A novel transcription factor, T-bet, directs Th1 lineage commitment

Kinetic analysis of genomewide gene expression reveals molecule circuitries that control T cell activation and Th1/2 differentiation

The global gene expression profiling of early T helper (Th) 1 and Th2 differentiation reveals that this process can be divided into two stages, activation and differentiation. The activation stage is manifested in coordinated mobilization of the replication machinery, a process that we hypothesize may be responsible for establishing genomewide opening of transcription loci. The molecular programs underlying the differentiation stage consist of highly regulated expression of functional groups of genes that are important for the biological properties of Th1/2 cells and transcription factors that are likely important in establishing terminal differentiation of these cells. The kinetics of expression pattern of a number of transcription factors shed new light on the molecular events that shape the outcome of Th1/2 differentiation.

Identification of novel genes regulated by IL-12, IL-4, or TGF-beta during the early polarization of CD4+ lymphocytes

Th1 and Th2 cells arise from a common precursor cell in response to triggering through the TCR and cytokine receptors for IL-12 or IL-4. This leads to activation of complex signaling pathways, which are not known in detail. Disturbances in the balance between type 1 and type 2 responses can lead to certain immune-mediated diseases. Thus, it is important to understand how Th1 and Th2 cells are generated. To clarify the mechanisms as to how IL-12 and IL-4 induce Th1 and Th2 differentiation and how TGF-beta can inhibit this process, we have used oligonucleotide arrays to examine the early polarization of Th1 and Th2 cells in the presence and absence of TGF-beta. In addition to genes previously implicated in the process, we have identified 20 genes with various known and unknown functions not previously associated with Th1/2 polarization. We have also further determined which genes are targets of IL-12, IL-4, and TGF-beta regulation in the cells induced to polarize to Th1 and Th2 directions. Interestingly, a subset of the genes was coregulated by IL-12 or IL-4 and TGF-beta. Among these genes are candidates that may modulate the balance between Th1 and Th2 responses.

A Distal Enhancer in the Interferon-γ (IFN-γ) Locus Revealed by Genome Sequence Comparison

Large-scale cross-species DNA sequence comparison has become a powerful tool to identify conserved cis-regulatory modules of genes. However, bioinformatic analysis alone cannot reveal how an evolutionarily conserved region regulates gene expression: whether it functions as an enhancer, silencer, or insulator; whether its function is cell-type restricted; and whether biologically relevant transcription factors bind to the element. Here we combine bioinformatics with wet-lab techniques to illustrate a general and systematic method of identifying functional conserved regulatory regions of genes. We applied this approach to the interferon-gamma (IFN-gamma) gene. Comparison of human and mouse IFN-gamma reveals a highly conserved non-coding sequence located approximately 5 kb 5' of the transcription start site. This region coincides with constitutive and inducible DNase I hypersensitivity sites present in IFN-gamma-producing Th1 cells but not in Th2 cells that do not produce IFN-gamma. Histone methylation at the 5' conserved non-coding sequences indicates a more accessible chromatin structure in Th1 cells compared with Th2 cells. This element binds two transcription factors known to be essential for IFN-gamma expression: nuclear factor of activated T cells, an inducible transcription factor, and T-box protein expressed in T cells, a cell lineage-restricted transcription factor. Together, these findings identify a highly conserved distal enhancer in the IFN-gamma cytokine locus and validate our approach as a successful method to detect cis-regulatory elements.

In vitro allergen-induced mRNA expression of signaling lymphocytic activation molecule by PBMC of patients with allergic rhinitis is increased during specific pollen immunotherapy

BACKGROUND

Specific immunotherapy (SIT) acts by inducing a shift from T(H)2 to T(H)1 cell response on mucous membranes, reducing allergic inflammation. New genes expressed primarily in T(H)1-type cells have been found. Of these genes, signaling lymphocytic activation molecule (SLAM) promotes T-cell proliferation and IFN-gamma production. Nothing is known about its role in T(H)2-T(H)1 switch during SIT.

OBJECTIVE

We sought to analyze the mRNA expression of SLAM and other T(H)1-associated genes, interleukin-12 receptor beta2 (IL-12Rbeta2) and T-box expressed in T cells (T-bet), and compare them with the clinical outcome of the therapy.

METHODS

PBMC from 30 patients allergic to pollen undergoing SIT were collected during the therapy. Control PBMC were collected from 10 patients with allergic rhinitis not participating in SIT and from 10 nonallergic subjects. Cells were stimulated in vitro with pollen allergen extracts. SLAM, IL-12Rbeta2, and T-bet mRNA expressions were studied by real-time quantitative RT-PCR technique (Taqman). Symptom scoring and medication scoring were registered before commencement of SIT and after 1 year of the therapy.

RESULTS

Before the treatment, in vitro allergen-induced SLAM mRNA expression in PBMC was significantly lower in the patients with allergic rhinitis than in the healthy control subjects. After 1 year of the treatment, SLAM mRNA expression was increased in the patients undergoing SIT and was associated with IFN-gamma mRNA expression and inversely associated with the symptom improvement. At the maintenance dose, an increase in SLAM mRNA expression was associated with the clinical symptom improvement at 1 year. No changes were seen in IL-12Rbeta(2) or T-bet mRNA expressions.

CONCLUSIONS

SLAM mRNA expression in PBMC is modulated during the course of SIT, and an early and transient increase of SLAM mRNA expression is associated with clinical symptom improvement.

Cytokines and transcription factors that regulate T helper cell differentiation: new players and new insights

The differentiation of naive CD4+ T cells into subsets of T helper cells is a pivotal process with major implications for host defense and the pathogenesis of immune-mediated diseases. Though the basic paradigm was discovered more than 15 years ago, new discoveries continue to be made that offer fresh insights into the regulation of this process. T helper (TH)1 cells produce interferon (IFN)-gamma, promoting cell-mediated immunity and control of intracellular pathogens. We now know that TH1 differentiation is regulated by transcription factors such as T-bet, Stat1, and Stat4, as well as cytokines such as IL-12, IL-23, IL-27, type I IFNs, and IFN-gamma. In contrast, TH2 cells produce IL-4, which promotes allergic responses and is important in host defense against helminths. The transcription factors Stat6, GATA-3, c-Maf, NFATs, and the cytokine IL-4 promote TH2 differentiation. These key regulators of TH differentiation are the subject of this review.

