Efficient targeting of the IL-4 gene in a BALB/c embryonic stem cell line

Interleukin 4 deficiency limits the development of a lupus-like disease in mice triggered by phospholipids in a non-bilayer arrangement

Non-bilayer phospholipids arrangements (NPAs) are transient molecular associations different from lipid bilayers. When they become stable, they can trigger a disease in mice resembling human lupus, which is mainly characterized by the production of anti-NPA IgG antibodies. NPAs are stabilized on liposomes or cell bilayers by the drugs procainamide or chlorpromazine, which produce drug-induced lupus in humans. Here, we evaluated the participation of the T_H 2 response, through its hallmark cytokine IL-4, on the development of the lupus-like disease in mice. Wild-type or IL-4 knockout BALB/c mice received liposomes bearing drug-induced NPAs, the drugs alone, or an anti-NPA monoclonal antibody (H308) to induce the lupus-like disease (the last two procedures stabilize NPAs on mice cells). IL-4 KO mice showed minor disease manifestations, compared to wild-type mice, with decreased production of anti-NPA IgG antibodies, no anti-cardiolipin, anti-histones and anticoagulant antibodies, and no kidney or skin lesions. In these mice, H308 was the only inducer of anti-NPA IgG antibodies. These findings indicate that IL-4 has a central role in the development of the murine lupus-like disease induced by NPA stabilization.

Modulation of the humoral immune response by constitutively active STAT6 expression in murine B cells

The transcription factor STAT6 regulates gene expression in response to IL-4 and IL-13. To further investigate how activated STAT6 modulates B cells development and function in vivo, we characterized mice that express a constitutively active version specifically in B cells. CD19Cre_STAT6vt mice show spontaneous phosphorylation and nuclear translocation of STAT6 in B cells. About 80 genes were more than twofold up- or downregulated in splenic B cells from CD19Cre_STAT6vt as compared to control mice. B cell development, tissue localization, and populations of follicular and marginal zone B cells, B1 B cells, GC B cells, and plasma cells (PCs) appeared to be normal. However, the number of IgE⁺ and IgG1⁺ GC B cells and PCs as well as serum IgE and IgG1 levels were increased in CD19Cre_STAT6vt mice. Infection with Lymphocytic choriomeningitis virus associated with high levels of TNF and IFN-γ did not prevent the development of a significantly increased IgE and IgG1 response against the virus in CD19Cre_STAT6vt mice. These results suggest that prolonged STAT6 activation during chronic allergic inflammation may result in IgE responses during subsequent viral or bacterial infection that could further stimulate mast cell activation even in the absence of the initial allergic response.

Selective expression of constitutively activated STAT6 in intestinal epithelial cells promotes differentiation of secretory cells and protection against helminths

Intestinal epithelial cells (IECs) constitute an important barrier between host and pathogen. Immune mechanisms that provide protection against gastrointestinal helminths often require IL-4Rα-induced activation of STAT6-regulated genes in IECs. However, it is not known whether STAT6 activation in IECs enhances protective immunity against helminths. Furthermore, the regulation of proliferation and differentiation processes of the intestinal epithelium by IEC-intrinsic STAT6 signaling remains unclear. To address these questions, we generated mice with specific expression of a constitutively active version of STAT6 in IECs. These VillinCre_STAT6vt mice show accumulation of secretory IECs, increased proliferation of IECs and lengthening of the small intestine. They rapidly expelled Nippostrongylus brasiliensis worms even in the absence of T cells. Furthermore, primary infection with Heligmosomoides polygyrus resulted in larval trapping in the submucosa and the fecundity of adult worms was severely impaired. Our results reveal an important IEC-intrinsic role of STAT6-regulated genes for intestinal homeostasis and protective immunity against helminths.

Conditional Selection of B Cells in Mice With an Inducible B Cell Development

Developing B cells undergo defined maturation steps in the bone marrow and in the spleen. The timing and the factors that control these differentiation steps are not fully understood. By targeting the B cell-restricted mb-1 locus to generate an mb-1 allele that expresses a tamoxifen inducible Cre and another allele in which mb-1 expression can be controlled by Cre, we have established a mouse model with an inducible B cell compartment. With these mice, we studied in detail the kinetics of B cell development and the consequence of BCR activation at a defined B cell maturation stage. Contrary to expectations, transitional 1-B cells exposed to anti-IgM reagents in vivo did not die but instead developed into transitional 2 (T2)-B cells with upregulated Bcl-2 expression. We show, however, that these T2-B cells had an increased dependency on the B cell survival factor B cell activating factor when compared to non-stimulated B cells. Overall, our findings indicate that the inducible mb-1 mouse strain represents a useful model, which allows studying the signals that control the selection of B cells in greater detail.

Eosinophil-derived IL-4 drives progression of myocarditis to inflammatory dilated cardiomyopathy

Diny et al. report a pathogenic role for eosinophils in autoimmune myocarditis and dilated cardiomyopathy. Eosinophils are required for progression of myocarditis to dilated cardiomyopathy and drive severe disease when present in large numbers. Activated cardiac eosinophils mediate this process through IL-4.

Inflammatory dilated cardiomyopathy (DCMi) is a major cause of heart failure in children and young adults. DCMi develops in up to 30% of myocarditis patients, but the mechanisms involved in disease progression are poorly understood. Patients with eosinophilia frequently develop cardiomyopathies. In this study, we used the experimental autoimmune myocarditis (EAM) model to determine the role of eosinophils in myocarditis and DCMi. Eosinophils were dispensable for myocarditis induction but were required for progression to DCMi. Eosinophil-deficient ΔdblGATA1 mice, in contrast to WT mice, showed no signs of heart failure by echocardiography. Induction of EAM in hypereosinophilic IL-5Tg mice resulted in eosinophilic myocarditis with severe ventricular and atrial inflammation, which progressed to severe DCMi. This was not a direct effect of IL-5, as IL-5TgΔdblGATA1 mice were protected from DCMi, whereas IL-5^−/− mice exhibited DCMi comparable with WT mice. Eosinophils drove progression to DCMi through their production of IL-4. Our experiments showed eosinophils were the major IL-4–expressing cell type in the heart during EAM, IL-4^−/− mice were protected from DCMi like ΔdblGATA1 mice, and eosinophil-specific IL-4 deletion resulted in improved heart function. In conclusion, eosinophils drive progression of myocarditis to DCMi, cause severe DCMi when present in large numbers, and mediate this process through IL-4.

Exclusive transmission of the embryonic stem cell-derived genome through the mouse germline

Gene targeting in embryonic stem (ES) cells remains best practice for introducing complex mutations into the mouse germline. One aspect in this multistep process that has not been streamlined with regard to the logistics and ethics of mouse breeding is the efficiency of germline transmission: the transmission of the ES cell‐derived genome through the germline of chimeras to their offspring. A method whereby male chimeras transmit exclusively the genome of the injected ES cells to their offspring has been developed. The new technology, referred to as goGermline, entails injecting ES cells into blastocysts produced by superovulated homozygous Tsc22d3 floxed females mated with homozygous ROSA26‐Cre males. This cross produces males that are sterile due to a complete cell‐autonomous defect in spermatogenesis. The resulting male chimeras can be sterile but when fertile, they transmit the ES cell‐derived genome to 100% of their offspring. The method was validated extensively and in two laboratories for gene‐targeted ES clones that were derived from the commonly used parental ES cell lines Bruce4, E14, and JM8A3. The complete elimination of the collateral birth of undesired, non‐ES cell‐derived offspring in goGermline technology fulfills the reduction imperative of the 3R principle of humane experimental technique with animals. genesis 54:326–333, 2016. © 2016 The Authors. Genesis Published by Wiley Periodicals, Inc.

