An instructive component in T helper cell type 2 (Th2) development mediated by GATA-3

Unintended Consequences: Risk of Opportunistic Infections Associated With Long-term Glucocorticoid Therapies in Adults

Glucocorticoids are widespread anti-inflammatory medications used in medical practice. The immunosuppressive effects of systemic glucocorticoids and increased susceptibility to infections are widely appreciated. However, the dose-dependent model frequently used may not accurately predict the risk of infection in all patients treated with long-term glucocorticoids. In this review, we examine the risks of opportunistic infections (OIs) in patients requiring glucocorticoid therapy by evaluating the influence of the glucocorticoid dose, duration, and potency, combined with biological and host clinical factors and concomitant immunosuppressive therapy. We propose strategies to prevent OIs, which involve screening, antimicrobial prophylaxis, and immunizations. While this review focuses on patients with autoimmune, inflammatory, or neoplastic diseases, the potential risks and preventative strategies are likely applicable to other populations. Clinicians should actively assess the benefit-harm ratios of systemic glucocorticoids and implement preventive efforts to decrease their associated infections complications.

Cell-mediated immune response against mycolic acids of Mycobacteroides salmoniphilum in rainbow trout Oncorhynchus mykiss

Mycobacteriosis caused by Mycobacterium spp. causes economic damages to the world aquaculture industry. In mammals, mycolic acids contained in the cell wall of Mycobacterium spp. are presented by CD1b molecule as lipid antigens and induce cell-mediated immunity (CMI). Here, we investigated CMI responses against the mycolic acids of Mycobacterioides salmoniphilum in a CD1-lacking teleost fish, rainbow trout. After stimulation of trout leukocytes with mycolic acids, the number and percentage of CD8α⁺ T cells increased. Fish immunized with mycolic acids showed an up-regulation of IFN-γ. Further, in vitro re-stimulation of leukocytes derived from immunized fish resulted in proliferation of CD8α⁺ cells. These data suggest that mycolic acids are recognized as lipid antigens resulting in an activation of rainbow trout CD8α⁺ cells and up-regulation of the Th1 cytokine IFN-γ. The mycolic acids are promising candidates for vaccines to activate CD8α⁺ T cells against fish mycobacteriosis.

Pioneer factors in development and cancer

Transcription factors (TFs) are essential mediators of epigenetic regulation and modifiers of penetrance. Studies from the past decades have revealed a sub-class of TF that is capable of remodeling closed chromatin states through targeting nucleosomal motifs. This pioneer factor (PF) class of chromatin remodeler is ATP independent in its roles in epigenetic initiation, with nucleosome-motif recognition and association with repressive chromatin regions. Increasing evidence suggests that the fundamental properties of PFs can be coopted in human cancers. We explore the role of PFs in the larger context of tissue-specific epigenetic regulation. Moreover, we highlight an emerging class of chimeric PF derived from translocation partners in human disease and PFs associated with rare tumors. In the age of site-directed genome editing and targeted protein degradation, increasing our understanding of PFs will provide access to next-generation therapy for human disease driven from altered transcriptional circuitry.

PD-1 Affects the Immunosuppressive Function of Group 2 Innate Lymphoid Cells in Human Non-Small Cell Lung Cancer

Background

There is increasing evidence that group 2 innate lymphoid cells (ILC2s) play an essential role in allergy and parasitic infection. However, the role of ILC2s in human lung cancer remains unclear.

Methods

ILC2s from peripheral blood mononuclear cells (PBMCs) obtained from healthy donors (HDs) and non-small cell lung cancer (NSCLC) patients, and NSCLC tumor tissues were analyzed via multicolor flow cytometry. ILC2s or CD14⁺ cells were sorted by fluorescence-activated cell sorting. qPCR and flow cytometry were performed to assess the gene and protein expression of the indicated molecules. M1-like and M2-like macrophages were induced from CD14⁺ monocytes in vitro.

Results

ILC2s were significantly more enriched in PBMCs and tumor tissues from NSCLC patients than in HDs. After screening for the main immune checkpoint molecules, we found that PD-1 was upregulated in ILC2s in NSCLC patients. Functionally, PD-1^high ILC2s from tumor tissues expressed higher levels of IL-4 and IL-13 regarding both mRNA and protein levels than PD-1^low ILC2s. Furthermore, PD-1^high ILC2s robustly boosted M2-like macrophage polarization in vitro, by secreting IL-4 and IL-13, while neutralization of IL-4 and IL-13 by antibodies abrogated M2-like macrophage polarization.

Conclusion

ILC2s are enriched in NSCLC patients and upregulate PD-1 expression. Upregulation of PD-1 facilitates the immunosuppressive function of ILC2s. PD-1^high ILC2s enhance M2-like macrophage polarization by secreting IL-4 and IL-13. PD-1 acts as a positive regulator of the immunosuppressive function of ILC2s in human NSCLC.

Thrombocytopenia in solid tumors: Prognostic significance

Solid tumors are a heterogeneous group of malignancies that result from out-of-control proliferation of cells. Thrombocytopenia is a common complication among patients with solid tumors that predispose them to bleeding disorders. The aim of this review article is to investigate the underlying mechanisms of the risk and incidence of thrombocytopenia in solid tumors. It can be argued that thrombocytopenia is a poor prognostic factor in solid tumors that can result from several factors such as polymorphism and mutation in some transcription factors and cytokines involved in megakaryocytic maturation or from the adverse effects of treatment. Therefore, an understanding of the exact mechanism of thrombocytopenia pathogenesis in each stage of solid tumors can help in developing therapeutic strategies to decrease bleeding complications in these malignancies.

Regulatory and Mechanistic Actions of Glucocorticoids on T and Inflammatory Cells

Glucocorticoids (GCs) play an important role in regulating the inflammatory and immune response and have been used since decades to treat various inflammatory and autoimmune disorders. Fine-tuning the glucocorticoid receptor (GR) activity is instrumental in the search for novel therapeutic strategies aimed to reduce pathological signaling and restoring homeostasis. Despite the primary anti-inflammatory actions of GCs, there are studies suggesting that under certain conditions GCs may also exert pro-inflammatory responses. For these reasons the understanding of the GR basic mechanisms of action on different immune cells in the periphery (e.g., macrophages, dendritic cells, neutrophils, and T cells) and in the brain (microglia) contexts, that we review in this chapter, is a continuous matter of interest and may reveal novel therapeutic targets for the treatment of immune and inflammatory response.

