GATA-Dependent expression of the interleukin-1 receptor-related T1 gene in mast cells

Therapeutic potential of progesterone in spinal cord injury-induced neuropathic pain: At the crossroads between neuroinflammation and N-methyl-D-aspartate receptor

In recent decades, an area of active research has supported the notion that progesterone promotes a wide range of remarkable protective actions in experimental models of nervous system trauma or disease, and has also provided a strong basis for considering this steroid as a promising molecule for modulating the complex maladaptive changes that lead to neuropathic pain, especially after spinal cord injury. In this review, we intend to give the readers a brief appraisal of the main mechanisms underlying the increased excitability of the spinal circuit in the pain pathway after trauma, with particular emphasis on those mediated by the activation of resident glial cells, the subsequent release of proinflammatory cytokines and their impact on N-methyl-D-aspartate receptor function. We then summarize the available preclinical data pointing to progesterone as a valuable repurposing molecule for blocking critical cellular and molecular events that occur in the dorsal horn of the injured spinal cord and are related to the development of chronic pain. Since the treatment and management of neuropathic pain after spinal injury remains challenging, the potential therapeutic value of progesterone opens new traslational perspectives to prevent central pain.

Gastric alarmin release: A warning signal in the development of gastric mucosal diseases

Alarmins exist outside cells and are early warning signals to the immune system; as such, alarmin receptors are widely distributed on various immune cells. Alarmins, proinflammatory molecular patterns associated with tissue damage, are usually released into the extracellular space, where they induce immune responses and participate in the damage and repair processes of mucosal diseases.In the stomach, gastric alarmin release has been shown to be involved in gastric mucosal inflammation, antibacterial defense, adaptive immunity, and wound healing; moreover, this release causes damage and results in the development of gastric mucosal diseases, including various types of gastritis, ulcers, and gastric cancer. Therefore, it is necessary to understand the role of alarmins in gastric mucosal diseases. This review focuses on the contribution of alarmins, including IL33, HMGB1, defensins and cathelicidins, to the gastric mucosal barrier and their role in gastric mucosal diseases. Here, we offer a new perspective on the prevention and treatment of gastric mucosal diseases.

Epithelial cell-derived cytokines: more than just signaling the alarm

The epithelial cell-derived cytokines thymic stromal lymphopoietin (TSLP), IL-33, and IL-25 are central regulators of type 2 immunity, which drives a broad array of allergic responses. Often characterized as "alarmins" that are released by the barrier epithelium in response to external insults, these epithelial cell-derived cytokines were initially thought to act only early in allergic inflammation. Indeed, TSLP can condition dendritic cells to initiate type 2 responses, and IL-33 may influence susceptibility to asthma through its role in establishing the immune environment in the perinatal lungs. However, TSLP, IL-33, and IL-25 all regulate a broad spectrum of innate immune cell populations and are particularly potent in eliciting and activating type 2 innate lymphoid cells (ILC2s) that may act throughout allergic inflammation. Recent data suggest that a TSLP/ILC axis may mediate steroid resistance in asthma. Recent identification of memory Th2 cell subsets that are characterized by high receptor expression for TSLP, IL-33, and IL-25 further supports a role for these cytokines in allergic exacerbations. There is therefore growing interest in developing biologics that target TSLP, IL-33, and IL-25. This Review provides an overview of TSLP, IL-33, and IL-25 and the development of blocking antibodies that target these epithelial cell-derived cytokines.

Runx2 mediated Induction of Novel Targets ST2 and Runx3 Leads to Cooperative Regulation of Hypertrophic Differentiation in ATDC5 Chondrocytes

Knowledge concerning expression and function of Suppression of Tumorigenicity 2 (ST2) in chondrocytes is at present, limited. Analysis of murine growth plates and ATDC5 chondrocytes indicated peak expression of the ST2 transmembrane receptor (ST2L) and soluble (sST2) isoforms during the hypertrophic differentiation concomitant with the expression of the hypertrophic markers Collagen X (Col X), Runx2 and MMP-13. Gain- and loss-of-function experiments in ATDC5 and primary human growth plate chondrocytes (PHCs), confirmed regulation of ST2 by the key transcription factor Runx2, indicating ST2 to be a novel Runx2 target. ST2 knock-out mice (ST2−/−) exhibited noticeable hypertrophic zone (HZ) reduction in murine growth plates, accompanied by lower expression of Col X and Osteocalcin (OSC) compared to wild-type (WT) mice. Likewise, ST2 knockdown resulted in decreased Col X expression and downregulation of OSC and Vascular Endothelial Growth Factor (VEGF) in ATDC5 cells. The ST2 suppression was also associated with upregulation of the proliferative stage markers Sox9 and Collagen II (Col II), indicating ST2 to be a new regulator of ATDC5 chondrocyte differentiation. Runx3 was, furthermore, identified as a novel Runx2 target in chondrocytes. This study suggests that Runx2 mediates ST2 and Runx3 induction to cooperatively regulate hypertrophic differentiation of ATDC5 chondrocytes.