The role of IL-33/ST2, IL-4, and eosinophils on the airway hyperresponsiveness induced by Strongyloides venezuelensis in BALB/c mice

Strongyloidiasis is a neglected chronic nematode infection, in which the control of autoinfection rate and severity of disease is dependent on type 2 immune responses. Strongyloides also causes Th2 responses in the lung of infected animals and changes in airway function, including airway hyperresponsiveness (AHR). Mechanisms of AHR during Strongyloides venezuelensis infection are not entirely known, and we investigate here the role of IL-4, eosinophils, and IL-33/ST2. AHR was evaluated in infected mice by determining changes in lung function after increasing doses of methacholine. Balb/C, but no C57Bl/6, mice developed AHR, tissue eosinophilia, and increased local IL-4 and IL-5 production. Functional changes peaked at day 4 and 7, after the larva had left the lungs. AHR was clearly dependent on IL-4 but not on eosinophils, as evaluated by experiments in IL-4 and Gata-1-deficient mice. Experiments in ST2-deficient mice showed that this pathway was not needed for induction of AHR but was necessary for the maintenance of AHR and for Th2 responses in the lung. These studies clearly show a crucial role for IL-4 in the induction of AHR following S. venezuelensis infection and for IL-33/ST2 in maintaining AHR and lung Th2 responses.

Gene Targeting Using Homologous Recombination in Embryonic Stem Cells: The Future for Behavior Genetics?

Gene targeting with homologous recombination in embryonic stem cells created a revolution in the analysis of the function of genes in behavioral brain research. The technology allowed unprecedented precision with which one could manipulate genes and study the effect of this manipulation on the central nervous system. With gene targeting, the uncertainty inherent in psychopharmacology regarding whether a particular compound would act only through a specific target was removed. Thus, gene targeting became highly popular. However, with this popularity came the realization that like other methods, gene targeting also suffered from some technical and principal problems. For example, two decades ago, issues about compensatory changes and about genetic linkage were raised. Since then, the technology developed, and its utility has been better delineated. This review will discuss the pros and cons of the technique along with these advancements from the perspective of the neuroscientist user. It will also compare and contrast methods that may represent novel alternatives to the homologous recombination based gene targeting approach, including the TALEN and the CRISPR/Cas9 systems. The goal of the review is not to provide detailed recipes, but to attempt to present a short summary of these approaches a behavioral geneticist or neuroscientist may consider for the analysis of brain function and behavior.

Structural integrity of the antigen is a determinant for the induction of T-helper type-1 immunity in mice by gene gun vaccines against E. coli beta-galactosidase

The type of immune response is critical for successful protection and typically determined by pathogen-associated danger molecules. In contrast, protein antigens are usually regarded as passive target structures. Here, we provide evidence that the structure of the antigen can profoundly influence the type of response that is elicited under else identical conditions. In mice, gene gun vaccines induce predominantly Th2-biased immune reactions against most antigens. One exception is E. coli beta-galactosidase (βGal) that induces a balanced Th1/Th2 response. Because both, the delivered material (plasmid DNA-coated gold particles) as well as the procedure (biolistic delivery to the skin surface) is the same as for other antigens we hypothesized that Th1 induction could be a function of βGal protein expressed in transfected cells. To test this we examined gene gun vaccines encoding structural or functional variants of the antigen. Employing a series of gene gun vaccines encoding individual structural domains of βGal, we found that neither of them induced IgG2a antibodies. Even disruption of the homo-tetramer association of the native protein by deletion of a few N-terminal amino acids was sufficient to abrogate IgG2a production. However, enzymatically inactive βGal with only one point mutation in the catalytic center retained the ability to induce Th1 reactions. Thus, structural but not functional integrity of the antigen must be retained for Th1 induction. βGal is not a Th1 adjuvant in the classical sense because neither were βGal-transgenic ROSA26 mice particularly Th1-biased nor did co-administration of a βGal-encoding plasmid induce IgG2a against other antigens. Despite this, gene gun vaccines elicited Th1 reactions to antigens fused to the open reading frame of βGal. We interpret these findings as evidence that different skin-borne antigens may be differentially handled by the immune system and that the three-dimensional structure of an antigen is an important determinant for this.

Facilitation of endoglin-targeting cancer therapy by development/utilization of a novel genetically engineered mouse model expressing humanized endoglin (CD105)

Endoglin (ENG) is a TGF-β coreceptor and essential for vascular development and angiogenesis. A chimeric antihuman ENG (hENG) monoclonal antibody (mAb) c-SN6j (also known as TRC105) shows promising safety and clinical efficacy features in multiple clinical trials of patients with various advanced solid tumors. Here we developed a novel genetically engineered mouse model to optimize the ENG-targeting clinical trials. We designed a new targeting vector that contains exons 4-8 of hENG gene to generate novel genetically engineered mice (GEMs) expressing functional human/mouse chimeric (humanized) ENG with desired epitopes. Genotyping of the generated mice confirmed that we generated the desired GEMs. Immunohistochemical analysis demonstrated that humanized ENG protein of the GEMs expresses epitopes defined by 7 of our 8 anti-hENG mAbs tested. Surprisingly the homozygous GEMs develop normally and are healthy. Established breast and colon tumors as well as metastasis and tumor microvessels in the GEMs were effectively suppressed by systemic administration of anti-hENG mAbs. Additionally, test result indicates that synergistic potentiation of antitumor efficacy can be induced by simultaneous targeting of two distinct epitopes by anti-hENG mAbs. Sorafenib and capecitabine also showed antitumor efficacy in the GEMs. The presented novel GEMs are the first GEMs that express the targetable humanized ENG. Test results indicate utility of the GEMs for the clinically relevant studies. Additionally, we generated GEMs expressing a different humanized ENG containing exons 5-6 of hENG gene, and the homozygous GEMs develop normally and are healthy.

The ligand-binding domain of Siglec-G is crucial for its selective inhibitory function on B1 cells

Siglec-G is an inhibitory receptor on B1 cells. Siglec-G-deficient mice show a large B1 cell expansion, owing to higher BCR-induced Ca(2+) signaling and enhanced cellular survival. It was unknown why Siglec-G shows a B1 cell-restricted inhibitory function. With a new mAb we could show a comparable Siglec-G expression on B1 cells and conventional B2 cells. However, Siglec-G has a different ligand sialic acid-binding pattern on peritoneal B1 cells than on splenic B cells, and its sialic acid ligands are expressed differentially on these two B cell populations, suggesting that cis-ligand binding plays a crucial role on B1 cells. This observation was further studied by generation of Siglec-G knockin mice with a mutated ligand-binding domain. These mice show increased B1 cell numbers, increased B1 cell Ca(2+) signaling, better B1 cell survival, and changes in the B1 cell Ig repertoire. These phenotypes are very similar to Siglec-G-deficient mice. The mutation of the ligand-binding domain of Siglec-G strongly reduces the Siglec-G-IgM association on the B cell surface. Thus, Siglec-G sialic acid-dependent binding to the BCR is crucial for the B1 cell-restricted inhibitory function of Siglec-G and is regulated in an opposite way to that of the related protein CD22 (Siglec-2) on B cells.