CD226 (DNAM-1) is involved in lymphocyte function-associated antigen 1 costimulatory signal for naive T cell differentiation and proliferation

Upon antigen recognition by the T cell receptor, lymphocyte function–associated antigen 1 (LFA-1) physically associates with the leukocyte adhesion molecule CD226 (DNAM-1) and the protein tyrosine kinase Fyn. We show that lentiviral vector-mediated mutant (Y-F³²²) CD226 transferred into naive CD4⁺ helper T cells (Ths) inhibited interleukin (IL)-12–independent Th1 development initiated by CD3 and LFA-1 ligations. Moreover, proliferation induced by LFA-1 costimulatory signal was suppressed in mutant (Y-F³²²) CD226-transduced naive CD4⁺ and CD8⁺ T cells in the absence of IL-2. These results suggest that CD226 is involved in LFA-1–mediated costimulatory signals for triggering naive T cell differentiation and proliferation. We also demonstrate that although LFA-1, CD226, and Fyn are polarized at the immunological synapse upon stimulation with anti-CD3 in CD4⁺ and CD8⁺ T cells, lipid rafts are polarized in CD4⁺, but not CD8⁺, T cells. Moreover, proliferation initiated by LFA-1 costimulatory signal is suppressed by lipid raft disruption in CD4⁺, but not CD8⁺, T cells, suggesting that the LFA-1 costimulatory signal is independent of lipid rafts in CD8⁺ T cells.

Absence of the T-bet gene coding for the Th1-related transcription factor does not affect diabetes-associated phenotypes in Balb/c mice

The T-box expressed in T cells gene (T-bet) is a member of the T-box family of transcription factors. T-bet-deficient mice show normal lymphoid development, but exhibit profound defects in their Th1-mediated immune responses. As the balance between Th1- and Th2-mediated immune responses plays a role in autoimmune-prone diseases, we have investigated the diabetes-related insulin autoantibody (IAA) and cellular immune responses (insulitis), in the absence of Th1 lineage commitment, in T-bet KO Balb/c mice, after immunization with the B9-23 insulin peptide. We have therefore investigated whether absence of the T-bet gene influences diabetes-related phenotypes in Balb/c T-bet KO mice.

Tpit-independent function of NeuroD1(BETA2) in pituitary corticotroph differentiation

NeuroD1(BETA2) and Tpit are cell-specific activators of pituitary proopiomelanocortin (POMC) gene transcription. Expression of both factors slightly precedes that of POMC at embryonic d 12.5 of mouse pituitary development. We now report that NeuroD1(BETA2) is required for early corticotroph differentiation. In agreement with the transcriptional synergism observed between Tpit and basic helix-loop-helix dimers containing NeuroD1(BETA2), POMC expression is delayed in NeuroD1-deficient mice. However, this differentiation defect does not reflect a change of corticotroph commitment as revealed by Tpit expression. The delay of corticotroph terminal differentiation is transient and coincides with the developmental window of NeuroD1 expression in corticotrophs. In contrast to their requirement in other NeuroD1-expressing cells, the neurogenin genes do not appear to be necessary for corticotroph differentiation. Taken together with a similar requirement of Tpit for corticotroph differentiation but not for commitment, the present data indicate that the POMC promoter is a point of convergence for independent corticotroph differentiating signals.

Reversal of allergic airway hyperreactivity after long-term allergen challenge depends on gammadelta T cells

Long-term allergen exposure can attenuate inflammation and revert airway hyperreactivity to normal responsiveness. A model of such reversal was established in which airway hyperreactivity and inflammation in ovalbumin-sensitized and challenged mice were decreased after multiple daily airway challenges. This change in responsiveness and inflammation was associated with a transition from a helper T cell Type 2 to a helper T cell Type 1 cytokine-biased profile in bronchoalveolar lavage fluid. Cell transfer from long-term exposed mice into hyperreactive mice also restored normal airway responsiveness, establishing the mechanism underlying the reversal of the hyperreactivity as active suppression, but did not affect eosinophilic airway inflammation. Conversely, airway hyperreactivity, suppressed as a result of long-term allergen exposure, could be reestablished by depleting gammadelta T cells, in particular Vgamma4+ cells. Antigen-specific tolerance of alphabeta T cells or suppression by non-gammadelta T cells did not play a role in the reversal to normal airway responsiveness and gammadelta T cells did not play a role in the regulation of the allergic inflammatory response. These findings show that normal responsiveness in previously hyperreactive mice, achieved after long-term allergen challenge, is based on several, apparently independent regulatory mechanisms. One of these, focused on airway responsiveness, involves active suppression and requires gammadelta T cells.

Genetic reprogramming of primary human T cells reveals functional plasticity in Th cell differentiation

Activation of naive T cells through the TCR and cytokine signals directs their differentiation into effector or memory subsets with different cytokine profiles. Here, we tested the flexibility of human Th1 or Th2 differentiation by forced expression of transcription factors T-bet and GATA-3. Ectopic expression of T-bet and GATA-3 in freshly isolated human T(N) cells resulted in their differentiation to a Th1 and Th2 phenotype, respectively, in the absence of polarizing cytokines. Introduction of GATA-3 into lineage-committed Th1 cells induced the expression of Th2-specific cytokines (IL-4 and IL-5) and chemotactic receptors (CCR4, chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2). However, these cells partially maintained their Th1-specific profile (IFN-gamma and IL-12Rbeta2 expression). Conversely, expression of T-bet in lineage-committed Th2 cells caused a more profound switch to the Th1 phenotype, including the up-regulation of CXCR3 and down-regulation of CCR4 and CRTH2. Interestingly, similar to the naive T cell subset, central memory T cells were also largely programmed toward Th1 or Th2 effector cells upon expression of T-bet and GATA-3, respectively. However, expression of these transcription factors in effector memory T cells was much less influential on cytokine and chemokine receptor expression profiles. Our results reveal remarkable plasticity in the differentiation programs of human memory T cells. This flexibility is progressively diminished as cells mature from naive to effector T cells. These findings have important implications in understanding the molecular mechanisms of human T cell differentiation and for devising novel therapeutic strategies aimed at immunomodulation of skewed effector T cell responses.

