GATA-3 Is an Important Transcription Factor for Regulating Human NKG2A Gene Expression

CD94/NKG2A is an inhibitory receptor expressed by most human NK cells and a subset of T cells that recognizes HLA-E on potential target cells. To study the transcriptional regulation of the human NKG2A gene, we cloned a 3.9-kb genomic fragment that contains a 1.65-kb region upstream of the exon 1, as well as exon 1 (untranslated), intron 1 and exon 2. Using deletion mutants, we identified a region immediately upstream from the most upstream transcriptional initiation site that led to increased transcriptional activity from a luciferase reporter construct in YT-Indy (NKG2A positive) cells relative to Jurkat and K562 (both NKG2A negative) cells. We also localized a DNase I hypersensitivity site to this region. Within this 80-bp segment, we identified two GATA binding sites. Mutation of GATA binding site II (-2302 bp) but not GATA binding site I (-2332 bp) led to decreased transcriptional activity. Pull-down assays revealed that GATA-3 could bind oligonucleotide probes containing the wild type but not a mutated GATA site II. Using chromatin immunoprecipitation assays, we showed that GATA-3 specifically binds to the NKG2A promoter in situ in NKL and primary NK cells, but not in Jurkat T cells. Moreover, coexpression of human GATA-3 with an NKG2A promoter construct in K562 cells led to enhanced promoter activity, and transfection of NKL cells with small interfering RNA specific for GATA-3 reduced NKG2A cell surface expression. Taken together, our data indicate that GATA-3 is an important transcription factor for regulating NKG2A gene expression.

T helper cell fate specified by kinase-mediated interaction of T-bet with GATA-3

Cell lineage specification depends on both gene activation and gene silencing, and in the differentiation of T helper progenitors to Th1 or Th2 effector cells, this requires the action of two opposing transcription factors, T-bet and GATA-3. T-bet is essential for the development of Th1 cells, and GATA-3 performs an equivalent role in Th2 development. We report that T-bet represses Th2 lineage commitment through tyrosine kinase-mediated interaction between the two transcription factors that interferes with the binding of GATA-3 to its target DNA. These results provide a novel function for tyrosine phosphorylation of a transcription factor in specifying alternate fates of a common progenitor cell.

Nuclear repositioning marks the selective exclusion of lineage-inappropriate transcription factor loci during T helper cell differentiation

To address how heritable patterns of gene expression are acquired during the differentiation of Th1 and Th2 cells, we analyzed the nuclear position of lineage-restricted cytokine genes and their upstream regulators by 3-dimensional fluorescence in situ hybridization. During Th1 differentiation, GATA-3 and c-maf loci, which encode upstream regulators of Th2 cytokines, were progressively repositioned to centromeric heterochromatin as defined by a gamma-satellite repeat probe and/or the nuclear periphery, compartments that have been associated with transcriptional repression. A third transcription factor locus, T-bet, which controls Th1-specific programs, was subject to de novo CpG methylation in a Th2 cell clone. In contrast, we did not find repositioning of the cytokine gene loci IL-2, IL-3, IL-4 or IFN-gamma during T helper cell differentiation. Instead, IFN-gamma was constitutively associated with the nuclear periphery, even when primed for expression in Th1 cells. Our results suggest that Th1/Th2 lineage commitment and differentiation involve repositioning of the regulators of cytokine expression, rather than the cytokine genes themselves.

Regulation of GATA gene expression during vertebrate development

GATA factors regulate critical events in hematopoietic lineages (GATA-1/2/3), the heart and gut (GATA-4/5/6) and various other tissues. Transgenic approaches have revealed that GATA genes are regulated in a modular fashion by sets of enhancers that govern distinct temporal and/or spatial facets of the overall expression patterns. Efforts are underway to resolve how these GATA gene enhancers are themselves regulated in order to elucidate the genetic and molecular hierarchies that govern GATA expression in particular developmental contexts. These enhancers also afford a raft of tools that can be used to selectively perturb and probe various developmental events in transgenic animals.