Potential Role of Hepatitis C Virus Alternate Reading Frame Protein in Negative Regulation of T-Bet Gene Expression

Hepatitis C virus (HCV) is a major cause of chronic liver disease and has led to cirrhosis or hepatocellular carcinoma in a majority of infected individuals. We have previously demonstrated that the HCV alternate reading frame protein (F protein) is related to Th1/Th2 bias in chronic hepatitis C (CHC) patients, and we aimed to explore the relative molecular mechanisms here. A total of 104 cases including CHC patients and healthy donors were enrolled. T-bet and GATA-3 expression levels were analyzed in peripheral blood mononuclear cells (PBMCs). The levels of signal transducer and activator of transcription-1/-6(STAT1/6) and phosphorylated STAT1/6(pSTAT1/6) in PBMCs were measured by Western blotting. Our results showed that the levels of T-bet in PBMCs, as well as the levels of gamma interferon (IFN-γ) in sera, were decreased in anti-F protein antibody seropositive patients compared with anti-F protein antibody seronegative patients, whereas the levels of GATA-3 did not show difference between the two groups. Moreover, the decreased pSTAT1 and increased pSTAT6 were observed in PBMCs by HCV core/F protein stimulation with constant STAT1/6 expression. Taken together, it suggested that T-bet may be involved in Th1/Th2 bias induced by HCV F protein, and the disruption of STAT phosphorylation may participate in this mediation.

The Wnt Antagonist Dickkopf-1 Promotes Pathological Type 2 Cell-Mediated Inflammation

Exposure to a plethora of environmental challenges commonly triggers pathological type 2 cell-mediated inflammation. Here we report the pathological role of the Wnt antagonist Dickkopf-1 (Dkk-1) upon allergen challenge or non-healing parasitic infection. The increased circulating amounts of Dkk-1 polarized T cells to T helper 2 (Th2) cells, stimulating a marked simultaneous induction of the transcription factors c-Maf and Gata-3, mediated by the kinases p38 MAPK and SGK-1, resulting in Th2 cell cytokine production. Circulating Dkk-1 was primarily from platelets, and the increase of Dkk-1 resulted in formation of leukocyte-platelet aggregates (LPA) that facilitated leukocyte infiltration to the affected tissue. Functional inhibition of Dkk-1 impaired Th2 cell cytokine production and leukocyte infiltration, protecting mice from house dust mite (HDM)-induced asthma or Leishmania major infection. These results highlight that Dkk-1 from thrombocytes is an important regulator of leukocyte infiltration and polarization of immune responses in pathological type 2 cell-mediated inflammation.

High mobility group box 1: a novel mediator of Th2-type response-induced airway inflammation of acute allergic asthma

BACKGROUND

High mobility group box 1 (HMGB1) is an inflammatory mediator involved into the advanced stage of systemic inflammatory response syndrome (SIRS), and is over-expressed in bacterial sepsis and hemorrhagic shock. Recently, it has been found that the HMGB1 was abnormally expressed in induced sputum and plasma of asthmatic patients. However, the precise role of HMGB1 in the acute allergic asthma is unclear. Therefore, we aim to investigate the role HMGB1 in regulating airway inflammation of acute allergic asthma and its possible mechanism in this study.

METHODS

Forty-eight BALB/c female mice were randomly divided into four groups: control group (Control), asthma group (Asthma), HMGB1 group (HMGB1) and anti-HMGB1 (HMGB1 monoclonal antibody of mice) group (Anti-HMGB1). Acute allergic asthma mice models were established by ovalbumin (OVA)-challenge. Then, we measured the levels of HMGB1 in bronchoalveolar lavage fluid (BALF) and lung tissue of mice. Finally, after exogenous HMGB1 and/or anti-HMGB1 administration, pulmonary function test, histological analysis, Western blot, cytological analysis and ELISA assay were performed to explore the effect of HMGB1 in acute allergic asthma.

RESULTS

The levels of HMGB1 in BALF and lung tissue and the expression of HMGB1 protein in the lung tissue of asthma group were significantly higher than those in control group, respectively (P<0.01). Moreover, the HMGB1 group was showed an increased mucus secretion and infiltration of eosinophils and neutrophils in the airway of asthma mice, and a decrease of pulmonary function, compared to control group (P<0.01, respectively). Meanwhile, exogenous HMGB1 could increase the levels of IL-4, IL-5, IL-6, IL-8 and IL-17, whereas could reduce the IFN-γ in the BALF and lung tissue (P<0.05, respectively). Exogenous HMGB1 could enhance GATA3 expression of Th2 cells and attenuate the T-bet expression of Th1 cells (P<0.05, respectively), which could be abrogated after inhibiting HMGB1.

CONCLUSIONS

HMGB1 could aggravate eosinophilic inflammation in the airway of acute allergic asthma through inducing a dominance of Th2-type response and promoting the neutrophilic inflammation.

Qualitative differences in brain-infiltrating T cells are associated with a fatal outcome in mice infected with Japanese encephalitis virus

Japanese encephalitis (JE) is the most important form of viral encephalitis in Asia. The critical factors determining mortality and severity of JE virus (JEV) infection remain unclear. We identified brain-infiltrating T cells associated with a fatal outcome of JEV infection in mice. Dying mice were defined as those that lost more than 25 % of their body weight by day 13 and died by day 21, while surviving mice were defined as those that lost less than 10 % by day 13, based on the result of the survival time course study. Two groups of five mice that demonstrated brain virus titers of >1 × 10(6) pfu/g were randomly selected from the dying and surviving groups and used in the analyses. Cytokine patterns in brains were first examined, revealing a higher ratio of Th1-related cytokine genes in dying mice. The expression levels of CD3, CD8, CD25, and CD69 increased in JEV-infected mice relative to mock-infected mice. However, expression levels of these cell-surface markers did not differ between the two groups. T-cell receptor (TCR) usage and complementary determining region 3 (CDR3) sequences were analyzed in the brain-infiltrating T cells. T cells expressing VA8-1, VA10-1, and VB2-1 increased in both groups. However, the dominant T-cell clones as defined by CDR3 amino acid sequence differed between the two groups. The results indicate that the outcome of JEV infection, death or survival, was determined by qualitative differences in infiltrating T-cell clones with unique CDR3 amino acid sequences.

Downregulation of T-bet/GATA-3 ratio induced by IL-11 treatment is responsible for Th1/Th2 balance restoration in human immune thrombocytopenic purpura (ITP)

Abnormal cellular immunity induced by deranged Th1/Th2 profile has been revealed to play a critical role in the pathogenesis of immune thrombocytopenic purpura (ITP). Correction of the shifted Th1/Th2 balance represents a potential therapeutic approach to treat ITP. Here, we investigated the effects of IL-11 on the restoration of Th1/Th2 balance in the peripheral blood mononuclear cells (PBMCs) isolated from adult ITP patients. As shown here, we observed a higher ratio of T-bet/GATA-3 gene expression by quantitative real-time PCR in the PBMCs from ITP patients, consistent with the presence of an abnormally high Th1/Th2 ratio. Remarkably, upon IL-11 treatment, a reversal of T-bet/GATA-3 ratio in ITP was achieved and was shown to be responsible for the restoration of Th1/Th2 balance, with IL-11 at 100 ng/ml demonstrating the highest efficiency. T-bet and GATA-3 are the two transcriptional factors that have been indicated to be the master regulators for Th1 and Th2 lineage commitment, respectively. In the presence of 100 ng/ml IL-11, GATA-3 transcript abundance rose up to ~85-fold of that measured in untreated cells, whereas T-bet transcripts were lowered merely to ~41%, suggesting that GATA-3 was the major contributor for the reversal of T-bet/GATA-3 ratio. Thus, our findings may very well encourage the development of novel medicines that specifically target and correct the T-bet/GATA-3 imbalance identified in ITP.