Germline transmission of an embryonic stem cell line derived from BALB/c cataract mice

Mice embryonic stem (ES) cells have enabled the generation of mouse strains with defined mutation(s) in their genome for putative disease loci analysis. In the study of cataract, the complex genetic background of this disease and lack of long-term self-renewal ES cells have hampered the functional researches of cataract-related genes. In this study, we aimed to establish ES cells from inherited cataract mice (BALB/CCat/Cat). Embryos of cataract mice were cultured in chemical-defined N2B27 medium with the presence of two small molecules PD0325901 and CHIR99021 (2i) and an ES cell line (named EH-BES) was successfully established. EH-BES showed long-term self-renewal in 2i medium and maintained capacity of germline transmission. Most importantly, the produced chimera and offspring developed congenital cataract as well. Flow cytometry assay revealed that EH-BES are homogeneous in expression of Oct4 and Rex1in 2i medium, which may account for their self-renewal ability. With long-term self-renewal ability and germline-competent, EH-BES cell line can facilitate genetic and functional researches of cataract-related genes and better address mechanisms of cataract.

IL-4 directly signals tissue-resident macrophages to proliferate beyond homeostatic levels controlled by CSF-1

Macrophages (MΦs) colonize tissues during inflammation in two distinct ways: recruitment of monocyte precursors and proliferation of resident cells. We recently revealed a major role for IL-4 in the proliferative expansion of resident MΦs during a Th2-biased tissue nematode infection. We now show that proliferation of MΦs during intestinal as well as tissue nematode infection is restricted to sites of IL-4 production and requires MΦ-intrinsic IL-4R signaling. However, both IL-4Rα-dependent and -independent mechanisms contributed to MΦ proliferation during nematode infections. IL-4R-independent proliferation was controlled by a rise in local CSF-1 levels, but IL-4Rα expression conferred a competitive advantage with higher and more sustained proliferation and increased accumulation of IL-4Rα(+) compared with IL-4Rα(-) cells. Mechanistically, this occurred by conversion of IL-4Rα(+) MΦs from a CSF-1-dependent to -independent program of proliferation. Thus, IL-4 increases the relative density of tissue MΦs by overcoming the constraints mediated by the availability of CSF-1. Finally, although both elevated CSF1R and IL-4Rα signaling triggered proliferation above homeostatic levels, only CSF-1 led to the recruitment of monocytes and neutrophils. Thus, the IL-4 pathway of proliferation may have developed as an alternative to CSF-1 to increase resident MΦ numbers without coincident monocyte recruitment.

Interleukin-4 deficiency protects mice from acetaminophen-induced liver injury and inflammation by prevention of glutathione depletion

OBJECTIVE

Interleukin-4 (IL-4) is a multifunctional cytokine involved in many diseases such as autoimmune hepatitis and idiosyncratic drug reactions. However, its role in acetaminophen (APAP)-induced liver injury remains unclear. Our objective was to evaluate the contribution of IL-4 to the pathogenesis of APAP-induced liver injury.

METHODS

Balb/C (WT) and IL-4 knockout (IL-4(-/-)) mice were orally overdosed with APAP. After 24 h, survival percentage, biochemical and morphological markers of liver injury, and tissue inflammation were assessed.

RESULTS

IL-4(-/-) mice were protected from APAP toxicity. Intravital confocal microscopy, tissue histology and serum ALT levels showed significantly less liver injury and inflammation than in the WT group, which may explain the increased survival rate of IL-4(-/-) mice. In addition, IL-4(-/-) mice had decreased production of tumor necrosis factor α, CXCL1 and interleukin-1β in the liver, but not in a remote site such as the lungs. Hepatic macrophage activation was markedly reduced in IL-4-deficient mice. In addition, glutathione depletion-a primary cause of APAP-mediated injury-was significantly attenuated in IL-4(-/-) mice.

CONCLUSIONS

Taken together, our data demonstrate that IL-4(-/-) mice are protected from APAP-induced liver injury due to reduced depletion of glutathione, which prevented liver damage and tissue inflammation.

Loss of mammal-specific tectorial membrane component carcinoembryonic antigen cell adhesion molecule 16 (CEACAM16) leads to hearing impairment at low and high frequencies

The vertebrate-restricted carcinoembryonic antigen gene family evolves extremely rapidly. Among their widely expressed members, the mammal-specific, secreted CEACAM16 is exceptionally well conserved and specifically expressed in the inner ear. To elucidate a potential auditory function, we inactivated murine Ceacam16 by homologous recombination. In young Ceacam16(-/-) mice the hearing threshold for frequencies below 10 kHz and above 22 kHz was raised. This hearing impairment progressed with age. A similar phenotype is observed in hearing-impaired members of Family 1070 with non-syndromic autosomal dominant hearing loss (DFNA4) who carry a missense mutation in CEACAM16. CEACAM16 was found in interdental and Deiters cells and was deposited in the tectorial membrane of the cochlea between postnatal days 12 and 15, when hearing starts in mice. In cochlear sections of Ceacam16(-/-) mice tectorial membranes were significantly more often stretched out as compared with wild-type mice where they were mostly contracted and detached from the outer hair cells. Homotypic cell sorting observed after ectopic cell surface expression of the carboxyl-terminal immunoglobulin variable-like N2 domain of CEACAM16 indicated that CEACAM16 can interact in trans. Furthermore, Western blot analyses of CEACAM16 under reducing and non-reducing conditions demonstrated oligomerization via unpaired cysteines. Taken together, CEACAM16 can probably form higher order structures with other tectorial membrane proteins such as α-tectorin and β-tectorin and influences the physical properties of the tectorial membrane. Evolution of CEACAM16 might have been an important step for the specialization of the mammalian cochlea, allowing hearing over an extended frequency range.

Grb2 regulates B-cell maturation, B-cell memory responses and inhibits B-cell Ca2+ signalling

Grb2 is a ubiquitously expressed adaptor protein, which activates Ras and MAP kinases in growth factor receptor signalling, while in B-cell receptor (BCR) signalling this role is controversial. In B cell lines it was shown that Grb2 can inhibit BCR-induced Ca(2+) signalling. Nonetheless, the physiological role of Grb2 in primary B cells is still unknown. We generated a B-cell-specific Grb2-deficient mouse line, which had a severe reduction of mature follicular B cells in the periphery due to a differentiation block and decreased B-cell survival. Moreover, we found several changes in important signalling pathways: enhanced BCR-induced Ca(2+) signalling, alterations in mitogen-activated protein kinase activation patterns and strongly impaired Akt activation, the latter pointing towards a defect in PI3K signalling. Interestingly, B-cell-specific Grb2-deficient mice showed impaired IgG and B-cell memory responses, and impaired germinal centre formation. Thus, Grb2-dependent signalling pathways are crucial for lymphocyte differentiation processes, as well as for control of secondary humoral immune responses.

