intermediate polarization statuses between the M1 and M2 extremes, characterizes this field. Moreover, the detailed features of metabolic reprogramming crucial for macrophage polarization are largely unknown; in particular, the role of β-oxidation is highly controversial. Future Directions: Manipulating the metabolism to redirect macrophage polarization might be useful in various pathologies, including an efficient skeletal muscle regeneration. Unraveling the complexity pertaining to metabolic signatures that are specific for the different macrophage subsets is crucial for identifying new compounds that are able to trigger macrophage polarization and that might be used for therapeutical purposes.

Alteration of human macrophage phenotypes by the anti-fibrotic drug nintedanib

The tyrosine kinase inhibitor, Nintedanib (NTD), has been approved for the treatment of idiopathic pulmonary fibrosis (IPF). In cell-free systems, NTD was recently shown to inhibit kinase activity of the human recombinant colony-stimulating factor 1 (CSF1) receptor (CSF1R) which mediates major functions of pulmonary macrophages. In the present study, we have investigated the effects of NTD on the phenotype of human monocyte-derived macrophages controlled by CSF1 in order to identify its anti-inflammatory properties via CSF1R inhibition. NTD (0.01 to 1 μM) prevented the CSF1-induced phosphorylation of CSF1R and activation of the downstream signaling pathways. NTD, like the CSF1R inhibitor GW2580, significantly decreased the adhesion of macrophages and production of the chemokine ligand (CCL) 2. NTD also altered the polarization of macrophages to classical M1 and alternative M2a macrophages. It reduced the secretion of several pro-inflammatory and/or pro-fibrotic cytokines (IL-1β, IL-8, IL-10 and CXCL13) by M1 macrophages but did not prevent the expression of M1 markers. While NTD (50-200 nM) partially blocked the synthesis of M2a markers (CD11b, CD200R, CD206, and CD209), it did not reduce synthesis of the M2a pro-fibrotic cytokines CCL22 and PDGF-BB, and increased CCL18 release when used at its highest concentration (1 μM). The effects of NTD on macrophage polarization only was partially mimicked by GW2580, suggesting that the drug inhibits other molecules in addition to CSF1R. In conclusion, NTD alters the CSF1-controlled phenotype of human macrophages mainly by blocking the activation of CSF1R that thus constitutes a new molecular target of NTD, at least in vitro.

Pentraxin 3 is up-regulated in epithelial mammary cells during Staphylococcus aureus intra-mammary infection in goat

Pentraxin 3 is the prototypic long pentraxin and is produced by different cell populations (dendritic cells, monocytes/macrophages, endothelial cells, and fibroblasts) after pro-inflammatory stimulation. Different studies demonstrated the up-regulation of PTX3 during mastitis in ruminants, but its role is still unknown. We first investigated the conservation of PTX3 sequence among different species and its pattern of expression in a wide panel of organs from healthy goats. We studied the modulation of PTX3 during natural and experimental mammary infection, comparing its expression in blood, milk and mammary tissues from healthy and Staphylococcus aureus infected animals. We confirmed the high conservation of the molecule among different species. Goat PTX3 was expressed at high levels in bone marrow, mammary gland, aorta, rectum, pancreas, skin and lungs. PTX3 was up-regulated in epithelial mammary cells and in milk cells after S. aureus infection, suggesting that it represents a first line of defense in goat udder.

Unified nexus of macrophages and maresins in cardiac reparative mechanisms

Macrophages are immune-sensing "big eater" phagocytic cells responsible for an innate, adaptive, and regenerative response. After myocardial infarction, macrophages predominantly clear the deceased cardiomyocyte apoptotic or necrotic neutrophils to develop a regenerative and reparative program with the activation of the lipoxygenase-mediated maresin (MaR) metabolome at the site of ischemic injury. The specialized proresolving molecule and macrophage mediator in resolving inflammation, MaR-1, produced by human macrophages, has potent defining effects that limit polymorphonuclear neutrophil infiltration, enhance uptake of apoptotic PMNs, regulate inflammation resolution and tissue regeneration, and reduce pain. In addition to proresolving and anti-inflammatory actions, MaR-1 displays potent tissue regenerative effects in stroke and is an antinociceptive. Macrophages actively participate in the biosynthesis of bioactive MaR-2, which exhibits anti-inflammatory, proresolving, and atherosclerotic effects. A new class of macrophage-derived molecules, MaR conjugates in tissue regeneration, is identified that regulates phagocytosis and the repair and regeneration of damaged tissue. The presented review provides a current summary of the effect of MaR in resolution pathophysiology, with relevance to a cardiac repair program.-Jadapalli, J. K., Halade, G. V. Unified nexus of macrophages and maresins in cardiac reparative mechanisms.

A Novel Role for C5a in B-1 Cell Homeostasis

B-1 cells constitute a unique subpopulation of lymphocytes residing mainly in body cavities like the peritoneal cavity (PerC) but are also found in spleen and bone marrow (BM). As innate-like B cells, they mediate first line immune defense through low-affinity natural IgM (nIgM) antibodies. PerC B-1 cells can egress to the spleen and differentiate into nIgM antibody-secreting plasma cells that recognize conserved exogenous and endogenous cellular structures. Homing to and homeostasis within the PerC are regulated by the chemokine CXCL13 released by PerC macrophages and stroma cells. However, the exact mechanisms underlying the regulation of CXCL13 and B-1 homeostasis are not fully explored. B-1 cells play important roles in the inflammatory response to infection, autoimmunity, ischemia/reperfusion injury, obesity, and atherosclerosis. Remarkably, this list of inflammatory entities has a strong overlap with diseases that are regulated by complement suggesting a link between B-1 cells and the complement system. Interestingly, up to now, no data exist regarding the role of complement in B-1 cell biology. Here, we demonstrate for the first time that C5a regulates B-1 cell steady-state dynamics within the peritoneum, the spleen, and the BM. We found decreased B-1a cell numbers in the peritoneum and the spleen of C5aR1^−/− mice associated with increased B1-a and B1-b numbers in the spleen and high serum titers of nIgM antibodies directed against phosphorylcholine and several pneumococcal polysaccharides. Similarly, peritoneal B-1a cells were decreased in the peritoneum and splenic B-1a and B-1b cells were increased in C5aR2^−/− mice. The decrease in peritoneal B-1 cell numbers was associated with decreased peritoneal CXCL13 levels in C5aR1^−/− and C5aR2^−/− mice. In search for mechanisms, we found that combined TLR2 and IL-10 receptor activation in PerC macrophages induced strong CXCL13 production, which was significantly reduced in cells from C5aR1- and C5aR2-deficient mice and after combined C5aR-targeting. Such stimulation also induced marked local C5 production by PerC macrophages and C5a generation. Importantly, peritoneal in vivo administration of C5a increased CXCL13 production. Taken together, our findings suggest that local non-canonical C5 activation in PerC macrophages fuels CXCL13 production as a novel mechanism to control B-1 cell homeostasis.