An NLRP3 inflammasome-triggered Th2-biased adaptive immune response promotes leishmaniasis

Leishmaniasis is a major tropical disease that can present with cutaneous, mucocutaneous, or visceral manifestation and affects millions of individuals, causing substantial morbidity and mortality in third-world countries. The development of a Th1-adaptive immune response is associated with resistance to developing Leishmania major (L. major) infection. Inflammasomes are key components of the innate immune system that contribute to host defense against bacterial and viral pathogens; however, their role in regulating adaptive immunity during infection with protozoan parasites is less studied. Here, we demonstrated that the NLRP3 inflammasome balances Th1/Th2 responses during leishmaniasis. Mice lacking the inflammasome components NLRP3, ASC, or caspase 1 on a Leishmania-susceptible BALB/c background exhibited defective IL-1β and IL-18 production at the infection site and were resistant to cutaneous L. major infection. Moreover, we determined that production of IL-18 propagates disease in susceptible BALB/c mice by promoting the Th2 cytokine IL-4, and neutralization of IL-18 in these animals reduced L. major titers and footpad swelling. In conclusion, our results indicate that activation of the NLRP3 inflammasome is detrimental during leishmaniasis and suggest that IL-18 neutralization has potential as a therapeutic strategy to treat leishmaniasis patients.

Fbw7 targets GATA3 through cyclin-dependent kinase 2-dependent proteolysis and contributes to regulation of T-cell development

Proper development of T cells depends on lineage-specific regulators controlled transcriptionally and posttranslationally to ensure precise levels at appropriate times. Conditional inactivation of F-box protein Fbw7 in mouse T-cell development resulted in reduced thymic CD4 single-positive (SP) and splenic CD4(+) and CD8(+) cell proportions. Fbw7 deficiency skewed CD8 SP lineage differentiation, which exhibited a higher incidence of apoptosis. Similar perturbations during development of CD8-positive cells were reported with transgenic mice, which enforced GATA3 (T-cell differentiation regulator) expression throughout T-cell development. We observed augmented GATA3 in CD4/CD8 double negative (DN) stage 4, CD4 SP, and CD8 SP lineages in Fbw7-deficient thymocytes. Using overexpressed proteins in cultured cells, we demonstrated that Fbw7 bound to, ubiquitylated, and destabilized GATA3. Two Cdc4 phosphodegron (CPD) candidate sequences, consensus Fbw7 recognition domains, were identified in GATA3, and phosphorylation of Thr-156 in CPD was required for Fbw7-mediated ubiquitylation and degradation. Phosphorylation of GATA3 Thr-156 was detected in mouse thymocytes, and cyclin-dependent kinase 2 (CDK2) was identified as a respondent for phosphorylation at Thr-156. These observations suggest that Fbw7-mediated GATA3 regulation with CDK2-mediated phosphorylation of CPD contributes to the precise differentiation of T-cell lineages.

IFN-α suppresses GATA3 transcription from a distal exon and promotes H3K27 trimethylation of the CNS-1 enhancer in human Th2 cells

CD4(+) Th2 development is regulated by the zinc finger transcription factor GATA3. Once induced by acute priming signals, such as IL-4, GATA3 poises the Th2 cytokine locus for rapid activation and establishes a positive-feedback loop that maintains elevated GATA3 expression. Type I IFN (IFN-α/β) inhibits Th2 cells by blocking the expression of GATA3 during Th2 development and in fully committed Th2 cells. In this study, we uncovered a unique mechanism by which IFN-α/β signaling represses the GATA3 gene in human Th2 cells. IFN-α/β suppressed expression of GATA3 mRNA that was transcribed from an alternative distal upstream exon (1A). This suppression was not mediated through DNA methylation, but rather by histone modifications localized to a conserved noncoding sequence (CNS-1) upstream of exon 1A. IFN-α/β treatment led to a closed conformation of CNS-1, as assessed by DNase I hypersensitivity, along with enhanced accumulation of H3K27me3 mark at this CNS region, which correlated with increased density of total nucleosomes at this putative enhancer. Consequently, accessibility of CNS-1 to GATA3 DNA binding activity was reduced in response to IFN-α/β signaling, even in the presence of IL-4. Thus, IFN-α/β disrupts the GATA3-autoactivation loop and promotes epigenetic silencing of a Th2-specific regulatory region within the GATA3 gene.

Lentivirally overexpressed T-bet regulates T-helper cell lineage commitment in chronic hepatitis B patients

Chronic hepatitis B virus (HBV) infection is commonly considered to occur as a result of disturbance of the immune system. T-box expressed in T cells (T-bet) is an essential transcription factor for T helper (Th) cell differentiation and function. The aim of this study was to investigate the effect of T-bet overexpression on Th cell differentiation and the possible mechanism in chronic hepatitis B (CHB) patients. CD4+ T cells from the peripheral blood of 23 CHB patients, 8 acute hepatitis B (AHB) patients and 10 healthy controls were isolated. T-bet mRNA expression of CD4+ T cells was detected by quantitative real-time polymerase chain reaction (PCR). The T-bet DNA fragment was subcloned into the pGC-FU vector containing GFP to generate a recombinant lentiviral vector, pGC-FU-T-bet, while a no-load pGC-FU vector was used as the negative control. After transduction into CD4+ T cells from another 22 CHB patients, the induction of Th1- and Th2-type cytokines was assayed by an enzyme-linked immunosorbent assay (ELISA), and RT-PCR and western blot analysis were used to measure the mRNA and transcription levels of H2.0-like homeobox (HLX1), GATA-3 and STAT-6. T-bet mRNA expression in CD4+ T cells from AHB patients was enhanced compared with CHB patients and healthy controls. Th1-type cytokines and HLX1 expression was upregulated, while Th2-type cytokines and GATA-3 and STAT-6 expression was repressed after lentiviral introduction of T-bet. In conclusion, lentivirally overexpressed T-bet regulates Th cell lineage commitment in CHB patients, which may be mediated by regulating HLX1, GATA-3 and STAT-6 expression.