Akt is a neutral amplifier for Th cell differentiation

Both CD28 and its relative, inducible costimulator (ICOS), have a binding motif for phosphatidylinositol 3-kinase (PI3K) in their cytoplasmic tail, and the binding of PI3K leads to activation of a serine/threonine kinase, Akt. The role of Akt in cytokine production and helper T (Th) cell differentiation remains obscure. In this study, we found that enforced expression of the constitutively active form (E40K) of Akt rendered CD4(+) T cells activated. Wild-type of Akt and E40K promoted Th1 cell differentiation in C57BL/6-derived and Th1-polarized BALB/c-derived CD4(+) T cells, while both promoted Th2 cell differentiation in BALB/c-derived and Th2-polarized C57BL/6 CD4(+) T cells. E40K also facilitated Th1 differentiation in CD4(+) T cells from IL-4-deficient mice with the BALB/c background. E40K up-regulated expression of NF-AT and c-Myb, which may be related to the augmentation of cytokine production by E40K. These findings indicate that the mechanism by which Akt augments cytokine production via CD28 and ICOS is Th cell type-specific and reflects the intracellular status affected by the cytokine milieu. We conclude that Akt is a neutral amplifier of T cell activation and Th differentiation.

Marginal Zone, but Not Follicular B Cells, Are Potent Activators of Naive CD4 T Cells

The early involvement of marginal zone (MZ) B lymphocytes in T-independent immune responses is well established. In this study we compared the abilities of MZ and follicular (FO) B cells to collaborate with T cells. After immunization with soluble hen egg lysozyme, both MZ and FO B cells captured Ag and migrated to T cell areas in the response to hen egg lysozyme. MZ B cells were far superior to FO B cells in inducing CD4+ T cell expansion both in vitro and in vivo. MZ, but not FO, B cells, after interaction with T cells, differentiated into plasma cells, and in addition they stimulated Ag-specific CD4+ T cells to produce high levels of Th1-like cytokines upon primary stimulation in vitro. These results indicate that MZ B cells rapidly and effectively capture soluble Ag and activate CD4+ T cells to become effector T cells. The enhanced capacity of MZ B cells to prime T cells in this study appeared to be intrinsic to MZ B cells, as both MZ and FO B cell populations express an identical Ag receptor.

Potential Targets of 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase Inhibitor for Multiple Sclerosis Therapy

The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors or statins are newly identified immunomodulators. In vivo treatment of SJL/J mice with lovastatin reduced the duration and clinical severity of active and passive experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis. Lovastatin induced the expression of GATA3 and the phosphorylation of STAT6, whereas it inhibited tyrosine phosphorylation of Janus kinase 2, tyrosine kinase 2, and STAT4. Inhibition of the Janus kinase-STAT4 pathway by lovastatin modulated T0 to Th1 differentiation and reduced cytokine (IFN-gamma and TNF-alpha) production, thus inducing Th2 cytokines (IL-4, IL-5, and IL-10). It inhibited T-bet (T box transcription factor) and NF-kappaB in activated T cells and significantly reduced infiltration of CD4- and MHC class II-positive cells to CNS. Further, it stabilized IL-4 production and GATA-3 expression in differentiated Th2 cells, whereas in differentiated Th1 cells it inhibited the expression of T-bet and reduced the production of IFN-gamma. Moreover, lovastatin-exposed macrophage and BV2 (microglia) in allogeneic MLRs induced the production of the anti-inflammatory cytokine IL-10. These observations indicate that the anti-inflammatory effects of lovastatin are mediated via T cells as well as APCs, because it modulates the polarization patterns of naive T cell activation in an APC-independent system. Together, these findings reveal that lovastatin may have possible therapeutic value involving new targets (in both APCs and T cells) for the treatment of multiple sclerosis and other inflammatory diseases.

Immunomodulatory Effect of Astragali Radix Extract on Murine Th1/Th2 Cell Lineage Development

Astragali Radix (AR), is a popular herbal medicine used to treat allergic diseases in Korea, Japan and China. Our study examined the effect of an AR ethanol extract on both in vitro and in vivo murine CD4 T cells' differentiation into Th1 and Th2 subsets. CD4 T cells from Balb/c mice were activated with anti-CD3/anti-CD28 mAb in the presence of AR for 2 d. AR treated cells showed an elevated level of IL-4 but a reduced level of IFN-gamma secretion. In addition, in vitro Th1/Th2 polarization experiments revealed that AR enhanced the levels of IL-4 in Th2 cells but reduced the levels of IFN-gamma in Th1 cells. To elucidate the effects of AR in Th1/Th2 lineage development during the in vivo condition, AR was administrated orally to BALB/c mice. The results demonstrated that AR administration significantly increased IL-4 production in both the serum and supernatant of splenocyte culture, while IFN-gamma secretion was diminished upon in vivo activation with anti-CD3 antibody. Our data clearly indicates that AR selectively alters Th1/Th2 cytokine secretion patterns and provides the pharmacological basis for AR's clinical applications.

Development of synthetic pan-selectin antagonists: a new treatment strategy for chronic inflammation in asthma

Asthma is characterized by chronic inflammation of large and small airways maintained by extravasation of leukocytes from the bloodstream into the surrounding peribronchial tissue. The process of extravasation is of crucial importance in inflammation and is mediated by a sequenced and concerted action between different adhesion molecules on endothelial cells and ligands on leukocytes. In this context, initial rolling and tethering is generally considered to be the primary event which is mediated by selectins, a family of glycoproteins comprised of E-, P- and L-selectin. Their role in asthma has been demonstrated in a variety of animal models, showing that all three selectins are involved in the chronic inflammation in asthma. Therefore, selectins are an attractive target where pan-selectin antagonism is the desired treatment strategy. Here, we give an overview of the status of the preclinical and clinical development of bimosiamose, the most advanced synthetic pan-selectin antagonist as a treatment for asthma.

Transcription factors: new targets for antiallergic therapy

Due to their pivotal role in the fast transmission of signals from cell surface receptors to the nucleus, resulting in gene expression, transcriptional factors play an important part in the physiology of cells. Recently, a number of transcription factors have been identified that are involved in the pathogenesis of allergic diseases. In order to attenuate the development of allergen-mediated diseases, new strategies have been developed to influence these transcription factors in vivo. Among these, the use of oligodeoxynucleotide decoy has emerged as a new tool with promising results for therapeutical and experimental purposes.