TGF-β interactions with IL-1 family members trigger IL-4-independent IL-9 production by mouse CD4(+) T cells

TGF-β and IL-4 were recently shown to selectively upregulate IL-9 production by naïve CD4(+) T cells. We report here that TGF-β interactions with IL-1α, IL-1β, IL-18, and IL-33 have equivalent IL-9-stimulating activities that function even in IL-4-deficient animals. This was observed after in vitro antigenic stimulation of immunized or unprimed mice and after polyclonal T-cell activation. Based on intracellular IL-9 staining, all IL-9-producing cells were CD4(+) and 80-90% had proliferated, as indicated by reduced CFSE staining. In contrast to IL-9, IL-13 and IL-17 were strongly stimulated by IL-1 and either inhibited (IL-13) or were unaffected (IL-17) by addition of TGF-β. IL-9 and IL-17 production also differed in their dependence on IL-2 and regulation by IL-1/IL-23. As IL-9 levels were much lower in Th2 and Th17 cultures, our results identify TGF-β/IL-1 and TGF-β/IL-4 as the main control points of IL-9 synthesis.

Induction of B-cell development in adult mice reveals the ability of bone marrow to produce B-1a cells

To study B-cell development from bone marrow (BM), we generated recombination-activating gene 1 (Rag1)–targeted mice lacking mature lymphocytes. B-cell development can be induced in such mice by B cell–specific restoration of a functional Rag1 transcription unit. Follicular and marginal zone B cells populated the spleen when Rag1 expression was permitted. Notably, the peritoneal cavity was dominated by bona fide B-1a cells, as judged by surface markers and functional properties. These BM-derived B-1a cells exhibited a polyclonal VDJ repertoire with substantial N nucleotide insertions. Nevertheless, physiologic frequencies of phosphatidylcholine-specific B cells were detected. Importantly, the BM of young and 5-month-old mice was indistinguishable with regard to the potential to generate B-1a cells.

Manipulation of mouse embryonic stem cells for knockout mouse production

The establishment of mouse embryonic stem (ES) cell lines has allowed for the gene?ration of the knockout mouse. ES cells that are genetically altered in culture can then be manipulated to derive a whole mouse containing the desired mutation. To successfully generate a knockout mouse, however, the ES cells must be carefully cultivated in a pluripotent state throughout the gene-targeting experiment. This unit describes detailed step-by-step protocols, reagents, equipment, and strategies needed for the successful generation of gene knockout embryonic stem cells using homologous recombination technologies.

Disruption of Th2 immunity results in a gender-specific expansion of IL-13 producing accessory NK cells during helminth infection

Host gender has previously been identified as a determining factor in the resolution of Trichuris muris infection in mice lacking IL-4 (IL-4KO BALB/c). Worm expulsion in these mice is delayed, but occurs in females. In this study we were able to demonstrate delayed expulsion occurs at day 26 post infection and is associated with the production of the key Th2-associated cytokine IL-13 by both CD4(+) T cells and an auxiliary DX5(+) NK cell source, as well as a concurrent reduction in proinflammatory cytokines. NK cell number was comparably increased in both sexes, but NK cells from male mice were found to express higher levels of the chemokine receptor CXCR3. Depletion of CD4(+) T cells completely prevented parasite expulsion, whereas loss of NK cells resulted in a mild, but significant delay. Furthermore, IL-18 is a cytokine with the capacity to enhance both Th1 and Th2 responses found to be dispensable for worm expulsion in female mice but was a key factor for the suppression of the Th2 response in male IL-4KO mice. In contrast neutralization of IFN-gamma resulted in a complete restoration of typical wild-type BALB/c expulsion kinetics. This study sheds further light on the role of accessory NK cells in supplementing the IL-13-driven immune response when normal Th2 immunity is disrupted, and further identifies host gender as a key factor in determining the generation of "NK cell help".

Endogenously produced IL-4 nonredundantly stimulates CD8+ T cell proliferation

T cell proliferation and survival are regulated by the cytokine receptor common gamma-chain-associated cytokines IL-2, IL-7, and IL-15, while IL-4, another gamma-chain-associated cytokine, is thought to primarily affect T cell quality rather than quantity. In contrast, our experiments reveal that endogenously produced IL-4 is a direct, nonredundant, and potent stimulator of CD8(+) T cell proliferation in Ag- and pathogen-induced CD8(+) T cell responses. These stimulatory effects of IL-4 are observed in both BALB/c and C57BL/6 mice and activate both naive and memory/activated phenotype CD8(+) T cells, although the former are stimulated less than are the latter. IL-4 effects are IL-7- and IL-15-independent, but MHC class I-dependent stimulation appears to be required for the mitogenic effect of IL-4 on naive phenotype CD8(+) T cells. Thus, endogenously produced IL-4 is an important regulator of quantitative as well as qualitative aspects of T cell immunity.

Mast cell degranulation contributes to susceptibility to Leishmania major

Leishmaniasis causes high morbidity and mortality in tropical and subtropical areas. Mast cells can be activated by Leishmania or Leishmania products in vitro and in vivo. Several innate immunity mediators, including some released by mast cells, play roles in the outcome of the disease. In this study, we examined whether pharmacological inactivation of mast cells before infection with L. major interferes with the progressive disease in BALB/c mice. The results show that, when mast cells are degranulated before challenge with L. major, susceptible mice become more resistant to infection, as measured by decrease of lesion size and lower parasite loads. Mast cell degranulation reduced IL-4 production. Moreover, mast cells degranulation enhanced mRNA expression for IFN-gamma, inducible nitric oxide, CCL2 and CCL5 in response to infection. Mast cell degranulation also decreased parasite loads in IL-4 KO animals, indicating that mediators other than IL-4 are involved in susceptibility in vivo. Taken together, our results disclose a role for mast cells in the induction of susceptibility to infection. This work contributes to a better understanding of the role of mast cells in Leishmania infection, and suggests a new field of study for strategies to contain the parasite, restricting its dissemination.

ES cell line establishment

A method is described to establish mouse embryonic stem cell (ESC) lines from hybrid and inbred strains of mice. Attention is paid not only to the methodology for isolation and culture but also to the validation of freshly derived lines, in order to be maintained for prolonged time without significant differentiation or karyotype instability, and to provide reproducible germline transmission in chimaeric mice.

IL-4/IL-13 independent goblet cell hyperplasia in experimental helminth infections

BACKGROUND

Intestinal mucus production by hyperplasic goblet cells is a striking pathological feature of many parasitic helminth infections and is related to intestinal protection and worm expulsion. Induction of goblet cell hyperplasia is associated with TH2 immune responses, which in helminth infections are controlled primarily by IL-13, and also IL-4. In the study presented here we examine the goblet cell hyperplasic response to three experimental parasitic helminth infections; namely Nippostrongylus brasiliensis, Syphacia obvelata and Schistosoma mansoni.

RESULTS

As expected N. brasiliensis infection induced a strong goblet cell hyperplasia dependent on IL-4/IL-13/IL-4Ralpha expression. In contrast, and despite previously published transiently elevated IL-4/IL-13 levels, S. obvelata infections did not increase goblet cell hyperplasia in the colon. Furthermore, induction of goblet cell hyperplasia in response to S. mansoni eggs traversing the intestine was equivalent between BALB/c, IL-4/IL-13-/- and IL-4Ralpha-/- mice.

CONCLUSION

Together these data demonstrate that intestinal goblet cell hyperplasia can be independent of TH2 immune responses associated with parasitic helminth infections.

Mouse embryonic stem (ES) cell isolation

Building on the technology presented in earlier units of Chapter 23, this unit describes the basic method for the isolation of mouse embryonic (ES) stem cells. ES cells from wild-type mice may be used for the production of mouse mutants by homologous recombination and blastocyst-mediated transgenesis. ES cells from mutant mouse lines may be used in the analysis of mutant phenotypes.