From the cradle to the grave: activities of GATA-3 throughout T-cell development and differentiation

GATA family transcription factors play multiple vital roles in hematopoiesis in many cell lineages, and in particular, T cells require GATA-3 for execution of several developmental steps. Transcriptional activation of the Gata3 gene is observed throughout T-cell development and differentiation in a stage-specific fashion. GATA-3 has been described as a master regulator of T-helper 2 (Th2) cell differentiation in mature CD4(+) T cells. During T-cell development in the thymus, its roles in the CD4 versus CD8 lineage choice and at the β-selection checkpoint are the best characterized. In contrast, its importance prior to β-selection has been obscured both by the developmental heterogeneity of double negative (DN) 1 thymocytes and the paucity of early T-lineage progenitors (ETPs), a subpopulation of DN1 cells that contains the most immature thymic progenitors that retain potent T-lineage developmental potential. By examining multiple lines of in vivo evidence procured through the analysis of Gata3 mutant mice, we have recently demonstrated that GATA-3 is additionally required at the earliest stage of thymopoiesis for the development of the ETP population. Here, we review the characterized functions of GATA-3 at each stage of T-cell development and discuss hypothetical molecular pathways that mediate these functions.

Regulation of effector and memory T-cell functions by type I interferon

Type I interferon (IFN-α/β) is comprised of a family of highly related molecules that exert potent antiviral activity by interfering with virus replication and spread. IFN-α/β secretion is tightly regulated through pathogen sensing pathways that are operative in most somatic cells. However, specialized antigen-presenting plasmacytoid dendritic cells are uniquely equipped with the capacity to secrete extremely high levels of IFN-α/β, suggesting a key role for this cytokine in priming adaptive T-cell responses. Recent studies in both mice and humans have demonstrated a role for IFN-α/β in directly influencing the fate of both CD4(+) and CD8(+) T cells during the initial phases of antigen recognition. As such, IFN-α/β, among other innate cytokines, is considered an important 'third signal' that shapes the effector and memory T-cell pool. Moreover, IFN-α/β also serves as a counter-regulator of T helper type 2 and type 17 responses, which may be important in the treatment of atopy and autoimmunity, and in the development of novel vaccine adjuvants.

T helper cell differentiation more than just cytokines

CD4(+) T helper (T(H)) cells play a critical role in orchestrating a pleiotropy of immune activities against a large variety of pathogens. It is generally thought that this is achieved through the acquisition of highly specialized functions after activation followed by the differentiation into various functional subsets. The differentiation process of naive precursor T(H) cells into defined effector subsets is controlled by cells of the innate immune system and their complex array of effector molecules such as secreted cytokines and membrane bound costimulatory molecules. These provide a unique quantitative or qualitative signal initiating T(H) development, which is subsequently reinforced via T cell-mediated feedback signals and selective survival and proliferative cues, ultimately resulting in the predominance of a particular T cell subset. In recent years, the number of defined T(H)cell subsets has expanded and the once rigid division of labor among them has been blurred with reports of plasticity among the subsets. In this chapter, we summarize and speculate on the current knowledge of the differentiation requirements of T(H) cell lineages, with particular focus on the T(H)17 subset.

Effector T cell plasticity: flexibility in the face of changing circumstances

As more states of CD4 T cell differentiation are uncovered, their flexibility is also beginning to be recognized. Components that control the plasticity of CD4 T cell populations include cellular conditions, clonality, transcriptional circuitry and chromatin modifications. Appearance of cellular flexibility may arise from truly flexible genetic programs or, alternatively, from heterogeneous populations. New tools will be needed to define the rules that allow or prohibit cellular transitions.

T-bet, GATA-3, and Foxp3 expression and Th1/Th2 cytokine production in the clinical outcome of human infection with Leishmania (Viannia) species

BACKGROUND

T cell differentiation determines susceptibility and resistance to experimental cutaneous leishmaniasis, yet mixed T1/Th2 responses characterize the clinical spectrum of human infection with Leishmania (Viannia) species.

MATERIALS AND METHODS

To discern the interrelationship of T cell differentiation and outcome of human infection, we examined factors that regulate T cell differentiation and Th1/Th2 cytokine responses in asymptomatic infection, active and historical chronic and recurrent cutaneous leishmaniasis. T-bet, GATA-3, Foxp3, and cytokine gene expression were quantified by real-time polymerase chain reaction and correlated with interleukin 2, interferon gamma, tumor necrosis factor alpha, interleukin 4, interleukin 13, and interleukin 10 secretion during in vitro response to live Leishmania panamensis.

RESULTS

Higher GATA-3 expression than T-bet expression occurred throughout the 15 days of coculture with promastigotes; however, neither transcription nor secretion of interleukin 4 was detected. A sustained inverse correlation between GATA-3 expression and secretion of proinflammatory cytokines interferon gamma and tumor necrosis factor alpha was observed in asymptomatic infection. In contrast, higher T-bet expression and a higher ratio of T-bet to GATA-3 characterized active recurrent disease. Down-regulation of T-bet and GATA-3 expression and increased interleukin 2 secretion, compared with control subjects, was directly correlated with Foxp3 expression and interleukin 13 secretion in chronic disease.

CONCLUSIONS

Regulation of the inflammatory response rather than biased Th1/Th2 response distinguished asymptomatic and recalcitrant outcomes of infection with Leishmnania viannia species.

Cutting edge: Type I IFN reverses human Th2 commitment and stability by suppressing GATA3

T helper 2 cells regulate inflammatory responses to helminth infections while also mediating pathological processes of asthma and allergy. IL-4 promotes Th2 development by inducing the expression of the GATA3 transcription factor, and the Th2 phenotype is stabilized by a GATA3-dependent autoregulatory loop. In this study, we found that type I IFN (IFN-alpha/beta) blocked human Th2 development and inhibited cytokine secretion from committed Th2 cells. This negative regulatory pathway was operative in human but not mouse CD4(+) T cells and was selective to type I IFN, as neither IFN-gamma nor IL-12 mediated such inhibition. IFN-alpha/beta blocked Th2 cytokine secretion through the inhibition of GATA3 during Th2 development and in fully committed Th2 cells. Ectopic expression of GATA3 via retrovirus did not overcome IFN-alpha/beta-mediated inhibition of Th2 commitment. Thus, we demonstrate a novel role for IFN-alpha/beta in blocking Th2 cells, suggesting its potential as a promising therapy for atopy and asthma.

The role of the glucocorticoid receptor in inflammation and immunity

Glucocorticoids are potent immunosuppressive agents with complex actions on immune cells evoking the following effects: inducing apoptosis, changing differentiation fate, inhibition of cytokine release, inhibition of migration and other features. Distinct molecular mechanisms of the glucocorticoid receptor (GR) contribute to different anti-inflammatory effects. Recently inflammatory models have been investigated using conditional knockout and function selective mice shedding light on critical cell types and molecular mechanisms of endogenous and therapeutic GC actions. Here we review the multiple effects of GCs on major immune cells, dendritic cells, myeloid cells and B- and T-lymphocytes and give a summary of studies using conditional GR knockout mice.