GATA-3 promotes maturation, IFN-gamma production, and liver-specific homing of NK cells

The GATA-3 transcription factor has a determinant role in T cell specification and is an essential mediator of T helper 2-type polarized immune responses. While both committed NK precursors and mature NK cells express GATA-3, a role of this transcription factor in murine NK cell differentiation is not known. We found that NK cells, in contrast to T cells, can be generated in the absence of GATA-3. However, while GATA-3 antagonizes IFN-gamma production in differentiating T cells, GATA-3-deficient NK cells paradoxically produced less IFN-gamma compared to control NK cells and failed to provide early protection in vivo against infection with Listeria monocytogenes. Surprisingly, GATA-3 was essential for NK cell homing to the liver. Our results suggest that GATA-3 promotes NK cell maturation and acts in this lineage to specify distinct effector phenotypes.

Control of effector CD8+ T cell function by the transcription factor Eomesodermin

Activated CD8+ T cells play a critical role in host defense against viruses, intracellular microbes, and tumors. It is not clear if a key regulatory transcription factor unites the effector functions of CD8+ T cells. We now show that Eomesodermin (Eomes), a paralogue of T-bet, is induced in effector CD8+ T cells in vitro and in vivo. Ectopic expression of Eomes was sufficient to invoke attributes of effector CD8+ T cells, including interferon-gamma (IFN-gamma), perforin, and granzyme B. Loss-of-function analysis suggests Eomes may also be necessary for full effector differentiation of CD8+ T cells. We suggest that Eomesodermin is likely to complement the actions of T-bet and act as a key regulatory gene in the development of cell-mediated immunity.

Reduced expression of NFAT-associated genes in UCB versus adult CD4+ T lymphocytes during primary stimulation

The cellular and molecular mechanisms underlying the blunted allo-responsiveness of umbilical cord blood (UCB) T cells have not been fully elucidated. Protein expression of NFATc2 (nuclear factor of activated T cells c2), a critical transcription factor necessary for up-regulation of multiple cytokines known to amplify T-cell allogeneic responses, is reduced in UCB T cells. Affymetrix oligonucleotide microarrays were used to compare gene expression of primary purified CD4+ UCB T cells to adult peripheral blood CD4+ T cells (AB) at baseline, 6, and 16 hours of primary stimulation. NFAT-regulated genes exhibited lower expression in UCB CD4+ T cells including the following: granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), interleukin 3 (IL-3), IL-4, IL-5, IL-13, IL-2 receptor alpha (IL-2Ralpha; CD25), CD40L, and macrophage inflammatory protein 1 alpha (MIP-1alpha). Transcription factors involved in the NFAT pathway including C/EBPbeta, JunB, and Fosl1 (Fra-1), as well as Th1- and Th2-related transcription factors STAT4 (signal transducers and activators of transcription 4), T-bet, and c-maf showed reduced expression in UCB compared with AB during primary stimulation. Reduced cytokine, chemokine, and receptor expression was also found in UCB. Gene array data were confirmed using RNase protection assays, flow cytometry, and quantitative multiplexed cytokine measurements. Reduced global expression of NFAT-associated genes, as well as cytokines and chemokines, in UCB CD4+ T cells may contribute to the decreased graft-versus-host disease (GVHD) observed after UCB transplantation.

Antigen-driven effector CD8 T cell function regulated by T-bet

Type 1 immunity relies on the differentiation of two major subsets of T lymphocytes, the CD4+ T helper (Th) cell and the CD8+ cytotoxic T cell, that direct inflammatory and cytotoxic responses essential for the destruction of intracellular and extracellular pathogens. In contrast to CD4 cells, little is known about transcription factors that control the transition from the CD8 naïve to effector cell stage. Here, we report that the transcription factor T-bet, known to regulate Th cell differentiation, also controls the generation of the CD8+ cytotoxic effector cell. Antigen-driven generation of effector CD8+ cells was impaired in OT-I T cell receptor transgenic mice lacking T-bet, resulting in diminished cytotoxicity and a marked shift in cytokine secretion profiles. Furthermore, mice lacking T-bet responded poorly to infection with lymphocytic choriomeningitis virus. T-bet is a key player in the generation of type 1 immunity, in both Th and T cytotoxic cells.

A key pathogenic role for the STAT1/T-bet signaling pathway in T-cell-mediated liver inflammation

TH1 cytokines have been suggested to contribute to the pathogenesis of T-cell-mediated liver injury and inflammation. However, the molecular signaling pathways involved in such injury are still poorly understood. In the present study, we investigated the role of the STAT1/T-bet signaling pathway in a murine model of T-cell-mediated liver inflammation induced by the application of concanavalin A (Con A) using newly created STAT1 transgenic mice as well as STAT1- and T-bet-deficient mice. Liver injury induced by Con A was associated with an increase of both pSTAT1 and T-bet levels in the liver. Furthermore, functional studies suggested a pathogenic role for STAT1 in Con A-induced liver injury, because transgenic mice overexpressing STAT1 under the control of the CD2 promoter/enhancer construct showed elevated interferon gamma (IFN-gamma) and IRF-1 levels as well as significantly augmented liver injury following administration of Con A. Consistently, we observed that both STAT1-deficient and T-bet-deficient mice were protected from such T-cell-dependent liver injury. In conclusion, these findings suggest a key pathogenic role for the STAT1/T-bet signaling pathway for T-cell activation in the Con A model of T-cell-mediated liver pathology.

IL-27 regulates IL-12 responsiveness of naive CD4+ T cells through Stat1-dependent and -independent mechanisms

IL-27, a novel heterodimeric cytokine produced by antigen-presenting cells, signals through the T cell cytokine receptor (TCCR)/WSX-1 expressed on naïve CD4+ T cells and natural killer cells. TCCR/WSX-1 deficiency results in delayed T helper type 1 (TH1) development through an unresolved mechanism. We report here that IL-27 stimulation in developing murine T helper cells potently induces the expression of the major TH1-specific transcription factor T-bet and its downstream target IL-12R beta2, independently of IFN gamma. In addition, IL-27 suppresses basal expression of GATA-3, the critical TH2-specific transcription factor that inhibits TH1 development by down-regulating signal transducer and activator of transcription (Stat) 4. IL-27 signaling through TCCR/WSX-1 induces phosphorylation of Stat1, Stat3, Stat4, and Stat5. Stat1 is required for suppression of GATA-3, but T-bet induction by IL-27 can also be mediated through a Stat1-independent pathway. Despite its TH1-like signaling profile, IL-27 is not sufficient to drive the differentiation of CD4+ T cells into IFN gamma-producing cells. Similarly, IL-27 induces T-bet expression in primary natural killer cells, but this does not result in an increase of IFN gamma production or cytotoxic activity. Therefore, although IL-27 is unable to drive IFN gamma production on its own, it plays an important role in the early steps of TH1 commitment by contributing in a paracrine manner to the control of IL-12 responsiveness.