Dexamethasone and Monophosphoryl Lipid A Induce a Distinctive Profile on Monocyte-Derived Dendritic Cells through Transcriptional Modulation of Genes Associated With Essential Processes of the Immune Response

There is growing interest in the use of tolerogenic dendritic cells (tolDCs) as a potential target for immunotherapy. However, the molecular bases that drive the differentiation of monocyte-derived DCs (moDCs) toward a tolerogenic state are still poorly understood. Here, we studied the transcriptional profile of moDCs from healthy subjects, modulated with dexamethasone (Dex) and activated with monophosphoryl lipid A (MPLA), referred to as Dex-modulated and MPLA-activated DCs (DM-DCs), as an approach to identify molecular regulators and pathways associated with the induction of tolerogenic properties in tolDCs. We found that DM-DCs exhibit a distinctive transcriptional profile compared to untreated (DCs) and MPLA-matured DCs. Differentially expressed genes downregulated by DM included MMP12, CD1c, IL-1B, and FCER1A involved in DC maturation/inflammation and genes upregulated by DM included JAG1, MERTK, IL-10, and IDO1 involved in tolerance. Genes related to chemotactic responses, cell-to-cell signaling and interaction, fatty acid oxidation, metal homeostasis, and free radical scavenging were strongly enriched, predicting the activation of alternative metabolic processes than those driven by counterpart DCs. Furthermore, we identified a set of genes that were regulated exclusively by the combined action of Dex and MPLA, which are mainly involved in the control of zinc homeostasis and reactive oxygen species production. These data further support the important role of metabolic processes on the control of the DC-driven regulatory immune response. Thus, Dex and MPLA treatments modify gene expression in moDCs by inducing a particular transcriptional profile characterized by the activation of tolerance-associated genes and suppression of the expression of inflammatory genes, conferring the potential to exert regulatory functions and immune response modulation.

Tumor-derived factors affecting immune cells

Tumor progression is accompanied by the production of a wide array of immunosuppressive factors by tumor and non-tumor cells forming the tumor microenvironment. These factors belonging to cytokines, growth factors, metabolites, glycan-binding proteins and glycoproteins are responsible for the establishment of immunosuppressive networks leading towards tumor promotion, invasion and metastasis. In pre-clinical tumor models, the inactivation of some of these suppressive networks reprograms the phenotypic and functional features of tumor-infiltrating immune cells, ultimately favoring effective anti-tumor immune responses. We will discuss factors and mechanisms identified in both mouse and human tumors, and the possibility to associate drugs inhibiting these mechanisms with new immunotherapy strategies already entered in the clinical practice.

Evidence of perturbed germinal center dynamics, but preserved antibody diversity, in end-stage renal disease

INTRODUCTION

End-stage renal disease (ESRD) is associated with increased infectious susceptibility and with reduced vaccine responses consistent with compromised humoral immunity. Whether the compromised humoral immunity is due to reduced antibody diversity (reduced somatic hypermutation [SHM]) or altered germinal center (GC) dynamics is not known. The GC-derived chemokine CXCL13 as well as peripheral T follicular helper cells (pTFH) reflect GC dynamics, but have, similar to SHM, never been characterized in relation to ESRD.

METHODS

Serum CXCL 13 was determined by ELISA. PTFH were flow-cytometrically defined as CD4⁺ CD45RA^- CCR7⁺ CXCR5⁺ lymphocytes. Apoptotic lymphocyte subsets were in addition annexin V⁺. SHM was determined, by next-generation sequencing and bioinformatics, as nucleotide mutations within the IgG V_H (comprising the important antigen-binding domains of IgG, CDR1, and CDR2).

RESULTS

Elevated CXCL13 levels characterized ESRD (n = 19; [median] 90 pg/ml, P < 0.01) (controls, n = 18; 62 pg/ml). ESRD pTFH frequencies (n = 19; 11.6% [of CD4⁺ memory T cells], P < 0.02*, *Bonferroni corrected) (controls, n = 22; 14.9%) and concentrations (n = 19; 0.03 × 10⁹/L, P < 0.02*) (controls, n = 22; 0.07 × 10⁹/L) were reduced. ESRD pTFH were more apoptotic (n = 9; 25.7%, P = 0.04*) (controls, n = 10; 15.9%). SHM did not discriminate between ESRD (n = 10; 7.4%, P = 0.21) and controls (n = 10; 8.4%).

CONCLUSIONS

Elevated CXCL13 levels, reduced pTFH levels, and increased pTFH apoptosis suggest that perturbed GC dynamics, and not reduced antibody diversity, underlie the diminished vaccine responses and the compromised humoral immunity in ESRD. However, largely preserved SHM provides a rationale for pursuing vaccination in relation to ESRD.

Stromal Fibroblasts in Tertiary Lymphoid Structures: A Novel Target in Chronic Inflammation

Tertiary lymphoid structures (TLS) are organized aggregates of lymphocytes, myeloid, and stromal cells that provide ectopic hubs for acquired immune responses. TLS share phenotypical and functional features with secondary lymphoid organs (SLO); however, they require persistent inflammatory signals to arise and are often observed at target sites of autoimmune disease, chronic infection, cancer, and organ transplantation. Over the past 10 years, important progress has been made in our understanding of the role of stromal fibroblasts in SLO development, organization, and function. A complex and stereotyped series of events regulate fibroblast differentiation from embryonic life in SLOs to lymphoid organ architecture observed in adults. In contrast, TLS-associated fibroblasts differentiate from postnatal, locally activated mesenchyme, predominantly in settings of inflammation and persistent antigen presentation. Therefore, there are critical differences in the cellular and molecular requirements that regulate SLO versus TLS development that ultimately impact on stromal and hematopoietic cell function. These differences may contribute to the pathogenic nature of TLS in the context of chronic inflammation and malignant transformation and offer a window of opportunity for therapeutic interventions in TLS associated pathologies.

Cytokine decoy and scavenger receptors as key regulators of immunity and inflammation

IL-1R2 was the first decoy receptor to be described. Subsequently receptors which act as pure decoys or scavengers or trigger dampening of cytokine signaling have been described for cytokines and chemokines. Here we review the current understanding of the mode of action and significance in pathology of the chemokine atypical receptor ACKR2, the IL-1 decoy receptor IL-1R2 and the atypical IL-1 receptor family IL-1R8. Decoy and scavenger receptors with no or atypical signaling have emerged as a general strategy conserved in evolution to tune the action of cytokines, chemokines and growth factors.