PU.1 regulates TCR expression by modulating GATA-3 activity

The Ets transcription factor PU.1 is a master regulator for the development of multiple lineages during hematopoiesis. The expression pattern of PU.1 is dynamically regulated during early T lineage development in the thymus. We previously revealed that PU.1 delineates heterogeneity of effector Th2 populations. In this study, we further define the function of PU.1 on the Th2 phenotype using mice that specifically lack PU.1 in T cells using an lck-Cre transgene with a conditional Sfpi1 allele (Sfpi1(lck-/-)). Although deletion of PU.1 by the lck-Cre transgene does not affect T cell development, Sfpi1(lck-/-) T cells have a lower activation threshold than wild-type T cells. When TCR engagement is limiting, Sfpi1(lck-/-) T cells cultured in Th2 polarizing conditions secrete higher levels of Th2 cytokines and have greater cytokine homogeneity than wild-type cells. We show that PU.1 modulates the levels of TCR expression in CD4(+) T cells by regulating the DNA-binding activity of GATA-3 and limiting GATA-3 regulation of TCR gene expression. GATA-3-dependent regulation of TCR expression is also observed in Th1 and Th2 cells. In CD4(+) T cells, PU.1 expression segregates into subpopulations of cells that have lower levels of surface TCR, suggesting that PU.1 contributes to the heterogeneity of TCR expression. Thus, we have identified a mechanism whereby increased GATA-3 function in the absence of the antagonizing activity of PU.1 leads to increased TCR expression, a reduced activation threshold, and increased homogeneity in Th2 populations.

Downregulation of CXCR6 and CXCR3 in lymphocytes from birch-allergic patients

Preferential expression of chemokine receptors on Th1 or Th2 T-helper cells has mostly been studied in cell lines generated in vitro or in animal models; however, results are less well characterized in humans. We determined T-cell responses through chemokine receptor expression on lymphocytes, and cytokine secretion in plasma from birch-allergic and healthy subjects. The expression of CCR2, CCR3, CCR4, CCR5, CCR7, CXCR3, CXCR4, CXCR6, IL-12 and IL-18R receptors was studied on CD4(+) and CD8(+) cells from birch-allergic (n = 14) and healthy (n = 14) subjects by flow cytometry. The concentration of IL-4, IL-5, IL-10, IL-12, IFN-gamma and TNF-alpha cytokines was measured in plasma from the same individuals using a cytometric bead array human cytokines kit. The similar expression of CCR4 in T cells from atopic and healthy individuals argues against the use of the receptor as an in vivo marker of Th2 immune responses. Reduced percentages of CD4(+) cells expressing IL-18R, CXCR6 and CXCR3 were found in the same group of samples. TNF-alpha, IFN-gamma, IL-10, IL-5, IL-4 and IL-12 cytokines were elevated in samples from allergic individuals. Reduced expression of Th1-associated chemokine receptors together with higher levels of Th1, Th2 and anti-inflammatory cytokines in samples from allergic patients indicate that immune responses in peripheral blood in atopic diseases are complex and cannot be simplified to the Th1/Th2 paradigm. Not only the clinical picture of atopic diseases but also the clinical state at different time points of the disease might influence the results of studies including immunological markers associated with Th1- or Th2-type immune responses.

The protein tyrosine phosphatase PTPN4/PTP-MEG1, an enzyme capable of dephosphorylating the TCR ITAMs and regulating NF-kappaB, is dispensable for T cell development and/or T cell effector functions

T cell receptor signaling processes are controlled by the integrated actions of families of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPases). Several distinct cytosolic protein tyrosine phosphatases have been described that are able to negatively regulate TCR signaling pathways, including SHP-1, SHP-2, PTPH1, and PEP. Using PTPase substrate-trapping mutants and wild type enzymes, we determined that PTPN4/PTP-MEG1, a PTPH1-family member, could complex and dephosphorylate the ITAMs of the TCR zeta subunit. In addition, the substrate-trapping derivative augmented basal and TCR-induced activation of NF-kappaB in T cells. To characterize the contribution of this PTPase in T cells, we developed PTPN4-deficient mice. T cell development and TCR signaling events were comparable between wild type and PTPN4-deficient animals. The magnitude and duration of TCR-regulated ITAM phosphorylation, as well as overall protein phosphorylation, was unaltered in the absence of PTPN4. Finally, Th1- and Th2-derived cytokines and in vivo immune responses to Listeria monocytogenes were equivalent between wild type and PTPN4-deficient mice. These findings suggest that additional PTPases are involved in controlling ITAM phosphorylations.

Notch and presenilin regulate cellular expansion and cytokine secretion but cannot instruct Th1/Th2 fate acquisition

Recent reports suggested that Delta1, 4 and Jagged1, 2 possessed the ability to instruct CD4⁺ T cell into selection of Th1 or Th2 fates, respectively, although the underlying mechanism endowing the cleaved Notch receptor with memory of ligand involved in its activation remains elusive. To examine this, we prepared artificial antigen-presenting cells expressing either DLL1 or Jag1. Although both ligands were efficient in inducing Notch2 cleavage and activation in CD4⁺ T or reporter cells, the presence of Lunatic Fringe in CD4⁺ T cells inhibited Jag1 activation of Notch1 receptor. Neither ligand could induce Th1 or Th2 fate choice independently of cytokines or redirect cytokine-driven Th1 or Th2 development. Instead, we find that Notch ligands only augment cytokine production during T cell differentiation in the presence of polarizing IL-12 and IL-4. Moreover, the differentiation choices of naïve CD4⁺ T cells lacking γ-secretase, RBP-J, or both in response to polarizing cytokines revealed that neither presenilin proteins nor RBP-J were required for cytokine-induced Th1/Th2 fate selection. However, presenilins facilitate cellular proliferation and cytokine secretion in an RBP-J (and thus, Notch) independent manner. The controversies surrounding the role of Notch and presenilins in Th1/Th2 polarization may reflect their role as genetic modifiers of T-helper cells differentiation.

Effects of environmental tobacco smoke exposure on pulmonary immune response in infant monkeys

BACKGROUND

Exposure to environmental tobacco smoke (ETS) in early life has adverse effects on lung development and increases asthma incidence and susceptibility to infection. We have previously reported that perinatal and postnatal exposure to ETS in infant monkeys leads to an impaired T(H)1 immune response in peripheral blood.

OBJECTIVE

Determine whether ETS exposure during the perinatal period alters pulmonary immune maturation in the neonatal lung.

METHODS

Nonhuman primates were exposed to ETS from gestation day 50 to 13 months postnatal age (perinatal ETS) or from 6 to 13 months (postnatal ETS). Control animals were only exposed to filtered air. T(H)1 and T(H)2-related cytokines, chemokines, and their corresponding receptors as well as transcription factors were analyzed in lung tissues at 13 months.

