Cytokine reporter mice: the special case of IL-10

Inflammatory pathways of Toxoplasmagondii infection in pregnancy

Toxoplasma gondii (T. gondii), an obligate intracellular parasite, is considered as an opportunistic infection and causes toxoplasmosis in humans and animals. Congenital toxoplasmosis can influence pregnancy and cause mild to severe consequences for the fetal and neonatal. During early T. gondii infection, neutrophils as the most abundant white blood cells provide a front line of defense mechanism against infection. The activated dendritic cells are then responsible for initiating an inflammatory response via T-helper 1 (Th1) cells. As part of its robust immune response, the infected host cells produce interferon (IFN-γ). IFN-γ inhibits T. gondii replication and promotes its transformation from an active form to tissue cysts. Although anti- T. gondii antibodies play an important role in infection control, T-helper 2 (Th2) immune response, can facilitate the growth and proliferation of T. gondii in the host cell. In pregnant women infected with T. gondii, the expression of cytokines may vary and in response diverse outcomes are expected. Cytokine profiles serve as valuable indicators for estimating the patho-immunological effects of T. gondii infection. This demonstrates the intricate relationship between pro-inflammatory and anti-inflammatory cytokines, as well as their influence on the various pregnancy outcomes in T. gondii infection.

CD169+ macrophage intrinsic IL-10 production regulates immune homeostasis during sepsis

Macrophages facilitate critical functions in regulating pathogen clearance and immune homeostasis in tissues. The remarkable functional diversity exhibited by macrophage subsets is dependent on tissue environment and the nature of the pathological insult. Our current knowledge of the mechanisms that regulate the multifaceted counter-inflammatory responses mediated by macrophages remains incomplete. Here, we report that CD169+ macrophage subsets are necessary for protection under excessive inflammatory conditions. We show that in the absence of these macrophages, even under mild septic conditions, mice fail to survive and exhibit increased production of inflammatory cytokines. Mechanistically, CD169+ macrophages control inflammatory responses via interleukin-10 (IL-10), as CD169+ macrophage-specific deletion of IL-10 was lethal during septic conditions, and recombinant IL-10 treatment reduced lipopolysaccharide (LPS)-induced lethality in mice lacking CD169+ macrophages. Collectively, our findings show a pivotal homeostatic role for CD169+ macrophages and suggest they may serve as an important target for therapy under damaging inflammatory conditions.

Kaurenoic acid nanocarriers regulates cytokine production and inhibit breast cancer cell migration

Breast cancer is the type of cancer with the highest incidence in women around the world. Noteworthy, the triple-negative subtype affects 20% of the patients while presenting the highest death rate among subtypes. This is due to its aggressive phenotype and the capability of invading other tissues. In general, tumor-associated macrophages (TAM) and other immune cells, are responsible for maintaining a favorable tumor microenvironment for inflammation and metastasis by secreting several mediators such as pro-inflammatory cytokines IL-1β, IL-6, and TNF-α, chemokines like CCL2, and other proteins, as metalloproteinases of matrix (MMP). On the other hand, immunomodulatory agents can interfere in the immune response of TAM and change the disease prognosis. In this work, we prepared nanostructured lipid carriers containing kaurenoic acid (NLC-KA) to evaluate the effect on cytokine production in vitro of bone marrow-derived macrophages (BMDM) and the migratory process of 4 T1 breast cancer cells. NLC-KA prepared from a blend of natural lipids was shown to have approximately 90 nm in diameter with low polydispersity index. To test the effect on cytokine production in vitro in NLC-KA treated BMDM, ELISA assay was performed and pro-inflammatory cytokines IL-1β, IL-6, and TNF-α were quantified. The formulation reduced the secretion of IL-1β and TNF-α cytokines while presenting no hemolytic activity. Noteworthy, an anti-migratory effect in 4 T1 breast cancer cells treated with NLC-KA was observed in scratch assays. Further, MMP9 and CCL2 gene expressions in both BMDM and 4 T1 treated cells confirmed that the mechanism of inhibition of migration is related to the blockade of this pathway by KA. Finally, cell invasion assays confirmed that NLC-KA treatment resulted in less invasiveness of 4 T1 cells than control, and it is independent of CCL2 stimulus or BMDM direct stimulus. Ultimately, NLC-KA was able to regulate the cytokine production in vitro and reduce the migration of 4 T1 breast cancer cells by decreasing MMP9 gene expression.