Association of plasmacytoid dendritic cells with B cell infiltration in minor salivary glands in patients with Sjögren's syndrome

OBJECTIVES

Sjogren's syndrome (SS) is an autoimmune disease with features of both over-production of specific autoantibodies and organ-specific disorders, mainly sialadenitis and dacryoadenitis. However, little is known about the factors that contribute to lymphocytic infiltration of SS.

METHODS

Minor salivary gland (MSG) tissue was obtained from 83 patients with primary SS (pSS) and 95 patients with secondary SS and examined pathologically, and correlation between infiltrated immune cells and histological features was evaluated.

RESULTS

Plasmacytoid dendritic cells (pDCs) were increased in MSG of SS compared to Sicca syndrome. The density of pDCs was characteristically correlated with the accumulation of CXCL13(+)CD68(+) macrophages and CXCR5(+)CD19(+) B in the MSG of pSS. In vitro analysis indicated that Type I interferon (IFN) enhanced CXCL13 production by macrophages. Type I IFN was mainly expressed in pDCs and its expression was correlated with the accumulation of CXCL13(+) macrophages in the MSG of pSS.

CONCLUSIONS

Our histological findings suggest the possible mechanism of type I IFN-CXCL13 axis during the pathological processes of acute/chronic salivary inflammation in SS; local production of type I IFN by pDCs, induction of CXCL13 production in macrophages by type I IFN, induction of accumulation of CXCR5(+)CD19(+) B cells by CXCL13 in the MSG.

R4 Regulator of G Protein Signaling (RGS) Proteins in Inflammation and Immunity

G protein-coupled receptors (GPCRs) have important functions in both innate and adaptive immunity, with the capacity to bridge interactions between the two arms of the host responses to pathogens through direct recognition of secreted microbial products or the by-products of host cells damaged by pathogen exposure. In the mid-1990s, a large group of intracellular proteins was discovered, the regulator of G protein signaling (RGS) family, whose main, but not exclusive, function appears to be to constrain the intensity and duration of GPCR signaling. The R4/B subfamily--the focus of this review--includes RGS1-5, 8, 13, 16, 18, and 21, which are the smallest RGS proteins in size, with the exception of RGS3. Prominent roles in the trafficking of B and T lymphocytes and macrophages have been described for RGS1, RGS13, and RGS16, while RGS18 appears to control platelet and osteoclast functions. Additional G protein independent functions of RGS13 have been uncovered in gene expression in B lymphocytes and mast cell-mediated allergic reactions. In this review, we discuss potential physiological roles of this RGS protein subfamily, primarily in leukocytes having central roles in immune and inflammatory responses. We also discuss approaches to target RGS proteins therapeutically, which represents a virtually untapped strategy to combat exaggerated immune responses leading to inflammation.

Gene Expression Profiling of Human Monocyte-derived Dendritic Cells - Searching for Molecular Regulators of Tolerogenicity

The ability of dendritic cells (DCs) to initiate and modulate antigen-specific immune responses has made them attractive targets for immunotherapy. Since DC research in humans is limited by the scarcity of DC populations in the blood circulation, most of our knowledge about DC biology and function has been obtained in vitro from monocyte-derived DCs (moDCs), which can be readily generated in sufficient numbers and are able to differentiate into distinct functional subsets depending on the nature of stimulus. In particular, moDCs with tolerogenic properties (tolDCs) possess great therapeutic potential for the treatment of autoimmune diseases. Several protocols have been developed to generate tolDCs in vitro, able to reinstruct auto-reactive T cells and to promote regulatory cells. While ligands and soluble mediators, by which DCs shape immune responses, have been vastly studied, the intracellular pathways and transcriptional regulators that govern tolDC differentiation and function are poorly understood. Whole-genome microarrays and proteomics provide useful strategies to dissect the complex molecular processes that promote tolerogenicity. Only few attempts have been made to understand tolDC biology through a global view on "omics" profiles. So far, the identification of a common regulator of tolerogenicity has been hampered by the fact that each protocol, used for tolDC generation, targets distinct signaling pathways. Here, we review the progress in understanding the transcriptional regulation of moDC differentiation, with a special focus on tolDCs, and highlight candidate molecules that might be associated with DC tolerogenicity.

HIV-1 single-stranded RNA induces CXCL13 secretion in human monocytes via TLR7 activation and plasmacytoid dendritic cell-derived type I IFN

Elevated levels of the chemokine CXCL13 have been observed in the plasma of chronically HIV-1-infected subjects and have been correlated with plasma viremia, which in turn has been linked to progressive dysregulation of humoral responses. In this study we sought to identify mechanisms of CXCL13 induction in response to HIV-1 infection. Plasma levels of CXCL13 in HIV-1-infected antiretroviral therapy-naive subjects correlated with viral load and were higher compared with antiretroviral therapy-treated HIV-1-infected and HIV-1-uninfected subjects. To elucidate the relationship between HIV-1 viremia and CXCL13 plasma levels, PBMCs from uninfected donors were stimulated with HIV-1 infectious virions, HIV-1 ssRNA, TLR 7 and 8 agonists, or IFN-α. The cellular sources of CXCL13 were determined by intracellular cytokine staining of cell populations. CXCL13 was produced by monocytes after stimulation with TLR 7 and 8 ligands or HIV-1-derived ssRNA. CXCL13 production by monocytes required TLR7 activation of plasmacytoid dendritic cells and secretion of type I IFN. IFN-α alone was sufficient to induce CXCL13 expression in human monocytes. In sum, we identified a novel mechanism of HIV-1-induced CXCL13 secretion-one caused by TLR7 induction of type I IFN by plasmacytoid dendritic cells and subsequent IFN stimulation of monocytes. Our findings are relevant in understanding how HIV-1 infection leads to immune dysregulation and provide the opportunity to develop and test potential therapeutic interventions.

Current status of interleukin-10 and regulatory T-cells in cancer

PURPOSE OF REVIEW

Tumor growth elicits antigen-specific cytotoxic as well as immune suppressive responses. Interleukin-10 (IL-10) is a key immune-suppressive cytokine produced by regulatory T-cells and by helper T-cells. Here, we review pleiotropic functions of IL-10 that impact the immune pathology of cancer.

RECENT FINDINGS

The role of IL-10 in cancer has become less certain with the knowledge of its immune stimulatory functions. IL-10 is needed for T-helper cell functions, T-cell immune surveillance, and suppression of cancer-associated inflammation. By promoting tumor-specific immune surveillance and hindering pathogenic inflammation, IL-10 is emerging as a key cytokine in the battle of the host against cancer.

SUMMARY

IL-10 functions at the cross-roads of immune stimulation and immune suppression in cancer. Immunological mechanisms of action of IL-10 can be ultimately exploited to develop novel and effective cancer therapies.