RESULTS

Animals exposed to ETS beginning in utero exhibited more profound alterations in T(H)1 factors compared with animals exposed to ETS beginning at 6 months postnatal age. In perinatal ETS-exposed monkeys, mRNA for IFN-gamma, IL-2, IFN-gamma-inducible protein 10, monokine induced by IFN-gamma, IFN-gamma-inducible T-cell chemoattractant, CXC chemokine receptor 3, IL-12 bioactive p70 subunit, and T-bet were significantly downregulated, whereas in postnatal ETS-exposed monkeys, only IFN-gamma, CXC chemokine receptor 3, and IL-12p70 were significantly downregulated. ETS effects on T(H)2 factors were less apparent and more variable: mRNA for thymus and activation-regulated chemokine was increased, and IL-10 protein was reduced.

CONCLUSIONS

Environmental tobacco smoke exposure during early life enhances a local T(H)2 immunity by impairing normal pulmonary T(H)1 immune maturation. This effect was greater in animals beginning ETS exposure in utero.

IFN-alpha is not sufficient to drive Th1 development due to lack of stable T-bet expression

During inflammatory immune responses, the innate cytokine IL-12 promotes CD4+ Th-1 development through the activation of the second messenger STAT4 and the subsequent expression of T-bet. In addition, type I IFN (IFN-alphabeta), secreted primarily during viral and intracellular bacterial infections, can promote STAT4 activation in human CD4+ T cells. However, the role of IFN-alphabeta in regulating Th1 development is controversial, and previous studies have suggested a species-specific pathway leading to Th1 development in human but not mouse CD4+ T cells. In this study, we found that although both IFN-alpha and IL-12 can promote STAT4 activation, IFN-alpha failed to promote Th1 commitment in human CD4+ T cells. The difference between these innate signaling pathways lies with the ability of IL-12 to promote sustained STAT4 tyrosine phosphorylation, which correlated with stable T-bet expression in committed Th1 cells. IFN-alpha did not promote Th1 development in human CD4+ T cells because of attenuated STAT4 phosphorylation, which was insufficient to induce stable expression of T-bet. Further, the defect in IFN-alpha-driven Th1 development was corrected by ectopic expression of T-bet within primary naive human CD4+ T cells. These results indicate that IL-12 remains unique in its ability to drive Th1 development in human CD4+ T cells and that IFN-alpha lacks this activity due to its inability to promote sustained T-bet expression.

GATA-1, -2 and -3 genes expression in bone marrow microenviroment with chronic aplastic anemia

Both bone marrow stromal cells (BMSCs) and transcription factors (GATA-1, GATA-2 and GATA-3) are important in the normal hematopoiesis and the pathogenesis of hematopoietic disease. The purpose of this study was to investigate the expression of GATA-1, GATA-2 and GATA-3 genes in the bone marrow (BM) microenvironment from patients with chronic aplastic anemia (cAA) and normal individuals. Mononuclear cells (MNCs) were isolated from BM of patients with cAA (8 cases) and normal controls (9 cases). Adherent cells (i.e. BMSCs) were collected after long-term culture in vitro. The semi-quantitative expression levels of GATA genes were analyzed by using RT-PCR-enzyme linked immunosorbent assay (RT-PCR-ELISA). The BMSCs with cAA grew slowly compared with the normal BMSCs. In BMSCs, only the expression ratio of GATA-3 gene from cAA group (50.0%) was significant lower than the normal controls (P < 0.05), the expression ratios of other GATA genes from cAA group were similar to the normal controls. There was no difference in the expression level of GATA-1 gene in the BMSCs between normal controls and cAA group. The expression level of GATA-2 gene in BMSCs from cAA was significantly lower than that from normal controls (P < 0.05). The expression level of GATA-3 gene in BMSCs from cAA was significantly higher than that from normal controls (P < 0.05). The dominant expression of GATA-3 gene was found in the BMSCs from cAA and normal controls. GATA genes can be expressed in the BMSCs and may play a role in the regulation of hematopoiesis in normal individuals, as well as in patients with cAA. The change of expression levels of GATA genes may influence the hematopoiesis in BM microenvironment and relate to the pathogenesis and development of aplastic anemia.

Lung CD11c+ cells from mice deficient in Epstein-Barr virus-induced gene 3 (EBI-3) prevent airway hyper-responsiveness in experimental asthma

Epstein-Barr virus-induced gene (EBI)-3 codes for a soluble type 1 cytokine receptor homologous to the p40 subunit of IL-12 that is expressed by antigen-presenting cells following activation. Here, we analyzed the functional role of EBI-3 in a murine model of asthma associated with airway hyper-responsiveness (AHR) in ovalbumin-sensitized mice. Upon allergen challenge, EBI-3-/- mice showed less severe AHR, decreased numbers and degranulation of eosinophils and a significantly reduced number of VCAM-1+ cells in the lungs as compared to wild-type littermates. We thus analyzed lung CD11c+ cells before and after allergen challenge in these mice and found that before allergen challenge, lung CD11c+ cells isolated from EBI-3-/- mice express markers of a more plasmacytoid phenotype without releasing IFN-alpha as compared to those from wild-type littermates. Moreover, allergen challenge induced the development of myeloid CD11c+ cells in the lungs of EBI-3-/- mice, which released increased amounts of IL-10 and IL-12 while not expressing IFN-alpha. Finally, inhibition of EBI-3 expression in lung DC could prevent AHR in adoptive transfer studies by suppressing mediator release of effector cells into the airways. These results indicate a novel role for EBI-3 in controlling local immune responses in the lungs in experimental asthma.

The distinct effects of three tandem repeats of C3d in the immune responses against tumor-associated antigen hCGbeta by DNA immunization

Several examples have shown that C3d3, when fused to a corresponding antigen, had a strong adjuvant effect on certain specific antibody production. In a previous study, we attempted to prove that this was the case of the human chorionic gonadotrophin beta chain (hCGbeta)-induced immunity following DNA vaccination. However, we found that C3d3 when fused to hCGbeta inhibited rather than enhanced the antigen-specific immune response. In the present study, using hCGbeta DNA vaccine preparations, we demonstrated that C3d3 inhibited the antigen-specific humoral antibody response and several other immune responses, such as the hCGbeta specific lymphoproliferation. Such inhibitory effects of C3d3 were not related to the expression level of the target protein, the gender of the test mice, or the vector used. Contrastingly, C3d3 fused with the envelope protein of hepatitis B virus (PreS2/S) used as a control system resulted in the enhancement of both humoral and cell-mediated antigen-specific immune responses against HBV-preS2/S, which was consistent with other groups' adjuvant-effect findings. We further showed that the mechanisms involved in the inhibitory effect of C3d3 might be possible due to impairing the function of antigen presenting B lymphocytes and reducing the expression of transcription factors (T-bet and GATA-3) and cytokine IL-4. Collectively, unlike its usual expected adjuvant function, the fusion of C3d3 with the tumor-associated antigen hCGbeta was found to inhibit both humoral and cell-mediated antigen-specific immune responses. These findings indicate that research concerning tumor immune escapes and vaccine designs require further extensive attention.