Oral administration of K-11706 inhibits GATA binding activity, enhances hypoxia-inducible factor 1 binding activity, and restores indicators in an in vivo mouse model of anemia of chronic disease

Erythropoietin (Epo) gene expression is under the control of hypoxia-inducible factor 1 (HIF-1), and is negatively regulated by GATA. Interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α), which increase the binding activity of GATA and inhibit Epo promoter activity, are increased in patients with anemia of chronic disease (ACD). We previously demonstrated the ability of K-7174 (a GATA-specific inhibitor), when injected intraperitoneally, to improve Epo production that had been inhibited by IL-1β or TNF-α treatment. In the present study, we examined the ability of both K-11706, which inhibits GATA and enhances HIF-1 binding activity, and K-13144, which has no effect on GATA or HIF-1 binding activity, to improve Epo production following inhibition by IL-1β or TNF-α in Hep3B cells in vitro and in an in vivo mouse assay. Oral administration of K-11706 reversed the decreases in hemoglobin and serum Epo concentrations, reticulocyte counts, and numbers of erythroid colony-forming units (CFU-Es) induced by IL-1β or TNF-α. These results raise the possibility of using orally administered K-11706 for treating patients with ACD.

SAP regulates T(H)2 differentiation and PKC-theta-mediated activation of NF-kappaB1

XLP is caused by mutations affecting SAP, an adaptor that recruits Fyn to SLAM family receptors. SAP-deficient mice recapitulate features of XLP, including increased T cell activation and decreased humoral responses post-infection. SAP-deficient T cells also show increased TCR-induced IFN-gamma and decreased T(H)2 cytokine production. We demonstrate that the defect in IL-4 secretion in SAP-deficient T cells is independent of increased IFN-gamma production. SAP-deficient cells respond normally to polarizing cytokines, yet show impaired TCR-mediated induction of GATA-3 and IL-4. Examination of TCR signaling revealed normal Ca(2+) mobilization and ERK activation in SAP-deficient cells, but decreased PKC-theta recruitment, Bcl-10 phosphorylation, IkappaB-alpha degradation, and nuclear NF-kappaB1/p50 levels. Similar defects were observed in Fyn-deficient cells. SLAM engagement amplified PKC-theta recruitment in wt but not SAP- or Fyn-deficient cells, arguing that a SAP/Fyn-mediated pathway enhances PKC-theta/NF-kappaB1 activation and suggesting a role for this pathway in T(H)2 regulation.

The lung cytokine microenvironment influences molecular events in the lymph nodes during Th1 and Th2 respiratory mucosal sensitization to antigen in vivo

Originally defined by their patterns of cytokine production, Th1 and Th2 cells have been described more recently to express other genes differentially as well, at least in vitro. In this study we compared the expression of Th1- and Th2-associated genes directly during in vivo sensitization to ovalbumin (OVA) in Th1- and Th2-polarized models of airways inflammation. Th1-polarized airway inflammation was achieved by the intranasal instillation of adenoviral vectors (Ad) encoding granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-12, followed by daily aerosolizations of OVA; instillation of Ad/GM-CSF alone with OVA aerosolization led to Th2-polarized responses. Lymph nodes were obtained at various time-points, RNA extracted, and analysed by real-time quantitative polymerase chain reaction (PCR). Consistent with reports from in vitro and human studies, mice undergoing Th1-polarized inflammation showed preferential expression of the transcription factor t-bet, the chemokines IFN-gamma inducible protein (IP)-10 and macrophage inflammatory protein 1 alpha (MIP-1-alpha), and the chemokine receptor CCR5. In contrast, the transcription factor GATA-3, the chemokines I-309 and thymus and activation regulated chemokine (TARC), and the chemokine receptors CCR3 and CCR4 were preferentially expressed in the Th2 model. Importantly, we also show that Ad/transgene expression remains compartmentalized to the lung after intranasal instillation. Flow cytometric analysis of lung myeloid dendritic cells indicated that B7.1 was expressed more strongly in the Th1 model than in the Th2 model. These studies provide a direct comparison of gene expression in in vivo Th1- and Th2-polarized models, and demonstrate that molecular events in the lymph nodes can be altered fundamentally by cytokine expression at distant mucosal sites.