Elevated Plasma Pentraxin3 Levels and Its Association with Neovascular Age-related Macular Degeneration

PURPOSE

To evaluate pentraxin3 (PTX3) levels in patients with neovascular age-related macular degeneration (N-ARMD) and to investigate its role as a predictive biomarker.

METHODS

Thirty individuals with N-ARMD and 30 controls without N-ARMD were studied. Plasma concentrations of C-reactive protein (CRP) and PTX3 were measured in frozen samples using an enzyme-linked immunosorbent assay kit.

RESULTS

PTX3 concentration was 1341 ± 625 pg/mL (mean ± standard deviation) in N-ARMD patients, which was significantly higher than in control subjects (887 ± 478, p = 0.003). The mean CRP level was also significantly higher in N-ARMD (2121 ± 2300) than in control (748 ± 618, p = 0.004). Pearson's correlation analysis showed a significant positive correlation between PTX3 and CRP (r = 0.407, p = 0.002).

CONCLUSIONS

Our data support the role of chronic inflammation in the development of ARMD. They also show PTX3 may contribute to efforts to understand pathogenesis of N-ARMD.

The long pentraxin PTX3: a paradigm for humoral pattern recognition molecules

Pattern recognition molecules (PRMs) are components of the humoral arm of innate immunity; they recognize pathogen-associated molecular patterns (PAMP) and are functional ancestors of antibodies, promoting complement activation, opsonization, and agglutination. In addition, several PRMs have a regulatory function on inflammation. Pentraxins are a family of evolutionarily conserved PRMs characterized by a cyclic multimeric structure. On the basis of structure, pentraxins have been operationally divided into short and long families. C-reactive protein (CRP) and serum amyloid P component are prototypes of the short pentraxin family, while pentraxin 3 (PTX3) is a prototype of the long pentraxins. PTX3 is produced by somatic and immune cells in response to proinflammatory stimuli and Toll-like receptor engagement, and it interacts with several ligands and exerts multifunctional properties. Unlike CRP, PTX3 gene organization and regulation have been conserved in evolution, thus allowing its pathophysiological roles to be evaluated in genetically modified animals. Here we will briefly review the general properties of CRP and PTX3 as prototypes of short and long pentraxins, respectively, emphasizing in particular the functional role of PTX3 as a prototypic PRM with antibody-like properties.

LPS-induced chemokine expression in both MyD88-dependent and -independent manners is regulated by Cot/Tpl2-ERK axis in macrophages

LPS signaling is mediated through MyD88-dependent and -independent pathways, activating NF-?B, MAP kinases and IRF3. Cot/Tpl2 is an essential upstream kinase in LPS-mediated activation of ERKs. Here we explore the roles of MyD88 and Cot/Tpl2 in LPS-induced chemokine expression by studying myd88(-/-) and cot/tpl2(-/-) macrophages. Among the nine LPS-responsive chemokines examined, mRNA induction of ccl5, cxcl10, and cxcl13 is mediated through the MyD88-independent pathway. Notably, Cot/Tpl2-ERK signaling axis exerts negative effects on the expression of these three chemokines. In contrast, LPS-induced gene expression of ccl2, ccl7, cxcl2, cxcl3, ccl8, and cxcl9 is mediated in the MyD88-dependent manner. The Cot/Tpl2-ERK axis promotes the expression of the first four and inhibits the expression of the latter two. Thus, LPS induces expression of multiple chemokines through various signaling pathways in macrophages.

Macrophage diversity in cardiac inflammation: a review

Cardiac inflammatory disease represents a significant public health burden, and interesting questions of immunopathologic science and clinical inquiry. Novel insights into the diverse programming and functions within the macrophage lineages in recent years have yielded a view of these cells as dynamic effectors and regulators of immunity, host defense, and inflammatory disease. In this review, we examine and discuss recent investigations into the complex participation of mononuclear phagocytic cells in the pathology of animal models of myocarditis.

Stromal cell-immune cell interactions

Interaction between different types of hematopoietic cells is essential for proper functioning of the immune system. For instance, the cytokines produced by antigen-presenting dendritic cells will determine the type of T cell response that is induced. However, hematopoietic cells are also strongly influenced by the surrounding nonhematopoietic cells. The cells that form these microenvironments are collectively called stromal cells. Here, we focus on the stromal cells present within secondary lymphoid organs and discuss their importance for various aspects of the immune system.

A unique hybrid renal mononuclear phagocyte activation phenotype in murine systemic lupus erythematosus nephritis

Renal infiltration with mononuclear cells is associated with poor prognosis in systemic lupus erythematosus. A renal macrophage/dendritic cell signature is associated with the onset of nephritis in NZB/W mice, and immune-modulating therapies can reverse this signature and the associated renal damage despite ongoing immune complex deposition. In nephritic NZB/W mice, renal F4/80(hi)/CD11c(int) macrophages are located throughout the interstitium, whereas F4/80(lo)/CD11c(hi) dendritic cells accumulate in perivascular lymphoid aggregates. We show here that F4/80(hi)/CD11c(int) renal macrophages have a Gr1(lo)/Ly6C(lo)/VLA4(lo)/MHCII(hi)/CD43(lo)/CD62L(lo) phenotype different from that described for inflammatory macrophages. At nephritis onset, F4/80(hi)/CD11c(int) cells upregulate cell surface CD11b, acquire cathepsin and matrix metalloproteinase activity, and accumulate large numbers of autophagocytic vacuoles; these changes reverse after the induction of remission. Latex bead labeling of peripheral blood Gr1(lo) monocytes indicates that these are the source of F4/80(hi)/CD11c(int) macrophages. CD11c(hi)/MHCII(lo) dendritic cells are found in the kidneys only after proteinuria onset, turnover rapidly, and disappear rapidly after remission induction. Gene expression profiling of the F4/80(hi)/CD11c(int) population displays increased expression of proinflammatory, regulatory, and tissue repair/degradation-associated genes at nephritis onset that reverses with remission induction. Our findings suggest that mononuclear phagocytes with an aberrant activation profile contribute to tissue damage in lupus nephritis by mediating both local inflammation and excessive tissue remodeling.