In human B cells, IL-12 triggers a cascade of molecular events similar to Th1 commitment

Two functionally distinct subsets of B cells that produce Th1- and Th2-like patterns of cytokines have recently been identified. Interleukin-12 (IL-12) is a critical immunoregulatory cytokine that promotes Th1 differentiation through activation of signal transducer and activator of transcription 4 (STAT4). IL-12 has been reported to induce interferon gamma (IFN-gamma) production in B cells, but the relevant signaling pathways are poorly documented. Here, in human primary B cells, we found a functional IL-12 receptor (IL-12R) that internalizes following IL-12 binding. IFN-gamma and, to a lesser extent, IL-12 positively regulated the IL-12Rbeta2 subunit but had no effect on IL-12Rbeta1. On examining the effect of IL-12 on STAT4 and T-bet (2 key factors involved in IFN-gamma promoter activation), we found that IL-12 induced the phosphorylation and nuclear translocation of STAT4. IL-12-dependent constitutive STAT4 activation was also observed in the Epstein-Barr virus (EBV)-transformed B-cell line RPMI 8866 that spontaneously produces IL-12. T-bet expression has been shown to be dependent on STAT1. IL-12 had no direct effect on STAT1 activation or T-bet expression in primary B cells. In contrast, IL-12-induced IFN-gamma led to STAT1 activation, strong expression of T-bet, and IFN-gamma expression. IL-12 therefore initiates a cascade of events in B cells, including STAT4 activation, IL-12Rbeta2 up-regulation, IFN-gamma production, and T-bet up-regulation, potentially leading to Th1-like differentiation.

T-bet expression is upregulated in active Behçet's disease

AIM

To investigate T-bet mRNA and protein expression on peripheral blood mononuclear cells (PBMC) in patients with Behçet's disease with active uveitis.

METHODS

Blood samples were taken from 24 patients with Behçet's disease who had active uveitis and 16 healthy individuals. PBMC were subjected to analysis of T-bet mRNA and protein expression using semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and western blot, respectively. The products from PCR were sequenced. In order to determine the influence of activation on T-bet expression, the phytohaemagglutinin (PHA) stimulated PBMC from each sample were also evaluated for expression of T-bet mRNA and protein.

RESULTS

A significantly increased T-bet mRNA accumulation was detected in the samples from patients with active Behçet's disease compared with that in controls. A 62 kDa band was detectable in patients with active Behçet's disease, but not in controls. No difference was found between patients with Behçet's disease who had active uveitis and normal controls concerning the expression of either T-bet mRNA or its protein after stimulation with PHA for 72 hours.

CONCLUSION

Behçet's disease is associated with an upregulation of T-bet expression, which supports a role for the Th1 subset of T cells in the pathogenesis of this disease.

T cell directives for transcriptional regulation in asthma

Allergic asthma frequently starts in childhood, and environmental factors such as viruses, allergens and occupational exposure can regulate the evolution of the disease. The development of allergen-specific Th2 lymphocytes represents the triggering event for the recruitment and activation of IgE-producing B cells and fibroblasts, followed by the release of soluble factors, thus giving rise to the inflammatory reaction observed in this disease. GATA-3 was identified as a cell lineage-specific factor selectively expressed and activated in the Th2 lineage as a consequence of STAT-6 activation. However, recent literature indicates that blockade of CTLA-4-directed inhibitory signals is sufficient to induce STAT 6-independent Th2 differentiation. A new Th1-restricted transcription factor has been recently identified that transactivates the IFN-gamma gene promoter: T-bet (T-box expressed in T cells). T-bet expression during T cell activation is strongly dependent on IFN-gamma and STAT-1. Mice lacking T-bet have profound defects in the development of the Th1 subset and the production of IFN-gamma, but overproduce Th2 cytokines and, in the absence of immunological challenge, they exhibited airway hyperreactivity to methacholine associated with a peribronchial and perivascular infiltration with eosinophils and lymphocytes. Finally, a small subset of CD4 T cells called T-regulatory (T-reg) cells has been identified. These cells exhibit potent immunosuppressive properties. Although recent reports suggest that the induction of T-reg cells is under the control of the transcription factor Foxp3, the specific signals that preferentially induce development of T-reg cells instead of Th2 cells are still unclear.

Active recruitment of DNA methyltransferases regulates interleukin 4 in thymocytes and T cells

How T cells regulate interleukin 4 (IL-4) expression is not completely understood. We show here that single-positive thymocytes express IL-4, but attenuate GATA-3 expression, recruit DNA methyltransferases (Dnmts) to the Il4-Il13 locus and downregulate IL-4 expression as they mature into T cells. Type 2 polarization blocks Dnmt1 recruitment, enhances histone H3 Lys4 methylation (indicative of accessible chromatin) and initiates DNA demethylation of the locus. Dnmt1-/- CD4 and CD8 T cells derepress IL-4 expression considerably, demethylate DNA and increase H3 Lys4 methylation without affecting GATA-3 expression, demonstrating that Dnmt1 and DNA methylation are essential for proper Il4 regulation. These results indicate that Dnmts, DNA and histone methylation, and transcription factors 'collaborate' to determine appropriate Il4 expression patterns.

Stat5 Activation Plays a Critical Role in Th2 Differentiation

Upon TCR engagement, naive CD4 T cells differentiate toward the Th1 or Th2 phenotype. IL-4, acting through Stat6, plays a major role in Th2 differentiation; IL-2 has also been reported to be essential. Here, we report that retroviral (RV)-mediated expression of a constitutively active Stat5A mutant (STAT5A1*6) can fully restore IL-4 production when naive CD4 T cells are primed in the absence of IL-2. Furthermore, STAT5A1*6 expression causes Th2 differentiation in the absence of IL-4 or in Stat6- or IL-4Ralpha-deficient cells. Infection with STAT5A1*6-NGFR-RV does not enhance GATA-3 expression. STAT5A1*6-NGFR-RV and GATA-3-GFP-RV each render the Il4 gene accessible, but the sites of restriction enzyme accessibility are different. Stat5A binds to HSII and HSIII sites of the Il4 gene. Coinfection with STAT5A1*6-NGFR-RV and GATA-3-GFP-RV results in optimal Th2 priming.