Using the zebrafish model to study GATA transcription factors

The zebrafish is an established animal model system that profits from the availability of strong experimental approaches in both genetics and embryology. As a vertebrate, zebrafish can be used to model many aspects of human development and disease. GATA transcription factors play important roles in the development of many organ systems, including those for hematopoietic, cardiovascular, reproductive, and gut-endoderm derived tissues. The six vertebrate GATA factors are highly conserved in zebrafish at the level of sequence, expression pattern, and function. The identification of mutants, establishment of transgenic GFP reporter fish, and the ease of performing loss- and gain-of-function experiments have all contributed new insight into our understanding of the regulation and function of GATA factors. We review recent advances toward this goal using the zebrafish system with a focus on hematopoiesis and cardiogenesis, and suggest how comparative genetics using the zebrafish genes might reveal core conserved properties, as well as changes in gene function that reflect different morphogenetic programs utilized by various vertebrate embryos.

Mulan: multiple-sequence local alignment and visualization for studying function and evolution

Multiple-sequence alignment analysis is a powerful approach for understanding phylogenetic relationships, annotating genes, and detecting functional regulatory elements. With a growing number of partly or fully sequenced vertebrate genomes, effective tools for performing multiple comparisons are required to accurately and efficiently assist biological discoveries. Here we introduce Mulan (http://mulan.dcode.org/), a novel method and a network server for comparing multiple draft and finished-quality sequences to identify functional elements conserved over evolutionary time. Mulan brings together several novel algorithms: the TBA multi-aligner program for rapid identification of local sequence conservation, and the multiTF program for detecting evolutionarily conserved transcription factor binding sites in multiple alignments. In addition, Mulan supports two-way communication with the GALA database; alignments of multiple species dynamically generated in GALA can be viewed in Mulan, and conserved transcription factor binding sites identified with Mulan/multiTF can be integrated and overlaid with extensive genome annotation data using GALA. Local multiple alignments computed by Mulan ensure reliable representation of short- and large-scale genomic rearrangements in distant organisms. Mulan allows for interactive modification of critical conservation parameters to differentially predict conserved regions in comparisons of both closely and distantly related species. We illustrate the uses and applications of the Mulan tool through multispecies comparisons of the GATA3 gene locus and the identification of elements that are conserved in a different way in avians than in other genomes, allowing speculation on the evolution of birds. Source code for the aligners and the aligner-evaluation software can be freely downloaded from http://www.bx.psu.edu/miller_lab/.

The interaction between GATA proteins and activator protein-1 promotes the transcription of IL-13 in mast cells

IL-13 is considered to be a key modulator in the pathogenesis of Th2-induced allergic inflammation, although little is known about the regulation of IL-13 transcription in mast cells. In T cells, involvement of GATA-3 in cell type-specific expression of the IL-13 gene has been reported. However, the mechanisms that induce rapid transactivation of the IL-13 gene in response to various types of stimulation have hitherto remained unknown. In this report, we describe our investigation of the promoter region necessary for IL-13 transcription; we have found that both AP-1 and GATA proteins are indispensable for IL-13 transcription in mouse mast cells. In our investigation, we focused on the functional interaction between GATA and AP-1 in the IL-13 promoter context. Transfection experiments have revealed that GATA-1 and GATA-2 proteins are able to associate with AP-1 proteins. We have also shown that overexpression of GATA-1 induced excess AP-1 binding to the IL-13 promoter as well as a significant increase in IL-13 production in mast cells. The results of the present study have shown that direct interaction between AP-1 and GATA proteins plays an important role in IL-13 transcription in mast cells.