New concepts of IL-10-induced lung fibrosis: fibrocyte recruitment and M2 activation in a CCL2/CCR2 axis

IL-10 is most commonly recognized as an anti-inflammatory cytokine possessing immunosuppressive effects necessary for regulated resolution of proinflammation. However, its role in the development of fibrosis during inflammatory resolution has not been clear. Few prior studies have linked IL-10 with the inhibition of fibrosis principally on the basis of regulating inflammation thought to be driving fibroproliferation. In contrast, in a model of long-term overexpression of IL-10, we observed marked induction of lung fibrosis in mice. The total cell number retrieved by bronchoalveolar lavage (BAL) increased 10-fold in the IL-10 overexpression (IL-10 OE) mice, with significant infiltration of T and B lymphocytes and collagen-producing cells. The presence of increased fibrocytes, isolated from collagenase-digested lungs, was identified by flow cytometry using dual staining of CD45 and collagen 1. Quantitative PCR analysis on an array of chemokine/chemokine receptor genes showed that receptor CCR2 and its ligand, CCL2, were highly upregulated in IL-10 OE mice, suggesting that IL-10-induced fibrocyte recruitment was CCL2/CCR2 specific. Given the prior association of alternatively activated (M(2)) macrophages with development of fibrosis in other disease states, we also examined the effect of IL-10 OE on the M(2) macrophage axis. We observed significantly increased numbers of M(2) macrophages in both BAL and whole lung tissue from the IL-10 OE mice. Administration of rabbit anti-CCL2 antiserum to IL-10 OE mice for three consecutive weeks significantly decreased fibrosis as evidenced by lung hydroxyproline content, compared with mice that received preimmune rabbit serum. These results indicate that overexpression of IL-10 induces fibrosis, in part, by fibrocyte recruitment and M(2) macrophage activation, and likely in a CCL2/CCR2 axis.

The proteoglycan biglycan regulates expression of the B cell chemoattractant CXCL13 and aggravates murine lupus nephritis

CXCL13 is a key B cell chemoattractant and marker of disease activity in patients with SLE; however, the mechanism of its induction has not been identified yet. Here, we have shown that the proteoglycan biglycan triggers CXCL13 expression via TLR2/4 in macrophages and dendritic cells. In vivo, levels of biglycan were markedly elevated in the plasma and kidneys of human SLE patients and lupus-prone (MRL/lpr) mice. Overexpression of soluble biglycan in MRL/lpr mice raised plasma and renal levels of CXCL13 and caused accumulation of B cells with an enhanced B1/B cell ratio in the kidney, worsening of organ damage, and albuminuria. Importantly, biglycan also triggered CXCL13 expression and B cell infiltration in the healthy kidney. Conversely, biglycan deficiency improved systemic and renal outcome in lupus-prone mice, with lower levels of autoantibodies, less enlargement of the spleen and lymph nodes, and reduction in renal damage and albuminuria. This correlated with a marked decline in circulating and renal CXCL13 and a reduction in the number of B cells in the kidney. Collectively, our results describe what we believe to be a novel mechanism for the regulation of CXCL13 by biglycan, a host-derived ligand for TLR2/4. Blocking biglycan-TLR2/4 interactions might be a promising strategy for the management of SLE and other B cell-mediated inflammatory disease entities.

Elevation of serum CXCL13 in SLE as well as in sepsis

Recent studies have demonstrated that CXCL13 serum levels correlate significantly with systemic lupus erythematosus (SLE) disease activity. However, experimental studies show that CXCL13 production can also be induced by bacterial exposure as well as in response to inflammatory cytokines. This report asks whether CXCL13 serum levels are elevated in patients with evidence of bacterial infections and whether there is a correlation with the C-reactive protein (CRP) levels or the severity of illness in critically ill patients. CXCL13 levels were compared in 39 patients with active SLE (without concomitant infection), 40 non-SLE patients with sepsis, and 40 healthy controls by enzyme-linked immunosorbent assay (ELISA) methodology. We also tested storage conditions and freeze–thaw cycles for stability of CXCL13 in serum samples. Our studies demonstrated that the median CXCL13 serum levels were significantly elevated in patients with SLE [median 83 pg/ml (interquartile range 38–366)] or sepsis [359 pg/ml (151–459)] compared with healthy controls [32 pg/ml (27–41), p < 0.001]. The CXCL13 serum levels correlated with disease activity in SLE (CXCL13 vs. SLEDAI r = 0.65, p < 0.001), but were not associated with severity of illness score in critically ill patients (CXCL13 vs. SOFA r = −0.15, p = 0.35). However, CXCL13 serum levels were clearly associated with CRP levels in both sepsis ( r = 0.45, p = 0.003) and SLE ( r = 0.39, p = 0.02). In conclusion, CXCL13 is a stable serum marker for disease activity in SLE patients, but concomitant infections can also lead to increased CXCL13 levels.

Pentraxin 3 in maternal circulation: an association with preterm labor and preterm PROM, but not with intra-amniotic infection/inflammation

OBJECTIVE

Pentraxin 3 (PTX3) is an acute-phase protein that has an important role in the regulation of the innate immune response. The aim of this study was to determine if maternal plasma PTX3 concentration changes in the presence of intra-amniotic infection and/or inflammation (IAI) in women with preterm labor (PTL) and intact membranes, as well as those with preterm prelabor rupture of membranes (preterm PROM).

STUDY DESIGN

This cross-sectional study included women in the following groups: (1) nonpregnant (n=40); (2) uncomplicated pregnancies in the first (n=22), second (n=22) or third trimester (n=71, including 50 women at term not in labor); (3) uncomplicated pregnancies at term with spontaneous labor (n=49); (4) PTL and intact membranes who delivered at term (n=49); (5) PTL without IAI who delivered preterm (n=26); (6) PTL with IAI (n=65); (7) preterm PROM without IAI (n=25); and (8) preterm PROM with IAI (n=77). Maternal plasma PTX3 concentrations were determined by ELISA.

RESULTS

(1) Maternal plasma PTX3 concentrations increased with advancing gestational age (r=0.62, p<0.001); (2) women at term with spontaneous labor had a higher median plasma PTX3 concentration than those at term not in labor (8.29 ng/ml vs. 5.98  ng/ml, p=0.013); (3) patients with an episode of PTL, regardless of the presence or absence of IAI and whether these patients delivered preterm or at term had a higher median plasma PTX3 concentration than normal pregnant women (p<0.001 for all comparisons); (4) similarly, patients with preterm PROM, with or without IAI had a higher median plasma PTX3 concentration than normal pregnant women (p<0.001 for both comparisons); and (5) among patients with PTL and those with preterm PROM, IAI was not associated with significant changes in the median maternal plasma PTX3 concentrations.

CONCLUSIONS

The maternal plasma PTX3 concentration increases with advancing gestational age and is significantly elevated during labor at term and in the presence of spontaneous preterm labor or preterm PROM. These findings could not be explained by the presence of IAI, suggesting that the increased PTX3 concentration is part of the physiologic or pathologic activation of the pro-inflammatory response in the maternal circulation during the process of labor at term or preterm.

New insights into the development of lymphoid tissues

Secondary lymphoid organs are important locations for the initiation of adaptive immune responses. They develop before birth, and their formation requires interaction between lymphotoxin-α₁ß₂-expressing lymphoid-tissue inducer cells and lymphotoxin-ß receptor-expressing stromal organizer cells. Here, we discuss new insights into the earliest phases of peripheral lymph node and Peyer's patch formation that occur before lymphotoxin-ß receptor signalling and suggest a role for the developing nervous system. In addition, we discuss the differing requirements for the postnatal formation of mucosa-associated lymphoid tissues and tertiary lymphoid structures that develop at sites of chronic inflammation.