Different antigens trigger different Th1/Th2 reactions in neonatal mononuclear cells (MNCs) relating to T-bet/GATA-3 expression

Neonates are known to have poor cellular immunity, especially poor Th1 response. We investigated how neonatal mononuclear cells raised different Th1/Th2 reactions in response to different antigens. Employing Dermatophagoides pteronyssinus (Der p) extract and varicella zoster virus (VZV) as antigens, we assessed Th1/Th2 reactions as demonstrated by IL-4/IFNgamma production and mRNA expression, and transcriptional factors T-bet/GATA-3 mRNA expression in mononuclear cells from human umbilical cord blood (CBMC). Results showed that VZV induced a dramatic increase of IFNgamma production by adult peripheral blood mononuclear cells (PBMC), whereas VZV did not drive CBMC to release significant IFNgamma production (1614.7+/-362.0 vs. 49.0+/-29.3,p<0.005). However, Der p induced higher IFNgamma production by CBMC than VZV (298.1+/-171.8 vs. 49.0+/-29.3, P=0.047). In contrast, VZV did not induce significant IL-4 production either by CBMC or by PBMC. Der p induced a comparative IL-4 production by CBMC and PBMC (2.58+/-0.84 vs. 2.04+/-0.37, p>0.05). A real-time RT-PCR analysis of IL-4 and IFNgamma mRNA expression showed that VZV induced a significantly higher IFNgamma, but not IL-4, mRNA expression in PBMC than CBMC. Der p did not induce significant difference of IFNgamma or IL-4 mRNA expression in PBMC and CBMC. VZV enhanced Th1-related transcription factor T-bet mRNA expression, in association with later down-regulation of Th2-related GATA-3 mRNA expression in PBMC. However, VZV did not up-regulate T-bet or down-regulate GATA-3 expression significantly in CBMC. In contrast, Der p induced an early GATA-3 expression and later T-bet expression in CBMC. These results suggest that different antigens trigger various Th1/Th2 reactions in PBMC and CBMC resulting from kinetic changes of T-bet/GATA-3 expression.

The chemokine CX3CL1 regulates NK cell activity in vivo

In vitro, chemokines can both activate and induce migration of NK cells. However, little is known about how chemokines influence NK cell activity in vivo. We studied the role of CX(3)CL1 and its receptor, CX(3)CR1, in modulating NK cell activity in an established in vivo model of tumour cell clearance. Radiolabelled YAC-1 target cells intravenously injected into C57BL/6 mice rapidly localize to the lungs and are cleared by NK cells. In mice pre-treated with blocking anti-CX(3)CL1 or anti-CX(3)CR1 Ab, target cell clearance decreased by four- to fivefold (p<0.001). In vitro, we found no effect of anti-CX(3)CL1 or anti-CX(3)CR1 Ab on NK lysis of target cells. We further examined adhesion of NK cells to Py-4-1 endothelial cells. NK cell binding to activated endothelial monolayers was significantly inhibited by anti-CX(3)CR1 Ab or soluble CX(3)CL1 (p<0.001). These studies identify a critical role for CX(3)CL1 in modulating NK cell activity in vivo.

TCR-mediated Notch signaling regulates proliferation and IFN-gamma production in peripheral T cells

Notch genes encode membrane receptors that regulate cell fate decisions in metazoa. Notch receptors and ligands are expressed in developing lymphoid tissue and mature lymphocytes and the role of Notch signaling in early T and B cell development has been studied extensively. However, its contribution to mature T cell function is unknown. TCR-mediated T cell activation is a fundamental process of the adaptive immune system that has been studied for decades; however, the details of this process are incompletely understood. In this study, we present evidence that Notch is required for TCR-mediated activation of peripheral T cells. Inhibition of Notch activation dramatically decreases T cell proliferation in both CD4 and CD8 cells and blocks both NF-kappaB activity and IFN-gamma production in peripheral T cells. Our data reveal a new, nondevelopmental function of Notch as a previously unknown key link in peripheral T cell activation and cytokine secretion.

Differential requirement for CD18 in T-helper effector homing

To understand the integrin requirements of T-helper (T(H)) effector subsets, we investigated the contribution of CD18 (beta(2) integrin) to T(H)1 and T(H)2 function in vitro and in relevant disease models. CD18-deficient (Itgb2(-/-)) T cells showed largely normal in vitro function. Compared with wild-type mice, Itgb2(-/-) mice were better able to resolve Leishmania major infection and generated a superior T(H)1 immune response, as assessed from draining lymph nodes. In contrast, T(H)2-dependent allergic lung disease was markedly impaired in mutant mice. In both models, development of T(H)1 and T(H)2 cells in spleens was normal, but accumulation of T(H)2 (not T(H)1) cells at inflammatory sites was reduced. Thus, CD18 is selectively required for T(H)2, but not T(H)1, homing and has a minimal influence on T-effector development. These findings suggest a new integrin-based therapeutic approach in which the outcomes of diverse diseases may be favorably influenced by altering the homing of T(H)2 cells.

Effect of promoter methylation on the regulation of IFN-gamma gene during in vitro differentiation of human peripheral blood T cells into a Th2 population

The carefully orchestrated events that result in a protective immune response are coordinated to a large extent by cytokines produced by Th1 and Th2 cell subsets. Th1 cells preferentially produce IL-2 and IFN-gamma, resulting in a cellular response that helps to eliminate infected cells. In contrast, Th2 cells produce IL-4, IL-5, IL-6, and IL-10, stimulating an Ab response that attacks extracellular pathogens, thereby preventing the cells from becoming infected. To elucidate the mechanisms of differential regulation of cytokine genes by these two different subsets of T cells, we established an in vitro differentiation model of freshly isolated human peripheral blood T cells in which IFN-gamma was used as an index gene to study the transcriptional regulation. The data presented here demonstrate that the IFN-gamma promoter undergoes differential methylation during in vitro differentiation: the promoter becomes hypermethylated in Th2 cells, whereas it is hypomethylated in Th1 cells. Hypermethylation in Th2 cells results in chromatin condensation and exclusion of CREB proteins from the IFN-gamma promoter. Treatment with 5-azacytidine, a demethylating agent, causes Th2 cells to reverse histone condensation and enables CREB recruitment to the hypomethylated promoter. This results in the increased production of IFN-gamma. These data indicate the importance of promoter methylation in the regulation of the IFN-gamma gene during differentiation.