The capacity of the natural ligands for CD28 to drive IL-4 expression in naive and antigen-primed CD4+ and CD8+ T cells

The B7/CD28 costimulatory pathway plays a critical role in T cell activation including Th1/Th2 differentiation. However, little is known about whether CD28 costimulation favors polarization of either Th1 and Th2 or both. Here, we show a critical role of the natural ligands for CD28 molecules (B7.2-Ig or B7.1-Ig fusion proteins), particularly in the induction of type 2 T cell polarization. Upon TCR-triggering with suboptimal doses of anti-CD3, costimulation of naïve CD4+ T cells with anti-CD28 mAb or B7-Ig fusion proteins led to comparable levels of IFN-gamma production. Naïve T cells could produce IL-4 when CD28 costimulation was done with B7-Ig, but not with anti-CD28. IL-4-selective upregulation was also observed when T cells from anti-OVA TCR transgenic mice were stimulated with OVA in the presence of B7-Ig. Correlating with IL-4 expression, GATA-3 expression was induced much more potently by costimulation with B7-Ig than with anti-CD28 mAb, while T-bet induction by these two costimulatory reagents was comparable. This B7 effect was also applied for naïve and antigen-primed CD8+ T cells: IL-4-expressing CD8+ T cells were generated when naïve and alloantigen-primed T cells were stimulated with anti-CD3 and recall antigens, respectively, in the presence of B7-Ig costimulation. Importantly, such CD8+ T cell differentiation required the coexistence of CD4+ T cells during the initial TCR stimulation. These observations indicate that both type 2 CD4 and CD8 T cell polarizations are efficiently induced via costimulation of CD28 with its natural ligands, although the differentiation of CD8+ T cells is dependent on CD4+ cells.

Mutation of GATA3 in human breast tumors

GATA3 is an essential transcription factor that was first identified as a regulator of immune cell function. In recent microarray analyses of human breast tumors, both normal breast luminal epithelium and estrogen receptor (ESR1)-positive tumors showed high expression of GATA3. We sequenced genomic DNA from 111 breast tumors and three breast-tumor-derived cell lines and identified somatic mutations of GATA3 in five tumors and the MCF-7 cell line. These mutations cluster in the vicinity of the highly conserved second zinc-finger that is required for DNA binding. In addition to these five, we identified using cDNA sequencing a unique mis-splicing variant that caused a frameshift mutation. One of the somatic mutations we identified was identical to a germline GATA3 mutation reported in two kindreds with HDR syndrome/OMIM #146255, which is an autosomal dominant syndrome caused by the haplo-insufficiency of GATA3. The ectopic expression of GATA3 in human 293T cells caused the induction of 73 genes including six cytokeratins, and inhibited cell line doubling times. These data suggest that GATA3 is involved in growth control and the maintenance of the differentiated state in epithelial cells, and that GATA3 variants may contribute to tumorigenesis in ESR1-positive breast tumors.

Essential role of LFA-1 in activating Th2-like responses by alpha-galactosylceramide-activated NKT cells

NKT cells produce large amounts of cytokines associated with both the Th1 (IFN-gamma) and Th2 (IL-4) responses following stimulation of their invariant Valpha14 Ag receptor. The role of adhesion molecules in the activation of NKT cells by the Valpha14 ligand alpha-galactosylceramide (alpha-GalCer) remains unclear. To address this issue, LFA-1-/- (CD11a-/-) mice were used to investigate IL-4 and IFN-gamma production by NKT cells following alpha-GalCer stimulation. Intriguingly, LFA-1-/- mice showed increased IL-4, IL-5, and IL-13 production and polarized Th2-type responses in response to alpha-GalCer in vitro and in vivo. Furthermore, the Th2-specific transcription factor GATA-3 was up-regulated in alpha-GalCer-activated NKT cells from LFA-1-/- mice. These results provide the first genetic evidence that the adhesion receptor LFA-1 has a crucial role in Th2-polarizing functions of NKT cells.

Rationale for new treatments aimed at IgE immunomodulation

OBJECTIVE

To review potential or current therapies that decrease IgE synthesis or effects.

DATA SOURCES

Relevant literature in peer-reviewed journals and abstracts from national meetings.

STUDY SELECTION

Key articles were selected by the authors.