Tumor-conditioned macrophages secrete migration-stimulating factor: a new marker for M2-polarization, influencing tumor cell motility

Tumor-associated macrophages (TAMs) are key orchestrators of the tumor microenvironment directly affecting neoplastic cell growth, neoangiogenesis, and extracellular matrix remodeling. In turn, the tumor milieu strongly influences maturation of TAMs and shapes several of their features. To address the early macrophage (M) differentiation phase in a malignant context, we mimicked a tumor microenvironment by in vitro coculturing human blood monocytes with conditioned media from different cancer cell lines. Only 2 out of 16 tumor cell lines induced M differentiation due to secreted M-CSF isoforms, including high molecular mass species. A global gene profiling of tumor-conditioned M was performed. Comparison with other datasets (polarized M1-M, M2-M, and TAMs isolated from human tumors) highlighted the upregulation of several genes also shared by TAM and M2-polarized M. The most expressed genes were selenoprotein 1, osteoactivin, osteopontin, and, interestingly, migration-stimulating factor (MSF), a poorly studied oncofoetal isoform of fibronectin. MSF (present in fetal/cancer epithelial and stromal cells but not in healthy tissues) was never identified in M. MSF production was confirmed by immunohistochemistry in human TAMs. MSF was induced by M-CSF, IL-4, and TGFbeta but not by proinflammatory stimuli. RNA and protein analysis clearly demonstrated that it is specifically associated with the M2 polarization of M. Tumor-conditioned M-derived MSFs strongly stimulated tumor cell migration, thus contributing to the motile phenotype of neoplastic cells. In conclusion, MSF is a new molecule associated with the M2 polarization of M and expressed by TAMs. Its biological function may contribute to M-mediated promotion of cancer cell invasion and metastasis.

The cellular context of AID expressing cells in fish lymphoid tissues

It has long been held that the cold-blooded vertebrates lack mammalian-like germinal centers, though they do have affinity maturation and the immunoglobulin mutator activation-induced cytidine deaminase or AID. Using AID as a marker of sites of somatic hypermutation, we have identified discrete cell clusters of up to several thousand cells, in the spleen and kidney of channel catfish (Ictalurus punctatus), which may be primordial germinal centers. In situ hybridization revealed that AID expressing cells are interspersed or surrounded by a population of pigmented CSF1-R expressing cells called melano-macrophages. Significantly, melano-macrophages or associated reticular cells have been previously noted for their ability to retain soluble antigen on or near their surface for several weeks following vaccination. Laser capture microdissection and RT-PCR were used to establish that these cell clusters also contained cells expressing Ig heavy chain transcripts as well as transcripts of TcRbeta and the putative CD4 homologue of fish. These observations, coupled with past work showing that mutations develop in B-cell lineages in fishes, allow us to develop a model for how affinity maturation may have evolved in early gnathostome vertebrates.

Dendritic cells produce CXCL13 and participate in the development of murine small intestine lymphoid tissues

In the adult intestine, luminal microbiota induce cryptopatches to transform into isolated lymphoid follicles (ILFs), which subsequently act as sites for the generation of IgA responses. The events leading to this conversion are incompletely understood. Dendritic cells (DCs) are components of cryptopatches (CPs) and ILFs and were therefore evaluated in this process. We observed that the adult murine intestine contains clusters of DCs restricted to the CP/ILF continuum. A numerical and cell associative hierarchy in the adult intestine and a chronologic hierarchy in the neonatal intestine demonstrated that these clusters form after the coalescence of CD90+ cells to form CPs and before the influx of B220+ B lymphocytes to form ILFs. Cluster formation was dependent on lymphotoxin and the lymphotoxin beta receptor and independent of lymphocytes. The ILF DC population was distinguished from that of the lamina propria by the absence of CD4+CD11c+ cells and an increased proportion of CD11c+B220+ cells. The formation of clusters was not limited by DC numbers but was induced by luminal microbiota. Moreover, in the absence of the chemokine CXCL13, CP transformation into ILF was arrested. Furthermore, ILF DCs express CXCL13, and depletion of DCs resulted in regression of ILFs and disorganization of CPs. These results reveal DC participation in ILF transformation and maintenance and suggest that in part this may be due to CXCL13 production by these cells.

Pentraxin 3 in amniotic fluid: a novel association with intra-amniotic infection and inflammation

OBJECTIVE

Pentraxin 3 (PTX3) is a soluble pattern recognition receptor (PRR) that has an important role in immunoregulation and vascular integrity. The aim of this study was to determine if PTX3 is present in amniotic fluid (AF) and whether its concentration changes with gestational age (GA), in the presence of preterm or term labor, and in cases of intra-amniotic infection/inflammation (IAI) associated with spontaneous preterm labor (PTL) or preterm prelabor rupture of membranes (PROM).

STUDY DESIGN

This cross-sectional study included the following groups: 1) mid-trimester (n=45); 2) uncomplicated pregnancies at term with (n=48) and without (n=40) spontaneous labor; 3) women with PTL and intact membranes who: a) delivered at term (n=44); b) delivered preterm without IAI (n=40); or c) delivered preterm with IAI (n=62); 4) women with preterm PROM with (n=63) and without (n=36) IAI. PTX3 concentration in AF was determined by ELISA. Non-parametric statistics were used for analyses.

RESULTS

1) Among women with PTL and intact membranes, the median AF PTX3 concentration was significantly higher in women with IAI than in those without IAI (7.95 ng/mL vs. 0.38 ng/mL; P<0.001) and than in those who delivered at term (0.55 ng/mL; P<0.001); 2) women with preterm PROM and IAI had a higher median AF PTX3 concentration than those without IAI (9.12 ng/mL vs. 0.76 ng/mL; P<0.001); 3) the median AF PTX3 concentration did not change with GA (mid-trimester: 0.79 ng/mL vs. term not in labor: 0.58 ng/mL; P=0.09); and 4) labor at term was not associated with a significant change of AF PTX 3 concentration (in labor: 0.54 ng/mL vs. not in labor: 0.58 ng/mL, P=0.9).

CONCLUSIONS

PTX3 is a physiologic constituent of the AF, and its median concentration is elevated in the presence of IAI, suggesting that PTX3 may play a role in the innate immune response against IAI.