The threshold pattern of calcineurin-dependent gene expression is altered by loss of the endogenous inhibitor calcipressin

Calcineurin links calcium signaling to transcriptional responses in the immune, nervous and cardiovascular systems. To determine the function of the calcipressins, a family of putative calcineurin inhibitors, we assessed the calcineurin-dependent process of T cell activation in mice engineered to lack the gene encoding calcipressin 1 (Csp1). Csp1 regulated calcineurin in vivo, and genes triggered in an immune response had unique transactivation thresholds for T cell receptor stimulation. In the absence of Csp1, the apparent transactivation thresholds for all these genes were shifted because of enhanced calcineurin activity. This unbridled calcineurin activity drove Fas ligand expression, which normally requires high T cell receptor stimulation and results in the premature death of T helper type 1 cells. Thus, calcipressins modulate the pattern of calcineurin-dependent transcription, and may influence calcineurin activity beyond calcium to integrate a broad array of signals into the cellular response.

CD4+ T cells in atherosclerosis

Atherosclerosis is an inflammatory disease. T lymphocytes, occurring concomitantly with macrophages, are found in atherosclerotic lesions with substantial numbers in all stages. Most of the T cells in the lesions are CD4(+) T cells. The finding of activated T cells and macrophages in lesions and cloning of T cells specific for modified low-density lipoproteins from lesions suggest that a cell-mediated immune reaction is taking place in atherosclerosis. This review provides an overview of our current understanding of the roles of CD4(+) T cell subpopulations in atherosclerosis.

The regulation of immunoglobulin E class-switch recombination

Immunoglobulin E (IgE) isotype antibodies are associated with atopic disease, namely allergic rhinitis, asthma and atopic dermatitis, but are also involved in host immune defence mechanisms against parasitic infection. The commitment of a B cell to isotype class switch to an IgE-producing cell is a tightly regulated process, and our understanding of the regulation of IgE-antibody production is central to the prevention and treatment of atopic disease. Both those that are presently in use and potential future therapies to prevent IgE-mediated disease take advantage of our existing knowledge of the specific mechanisms that are required for IgE class switching.

Similarities and differences in CD4+ and CD8+ effector and memory T cell generation

Naive CD4+ and CD8+ T cells undergo unique developmental programs after activation, resulting in the generation of effector and long-lived memory T cells. Recent evidence indicates that both cell-intrinsic and cell-extrinsic factors regulate memory T cell differentiation. This review compares and contrasts how naive CD4+ and CD8+ T cells make the transition to effector and/or memory cells and discusses the implications of these findings for vaccine development.

Molecular mechanisms regulating Th1 immune responses

The T helper lymphocyte is responsible for orchestrating the appropriate immune response to a wide variety of pathogens. The recognition of the polarized T helper cell subsets Th1 and Th2 has led to an understanding of the role of these cells in coordinating a variety of immune responses, both in responses to pathogens and in autoimmune and allergic disease. Here, we discuss the mechanisms that control lineage commitment to the Th1 phenotype. What has recently emerged is a rich understanding of the cytokines, receptors, signal transduction pathways, and transcription factors involved in Th1 differentiation. Although the picture is still incomplete, the basic pathways leading to Th1 differentiation can now be understood in in vitro and a number of infection and disease models.

T cell-intrinsic requirement for NF-kappa B induction in postdifferentiation IFN-gamma production and clonal expansion in a Th1 response

NF-kappaB/Rel transcription factors are linked to innate immune responses and APC activation. Whether and how the induction of NF-kappaB signaling in normal CD4(+) T cells regulates effector function are not well-understood. The liberation of NF-kappaB dimers from inhibitors of kappaB (IkappaBs) constitutes a central checkpoint for physiologic regulation of most forms of NF-kappaB. To investigate the role of NF-kappaB induction in effector T cell responses, we targeted inhibition of the NF-kappaB/Rel pathway specifically to T cells. The Th1 response in vivo is dramatically weakened when T cells defective in their NF-kappaB induction (referred to as IkappaBalpha(DeltaN) transgenic cells) are activated by a normal APC population. Analyses in vivo, and IL-12-supplemented T cell cultures in vitro, reveal that the mechanism underlying this T cell-intrinsic requirement for NF-kappaB involves activation of the IFN-gamma gene in addition to clonal expansion efficiency. The role of NF-kappaB in IFN-gamma gene expression includes a modest decrease in Stat4 activation, T box expressed in T cell levels, and differentiation efficiency along with a more prominent postdifferentiation step. Further, induced expression of Bcl-3, a trans-activating IkappaB-like protein, is decreased in T cells as a consequence of NF-kappaB inhibition. Together, these findings indicate that NF-kappaB induction in T cells regulates efficient clonal expansion, Th1 differentiation, and IFN-gamma production by Th1 lymphocytes at a control point downstream from differentiation.

IL-23 and IL-27: new members of the growing family of IL-12-related cytokines with important implications for therapeutics

The recent discoveries of the two interleukin (IL)-12-related cytokines, IL-23 and IL-27, reveal that the regulation of cellular immunity is more complex than originally thought. Until these discoveries, the role of IL-12 in modulating cellular immune responses had been overestimated due to the belief that the IL-12 p40 subunit was unique to IL-12. However, because p40 is shared between IL-12 and IL-23, it would be expected that p40(-/-) mice are doubly deficient in IL-12 and IL-23. Indeed, the essential role previously attributed to IL-12 in experimental autoimmune encephalitis during studies of p40(-/-) mice has been shown to be due to IL-23 instead. The newest addition to the IL-12 cytokine family, IL-27, has unique features as well. Its specific action on naive CD4+ T cells in both mice and humans appears to distinguish it from the other IL-12 family members. Although related, the IL-12 family of cytokines and their receptors have distinct patterns of expression and unique effects on developing immune responses. This review summarises much of the pertinent literature on the IL-12 cytokine family and provides predictions regarding their potential therapeutic roles based on what has been learned about their functions in vitro and in vivo in gene-deficient mice.

CD8 T cell-specific downregulation of histone hyperacetylation and gene activation of the IL-4 gene locus by ROG, repressor of GATA

Chromatin remodeling of type 2 cytokine gene loci occurs during differentiation of naive CD4 and CD8 T cells into type 2 helper (Th2) and cytotoxic (Tc2) T cells. IL-4 production and histone hyperacetylation in IL-4-associated nucleosomes in developing Tc2 cells were significantly lower than those of Th2 cells; however, cytokine production and histone hyperacetylation of IL-5 and IL-13 genes were equivalent. Developing Tc2 cells expressed lower GATA3 levels and dramatically increased levels of repressor of GATA (ROG). A ROG response element in the IL-13 gene exon 4 displayed Tc2-specific binding of ROG, HDAC1, and HDAC2 and exhibited repression of IL-4 gene activation. Thus, ROG may confer CD8 T cell-specific repression of histone hyperacetylation and activation of the IL-4 gene locus.