RESULTS

Modulation of IgE-mediated diseases can occur at several levels. Transcription factors may be altered to differentiate lymphocytes into a TH1 phenotype, thus decreasing TH2-driven IgE production. This may be accomplished by inhibiting GATA-3 with peroxisome proliferator-activated receptor agonists or promoting T-bet expression with CpG motifs. Inhibiting IgE-promoting cytokines may be accomplished by blocking the effects or synthesis of interleukin 4 (IL-4) or IL-13 by suplatast tosilate. Cytokine therapy with anti-IL-4 or anti-IL-13 has the potential to directly influence IgE-mediated diseases, but strategies aimed at IL-4 alone have been disappointing. Clinical trials with interferon-gamma or IL-12, 2 cytokines important in promoting TH1 and inhibiting TH2 responses, have been fraught with adverse effects that make their use limited. The use of plasmids encoding interferon-gamma or IL-12 has shown promise in animal models. Inhibition of IgE synthesis has been demonstrated with anti-CD23 antibodies. Early human studies have been very encouraging, and larger studies are under way. The only IgE immunomodulator currently available for use is omalizumab. Omalizumab is effective for allergic asthma in children and adults.

CONCLUSIONS

Newer therapies hold great promise for the future treatment of allergic respiratory diseases, but clinical trials are necessary to accurately evaluate risk-benefit ratios of IgE immunomodulators.

Genetic Evidence Linking SAP, the X-Linked Lymphoproliferative Gene Product, to Src-Related Kinase FynT in TH2 Cytokine Regulation

SAP is an adaptor mutated in X-linked lymphoproliferative disease. It plays a critical role in T helper 2 (T(H)2) cytokine production. This function was suggested to reflect the capacity of SAP to associate with SLAM family receptors and enable tyrosine phosphorylation signaling by these receptors through SAP-mediated recruitment of Src-related kinase FynT. Here, we addressed by genetic means the importance of the SAP-FynT interaction in normal T cell functions. By creating a mouse in which the FynT binding site of SAP was inactivated in the germ line (sap(R78A) mouse) and by analyzing mice lacking SAP, FynT or SLAM, evidence was obtained that the SAP-FynT cascade is indeed crucial for normal T(H)2 functions in vitro and in vivo. These data imply that SAP is necessary for T(H)2 cytokine regulation primarily as a result of its capacity to recruit FynT. They also establish a previously unappreciated role for FynT in SAP-dependent T(H)2 cytokine regulation.

Immune response to a major Trypanosoma cruzi antigen, cruzipain, is differentially modulated in C57BL/6 and BALB/c mice

BALB/c mice immunized with cruzipain, a major Trypanosoma cruzi antigen, produce specific and autoreactive immune responses against heart myosin, associated with cardiac functional and structural abnormalities. Preferential activation of the Th2 phenotype and an increase in cell populations expressing CD19+, Mac-1+ and Gr-1+ markers were found in the spleens of these mice. The aim of the present study was to investigate whether cardiac autoimmunity could be induced by cruzipain immunization of C57BL/6 mice and to compare the immune response elicited with that of BALB/c mice. We demonstrate that immune C57BL/6 splenocytes, re-stimulated in vitro with cruzipain, produced high levels of IFNgamma and low levels of IL-4 compatible with a Th1 profile. In contrast to BALB/c mice, spleens from cruzipain immune C57BL/6 mice revealed no significant changes in the number of cells presenting CD19+, Mac-1+ and Gr-1+ markers. An increased secretion of TGFbeta and a greater number of CD4+ TGFbeta+ cells were found in immune C57BL/6 but not in BALB/c mice. These findings were associated with the lack of autoreactive response against heart myosin and a myosin- or cruzipain-derived peptide. Thus, the differential immune response elicited in C57BL/6 and BALB/c mice upon cruzipain immunization is implicated in the resistance or pathogenesis of experimental Chagas' disease.