B cell-mediated regulatory mechanisms control tumor-promoting intestinal inflammation

Mechanisms underlying tumor-promoting inflammatory processes in colitis-associated colorectal cancer (CAC) remain largely elusive. Here, we provide genetic evidence for distinct B cell-mediated immunoregulatory mechanisms that protect from chronic colitis versus CAC. We demonstrate an inherent capacity of interleukin-10 (IL-10)-producing B cells to differentiate into immunoglobulin A (IgA) plasma cells (PCs) upon Toll-like receptor (TLR) activation. Our data show that B cell-derived IL-10 is essential to limit pathogenic T helper type 1 (Th1)/Th17 T cell responses during chronic colitis, while IgA PCs derived from IL-10⁺ B cells are being implicated in restraining tumorigenesis during CAC. Formation of a tumor-protective intestinal environment was associated with clonal expansion of specific types of colonic IgA PCs and development of an altered microbiota that attenuated CAC. We thus propose that regulatory B cell-mediated immunomodulation entails temporal release of IL-10, which is superseded by the generation of specific IgA affecting the microbial community, thereby controlling chronic inflammation and tumorigenesis in a distinctive but interrelated manner.

N-(3-oxododecanoyl)-homoserine lactone disrupts intestinal barrier and induces systemic inflammation through perturbing gut microbiome in mice

As a quorum sensing signal molecule, N-(3-oxododecanoyl)-homoserine lactone (3OC12) regulate the population behavior of microorganisms. Many studies have proved that 3OC12 harm the physiological function of host intestinal epithelial cells. However, the detrimental effects of 3OC12 on intestinal health need verification in animals. Besides, the role of gut microbiome in 3OC12-induced intestinal damage also needs further understanding. In our study, 3OC12 was first administered to specific pathogen-free (SPF) mice, then the fecal microbiome of SPF mice was transplanted into germ-free (GF) mice to reveal the effects of 3OC12 on intestinal health and regulatory mechanisms of the intestinal microbiome. 3OC12 treatment significantly decreased body weight, shortened colonic length, disrupted the morphology of the colonic epithelium and increased the histopathological score of the colon in SPF mice. The levels of diamine peroxidase, d-lactate, TNF-α, IL-1β, and IL-8 were found to be significantly elevated in the serum of 3OC12 mice, while the levels of IL-10 were significantly reduced. Besides, the fecal microbial community of mice was also altered in the 3OC12-treated SPF mice. The results of fecal microbial transplantation (FMT) experiment showed that the phenotypes in SPF mice were almost reproduced in GF mice, manifested by body weight loss, colon damage and changed in serum chemical markers. More importantly, a joint analysis of fecal microbes in SPF and GF mice revealed Feature14_Elizabethkingia spp. was common differential bacteria in the feces of two kinds of mice treated with and without FMT. Our results demonstrated that 3OC12 challenge led to systemic inflammation and body weight loss in mice by disrupting intestinal barrier function, in which gut microbiome played a key role. These findings increased our understanding of the mechanism of intestinal injury caused by 3CO12, providing new ideas for the prevention and therapy of diseases caused by bacterial infection from the perspective of intestinal microbiome.