Regulation of antiapoptotic and cytoprotective pathways in colonic epithelial cells in ulcerative colitis

Ulcerative colitis is an inflammatory bowel disease involving the colon resulting in bloody diarrhea and increased risk of colorectal cancer in certain patient subgroups. Increased apoptosis in the epithelial cell layer causes increased permeability, especially during flares; this leads to translocation of luminal pathogens resulting in a continued inflammatory drive. The present work investigates how epithelial apoptosis is regulated in ulcerative colitis. The main results are that Fas mediated apoptosis is inhibited during flares of ulcerative colitis, probably by an upregulation of cellular inhibitor of apoptosis protein 2 (cIAP2) and cellular FLICE-like inhibitory protein. cIAP2 is upregulated in regenerative epithelial cells both in ulcerative colitis and in experimental intestinal wounds. Inhibition of cIAP2 decreases wound healing in vitro possibly through inhibition of migration. Altogether, it is shown that epithelial cells in ulcerative colitis responds to the hostile microenvironment by activation of cytoprotective pathways that tend to counteract the cytotoxic effects of inflammation. However, the present studies also show that epithelial cells produce increased amounts of reactive oxygen species during stimulation with tumor necrosis factor-α and interferon-γ resulting in DNA instability. The combined effect of increased DNA-instability and decreased apoptosis responses could lead to neoplasia.

Involvement of PU.1 in mast cell/basophil-specific function of the human IL1RL1/ST2 promoter

BACKGROUND

The human IL1RL1/ST2 gene encodes IL33 receptor. Recently, IL33 has been recognized as a key molecule for the development of Th2 response. Although mast cells and basophils are major targets of IL33 and play important roles in IL33-mediated Th2-type immune responses, the expression mechanism of ST2 in mast cells and basophils is largely unknown. In the present study, we analyzed regulation mechanism of the human ST2 promoter in the human mast cell line LAD2 and basophilic cell line KU812.

METHODS

Promoter activity was determined by reporter assay with plasmids carrying the wild-type ST2 promoter obtained from human genomic DNA and its mutant. The transcription factor binding to the identified cis-element was identified by an electrophoretic mobility shift assay (EMSA). The effect of candidate transcription factor on ST2 expression was confirmed by analyzing ST2 mRNA level in siRNA-introduced cells.

RESULTS

Reporter assay demonstrated that a cis-element of typical Ets-family binding sequence was critical for promoter activity in LAD2 and KU812. An Ets-family transcription factor PU.1 bound to this element in an EMSA. When PU.1 expression was suppressed by siRNA, ST2 mRNA level was significantly reduced in KU812.

CONCLUSIONS

These observations indicated that PU.1 positively regulates the ST2 promoter as a transcription factor that directly transactivates the ST2 promoter via Ets-family-related cis-element in mast cells and basophils.

GATA2 is a critical transactivator for the human IL1RL1/ST2 promoter in mast cells/basophils: opposing roles for GATA2 and GATA1 in human IL1RL1/ST2 gene expression

The IL1RL1/ST2 gene encodes a receptor for IL-33. Signaling from IL1RL1/ST2 induced by IL-33 binding was recently identified as a modulator of the Th2 response. The target cells for IL-33 are restricted in some hematopoietic lineages, including mast cells, basophils, eosinophils, Th2 cells, natural killer cells, and dendritic cells. To clarify the molecular mechanisms of cell type-specific IL1RL1/ST2 expression in mast cells and basophils, transcriptional regulation of the human IL1RL1/ST2 promoter was investigated using the mast cell line LAD2 and the basophilic cell line KU812. Reporter assays suggested that two GATA motifs just upstream of the transcription start site in the ST2 promoter are critical for transcriptional activity. These two GATA motifs possess the capacity to bind GATA1 and GATA2 in EMSA. ChIP assay showed that GATA2, but not GATA1, bound to the ST2 promoter in LAD2 cells and that histone H3 at the ST2 promoter was acetylated in LAD2 cells, whereas binding of GATA1 and GATA2 to the ST2 promoter was detected in KU812 cells. Knockdown of GATA2 mRNA by siRNA reduced ST2 mRNA levels in KU812 and LAD2 cells and ST2 protein levels in LAD2 cells; in contrast, GATA1 siRNA transfection up-regulated ST2 mRNA levels in KU812 cells. The ST2 promoter was transactivated by GATA2 and repressed by GATA1 in coexpression analysis. When these siRNAs were introduced into human peripheral blood basophils, GATA2 siRNA reduced ST2 mRNA, whereas GATA1 siRNA up-regulated ST2 mRNA. These results indicate that GATA2 and GATA1 positively and negatively control human ST2 gene transcription, respectively.