GATA3 and NeuroD distinguish auditory and vestibular neurons during development of the mammalian inner ear

The function of the zinc finger transcription factor GATA3 was studied in a newly established, conditionally immortal cell line derived to represent auditory sensory neuroblasts migrating from the mouse otic vesicle at embryonic day E10.5. The cell line, US/VOT-33, expressed GATA3, the bHLH transcription factor NeuroD and the POU-domain transcription factor Brn3a, as do auditory neuroblasts in vivo. When GATA3 was knocked down reversibly with antisense oligonucleotides, NeuroD was reversibly down-regulated. Auditory and vestibular neurons form from neuroblasts that express NeuroD and that migrate from the antero-ventral, otic epithelium at E9.5-10.5. On the medial side, neuroblasts and epithelial cells express GATA3 but on the lateral side they do not. At E13.5 most auditory neurons express GATA3 but no longer express NeuroD, whereas vestibular neurons express NeuroD but not GATA3. Neuroblasts expressing NeuroD and GATA3 were located in the ventral, otic epithelium, the adjacent mesenchyme and the developing auditory ganglion. The results suggest that auditory and vestibular neurons arise from different, otic epithelial domains and that they gain their identity prior to migration. In auditory neuroblasts, NeuroD appears to be dependent on the expression of GATA3.

Combining cytokine signalling with T-bet and GATA-3 regulation in Th1 and Th2 differentiation: a model for cellular decision-making

Differentiation of uncommitted T cells into Th1 and Th2 subpopulations depends on both intracellular events controlling expression of transcription factors T-bet and GATA-3 and interactions between cells mediated by cytokines, particularly IL4 and IFNgamma. A great deal is known about the intracellular and extracellular events involved in Th1 and Th2 (Th) differentiation, but how these are integrated in T-cell populations or indeed why extracellular cytokine control is required after a decision has been made at a transcriptional level is not at all understood. We present a mathematical model of CD4+ T-cell differentiation that describes both intracellular and extracellular processes and the interactions between them. It shows how antigen stimulation in conjunction with cytokines and other extracellular signals gives rise to rapid, reversible and mutually exclusive expression of T-bet or GATA-3 due to feedback between the transcription factors and their signalling pathways. After transient signalling by APC, continued Th1 and Th2 differentiation is shown to require cytokine production by the proliferating T cells. Moreover, intercellular communication by T-cell-derived cytokines lowers the threshold of APC signals required for Th differentiation. This provides an explanation for enhanced Th differentiation by pre-existing memory T cells. The model also predicts that Th differentiation can be reversed at the single cell level before commitment by manipulating the cytokine environment. It suggests a mechanism for switching between Th1 and Th2 in the so-called irreversible state that may be developed as a novel therapeutic means of manipulating Th1 and Th2 responses.

Molecular analysis of a locus control region in the T helper 2 cytokine gene cluster: a target for STAT6 but not GATA3

The linked IL-4 and IL-13 cytokine genes, which are activated and silenced in T helper (Th) 2 and Th1 cells, respectively, are flanked by the equivalently expressed RAD50 and KIF3A genes. A scan of DNase I hypersensitivity and DNA methylation across approximately 100 kb of the KIF3A/IL-4/IL-13/RAD50 cluster revealed differences in chromatin structure between Th1 and Th2 cells at the 3' end of the RAD50 gene, a region previously shown to contain a locus control region (LCR) regulating Th2-specific expression of IL-4 and IL-13. Naive CD4 T cells did not exhibit any DNase I hypersensitivity in this region, but stimulation under either Th1 or Th2 conditions caused rapid development of three hypersensitive sites. An additional hypersensitive site developed rapidly only under Th2 conditions, through a mechanism dependent on signal transducers and activators of transcription 6 (STAT6) but not GATA3. Our data point to a physical separation in the actions of STAT6 and its downstream effector GATA3 during Th2 differentiation: STAT6 directly remodels the RAD50 LCR, whereas GATA3 acts only in the vicinity of the IL-4 gene. We suggest that the RAD50 LCR has a complex and dual role in Th1 and Th2 differentiation, communicating early T cell antigen receptor and cytokine signals to the IL-4/IL-13 locus in both differentiating cell types.