The IL-10GFP (VeRT-X) mouse strain is not suitable for the detection of IL-10 production by granulocytes during lung inflammation

The clear and unequivocal identification of immune effector functions is essential to understand immune responses. The cytokine IL-10 is a critical immune regulator and was shown, for example, to limit pathology during various lung diseases. However, the clear identification of IL-10-producing cells is challenging and, therefore, reporter mouse lines were developed to facilitate their detection. Several such reporter lines utilize GFP, including the IL-10^GFP (VeRT-X) reporter strain studied here. In line with previous reports, we found that this IL-10^GFP line faithfully reports on the IL-10 production of lymphoid cells. However, we show that the IL-10^GFP reporter is not suitable to analyse IL-10 production of myeloid cells during inflammation. During inflammation, the autofluorescence of myeloid cells increased to an extent that entirely masked the IL-10-specific GFP-signal. Our data illustrate a general and important technical caveat using GFP-reporter lines for the analysis of myeloid cells and suggest that previous reports on effector functions of myeloid cells using such GFP-based reporters might require re-evaluation.

Evaluating cytokine production by flow cytometry using brefeldin A in mice

Characterizing cytokine production in situ is important for properly understanding immunologic responses. Cytokine reporter mice are limited by the need to cross markers into various knockout backgrounds and by availability of reporters of interest. To overcome this, we utilize injection of brefeldin A into mice to enable flow cytometric analysis of in situ cytokine production during a bacterial infection. While we evaluate IFN-γ production during Burkholderia thailandensis infection, this protocol can be applied to other cytokines and other mouse models. For complete details on the use and execution of this protocol, please refer to Kovacs et al. (2020) and Liu and Whitton (2005).

The identification, development and therapeutic potential of IL-10-producing regulatory B cells in multiple sclerosis

Regulatory B cells are a rare B-cell subset widely known to exert their immunosuppressive function via the production of interleukin-10 (IL-10) and other mechanisms. B10 cells are a special subset of regulatory B cells with immunoregulatory function that is fully attributed to IL-10. Their unique roles in the animal model of multiple sclerosis (MS) have been described, as well as their relevance in MS patients. This review specifically focuses on the identification and development of B10 cells, the signals that promote IL-10 production in B cells, the roles of B10 cells in MS, and the potential and major challenges of the application of B10-based therapies for MS.

Purification of Murine and Human IL-10-Producing B Cells from Different Anatomical Compartments

IL-10 is the best known and most studied anti-inflammatory cytokine and, in the last 20 years, it has acquired even greater fame as it has been associated with the regulatory phenotype of B cells. Indeed, although great efforts have been made to find a unique marker, to date IL-10 remains the main way to follow both murine and human regulatory B cells, hence the need of precise and reproducible methods to identify and purify IL-10-producing B cells for both functional and molecular downstream assays. In this chapter, we present our protocols to isolate these cells from the murine spleen and peritoneum and from human peripheral blood. Since the production of IL-10 by B cells is not only a weapon to counteract the adverse effect of pro-inflammatory cytokines but also a response to cellular activation, we focused on those B cells that are prone to IL-10 production and detectable following a short-term stimulation with phorbol-12-myristate-13-acetate, ionomycin, and lipopolysaccharide (murine system) or CpG (human system).

B-Cell Commitment to IL-10 Production: The VertX Il10egfp Mouse

Although the inflammatory cytokine IL-10 is pivotal in regulatory B-cell function, detecting IL-10-producing B cells by intracellular IL-10 staining requires multiple steps and tedious preparation. In contrast, the Il10-eGFP reporter mouse model (VertX), generated in 2009, allows easier and quicker detection of IL-10-producing B cells with the possibility of sorting viable cells without membrane permeabilization and ex vivo activation. Even though detecting IL-10⁺ cells is simpler, several nuances are important. For example, methanol-containing buffers delete GFP signal, while long-term fixation can maintain GFP intensity but decreases other intracellular signals (FOXP3, etc.). Here, we provide optimized and improved protocols for GFP detection in intestinal B cells and isolation techniques of lamina propria, spleen, mesenteric lymph node, peritoneum, and blood cells from VertX mice.