Differences in expression, affinity, and function of soluble (s)IL-4Ralpha and sIL-13Ralpha2 suggest opposite effects on allergic responses

IL-4 and IL-13 are each bound by soluble receptors (sRs) that block their activity. Both of these sRs (sIL-4Ralpha and sIL-13Ralpha2) are present in low nanogram per milliliter concentrations in the serum from unstimulated mice, but differences in affinity and half-life suggest differences in function. Serum IL-4/sIL-4Ralpha complexes rapidly dissociate, releasing active IL-4, whereas sIL-13Ralpha2 and IL-13 form a stable complex that has a considerably longer half-life than uncomplexed IL-13, sIL-13Ralpha2, IL-4, or sIL-4Ralpha. Approximately 25% of sIL-13Ralpha2 in serum is complexed to IL-13; this percentage and the absolute quantity of sIL-13Ralpha2 in serum increase considerably during a Th2 response. sIL-13Ralpha2 gene expression is up-regulated by both IL-4 and IL-13; the effect of IL-4 is totally IL-4Ralpha-dependent while the effect of IL-13 is partially IL-4Ralpha-independent. Inhalation of an IL-13/sIL-13Ralpha2 complex does not affect the expression of IL-13-inducible genes but increases the expression of two genes, Vnn1 and Pira-1, whose products activate APCs and promote neutrophilic inflammation. These observations suggest that sIL-4Ralpha predominantly sustains, increases, and diffuses the effects of IL-4, whereas sIL-13Ralpha2 limits the direct effects of IL-13 to the site of IL-13 production and forms a stable complex with IL-13 that may modify the quality and intensity of an allergic inflammatory response.

Interleukin-4 impairs granzyme-mediated cytotoxicity of Simian virus 40 large tumor antigen-specific CTL in BALB/c mice

In this report we analyzed the impact of interleukin-4 (IL-4) on tumor-associated simian virus 40 (SV40) large T-antigen (TAg)-specific CD8+ cytotoxic T cells during rejection of syngeneic SV40 transformed mKSA tumor cells in BALB/c mice. Strikingly, challenge of naïve mice with low doses of mKSA tumor cells revealed a CD8+ T cell-dependent prolonged survival time of naïve IL-4-/- mice. In mice immunized with SV40 TAg we observed in IL-4-/- mice, or in wild type mice treated with neutralizing anti-IL-4 monoclonal antibody, a strongly enhanced TAg-specific cytotoxicity of tumor associated CD8+ T cells. The enhanced cytotoxicity in IL-4-/- mice was accompanied by a significant increase in the fraction of CD8+ tumor associated T-cells expressing the cytotoxic effector molecules granzyme A and B and in granzyme B-specific enzymatic activity. The data suggest that endogenous IL-4 can suppress the generation of CD8+ CTL expressing cytotoxic effector molecules especially when the antigen induces only a very weak CTL response.

Maternal allergic contact dermatitis causes increased asthma risk in offspring

Background

Offspring of asthmatic mothers have increased risk of developing asthma, based on human epidemiologic data and experimental animal models. The objective of this study was to determine whether maternal allergy at non-pulmonary sites can increase asthma risk in offspring.

Methods

BALB/c female mice received 2 topical applications of vehicle, dinitrochlorobenzene, or toluene diisocyanate before mating with untreated males. Dinitrochlorobenzene is a skin-sensitizer only and known to induce a Th1 response, while toluene diisocyanate is both a skin and respiratory sensitizer that causes a Th2 response. Both cause allergic contact dermatitis. Offspring underwent an intentionally suboptimal protocol of allergen sensitization and aerosol challenge, followed by evaluation of airway hyperresponsiveness, allergic airway inflammation, and cytokine production. Mothers were tested for allergic airway disease, evidence of dermatitis, cellularity of the draining lymph nodes, and systemic cytokine levels. The role of interleukin-4 was also explored using interleukin-4 deficient mice.

Results

Offspring of toluene diisocyanate but not dinitrochlorobenzene-treated mothers developed an asthmatic phenotype following allergen sensitization and challenge, seen as increased Penh values, airway inflammation, bronchoalveolar lavage total cell counts and eosinophilia, and Th2 cytokine imbalance in the lung. Toluene diisocyanate treated interleukin-4 deficient mothers were able to transfer asthma risk to offspring. Mothers in both experimental groups developed allergic contact dermatitis, but not allergic airway disease.

Conclusion

Maternal non-respiratory allergy (Th2-skewed dermatitis caused by toluene diisocyanate) can result in the maternal transmission of asthma risk in mice.

Efficient derivation of embryonic stem cells by inhibition of glycogen synthase kinase-3

Embryonic stem (ES) cells are derived from the inner cell mass (ICM) of blastocysts. The use of ES cells as a source of differentiated cells holds great promise for cell transplantation therapy. The efficiency of ES cell derivation is affected by genetic variation in mice; that is, some mouse strains, such as C57BL/6, are amenable to ES cell derivation, whereas others, such as BALB/c, are refractory. Developing an efficient method to establish ES cells from strains of various genetic backgrounds should be valuable for derivation of ES cells in various mammalian species, including human. Although it is well-established that various signaling pathways, including phosphoinositide 3-kinase (PI3K)/Akt and Wnt/beta-catenin, regulate the maintenance of ES cell pluripotency, little is known about the signaling pathways involved in the derivation of ES cells from ICMs. In this study, we demonstrated that inhibition of glycogen synthase kinase-3 (GSK-3), one of the crucial molecules in the regulation of the Wnt/beta-catenin, Hedgehog, and Notch signaling pathways, dramatically augmented ES cell derivation from both C57BL/6 and BALB/c mouse strains. In contrast, Akt signaling activation enhanced the growth of ICM but did not increase the efficiency of ES cell derivation. Our study establishes an efficient means for ES cell derivation by pharmacological inhibition of GSK-3.

Siglec-G is a B1 cell–inhibitory receptor that controls expansion and calcium signaling of the B1 cell population

B1 cells are an important cell population for the production of natural antibodies and for antibacterial immunoglobulin responses. Here we identified the mouse protein Siglec-G as a B1 cell inhibitory receptor. Siglec-G was expressed in a B cell-restricted way, with large amounts present in B1 cells. When overexpressed, Siglec-G inhibited B cell receptor-mediated calcium signaling. Siglec-G-deficient mice had massive expansion of the B1a cell population, which began early in development and was B cell intrinsic. Siglec-G-deficient mice had higher titers of natural IgM antibodies but not a higher penetrance of IgG autoantibodies. Siglec-G-deficient B1 cells showed a strongly enhanced calcium signaling. Our results demonstrate that Siglec-G-dependent negative regulation exists in B1 cells, which may explain the naturally muted signaling response of B1 cells.

Alveolar bone loss in T helper 1/T helper 2 cytokine-deficient mice

BACKGROUND AND OBJECTIVES

The role of cytokines in bone loss is important in the context of periodontitis, where inflammation-induced bone destruction is a major manifestation. Numerous cytokines have been implicated as mediators of bone resorption. The purpose of this study was to observe the impact of targeted gene deletion of T helper 1 (Th1) and T helper 2 (Th2) cytokines on naturally occurring alveolar bone loss in genetically modified mice.