Altered Th1 Cell Differentiation Programming by CIITA Deficiency

CD4 T cell differentiation is a complex process affected by many transcription factors interacting in a tightly regulated manner. We have previously shown that CIITA-deficient mouse Th1 cells expressed Th2-type cytokines, while IFN-gamma expression was normal. In this study, we show that CIITA-deficient Th1 cells contain three distinct populations: cells secreting IL-4 alone, IFN-gamma alone, and both IL-4 and IFN-gamma together. This novel phenotype is stable over multiple rounds of stimulation in the presence of Th1-inducing factors. CIITA-deficient Th1 cells require TCR-mediated signaling to express Th2 cytokines, and this occurs with similar kinetics as wild-type Th2 cells. Both GATA-3 and IL-4 appear to be required for CIITA-deficient Th1 cells to express Th2-type cytokines. Interestingly, however, CIITA-deficient Th1 cells can produce IL-4 in the absence of exogenous IL-4. Introducing either CIITA or antisense GATA-3 during Th1 differentiation partially reduces Th2-type cytokine expression. With the exception of Th2-type cytokine expression, Th1 differentiation occurs normally in the absence of CIITA, as measured by expression of T-bet, IL-12Rbeta2, IL-18Ralpha, and IFN-gamma. Therefore, CIITA plays a key role to repress Th2-type cytokine expression as naive CD4 T cells differentiate toward the Th1 lineage.

Differential Regulation of Th1/Th2 Cytokine Responses by Placental Protein 14

The potency of TCR signaling during primary CD4+ T cell activation influences initial cytokine expression patterns and subsequent polarization toward either Th1 or Th2 subsets. In this study, we demonstrate that the T cell inhibitor placental protein 14 (PP14; glycodelin) preferentially inhibits Th1 cytokine responses and chemokine expression when present during ex vivo priming of CD4+ T cells. PP14 synergizes with exogenously added IL-4 in skewing T cell responses. Significantly, PP14 impairs the down-regulation of GATA-3 transcriptional regulator expression that normally accompanies T cell activation, which is a prerequisite for Th1 development. Taken together, these data document for the first time the ability of PP14 to skew Th responses.

STAT6-Dependent Differentiation and Production of IL-5 and IL-13 in Murine NK2 Cells

NK cells differentiate into either NK1 or NK2 cells that produce IFN-gamma or IL-5 and IL-13, respectively. Little is known, however, about the molecular mechanisms that control NK1 and NK2 cell differentiation. To address these questions, we established an in vitro mouse NK1/NK2 cell differentiation culture system. For NK1/NK2 cell differentiation, initial stimulation with PMA and ionomycin was required. The in vitro differentiated NK2 cells produced IL-5 and IL-13, but the levels were 20 times lower than those of Th2 or T cytotoxic (Tc)2 cells. No detectable IL-4 was produced. Freshly prepared NK cells express IL-2Rbeta, IL-2RgammaC, and IL-4Ralpha. After stimulation with PMA and ionomycin, NK cells expressed IL-2Ralpha. NK1 cells displayed higher cytotoxic activity against Yac-1 target cells. The levels of GATA3 protein in developing NK2 cells were approximately one-sixth of those in Th2 cells. Both NK1 and NK2 cells expressed large amounts of repressor of GATA, the levels of which were equivalent to CD8 Tc1 and Tc2 cells and significantly higher than those in Th2 cells. The levels of histone hyperacetylation of the IL-4 and IL-13 gene loci in NK2 cells were very low and equivalent to those in naive CD4 T cells. The production of IL-5 and IL-13 in NK2 cells was found to be STAT6 dependent. Thus, similar to Th2 cells, NK2 cell development is dependent on STAT6, and the low level expression of GATA3 and the high level expression of repressor of GATA may influence the unique type 2 cytokine production profiles of NK2 cells.