IL-10-producing NK cells exacerbate sublethal Streptococcus pneumoniae infection in the lung

Lung inflammation is tightly controlled to balance microbial clearance with the tissue damage that accompanies this response. Bacterial pathogens including Streptococcus pneumoniae (S. pneumoniae) modulate immune regulation by promoting secretion of the anti-inflammatory cytokine IL-10. The important cellular sources of IL-10 that impact protection against different bacterial infections are not well characterized. We find that S. pneumoniaeactivates IL-10 secretion from natural killer (NK) cells in the lung, which restrict host protection in a mouse model of sublethal infection. Direct transfer of wild-type NK cells into the lungs of IL-10-deficient mice drives bacterial expansion, identifying NK cells as a critical source of IL-10 promoting S. pneumoniae infection. The S. pneumoniae virulence protein Spr1875 was found to elicit NK cell IL-10 production in purified cells and in the lungs of live animals. These findings reveal therapeutic targets to combat bacterial-driven immune regulation in the lung.

Screening for new macrophage therapeutics

Myeloid derived macrophages play a key role in many human diseases, and their therapeutic modulation via pharmacological means is receiving considerable attention. Of particular interest is the fact that these cells are i) dynamic phenotypes well suited to therapeutic manipulation and ii) phagocytic, allowing them to be efficiently targeted with nanoformulations. However, it is important to consider that macrophages represent heterogeneous populations of subtypes with often competing biological behaviors and functions. In order to develop next generation therapeutics, it is therefore essential to screen for biological effects through a combination of in vitro and in vivo assays. Here, we review the state-of-the-art techniques, including both cell based screens and in vivo imaging tools that have been developed for assessment of macrophage phenotype. We conclude with a forward-looking perspective on the growing need for noninvasive macrophage assessment and laboratory assays to be put into clinical practice and the potential broader impact of myeloid-targeted therapeutics.

Regulator Versus Effector Paradigm: Interleukin-10 as Indicator of the Switching Response

The interleukin-10 (IL-10) is generally considered as the most important cytokine with anti-inflammatory properties and one of the key cytokines preventing inflammation-mediated tissue damage. In this respect, IL-10 producing cells play a crucial role in the outcome of infections, allergy, autoimmune reactions, tumor development, and transplant tolerance. Based on recent findings with regard to the mentioned clinical conditions, this review attempts to shed some light on the IL-10 functions, considering this cytokine as inherent inducer of the switching immunity. While acute infections and vaccinations are associated by IL-10 enhanced during few weeks, chronic parasitoses, tumor diseases, allergen-specific immunotherapy, transplants, and use of immune-suppressor drugs show an increased IL-10 level along months or years. With regard to autoimmune pathologies, the IL-10 increase is prevalently observed during early stages, whereas the successive stages are characterized by reaching of immune equilibrium independently to disease's activity. Together, these findings indicate that IL-10 is mainly produced during transient immune conditions and the persistent IL-10-related effect is the indication/prediction (and maybe effectuation) of the switching immunity. Actual knowledge emphasizes that any manipulation of the IL-10 response for treatment purposes should be considered very cautiously due to its potential hazards to the immune system. Probably, the IL-10 as potential switcher of immunity response should be used in association with co-stimulatory immune effectors that are necessary to determine the appropriate deviation during treatment of respective pathologies. Hopefully, further findings would open new avenues to study the biology of this "master switch" cytokine and its therapeutic potential.