Global analysis of alternative splicing during T-cell activation

The role of alternative splicing (AS) in eliciting immune responses is poorly understood. We used quantitative AS microarray profiling to survey changes in AS during activation of Jurkat cells, a leukemia-derived T-cell line. Our results indicate that approximately 10-15% of the profiled alternative exons undergo a >10% change in inclusion level during activation. The majority of the genes displaying differential AS levels are distinct from the set of genes displaying differential transcript levels. These two gene sets also have overlapping yet distinct functional roles. For example, genes that show differential AS patterns during T-cell activation are often closely associated with cell-cycle regulation, whereas genes with differential transcript levels are highly enriched in functions associated more directly with immune defense and cytoskeletal architecture. Previously unknown AS events were detected in genes that have important roles in T-cell activation, and these AS level changes were also observed during the activation of normal human peripheral CD4+ and CD8+ lymphocytes. In summary, by using AS microarray profiling, we have discovered many new AS changes associated with T-cell activation. Our results suggest an extensive role for AS in the regulation of the mammalian immune response.

Involvement of GATA3 in protein kinase C theta-induced Th2 cytokine expression

Protein kinase C theta (PKCtheta) is essential for T cell activation, as it is required for the activation of NF-kappaB and expression of IL-2. PKCtheta has also been shown to affect NFAT activation and Th2 differentiation. To better understand the role of PKCtheta in the regulation of T helper cells, we used PKCtheta-deficient DO11.10 transgenic T cells to study its role in vitro. DO11.10 Th1 cells deficient in PKCtheta produced significantly less TNF-alpha and IL-2. The expression of Th2 cytokines, including IL-4, IL-5, IL-10, IL-13 and IL-24 was significantly reduced in PKCtheta-deficient T cells. Moreover, the expression of the Th2 transcription factor, GATA3, was significantly reduced in PKCtheta-deficient T cells. Overexpression of GATA3 by retroviral infection in PKCtheta-deficient T cells resulted in increased expansion of IL-4-producing T cells and higher IL-4 production than that of wild type Th2 cells. IL-5, IL-10, IL-13 and IL-24 expressions were also rescued by GATA3 overexpression. Our observations suggest that PKCtheta regulates Th2 cytokine expression via GATA3.

GATA3 up-regulation associated with surface expression of CD294/CRTH2: a unique feature of human Th cells

GATA-3 and T-box expressed in T cells (T-bet) play central roles in Th-cell development and function. Consistently, studies in mice document their selective expression in Th1 and Th2 cells, respectively. In contrast, it is not clear whether these genes are regulated in human Th cells. Here we show that T-bet expression is polarized to a comparable degree in human and mouse Th-cell cultures, while only mouse GATA3 is subject to substantial regulation. This did not reflect differential skewing efficiency in human versus mouse cultures, as these contained similar frequencies of IFN-gamma- and IL-4-producing cells. However, GATA-3 was expressed at significantly higher levels in human IL-4-producing cells enriched via capture with monoclonal antibodies (mAbs) against the PGD(2) receptor, CRTH2, the best selective Th2-cell surface marker to date. Along with increased IL-4 and GATA-3, CRTH2(+) Th cells isolated from Th2-skewed cultures or the circulating memory pool exhibited markedly decreased IFN-gamma and T-bet expression. Thus, the human GATA-3 gene is not regulated in response to polarizing signals that are sufficient to direct Th2-specific expression in mouse cells. This postulates the involvement of an additional level of complexity in the regulation of human GATA-3 expression and stresses the existence of nontrivial differences in the regulation of human versus mouse T-cell function.

Gfi-1 plays an important role in IL-2-mediated Th2 cell expansion

Enforced expression of growth factor independent 1 (Gfi-1), a transcription repressor induced by T cell activation and IL-4/Stat6 signaling, strikingly enhances Th2 cell expansion. Using conditionally Gfi1-deficient mice prepared for this study, we show that in vitro or in vivo deletion of this factor dramatically reduces Th2, but not Th1, cell expansion in response to IL-2. Both increased cell apoptosis and reduced cell proliferation resulted from Gfi1 deletion. IL-2-Stat5 signaling was partially reduced in Gfi1-deficient Th2 cells, but overexpression of Stat5 failed to restore normal Th2 expansion in these cells, suggesting that Gfi-1 also functioned downstream of, or in parallel with, Stat5 signaling. Reduced Th2 cell expansion in the absence of Gfi-1 was confirmed by the diminished frequency of IL-4-producing cells when these mice were infected with Schistosoma mansoni.

In silico simulations suggest that Th‐cell development is regulated by both selective and instructive mechanisms

Th-cell differentiation is highly influenced by the local cytokine environment. Although cytokines such as IL-12 and IL-4 are known to polarize the Th-cell response towards Th1 or Th2, respectively, it is not known whether these cytokines instruct the developmental fate of uncommitted Th cells or select cells that have already been committed through a stochastic process. We present an individual based model that accommodates both stochastic and deterministic processes to simulate the dynamic behaviour of selective versus instructive Th-cell development. The predictions made by each model show distinct behaviours, which are compared with experimental observations. The simulations show that the instructive model generates an exclusive Th1 or Th2 response in the absence of an external cytokine source, whereas the selective model favours coexistence of the phenotypes. A hybrid model, including both instructive and selective development, shows behaviour similar to either the selective or the instructive model dependent on the strength of activation. The hybrid model shows the closest qualitative agreement with a number of well-established experimental observations. The predictions by each model suggest that neither pure selective nor instructive Th development is likely to be functional as exclusive mechanisms in Th1/Th2 development.

Human T helper (Th) cell lineage commitment is not directly linked to the secretion of IFN-gamma or IL-4: characterization of Th cells isolated by FACS based on IFN-gamma and IL-4 secretion

Upon activation in vitro, only a fraction of the bulk human T helper cell cultures secret the hallmark Th1/2 cytokines (IFN-gamma for Th1 and IL-4 for Th2, respectively). It is uncertain whether these IFN-gamma-/IL-4- cells are differentiated Th1 or Th2 cells. Here, we have characterized live IFN-gamma+, IL-4+ and IFN-gamma-/IL-4- cells isolated from Th cell cultures treated under Th1 or Th2 polarizing conditions by employing affinity matrix capture technology. RNA samples from the sorted cells were analyzed by real time RT-PCR and microarrays. The double negative cells from either Th1 or Th2 cultures expressed lower levels of Th1/Th2 marker cytokine genes (IFNgamma, IL4, and IL5). However, they were comparable with the IFN-gamma+ or IL-4+ cells in the expression levels of other Th1/Th2 marker genes (GATA3, Tbet, and IL12Rbeta2). Most importantly, these double negative cells were already committed in their Th1/Th2 lineages. Gene expression profiling analysis showed that very few previously identified Th1/Th2 marker genes were differentially expressed between the IFN-gamma or IL-4 producers and the non-producers, further underscoring the similarity between these two groups.