MATERIAL AND METHODS

Alveolar bone loss was measured histomorphometrically in interleukin-4, interleukin-10, interleukin-12p40, interferon-gamma (IFN-gamma) and tumor necrosis factor (TNF) knockout mice at 6, 16 and 30 wk of age.

RESULTS

Both Th1 (interleukin-12p40, IFN-gamma, TNF) and Th2 (interleukin-10, interleukin-4) knockout mice exhibited significantly more alveolar bone loss than their respective wild-type control mice (p<0.001). Interleukin-10-/- and interleukin-12p40-/- mice exhibited a three-fold increase in alveolar bone loss at 30 wk of age, whereas bone loss in IFN-gamma-/-, TNF-/- and interleukin-4-/- mice was 1.5- to two-fold higher compared with wild-type control mice.

CONCLUSION

The results of the present study indicate that both Th1 and Th2 cytokines play an important role in maintaining alveolar bone homeostasis. The kinetics of alveolar bone loss seen in cytokine gene knockout mice indicates that bone loss is age dependent and late in onset.

Infection with Syphacia obvelata (pinworm) induces protective Th2 immune responses and influences ovalbumin-induced allergic reactions

Infections with pinworms are common in rodent animal facilities. In this study, we show the consequence of an outbreak in a transgenic barrier facility of infection by Syphacia obvelata, a murine pinworm gastrointestinal nematode. Immune responses were defined in experimental infection studies with BALB/c mice. Infection with S. obvelata induced a transient Th2-type immune response with elevated interleukin 4 (IL-4), IL-5, and IL-13 cytokine production and parasite-specific immunoglobulin G1 (IgG1). In contrast, BALB/c mice deficient in IL-13, IL-4/13, or the IL-4 receptor alpha chain showed chronic disease, with a >100-fold higher parasite burden, increased gamma interferon production, parasite-specific IgG2b, and a default Th2 response. Interestingly, infected IL-4-/- BALB/c mice showed only slightly elevated parasite burdens compared to the control mice, suggesting that IL-13 plays the dominant role in the control of S. obvelata. The influence that pinworm infection has on the allergic response to a dietary antigen was found to be important. Helminth-infected mice immunized against ovalbumin (Ova) elicited more severe anaphylactic shock with reduced Ova-specific IL-4 and IL-5 than did noninfected controls, demonstrating that S. obvelata infection is able to influence nonrelated laboratory experiments. The latter outcome highlights the importance of maintaining mice for use as experimental models under pinworm-free conditions.

Testing gene function early in the B cell lineage in mb1-cre mice

The mb1 gene encodes the Ig-alpha signaling subunit of the B cell antigen receptor and is expressed exclusively in B cells beginning at the very early pro-B cell stage in the bone marrow. We examine here the efficacy of the mb1 gene as a host locus for cre recombinase expression in B cells. We show that by integrating a humanized cre recombinase into the mb1 locus we obtain extraordinarily efficient recombination of loxP sites in the B cell lineage. The results from a variety of reporter genes including the splicing factor SRp20 and the DNA methylase Dnmt1 suggest that mb1-cre is probably the best model so far described for pan-B cell-specific cre expression. The availability of a mouse line with efficient cre-mediated recombination at an early developmental stage in the B lineage provides an opportunity to study the role of various genes specifically in B cell development and function.

Immune-mediated neuroprotection of axotomized mouse facial motoneurons is dependent on the IL-4/STAT6 signaling pathway in CD4+ T cells

The CD4(+) T lymphocyte has recently been found to promote facial motoneuron (FMN) survival after nerve injury. Signal Transducer and Activator of Transcription (STAT)4 and STAT6 are key proteins involved in the CD4(+) T cell differentiation pathways leading to T helper type (Th)1 and Th2 cell development, respectively. To determine which CD4(+) T cell subset mediates FMN survival, the facial nerve axotomy paradigm was applied to STAT4-deficient (-/-) and STAT6-/- mice. A significant decrease in FMN survival 4 weeks after axotomy was observed in STAT6-/- mice compared to wild-type (WT) or STAT4-/- mice. Reconstituting STAT6-/- mice with CD4(+) T cells obtained from WT mice promoted WT levels of FMN survival after injury. Furthermore, rescue of FMN from axotomy-induced cell death in recombination activating gene (RAG)-2-/- mice (lacking T and B cells) could be achieved only by reconstitution with CD4(+) T cells expressing functional STAT6 protein. To determine if either the Th1 cytokine, interferon-gamma (IFN-gamma) or the Th2 cytokine IL-4 is involved in mediating FMN survival, facial nerve axotomy was applied to IFN-gamma-/- and IL-4-/- mice. A significant decrease in FMN survival after axotomy occurred in IL-4-/- but not in IFN-gamma-/- mice compared to WT mice, indicating that IL-4 but not IFN-gamma is important for FMN survival after nerve injury. In WT mice, intracellular IFN-gamma vs. IL-4 expression was examined in CD4(+) T cells from draining cervical lymph nodes 14 days after axotomy, and substantial increase in the production of both CD4(+) effector T cell subsets was found. Collectively, these data suggest that STAT6-mediated CD4(+) T cell differentiation into the Th2 subset is necessary for FMN survival. A hypothesis relevant to motoneuron disease progression is presented.

Identification of a common gene signature for type II cytokine–associated myeloid cells elicited in vivo in different pathologic conditions

Compared with type I cytokine–associated myeloid (M1) cells, the molecular repertoire and mechanisms underlying functional properties of type II cytokine–associated myeloid (M2) cells are poorly characterized. Moreover, most studies have been limited to in vitro–elicited M2 cells. Here, comparative gene expression profiling of M1 and M2 cells, elicited in murine models of parasitic infections and cancer, yielded a common signature for in vivo–induced M2 populations independent of disease model, mouse strain, and organ source of cells. Some of these genes, such as cadherin-1, selenoprotein P, platelet-activating factor acetylhydrolase, and prosaposin, had not been documented as associated with M2. Overall, the common signature genes provide a molecular basis for a number of documented or suggested properties of M2, including immunomodulation, down-regulation of inflammation, protection against oxidative damage, high capacity for phagocytosis, and tissue repair. Interestingly, several common M2 signature genes encode membrane-associated markers that could be useful for the identification and isolation of M2. Some of these genes were not induced by IL-4/IL-13 or IL-10 under various in vitro settings and thus were missed in approaches based on in vitro–activated cells, validating our choice of in vivo models for expression profiling of myeloid cells.