Local Microenvironment Controls the Compartmentalization of NK Cell Responses during Systemic Inflammation in Mice

Systemic inflammatory response syndrome is a whole-body reaction to a triggering insult that often results in life-threatening illness. Contributing to the development of this inflammatory cascade are numerous cellular partners, among which NK cells were shown to play a key role. Accumulating evidence points to organ-specific properties of systemic inflammation and NK cells. However, little is known about compartment-specific activation of NK cells during systemic inflammatory response syndrome or the relative contribution of NK cell-intrinsic properties and microenvironmental cues. In this study, we undertook a sequential characterization of NK responses in the spleen, lungs, bone marrow, peritoneum, and blood using a mouse model of endotoxemia. We report that, despite similar systemic dynamics of NK cell responses, expression of activation markers (CD69 and CD25) and effector molecules (IFN-γ, granzyme B, and IL-10) display organ-specific thresholds of maximum activation. Using adoptive transfers of spleen and lung NK cells, we found that these cells have the capacity to quickly adapt to a new environment and adjust their response levels to that of resident NK cells. This functional adaptation occurs without significant alterations in phenotype and independently of subpopulation-specific trafficking. Thus, using a dynamic in vivo-transfer system, to our knowledge our study is the first to report the compartmentalization of NK cells responses during systemic inflammation and to show that NK cell-intrinsic properties and microenvironmental cues are involved in this process, in a sequential manner.

Opposing roles of IL-10 in acute bacterial infection

Interleukin-10 (IL-10) is recognized as an anti-inflammatory cytokine that downmodulates inflammatory immune responses at multiple levels. In innate cells, production of this cytokine is usually triggered after pathogen recognition receptor (PRR) engagement by pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patters (DAMPs), as well as by other soluble factors. Importantly, IL-10 is frequently secreted during acute bacterial infections and has been described to play a key role in infection resolution, although its effects can significantly vary depending on the infecting bacterium. While the production of IL-10 might favor host survival in some cases, it may also result harmful for the host in other circumstances, as it can prevent appropriate bacterial clearance. In this review we discuss the role of IL-10 in bacterial clearance and propose that this cytokine is required to recover from infection caused by extracellular or highly pro-inflammatory bacteria. Altogether, we propose that IL-10 drives excessive suppression of the immune response upon infection with intracellular bacteria or in non-inflammatory bacterial infections, which ultimately favors bacterial persistence and dissemination within the host. Thus, the nature of the bacterium causing infection is an important factor that needs to be taken into account when considering new immunotherapies that consist on the modulation of inflammation, such as IL-10. Indeed, induction of this cytokine may significantly improve the host's immune response to certain bacteria when antibiotics are not completely effective.

Bacterial Manipulation of NK Cell Regulatory Activity Increases Susceptibility to Listeria monocytogenes Infection

Natural killer (NK) cells produce interferon (IFN)-γ and thus have been suggested to promote type I immunity during bacterial infections. Yet, Listeria monocytogenes (Lm) and some other pathogens encode proteins that cause increased NK cell activation. Here, we show that stimulation of NK cell activation increases susceptibility during Lm infection despite and independent from robust NK cell production of IFNγ. The increased susceptibility correlated with IL-10 production by responding NK cells. NK cells produced IL-10 as their IFNγ production waned and the Lm virulence protein p60 promoted induction of IL-10 production by mouse and human NK cells. NK cells consequently exerted regulatory effects to suppress accumulation and activation of inflammatory myeloid cells. Our results reveal new dimensions of the role played by NK cells during Lm infection and demonstrate the ability of this bacterial pathogen to exploit the induction of regulatory NK cell activity to increase host susceptibility.

Natural killer (NK) cells are an innate immune cell population known to promote antiviral immunity through cytolysis and production of cytokines. Yet, some pathogens encode proteins that cause increased NK cell activation. Here, using a model of systemic infection by the bacterial pathogen Listeria monocytogenes (Lm), we show that NK cell activation increases host susceptibility. Activated NK cells increased bacterial burdens in infected tissues despite their early production of the pro-inflammatory cytokine IFNγ. We found that the ability of NK cells to exacerbate infection was independent from their production of IFNγ and instead due to subsequent production of the anti-inflammatory cytokine IL-10. A single bacterial protein, p60, was sufficient to elicit NK cell production of both early IFNγ and delayed IL-10. IL-10-production by NK cells has been shown to occur in other systems, but our studies are first to show how this “regulatory” response impacts the course of a bacterial infection. We found that IL-10 producing NK cells suppress accumulation and activation of inflammatory myeloid cells. Our studies suggest that the exploitation of NK cell regulatory activity provides selective pressure for the evolution of pathogen proteins that promote NK cell activation.