SOCS-3 regulates onset and maintenance of T(H)2-mediated allergic responses

Members of the suppressor of cytokine signaling (SOCS) family are involved in the pathogenesis of many inflammatory diseases. SOCS-3 is predominantly expressed in T-helper type 2 (T(H)2) cells, but its role in T(H)2-related allergic diseases remains to be investigated. In this study we provide a strong correlation between SOCS-3 expression and the pathology of asthma and atopic dermatitis, as well as serum IgE levels in allergic human patients. SOCS-3 transgenic mice showed increased T(H)2 responses and multiple pathological features characteristic of asthma in an airway hypersensitivity model system. In contrast, dominant-negative mutant SOCS-3 transgenic mice, as well as mice with a heterozygous deletion of Socs3, had decreased T(H)2 development. These data indicate that SOCS-3 has an important role in regulating the onset and maintenance of T(H)2-mediated allergic immune disease, and suggest that SOCS-3 may be a new therapeutic target for the development of antiallergic drugs.

The Runx1 transcription factor inhibits the differentiation of naive CD4+ T cells into the Th2 lineage by repressing GATA3 expression

Differentiation of naive CD4+ T cells into helper T (Th) cells is controlled by a combination of several transcriptional factors. In this study, we examined the functional role of the Runx1 transcription factor in Th cell differentiation. Naive T cells from transgenic mice expressing a dominant interfering form of Runx1 exhibited enhanced interleukin 4 production and efficient Th2 differentiation. In contrast, transduction of Runx1 into wild-type T cells caused a complete attenuation of Th2 differentiation and was accompanied by the cessation of GATA3 expression. Furthermore, endogenous expression of Runx1 in naive T cells declined after T cell receptor stimulation, at the same time that expression of GATA3 increased. We conclude that Runx1 plays a novel role as a negative regulator of GATA3 expression, thereby inhibiting the Th2 cell differentiation.

CpG directly induces T-bet expression and inhibits IgG1 and IgE switching in B cells

CpG DNA has immunomodulatory effects, such as the suppression of allergic responses mediated by type II T cell help (T(H)2). Here we report that CpG, but not lipopolysaccharide (LPS), rapidly induces expression of T-bet mRNA in purified B cells. Up-regulation of T-bet by CpG is abrogated in mice deficient in Toll-like receptor 9 (TLR9) and MyD88, but remains intact in B cells deficient in STAT1 (signal transducer and activator of transcription 1). Interleukin 12 (IL-12) alone does not up-regulate T-bet mRNA, but greatly enhances CpG-induced T-bet expression. Furthermore, CpG inhibits immunoglobulin G1 (IgG1) and IgE switching induced by IL-4 and CD40 signaling in purified B cells, and this effect correlates with up-regulation of T-bet. Thus, CpG triggers anti-allergic immune responses by directly regulating T-bet expression via a signaling pathway in B cells that is dependent upon TLR9, independent of interferon-gamma (IFN-gamma)-STAT1 and synergistic with IL-12.

An epigenetic view of helper T cell differentiation

Antigen and cytokine receptor signals act in synergy to direct the differentiation of CD4+ T cells. These signals initiate reciprocal activation and silencing of the interferon-gamma (IFN-gamma) and interleukin 4 (IL-4) cytokine gene loci, changes that are heritably maintained in the resulting T helper type 1 (T(H)1) or T(H)2 cells and their progeny. Early, unpolarized transcription and chromatin remodeling of the poised cytokine genes of naive T cells is followed by consolidation and spreading of epigenetic changes and the establishment of self-reinforcing transcription factor networks. Recent studies have begun to elucidate the molecular mechanisms that establish and maintain polarized cytokine gene expression, and thus the cellular identity of differentiated helper T cells.

T-bet/GATA-3 ratio as a measure of the Th1/Th2 cytokine profile in mixed cell populations: predominant role of GATA-3

The differentiation of naive T-helper (Th) cells towards Th1 or Th2 cells is regulated by the transcription factors T-box expressed in T-cells (T-bet) and GATA-binding protein-3 (GATA-3). In the present study, the gene expression of T-bet and GATA-3 was measured by semi-quantitive reverse transcription polymerase chain reaction (RT-PCR) in Th1 and Th2 cells derived from purified splenic CD4+ T cells from DO11.10/Rag2(-/-) transgenic mice and control BioBreeding (BBc) Wistar rat splenic T cells stimulated under Th1 or Th2 conditions. In both sets of experiments, changes in the ratio of expression of T-bet and GATA-3 reflected changes in the Th1-specific cytokine interferon-gamma (IFN-gamma) and Th2-specific cytokine interleukin (IL)-4. T-bet gene expression was not maintained in fully polarized rat Th1 cells whereas GATA-3 gene expression was maintained in long-term polarized rat Th2 cells, indicating that maintenance of Th1/Th2 status occurred more as a result of altered GATA-3 mRNA expression than T-bet. These transcription factors are up-regulated in several cells that produce type 1 and type 2 cytokines and can be analyzed readily by RT-PCR using total RNA isolated from mixed cell populations or cultured splenocytes thereby providing a surrogate marker of Th1/Th2 cytokine balance under a variety of conditions.

Regulation of IL4 gene expression by T cells and therapeutic perspectives

Interleukin-4 (IL-4) is crucial for the differentiation of naive T helper (T(H)) cells into the T(H)2 effector cells that promote humoral (antibody) immunity and provide protection against intestinal helminths. IL-4 also has a central role in the pathogenesis of allergic inflammation. Many transcription factors are involved in the regulation of expression of the gene encoding IL-4. Initiation of transcription of the gene encoding IL-4 in naive T(H) cells is regulated by the T(H)2-specific transcription factor GATA3, whereas acute expression of the gene encoding IL-4 in T(H)2 cells is mediated by inducible, ubiquitous transcription factors after antigen encounter. This review focuses on acute activation of the gene encoding IL-4 in T cells and discusses therapeutic perspectives at the transcriptional level.