How tolerogenic dendritic cells induce regulatory T cells

Since their discovery by Steinman and Cohn in 1973, dendritic cells (DCs) have become increasingly recognized for their crucial role as regulators of innate and adaptive immunity. DCs are exquisitely adept at acquiring, processing, and presenting antigens to T cells. They also adjust the context (and hence the outcome) of antigen presentation in response to a plethora of environmental inputs that signal the occurrence of pathogens or tissue damage. Such signals generally boost DC maturation, which promotes their migration from peripheral tissues into and within secondary lymphoid organs and their capacity to induce and regulate effector T cell responses. Conversely, more recent observations indicate that DCs are also crucial to ensure immunological peace. Indeed, DCs constantly present innocuous self- and nonself-antigens in a fashion that promotes tolerance, at least in part, through the control of regulatory T cells (Tregs). Tregs are specialized T cells that exert their immunosuppressive function through a variety of mechanisms affecting both DCs and effector cells. Here, we review recent advances in our understanding of the relationship between tolerogenic DCs and Tregs.

Chemokine decoy receptors: structure-function and biological properties

Chemokines induce cell migration through the activation of a distinct family of structurally related heterotrimeric G protein-coupled receptors (GPCR). Over the last few years, several receptors in this family that recognize chemokines but do not induce cell migration have been identified. These "atypical" chemokine receptors are unable to activate transduction events that lead directly to cell migration, but appear nonetheless to play a nonredundant role in the control of leukocyte recruitment at inflammatory sites and in tumors by shaping the chemoattractant gradient, either by removing, transporting, or concentrating their cognate ligands.

Regulator of G protein signalling 16 is a target for a porcine circovirus type 2 protein

Interaction studies have suggested that the non-structural protein encoded by open reading frame 3 (ORF3) of porcine circovirus type 2 (PCV2) binds specifically to a regulator of G protein signalling (RGS) related to human RGS16 (huRGS16). The full-length clone of RGS16 was generated from porcine cells and sequence analysis revealed a close relationship to huRGS16 and murine RGS16. In vitro pull-down experiments verified an interaction between porcine RGS16 (poRGS16) and ORF3 from PCV2. Using GST-linked ORF3 proteins from three different genogroups of PCV2 and from porcine circovirus type 1 (PCV1) in the pull-down experiments indicated that there were differences in their ability to bind poRGS16. Quantitative RT-PCR demonstrated that the expression of poRGS16 mRNA could be induced by a number of cell activators including mitogens (LPS and PHA), interferon inducers (ODN 2216 and poly I : C) and the neurotransmitter norepinephrine. Immunofluorescence labelling confirmed the induced expression of poRGS16 at the protein level and suggested that the PCV2 ORF3 protein co-localized with poRGS16 in LPS-activated porcine PBMC. Furthermore, poRGS16 appeared to participate in the translocation of the ORF3 protein into the cell nucleus, suggesting that the observed interaction may play an important role in the infection biology of porcine circovirus.

The long pentraxin PTX3 as a prototypic humoral pattern recognition receptor: interplay with cellular innate immunity

The innate immune system consists of a cellular arm and a humoral arm. Components of humoral immunity include diverse molecular families, which represent functional ancestors of antibodies. They play a key role as effectors and modulators of innate resistance in animals and humans, interacting with cellular innate immunity. The prototypic long pentraxin, pentraxin 3 (PTX3), represents a case in point of this interplay. Gene targeting of this evolutionarily conserved long pentraxin has unequivocally defined its role at the crossroads of innate immunity, inflammation, matrix deposition, and female fertility. Phagocytes represent a key source of this fluid-phase pattern recognition receptor, which, in turn, facilitates microbial recognition by phagocytes acting as an opsonin. Moreover, PTX3 has modulatory functions on innate immunity and inflammation. Here, we review the studies on PTX3 which emphasize the complexity and complementarity of the crosstalk between the cellular and humoral arms of innate immunity.

Coregulation in human leukocytes of the long pentraxin PTX3 and TSG-6

The prototypic long PTX3 is a multifunctional protein involved in innate resistance to pathogens and in controlling inflammation. TSG-6 is a hyaluronan-binding protein that is involved in ECM remodeling and has anti-inflammatory and chondroprotective functions. PTX3 and TSG-6 are coregulated by growth differentiation factor-9 in granulosa cells, where they are produced during the periovulatory period and play essential roles in the incorporation of hyaluronan into the ECM during cumulus expansion. The present study was designed to assess whether PTX3 and TSG-6 are coregulated in leukocytes, in particular, in phagocytes and DC. Monocytes, macrophages, and myeloid DC were found to produce high levels of TSG-6 and PTX3 in response to proinflammatory mediators (LPS or cytokines). Unstimulated neutrophil polymorphonuclear granulocytes expressed high levels of TSG-6 mRNA, but not PTX3 transcript, and stored both proteins in granules. In contrast, endothelial cells expressed substantial amounts of PTX3 mRNA and low levels of TSG-6 transcript under the conditions tested. Anti-inflammatory cytokines, such as IL-4, dampened LPS-induced TSG-6 and PTX3 expression. Divergent effects were observed with IL-10, which synergizes with TLR-mediated PTX3 induction but inhibits LPS-induced TSG-6 transcription. Immunohistochemical analysis confirms the colocalization of the two proteins in inflammatory infiltrates and in endothelial cells of inflamed tissues. Thus, here we show that myelomonocytic cells and MoDC are a major source of TSG-6 and that PTX3 and TSG-6 are coregulated under most of the conditions tested. The coordinated expression of PTX3 and TSG-6 may play a role in ECM remodeling at sites of inflammation.

Nicotinamide phosphoribosyl transferase/pre-B cell colony-enhancing factor/visfatin is required for lymphocyte development and cellular resistance to genotoxic stress

Nicotinamide phosphoribosyl transferase (Nampt)/pre-B cell colony-enhancing factor (PBEF)/visfatin is a protein displaying multiple functional properties. Originally described as a cytokine-like protein able to regulate B cell development, apoptosis, and glucose metabolism, this protein also plays an important role in NAD biosynthesis. To gain insight into its physiological role, we have generated a mouse strain expressing a conditional Nampt allele. Lack of Nampt expression strongly affects development of both T and B lymphocytes. Analysis of hemizygous cells and in vitro cell lines expressing distinct levels of Nampt illustrates the critical role of this protein in regulating intracellular NAD levels. Consequently, a clear relationship was found between intracellular Nampt levels and cell death in response to the genotoxic agent MNNG (N-methyl-N'-nitro-N-nitrosoguanidine), confirming that this enzyme represents a key regulator of cell sensitivity to NAD-consuming stress secondary to poly(ADP-ribose) polymerases overactivation. By using mutant forms of this protein and a well-characterized pharmacological inhibitor (FK866), we unequivocally demonstrate that the ability of the Nampt to regulate cell viability during genotoxic stress requires its enzymatic activity. Collectively, these data demonstrate that Nampt participates in cellular resistance to genotoxic/oxidative stress, and it may confer to cells of the immune system the ability to survive during stressful situations such as inflammation.