All-trans retinoic acid biases immune response induced by DNA vaccine in a Th2 direction

Vitamin A deficiency diminishes Th2-mediated Ab responses. Providing Vitamin A or its active metabolites reverses this defect. All-trans retinoic acid (ATRA), an acid derivation of Vitamin A, regulates the balance of immune response induced by TR421-hCGbeta DNA vaccine. Compared to DNA vaccine alone or treatment with vehicle, significantly higher level of antibody against the protein encoded by DNA vaccine was observed in mice 6 weeks after the first immunization. The IgG2a/IgG1 ratio was lower in mice treated with ATRA. We also found that treatment with ATRA also diminishes specific cellular immune response induced by gene immunization by measuring the marker of cellular immune response. We conclude that ATRA biases the immune response to Th2 direction induced by DNA vaccine and acts as a candidate adjuvant and immunomodulatory molecule.

PU.1 expression delineates heterogeneity in primary Th2 cells

Primary T helper 2 cells are heterogeneous, expressing subsets of cytokines at varying levels. Mechanisms controlling this spectrum of phenotypes are still unclear. The ETS family transcription factor PU.1 is expressed in Th2 but not Th1 cells. Th2 cytokine production is decreased in cultures transduced with a PU.1-expressing retrovirus and increased in Th2 cells following RNAi that decreases PU.1 expression. In primary cultures, PU.1 expression is restricted to a subpopulation of Th2 cells that express CCL22 and a subset of Th2 cytokines. PU.1 regulates the Th2 phenotype by interfering with GATA-3 DNA binding without altering GATA-3 protein levels. Thus, the expression of PU.1 in subsets of Th2 cells establishes a defined cytokine profile and contributes towards establishing the spectrum of cytokine production observed in Th2 populations.

Targeted overexpression of IL-18 binding protein at the central nervous system overrides flexibility in functional polarization of antigen-specific Th2 cells

The current study shows that functional polarization of Ag-specific CD4(+) Th2 cells entering the CNS during the accelerating phase of experimental autoimmune encephalomyelitis is flexible and dependent on the cytokine milieu there. Thus, targeted cell/gene therapy by Ag-specific T cells overexpressing IL-18 binding protein overrides this flexibility and induces infectious spread of T cell tolerance. Using a congenic system, we demonstrated that at this time, Ag-specific Th2 cells accumulate at the CNS but then arrest of IL-4 production. A manipulation of targeted cell/gene delivery was then used to detect whether this function is dependent on the cytokine milieu there. Targeted overexpression of IL-18 binding protein, a natural inhibitor of IL-18, restored the ability of these Ag-specific Th2 cells to produce IL-4 and subsequently induce protective spread of Th2 polarization. These findings not only suggest a novel way of therapy, but also explain why shifting the balance of Ag-specific T cells toward Th2 suppresses ongoing experimental autoimmune encephalomyelitis, whereas a direct transfer of these cells is ineffective.

EBV-induced gene 3 transcription is induced by TLR signaling in primary dendritic cells via NF-kappa B activation

The EBV-induced gene 3 (EBI3) is expressed in dendritic cells (DCs) and part of the cytokine IL-27 that controls Th cell development. However, its regulated expression in DCs is poorly understood. In the present study we demonstrate that EBI3 is expressed in splenic CD8(-), CD8(+), and plasmacytoid DC subsets and is induced upon TLR signaling. Cloning and functional analysis of the EBI3 promoter using in vivo footprinting and mutagenesis showed that stimulation via TLR2, TLR4, and TLR9 transactivated the promoter in primary DCs via NF-kappaB and Ets binding sites at -90 and -73 bp upstream of the transcriptional start site, respectively. Furthermore, we observed that NF-kappaB p50/p65 and PU.1 were sufficient to transactivate the EBI3 promoter in EBI3-deficient 293 cells. Finally, induced EBI3 gene expression in DCs was reduced or abrogated in TLR-2/TLR4, TLR9, and MyD88 knockout mice, whereas both basal and inducible EBI3 mRNA levels in DCs were strongly suppressed in NF-kappaB p50-deficient mice. In summary, these data suggest that EBI3 expression in DCs is transcriptionally regulated by TLR signaling via MyD88 and NF-kappaB. Thus, EBI3 gene transcription in DCs is induced rapidly by TLR signaling during innate immune responses preceding cytokine driven Th cell development.

Regulation of the GATA3 promoter by human T-cell lymphotropic virus type I Tax protein

The Human T-cell leukemia virus type I (HTLV-I) non-structural protein Tax plays a crucial role in cellular transformation. It activates the transcription factors of various cellular genes and interacts with cellular proteins. There is limited data available on the interaction between specific T-cell transcription factor GATA3 and Tax. Implications for the significance of GATA3 in T-cell development and function, T helper2 (Th2) differentiation, and a role of GATA3 during the immune response have been reported. To determine the effect of the Tax protein on GATA3 gene expression, we investigated the interaction between this protein and the GATA3 promoter and repressor regions. Results demonstrated an interaction between Tax and the GATA3 promoter via the transcription factor Sp1 and a role for Tax in the negative regulation of GATA3 expression, through its interaction with the repressor ZEB. This interaction may be involved in the pathophysiology of adult T-cell leukemia/lymphoma (ATL) and tropical spastic paraparesis/HTLV-I-associated myelopathy (TSP/HAM).

GATA Transcription Factors Inhibit Cytokine-dependent Growth and Survival of a Hematopoietic Cell Line through the Inhibition of STAT3 Activity

Although GATA-1 and GATA-2 were shown to be essential for the development of hematopoietic cells by gene targeting experiments, they were also reported to inhibit the growth of hematopoietic cells. Therefore, in this study, we examined the effects of GATA-1 and GATA-2 on cytokine signals. A tamoxifen-inducible form of GATA-1 (GATA-1/ERT) showed a minor inhibitory effect on interleukin-3 (IL-3)-dependent growth of an IL-3-dependent cell line Ba/F3. On the other hand, it drastically inhibited TPO-dependent growth and gp130-mediated growth/survival of Ba/F3. Similarly, an estradiol-inducible form of GATA-2 (GATA-2/ER) disrupted thrombopoietin (TPO)-dependent growth and gp130-mediated growth/survival of Ba/F3. As for this mechanism, we found that both GATA-1 and GATA-2 directly bound to STAT3 both in vitro and in vivo and inhibited its DNA-binding activity in gel shift assays and chromatin immunoprecipitation assays, whereas they hardly affected STAT5 activity. In addition, endogenous GATA-1 was found to interact with STAT3 in normal megakaryocytes, suggesting that GATA-1 may inhibit STAT3 activity in normal hematopoietic cells. Furthermore, we found that GATA-1 suppressed STAT3 activity through its N-zinc finger domain. Together, these results suggest that, besides the roles as transcription factors, GATA family proteins modulate cytokine signals through protein-protein interactions, thereby regulating the growth and survival of hematopoietic cells.

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.

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.