IL-4-mediated inhibition of IFN-gamma production by CD4+ T cells proceeds by several developmentally regulated mechanisms

The mechanisms by which Th1 and Th2 cells inter-regulate in vivo are still poorly understood. In this study we examined the plasticity of Th1 cell differentiation and how Th2 cells may down-regulate these responses. We show here that IL-4 affects Th1 cell responses by two developmentally regulated mechanisms. During the commitment phase of naive CD4+ T cells, IL-4 inhibits Th1 cell differentiation and induces a reversion of developing Th1 cells to the Th2 lineage. In contrast, for effector Th1 cells IL-4 does not affect the developmental process, but only the transcription of the IFN-gamma gene. We further show that the difference in IL-4 responsiveness correlates with a loss, in effector Th1 cells, of IL-4-dependent up-regulation of GATA-3 expression despite normal activation of STAT6. Transient inhibition of IFN-gamma production by differentiated effector cells may explain why Th1 and Th2 responses can co-exist in vivo although Th2 effector cells dominate functionally, as observed in some infectious or autoimmune mice models.

Vitamin D receptor-deficient mice fail to develop experimental allergic asthma

The active metabolite of vitamin D (1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3))) is known to modulate the immune response in Th1 cell-directed diseases. To investigate the role of vitamin D in Th2 cell-directed diseases, experimental allergic asthma was induced in vitamin D receptor (VDR) knockout and in wild-type (WT) mice. As expected, WT mice developed symptoms of airway inflammation with an influx of eosinophils, elevated Th2 cytokine levels, mucous production, and airway hyperresponsiveness. The administration of 1,25(OH)(2)D(3) had no effect on asthma severity. The only discernable effect of 1,25(OH)(2)D(3) on experimental allergic asthma in WT mice was an increased expression of two Th2-related genes (soluble CD23 and GATA-3) in lungs of BALB/c mice exposed to Ag through the nasal route only. By contrast, asthma-induced VDR knockout mice failed to develop airway inflammation, eosinophilia, or airway hyperresponsiveness, despite high IgE concentrations and elevated Th2 cytokines. The data suggest that although 1,25(OH)(2)D(3) induced these Th2-type genes, the treatment failed to have any affect on experimental asthma severity. However, VDR-deficient mice failed to develop experimental allergic asthma, suggesting an important role for the vitamin D endocrine system in the generation of Th2-driven inflammation in the lung.

Chronic intestinal nematode infection induces Stat6-independent interleukin-5 production and causes eosinophilic inflammatory responses in mice

The role of Stat6 (signal transducers and activators of transcription) in the recruitment and activation of eosinophils has been studied in detail in asthma and other allergic diseases. In this study, we demonstrated that eosinophil responses occur in a Stat6-independent manner in mice infected with the intestinal nematode, Nippostrongylus brasiliensis. Stat6-deficient (Stat6(-/-)) mice cannot expel N. brasiliensis and establish chronic infections. Prominent blood and intestinal eosinophilia were induced after day 14 postinfection (p.i.) and maintained at this level in Stat6(-/-) mice, whereas in wild-type mice eosinophil responses reached a peak on day 10 p.i. and declined thereafter. The introduction of a secondary infection of N. brasiliensis into wild-type mice induced rapid and exaggerated eosinophilia, whereas secondary infection in Stat6(-/-) mice resulted in almost the same eosinophil responses as those of the primary infection, suggesting a lack of memory responses. Blood eosinophilia was also induced in Stat6(-/-) mice implanted with N. brasiliensis in the small intestine, suggesting that intestinal exposure to parasitic antigen is sufficient to induce eosinophil responses. Furthermore, this prominent eosinophil response of Stat6(-/-) mice after day 14 was closely associated with an increase of interleukin (IL)-5 production in serum and intestine. Neither IL-4 nor eotaxin were significantly induced in Stat6(-/-) mice after infection with N. brasiliensis. We also found that mRNA for IL-5, GATA-3 and eosinophil peroxidase (EPO) are induced in the intestine of Stat6(-/-) mice on day 14 p.i. Taken together, these results provide evidence for Stat6-independent IL-5 production and subsequent eosinophil responses after chronic infection with N. brasiliensis.