Regulators of G-protein signalling are modulated by bacterial lipopeptides and lipopolysaccharide

Regulators of G-protein signalling accelerate the GTPase activity of G(alpha) subunits, driving G proteins in their inactive GDP-bound form. This property defines them as GTPase activating proteins. Here the effect of different Toll-like receptor agonists on RGS1 and RGS2 expression in murine bone marrow-derived macrophages and J774 cells was analysed. After stimulation with TLR2/1 or TLR2/6 lipopeptide ligands and the TLR4/MD2 ligand lipopolysaccharide, microarray analyses show only modulation of RGS1 and RGS2 among all the regulators of G-protein signalling tested. Real-time PCR confirmed modulation of RGS1 and RGS2. In contrast to RGS2, which was always downregulated, RGS1 mRNA was upregulated during the first 30 min after stimulation, followed by downregulation. Similar results were also found in the murine macrophage cell line J774. The ligand for intracellular TLR9 modulates RGS1 and RGS2 in a similar manner. However, the TLR3 ligand poly(I:C) permanently upregulates RGS1 and RGS2 expression indicating a different modulation by the MyD88- and TRIF-signalling pathway. This was confirmed using MyD88(-/-) and TRIF(-/-) bone marrow-derived macrophages. Modulation of RGS1 and RGS2 by Toll-like receptor ligands plays an important role during inflammatory and immunological reactions after bacterial and viral infection.

A role for CXCL13 (BCA-1) in pregnancy and intra-amniotic infection/inflammation

OBJECTIVES

CXCL13 is a potent chemokine, produced by mature and recently recruited macrophages to sites of inflammation, which has antimicrobial and anti-angiogenic properties. The purpose of this study was to: (1) determine whether CXCL13 is present in maternal serum, umbilical cord blood, and amniotic fluid (AF); (2) to determine if AF concentration changes with intra-amniotic infection/inflammation (IAI); and (3) to localize the production of CXCL13 in chorioamniotic membranes and umbilical cord.

STUDY DESIGN

A cross-sectional study on maternal serum was performed including patients in the following groups: (1) non-pregnant women (n = 20), (2) normal pregnant women (n = 49), (3) patients at term not in labor (n = 30), and (4) patients in spontaneous labor at term (n = 29). Umbilical cord blood was collected from term neonates with (n = 30) and without labor (n = 28). Amniotic fluid was obtained from patients in the following groups: (1) midtrimester (n = 65); (2) term not in labor (n = 22); (3) term in labor (n = 47); (4) preterm labor (PTL) with intact membranes leading to term delivery (n = 70); and (5) PTL leading to preterm delivery with IAI (n = 79) and without IAI (n = 60). CXCL13 concentrations were determined by enzyme-linked immunosorbent assay. Chorioamniotic membranes and umbilical cords were examined with immunohistochemistry. Non-parametric statistics were used for analysis.

RESULTS

(1) CXCL13 was present in 100% of serum and cord blood samples, and 99% of AF samples (339/343). (2) Serum CXCL13 concentration was significantly higher in pregnant women when compared to non-pregnant women (median 313.3 pg/mL (interquartile range (IQR) 197.2-646.9) vs. 40.5 pg/mL (IQR 29.5-93.5), respectively; p < 0.001). (3) Serum CXCL13 concentration decreased with advancing gestational age (Spearman's Rho = -0.424; p < 0.001). (4) There were no significant differences in the median serum CXCL13 concentration between women at term with and without labor (371.6 pg/mL (IQR 194.3-614.3) vs. 235.1 pg/mL (IQR 182.8-354.7), respectively; p = 0.6). (5) The concentration of CXCL13 in AF did not change with gestational age (p = 0.1). (6) Patients with PTL and delivery with IAI had a significantly higher median concentration of CXCL13 than those without IAI (median 513.2 pg/mL (IQR 199.7-2505.5) vs. 137.3 pg/mL (IQR 96.7-209.6), respectively; p < 0.001) and those who delivered at term (133.7 pg/mL (IQR 97.8-174.8); p < 0.001). (7) Spontaneous labor did not result in a change in the median AF concentration of CXCL13 (labor: 86.9 pg/mL (IQR 55.6-152.0) vs. no labor: 77.8 pg/mL (IQR 68.0-98.0); p = 0.8). (8) CXCL13 was immunolocalized to macrophages in fetal membranes and umbilical vein.

CONCLUSIONS

(1) We report for the first time the presence of CXCL13 in AF. (2) AF CXCL13 concentrations are dramatically increased in IAI. (3) Unlike other chemokines, AF and serum CXCL13 concentrations did not change with spontaneous parturition.

Altered expression of the receptor-ligand pair CXCR5/CXCL13 in B cells during chronic HIV-1 infection

HIV-1 infection is associated with B-cell abnormalities, such as hypergammaglobulinemia, poor immunization responses, and loss of serologic memory. To determine whether altered expression of chemokine receptors and their ligands may play a role in B-cell dysfunctions during HIV-1 infection, the expression of CXC chemokine receptor 4 (CXCR4), CXCR5, and CC chemokine receptor 7 (CCR7) and their respective ligands on CD19(+) B cells were examined in HIV-1-infected patients and controls. We report a decreased CXCR5 expression on B cells from patients (P < .05), a phenomenon associated with a low CD4 T-cell count (< 350 cells/microL). Interestingly, an increased expression of CXC chemokine ligand 13 (CXCL13), the ligand for CXCR5, was found in peripheral B cells from HIV-1-infected patients. Moreover, on B-cell activation in vitro, CXCL13 was secreted in culture. CXCL13(+) B cells were also found in the lymph nodes of HIV-1-infected patients, but not in control tissue. B-cell migration toward CXCL13, CXCL12, and CC chemokine ligand 21 (CCL21), ligands for CXCR5, CXCR4, and CCR7 was also evaluated. In patients with a low CD4 T-cell count, migration toward all ligands was increased. Our findings indicate that altered expression of the chemokine receptor-ligand pair, CXCR5/CXCL13, may participate in the establishment of B-cell dysfunctions during HIV-1 infection.

Lymphoid chemokines in chronic neuroinflammation

Lymphoid chemokines play an essential role in the establishment and maintenance of lymphoid tissue microarchitecture and have been implicated in the formation of tertiary (or ectopic) lymphoid tissue in chronic inflammatory conditions. Here, we review recent advances in lymphoid chemokine research in central nervous system inflammation, focusing on multiple sclerosis and the animal model experimental autoimmune encephalomyelitis. We also highlight how the study of lymphoid chemokines, particularly CXCL13, has led to the identification of intrameningeal B-cell follicles in the multiple sclerosis brain paving the way to the discovery that these abnormal structures are highly enriched in Epstein–Barr virus-infected B cells and plasma cells.