Locally Produced IL-10 Limits Cutaneous Vaccinia Virus Spread

Skin infection with the poxvirus vaccinia (VV) elicits a powerful, inflammatory cellular response that clears virus infection in a coordinated, spatially organized manner. Given the high concentration of pro-inflammatory effectors at areas of viral infection, it is unclear how tissue pathology is limited while virus-infected cells are being eliminated. To better understand the spatial dynamics of the anti-inflammatory response to a cutaneous viral infection, we first screened cytokine mRNA expression levels after epicutaneous (ec.) VV infection and found a large increase the anti-inflammatory cytokine IL-10. Ex vivo analyses revealed that T cells in the skin were the primary IL-10-producing cells. To understand the distribution of IL-10-producing T cells in vivo, we performed multiphoton intravital microscopy (MPM) of VV-infected mice, assessing the location and dynamic behavior of IL-10 producing cells. Although virus-specific T cells were distributed throughout areas of the inflamed skin lacking overt virus-infection, IL-10+ cells closely associated with large keratinocytic foci of virus replication where they exhibited similar motility patterns to bulk antigen-specific CD8+ T cells. Paradoxically, neutralizing secreted IL-10 in vivo with an anti-IL-10 antibody increased viral lesion size and viral replication. Additional analyses demonstrated that IL-10 antibody administration decreased recruitment of CCR2+ inflammatory monocytes, which were important for reducing viral burden in the infected skin. Based upon these findings, we conclude that spatially concentrated IL-10 production limits cutaneous viral replication and dissemination, likely through modulation of the innate immune repertoire at the site of viral growth.

Amyloid fibrils activate B-1a lymphocytes to ameliorate inflammatory brain disease

Amyloid fibrils composed of peptides as short as six amino acids are therapeutic in experimental autoimmune encephalomyelitis (EAE), reducing paralysis and inflammation, while inducing several pathways of immune suppression. Intraperitoneal injection of fibrils selectively activates B-1a lymphocytes and two populations of resident macrophages (MΦs), increasing IL-10 production, and triggering their exodus from the peritoneum. The importance of IL-10-producing B-1a cells in this effective therapy was established in loss-of-function experiments where neither B-cell-deficient (μMT) nor IL10(-/-) mice with EAE responded to the fibrils. In gain-of-function experiments, B-1a cells, adoptively transferred to μMT mice with EAE, restored their therapeutic efficacy when Amylin 28-33 was administered. Stimulation of adoptively transferred bioluminescent MΦs and B-1a cells by amyloid fibrils resulted in rapid (within 60 min of injection) trafficking of both cell types to draining lymph nodes. Analysis of gene expression indicated that the fibrils activated the CD40/B-cell receptor pathway in B-1a cells and induced a set of immune-suppressive cell-surface proteins, including BTLA, IRF4, and Siglec G. Collectively, these data indicate that the fibrils activate B-1a cells and F4/80(+) MΦs, resulting in their migration to the lymph nodes, where IL-10 and cell-surface receptors associated with immune-suppression limit antigen presentation and T-cell activation. These mechanisms culminate in reduction of paralytic signs of EAE.