Nerve Growth Factor Translates Stress Response and Subsequent Murine Abortion via Adhesion Molecule-Dependent Pathways1

Spontaneous abortion is a frequent threat affecting 10%-25% of human pregnancies. Psychosocial stress has been suggested to be attributable for pregnancy losses by challenging the equilibrium of systems mandatory for pregnancy maintenance, including the nervous, endocrine, and immune system. Strong evidence indicates that stress-triggered abortion is mediated by adhesion molecules, i.e., intercellular adhesion molecule 1 (ICAM1) and leukocyte function associated molecule 1, now being referred to as integrin alpha L (ITGAL), which facilitate recruitment of inflammatory cells to the feto-maternal interface. The neurotrophin beta-nerve growth factor (NGFB), which has been shown to be upregulated in response to stress in multiple experimental settings including in the uterine lining (decidua) during pregnancy, increases ICAM1 expression on endothelial cells. Here, we investigated whether and how NGFB neutralization has a preventive effect on stress-triggered abortion in the murine CBA/J x DBA/2J model. We provide experimental evidence that stress exposure upregulates the frequency of abortion and the expression of uterine NGFB. Further, adhesion molecules ICAM1 and selectin platelet (SELP, formerly P-Selectin) and their ligands ITGAL and SELP ligand (SELPL, formerly P selectin glycoprotein ligand 1) respectively increase in murine deciduas in response to stress. Subsequently, decidual cytokines are biased toward a proinflammatory and abortogenic cytokine profile. Additionally, a decrease of pregnancy protective CD8alpha(+) decidual cells is present. Strikingly, all such uterine stress responses are abrogated by NGFB neutralization. Hence, NGFB acts as a proximal mediator in the hierarchical network of immune rejection by mediating an abortogenic environment comprised of classical signs of neurogenic inflammation.

Induction of surface CCR4 and its functionality in mouse Th2 cells is regulated differently during Th2 development

T helper cell type 1 (Th1) and Th2 cells express distinct sets of chemokine receptors. In contrast to Th1 chemokine receptors, it is largely unknown how Th2 chemokine receptors such as CC chemokine receptor 4 (CCR4) are induced during Th2 differentiation. Here, we investigated the induction of CCR4 surface expression and ligand responsiveness evaluated by functional assays such as chemokine binding and chemotaxis. This was done in comparison with those of a Th1 chemokine receptor, CXC chemokine receptor 3 (CXCR3). Resting T cells expressed neither CXCR3 nor CCR4. CXCR3 expression and ligand responsiveness were observed when resting T cells were stimulated with anti-CD3 plus anti-CD28 in the presence of [interleukin (IL)-12+anti-IL-4] and then recultured without T cell receptor (TCR) stimulation. Unlike CXCR3, CCR4 was induced immediately after anti-CD3/anti-CD28 stimulation in the presence of (IL-4+anti-interferon-gamma+anti-IL-12). However, these CCR4-positive cells failed to exhibit chemokine binding and chemotaxis. Although the levels of surface CCR4 expression were not increased after the subsequent reculture in the absence of TCR stimulation, CCR4 responsiveness was induced in this stage of Th2 cells. The induction of CCR4 expression and the acquisition of CCR4 responsiveness did not occur in IL-4-deficient (IL-4(-/-)) and signal transducer and activator of transcription (STAT)6(-/-) T cells. CCR4 expression and functionality were regained in IL-4(-/-) but not in STAT6(-/-) T cells by the addition of recombinant IL-4. Although surface expression and functionality of CCR4 are induced depending on the IL-4/STAT6 signaling pathway, the present results indicate that the functionality of CCR4 does not correlate with CCR4 expression but emerges at later stages of Th2 differentiation.

Strong and ubiquitous expression of transgenes targeted into the beta-actin locus by Cre/lox cassette replacement

Conventional approaches to produce transgenic mice recurrently yield unpredictable patterns and levels of transgene expression, a situation calling for the development of new techniques to overcome these drawbacks in the context of overexpression studies. Here we present an efficient method for rapid and reproducible transgenesis using the recombinase mediated cassette exchange (RMCE) (Bouhassira et al.: Blood 90:3332-3344, 1997) procedure. A lox511-EGFP-TK/neo-loxP cassette was placed under the control of the endogenous mouse beta-actin promoter. Heterozygous mice revealed strong and ubiquitous EGFP expression throughout embryogenesis and adulthood. Reproducibly, the same expression pattern was obtained with RMCE when it was used to replace the EGFP-harboring cassette by ECFP or placental alkaline phosphatase (PLAP) reporter genes (DePrimo et al.: Transgenic Res 5:459-466, 1996). Furthermore, the RMCE procedure proved efficient as well in embryonic stem (ES) cells as directly in zygotes. Our results demonstrate ubiquitous expression of floxed transgenes in the endogenous beta-actin locus and they support the general use of the beta-actin locus for targeted transgenesis.

IgE generation and mast cell effector function in mice deficient in IL-4 and IL-13

IL-4 and IL-13 are potent cytokines that drive production of IgE, which is critical to the development of atopic disease. In this study, we directly compared IgE generation and IgE-dependent mast cell effector function in mouse strains lacking IL-4, IL-13, IL-4 + IL-13, or their common receptor component, IL-4Ralpha. Although serum IgE was undetectable under resting conditions in most animals deficient in one or both cytokines, peritoneal mast cells from mice lacking IL-4 or IL-13 had only partial reductions in surface IgE level. In contrast, peritoneal mast cells from IL-4/13(-/-) and IL-4Ralpha(-/-) animals were severely deficient in surface IgE, and showed no detectable degranulation following treatment with anti-IgE in vitro. Surprisingly, however, intradermal challenge with high concentrations of anti-IgE Ab induced an ear-swelling response in these strains, implying some capacity for IgE-mediated effector function in tissue mast cells. Furthermore, upon specific immunization with OVA, both IL-4/IL-13(-/-) and IL-4Ralpha(-/-) mice produced detectable levels of serum IgE and Ag-specific IgG1, and generated strong ear-swelling responses to intradermal administration of anti-IgE. These findings suggest that a mechanism for IgE production exists in vivo that is independent of IL-4 or IL-13.

Reactive oxygen species and 12/15-lipoxygenase contribute to the antiproliferative capacity of alternatively activated myeloid cells elicited during helminth infection

Understanding the role of CD11b(+)GR-1(+) myeloid suppressor cells in the immune suppression and immunoregulation associated with a variety of diseases may provide therapeutic opportunities. In this article, we show, in a model of helminth infection, that CD11b(+)GR-1(+) myeloid suppressor cells but not CD11b(+)F4/80(high) mature macrophages expanded in the peritoneal cavity of BALB/c mice implanted with Taenia crassiceps. Peritoneal cell populations from early stage-infected animals impaired T cell proliferation by secreting NO. Yet, they lost their ability to secrete NO in the late stage of infection. Concomitantly, their capacity to exert arginase activity and to express mRNAs coding for FIZZ1 (found in inflammatory zone 1), Ym, and macrophage galactose-type C-type lectin increased. Furthermore, cells from early stage-infected mice triggered T cells to secrete IFN-gamma and IL-4, whereas in the late stage of infection, they only induced IL-4 production. These data suggest that CD11b(+)GR-1(+) myeloid suppressor cells displaying an alternative activation phenotype emerged gradually as T. crassiceps infection progressed. Corroborating the alternative activation status in the late stage of infection, the suppressive activity relied on arginase activity, which facilitated the production of reactive oxygen species including H(2)O(2) and superoxide. We also document that the suppressive activity of alternative myeloid suppressor cells depended on 12/15-lipoxygenase activation generating lipid mediators, which triggered peroxisome proliferator-activated receptor-gamma. IL-4 and IL-13 signaling contributed to the expansion of myeloid suppressor cells in the peritoneal cavity of T. crassiceps-infected animals and to their antiproliferative activity by allowing arginase and 12/15-lipoxygenase gene expression.