Fluorescence tagging and inducible depletion of PD-L2-expressing B-1 B cells in vivo

L2pB1 cells are a subpopulation of B-1a B cells that express programmed death ligand 2 (PD-L2) as their unique cell surface marker. In mice, about 50% of peritoneal B-1a cells are L2pB1 cells. The remaining B-1a cells are L2nB1 (PD-L2(-) ) B-1a cells. L2pB1 cells differ from L2nB1 cells in their immunoglobulin repertoire, expression of interleukin 10, and their capacity to phagocytose phosphatidylcholine. The physiological roles of L2pB1 cells have not been investigated owing to the lack of an animal model that allows for specific depletion of L2pB1 cells. Here, we report a mouse model that enables specific tracking and inducible depletion of L2pB1 cells in vivo. Our data show that depletion of L2pB1 cells significantly reduces serum anti-phosphorylcholine (PC) IgM levels and IL-10 expression in the peritoneal cavity. This animal model provides a tool for the study of the immune regulatory functions of L2pB1 cells in health and disease.

B10 cells: a functionally defined regulatory B cell subset

B cells are commonly thought to enhance inflammatory immune responses. However, specific regulatory B cell subsets recently were identified that downregulate adaptive and innate immunity, inflammation, and autoimmunity through diverse molecular mechanisms. In both mice and humans, a rare, but specific, subset of regulatory B cells is functionally characterized by its capacity to produce IL-10, a potent inhibitory cytokine. For clarity, this regulatory B cell subset has been labeled as B10 cells, because their ability to downregulate immune responses and inflammatory disease is fully attributable to IL-10, and their absence or loss exacerbates disease symptoms in mouse models. This review preferentially focuses on what is known about mouse B10 cell development, phenotype, and effector function, as well as on mechanistic studies that demonstrated their functional importance during inflammation, autoimmune disease, and immune responses.

B10 cell regulation of health and disease

While B cells are traditionally regarded as promoters of the immune response via antibody secretion and pro-inflammatory cytokine production, recent studies have also confirmed an important role for B-cell-mediated negative regulation of immunity. Tremendous advances in the characterization of the mechanisms by which regulatory B cells function has led to the identification of a novel subset of regulatory B cells known as B10 cells, which regulate immune responses through the production of the anti-inflammatory cytokine interleukin-10 (IL-10). B10 cells are best defined by their functional ability to produce IL-10, as they are not confined to any particular phenotypic subset. B10 cells function in an antigen-specific manner that requires cognate interactions with T cells in vivo to regulate immune responses and have been demonstrated to be potent regulators of allergic and autoimmune disease, cancer, infection, and transplant rejection. Importantly, the recent discovery of human B10 cells has accelerated this field to the forefront of clinical research where the possibility of harnessing the regulatory potential of B10 cells for treatment of aberrant immune responses and diseases may become feasible.

The generation of regulatory B cells by helminth parasites

The activation of B cells by pathogens to elicit antibody production is a central facet of immunity. Pathogens also evoke the expansion of B cells that can function in the regulation of immunity. Different pathogens have been described with the capacity to drive such regulatory B (Breg) cells. One group of pathogens, parasitic helminths, has been used experimentally to identify and explore immunological mechanisms of Breg cells. Several species of helminths have demonstrated the capacity to expand Breg cell populations in mice, while the presence of Breg cells in humans infected with certain helminths has also been identified. Herein, we outline how the helminth Schistosoma mansoni can expand Breg cellular responses in vitro. We describe the establishment of a laboratory-based S. mansoni life cycle and methodology for detecting Breg cells via flow cytometry.

Regulatory B cells in mouse models of intestinal inflammation

Inflammatory bowel disease (IBD) is a chronic intestinal inflammatory condition with increasing incidence and prevalence around the world. Although B cells had generally been believed to play a pathogenic role in IBD due to the production of autoantibodies, a growing body of evidence from mouse models suggests the coexistence of pathogenic B cells and regulatory B cells, termed Breg, in this disorder. Since some unique techniques are required to closely study the Breg in gut-associated lymphoid tissues (GALT), we herein describe how to induce colitis in mice and how to analyze the phenotype and function of GALT-specific Breg.