Macrophage galactose-type C-type lectins as novel markers for alternatively activated macrophages elicited by parasitic infections and allergic airway inflammation

Molecular markers, especially surface markers associated with type II, cytokine-dependent, alternatively activated macrophages (aaMF), remain scarce. Besides the earlier documented markers, macrophage mannose receptor and arginase 1, we demonstrated recently that murine aaMF are characterized by increased expression of found in inflammatory zone 1 (FIZZ1) and the secretory lectin Ym. We now document that expression of the two members of the mouse macrophage galactose-type C-type lectin gene family (mMGL1 and mMGL2) is induced in diverse populations of aaMF, including peritoneal macrophages elicited during infection with the protozoan Trypanosoma brucei brucei or the Helminth Taenia crassiceps and alveolar macrophages elicited in a mouse model of allergic asthma. In addition, we demonstrate that in vitro, interleukin-4 (IL-4) and IL-13 up-regulate mMGL1 and mMGL2 expression and that in vivo, induction of mMGL1 and mMGL2 is dependent on IL-4 receptor signaling. Moreover, we show that expression of MGL on human monocytes is also up-regulated by IL-4. Hence, macrophage galactose-type C-type lectins represent novel surface markers for murine and human aaMF.

Effective production of microinjectable blastocysts for germ-line transmission of embryonic stem cells

Blastocysts of C57BL/6 mice obtained either 2.5 or 3.5 days post-coitum (dpc) were examined for efficient microinjection after overnight in vitro culture. Incidences of zona-free embryos were much higher at 3.5 dpc after natural mating (1.05/mouse) and superovulation (2.83/mouse) than at 2.5 dpc after natural mating (0.05/mouse) and superovulation (0.01/mouse). By testing germ-line competency of gene-targeted J1 embryonic stem cells, superovulation and/or in vitro culture should be recommended for producing microinjectable blastocysts for production of high germ-line chimeras.

Parasite-induced Th2 polarization is associated with down-regulated dendritic cell responsiveness to Th1 stimuli and a transient delay in T lymphocyte cycling

The nature of the signals that bias Th effector choice is still not completely understood. Using parasite extracts from pathogens known to induce polarized Th1 or Th2 responses and an in vitro experimental model for priming murine CD4(+) cells, we demonstrated that splenic dendritic cells (DC), but not B cells, promote Th1/Th2 differentiation of naive CD4(+) lymphocytes. Th polarization in this system was found not to depend on DC secretion of the polarizing cytokines IL-12/IL-4, but instead correlated with distinct states of DC activation induced by the different parasite preparations. As expected, conditioning of DC for Th1 development was associated with up-regulation of costimulatory molecules and enhanced chemokine production and required intact MyD88 signaling. In contrast, conditioning of DC for Th2 differentiation correlated with down-regulation of many of the same functions and was MyD88 independent. This dampened DC activation was accompanied in the cocultures by a reduction in the frequency of CD4(+) lymphocytes exiting the first division of the cell cycle. When the latter was mimicked by drug-induced arrest of peptide-primed CD4(+) cells after the S phase of the first cycle, a marked Th2 polarization was also observed. Together, these findings suggest that the emergence of IL-4-producing CD4(+) lymphocytes results from a suppression in DC function leading to a temporary delay in initial T cell cycling.

The upper and lower respiratory tracts differ in their requirement of IFN-gamma and IL-4 in controlling respiratory mycoplasma infection and disease

The purpose of this study is to evaluate the significance of IFN-gamma and IL-4 production in controlling mycoplasma infection and the pathogenesis of disease in the upper and lower respiratory tract. By using IFN-gamma knockout and IL-4 knockout BALB/c mice, we were able to study the contribution of these cytokines in the development of pathogenesis and/or protection in response to mycoplasma respiratory infection, in both the upper and lower respiratory tracts. The loss of either IFN-gamma or IL-4 does not affect disease pathogenesis or mycoplasma organism numbers in the upper respiratory tract. However, in the absence of IL-4, the nasal passages developed a compensatory immune response, characterized by higher numbers of macrophages and CD8(+) T cells, which may be masking detrimental effects due to IL-4 deficiency. This is in contrast to the lower respiratory tract, where the loss of IFN-gamma, but not IL-4, leads to higher mycoplasma numbers and increased disease severity. The loss of IFN-gamma impacted the innate immune system's ability to effectively clear mycoplasma, as the number of organisms was higher by day 3 postinfection. This higher organism burden most likely impacted disease pathogenesis; however, the development of Th2 cell-mediated adaptive immune response most likely contributed to lesion severity at later time points during infection. Our studies demonstrate that the upper and lower respiratory tracts are separate and distinct in their cytokine requirements for generating immunity against mycoplasma infection.

Distinct contribution of IL-6, TNF-alpha, IL-1, and IL-10 to T cell-mediated spontaneous autoimmune arthritis in mice

Cytokines play key roles in spontaneous CD4(+) T cell-mediated chronic autoimmune arthritis in SKG mice, a new model of rheumatoid arthritis. Genetic deficiency in IL-6 completely suppressed the development of arthritis in SKG mice, irrespective of the persistence of circulating rheumatoid factor. Either IL-1 or TNF-alpha deficiency retarded the onset of arthritis and substantially reduced its incidence and severity. IL-10 deficiency, on the other hand, exacerbated disease, whereas IL-4 or IFN-gamma deficiency did not alter the disease course. Synovial fluid of arthritic SKG mice contained high amounts of IL-6, TNF-alpha, and IL-1, in accord with active transcription of these cytokine genes in the afflicted joints. Notably, immunohistochemistry revealed that distinct subsets of synovial cells produced different cytokines in the inflamed synovium: the superficial synovial lining cells mainly produced IL-1 and TNF-alpha, whereas scattered subsynovial cells produced IL-6. Thus, IL-6, IL-1, TNF-alpha, and IL-10 play distinct roles in the development of SKG arthritis; arthritogenic CD4(+) T cells are not required to skew to either Th1 or Th2; and the appearance of rheumatoid factor is independent of joint inflammation. The results also indicate that targeting not only each cytokine but also each cell population secreting distinct cytokines could be an effective treatment of rheumatoid arthritis.

Polarized type 1 cytokine response and cell-mediated immunity determine genetic resistance to mousepox

Ectromelia virus (ECTV), a natural mouse pathogen and an orthopoxvirus, has been used to investigate the correlation between polarized type 1 or type 2 immune responses and resistance to disease in poxvirus infections by using well defined resistant and susceptible mouse strains. Our data show that distinct differences exist in the cytokine profiles expressed in resistant and susceptible mice infected with ECTV. Resistant C57BL/6 mice generate a type 1 cytokine response [IFN-gamma, IL-2, and tumor necrosis factor (TNF)], within the first few days of infection, which is associated with strong cytotoxic T lymphocyte response (CTL) and recovery from ECTV infection. Susceptible strains of mice (BALB/c and A/J) on the other hand generate a type 2 cytokine response (IL-4 but little or no IFN-gamma and IL-2), which is associated with a weak or an absent CTL response, resulting in uncontrolled virus replication and death. Although deletion of IL-4 function alone did not change the outcome of infection in susceptible mice, the loss of IFN-gamma function in resistant mice abrogated natural killer (NK) cell and CTL effector functions resulting in fulminant disease and 100% mortality. Therefore, a clear link exists between the early production of specific type 1 cytokines, in particular, IFN-gamma, the nature of the cellular immune response, and disease outcome in this virus model. This finding in the mousepox model raises the possibility that inappropriate cytokine responses may result in increased susceptibility to smallpox in humans.