Glucose metabolism is altered after loss of L cells and α-cells but not influenced by loss of K cells

The enteroendocrine K and L cells are responsible for secretion of glucose-dependent insulinotropic polypeptide (GIP) and glucagon like-peptide 1 (GLP-1), whereas pancreatic α-cells are responsible for secretion of glucagon. In rodents and humans, dysregulation of the secretion of GIP, GLP-1, and glucagon is associated with impaired regulation of metabolism. This study evaluates the consequences of acute removal of Gip- or Gcg-expressing cells on glucose metabolism. Generation of the two diphtheria toxin receptor cellular knockout mice, TgN(GIP.DTR) and TgN(GCG.DTR), allowed us to study effects of acute ablation of K and L cells and α-cells. Diphtheria toxin administration reduced the expression of Gip and content of GIP in the proximal jejunum in TgN(GIP.DTR) and expression of Gcg and content of proglucagon-derived peptides in both proximal jejunum and terminal ileum as well as content of glucagon in pancreas in TgN(GCG.DTR) compared with wild-type mice. GIP response to oral glucose was attenuated following K cell loss, but oral and intraperitoneal glucose tolerances were unaffected. Intraperitoneal glucose tolerance was impaired following combined L cell and α-cell loss and normal following α-cell loss. Oral glucose tolerance was improved following L cell and α-cell loss and supernormal following α-cell loss. We present two mouse models that allow studies of the effects of K cell or L cell and α-cell loss as well as isolated α-cell loss. Our findings show that intraperitoneal glucose tolerance is dependent on an intact L cell mass and underscore the diabetogenic effects of α-cell signaling. Furthermore, the results suggest that K cells are less involved in acute regulation of mouse glucose metabolism than L cells and α-cells.

Gene targeting in mice: a review

The ability to introduce DNA sequences (e.g., genes) of interest into the germline genome has rendered the mouse a powerful and indispensable experimental model in fundamental and medical research. The DNA sequences can be integrated into the genome randomly or into a specific locus by homologous recombination, in order to: (1) delete or insert mutations into genes of interest to determine their function, (2) introduce human genes into the genome of mice to generate animal models enabling study of human-specific genes and diseases, e.g., mice susceptible to infections by human-specific pathogens of interest, (3) introduce individual genes or genomes of pathogens (such as viruses) in order to examine the contributions of such genes to the pathogenesis of the parent pathogens, (4) and last but not least introduce reporter genes that allow monitoring in vivo or ex vivo the expression of genes of interest. Furthermore, the use of recombination systems, such as Cre/loxP or FRT/FLP, enables conditional induction or suppression of gene expression of interest in a restricted period of mouse's lifetime, in a particular cell type, or in a specific tissue. In this review, we will give an updated summary of the gene targeting technology and discuss some important considerations in the design of gene-targeted mice.

Transcriptional regulation of the anti-inflammatory cytokine IL-10 in acquired immune cells

Although the major role of the immune response is host defense from a wide range of potentially pathogenic microorganisms, excess immune responses can result in severe host damage. The host thus requires anti-inflammatory mechanisms to prevent reactivity to self. Interleukin-10 (IL-10) is a cytokine with broad anti-inflammatory properties involved in the pathogenesis of various diseases. IL-10 was originally described as a T helper (T_H2) derived cytokine, but further studies indicated that IL-10 is expressed not only by many cells of the adaptive immune system, including T and B cells, but also by the innate immune cells, including dendritic cells (DCs), macrophages, mast cells, and natural killer (NK) cells. In addition, IL-10 can be induced in T_H1 and T_H17 cells by chronic inflammation as a system of feedback regulation. In this review, we focus on the molecular mechanisms underlying IL10 gene expression in adaptive immune cells and summarize the recent progresses in epigenetic and transcriptional regulation of the IL10 gene. Understanding the transcriptional regulatory events may help in the development of new strategies to control inflammatory diseases.