IL-33 is upregulated in colonocytes of ulcerative colitis

Interleukin-33 (IL-33) is a novel member of the IL-1 cytokine family. It has been shown to elicit a Th2-like cytokine response in immunocompetent cells through binding and activation of the T1/ST2 receptor. IL-33 has recently been associated with immune responses to helminthic intestinal infections, airway inflammation and arthritis in animal models. We now report IL-33 to be produced by colonic epithelial cells in humans and it is highly upregulated in ulcerative colitis (UC). Little mRNA expression was found in control subjects (N=9), whereas patients with UC in remission (N=7) and active UC (N=9) had a 3-fold (p<0.006) and 13-fold (p<0.0002) increased expression, respectively. On the protein level, IL-33 in its uncleaved form was overexpressed in active UC compared to controls (p<0.006) and inactive UC (p<0.03). Immunohistochemistry of IL-33 confirmed expression in active UC in colonic epithelial cells, whereas no detectable epithelial expression was seen in control specimens. Caspase 1, which is known to activate IL-33, was expressed in colonocytes, albeit at just detectable levels when the activated p20 caspase 1 was measured. Since IL-33 recently has been shown to be biologically active in its pro-form, and cleavage seems to inactivate IL-33, IL-33 is suggested to be active in UC. We found no IL-33 expression in Caco2 cells, regardless of stimulation by pro-inflammatory cytokines. In contrast to the IL-33 expression data, we could not show any difference in the production of another member of the IL-1 cytokine family, IL-1beta. This is the first study to describe that IL-33 is upregulated in UC. If IL-33 is driving a Th2-like cytokine response in UC, inhibition of the IL-33 T1/ST2 receptor pathway could be a future therapeutic option in UC.

IL-33: a tissue derived cytokine pathway involved in allergic inflammation and asthma

Besides classic T cell-derived T-helper type 2 (Th2) cytokines such as IL-4, IL-5 and IL-13, tissue-produced cytokines such as thymic stromal lymphopoietin, IL-25 and IL-33 are now recognized as important contributors to allergic inflammation. IL-33 is produced by various tissue dwelling cells and broadly enhances allergic inflammation through its effects on hematopoietic cell types. The environmental or endogenous triggers that provoke IL-33 cellular release may be associated with infection, inflammation or tissue damage. This review summarizes the wide range of documented IL-33 activities on human cellular mediators of inflammation as well as genetic evidence that IL-33 contributes to disease. Finally, there will be a discussion of still unanswered questions regarding the mechanisms by which cytokine activity is generated and IL-33's relationship with other Th2-associated cytokines.

Welcome to the neighborhood: epithelial cell-derived cytokines license innate and adaptive immune responses at mucosal sites

There is compelling evidence that epithelial cells (ECs) at mucosal surfaces, beyond their role in creating a physical barrier, are integral components of innate and adaptive immunity. The capacity of these cells to license the functions of specific immune cell populations in the airway and gastrointestinal tract offers the prospect of novel therapeutic strategies to target multiple inflammatory diseases in which barrier immunity is dysregulated. In this review, we discuss the critical functions of EC-derived thymic stromal lymphopoietin (TSLP), interleukin-25 (IL-25), and IL-33 in the development and regulation of T-helper 2 (Th2) cytokine-dependent immune responses. We first highlight recent data that have provided new insights into the factors that control expression of this triad of cytokines and their receptors. In addition, we review their proinflammatory and immunoregulatory functions in models of mucosal infection and inflammation. Lastly, we discuss new findings indicating that despite their diverse structural features and differential expression of their receptors, TSLP, IL-25, and IL-33 cross-regulate one another and share overlapping properties that influence Th2 cytokine-dependent responses at mucosal sites.

IL-33 amplifies both Th1- and Th2-type responses through its activity on human basophils, allergen-reactive Th2 cells, iNKT and NK cells

IL-33 is an IL-1 family member recently identified as the ligand for T1/ST2 (ST2), a member of the IL-1 receptor family. ST2 is stably expressed on mast cells and T(h)2 effector T cells and its function has been studied in the context of T(h)2-associated inflammation. Indeed, IL-33 induces T(h)2 cytokines from mast cells and polarized mouse T cells and leads to pulmonary and mucosal T(h)2 inflammation when administered in vivo. To better understand how this pathway modulates inflammatory responses, we examined the activity of IL-33 on a variety of human immune cells. Human blood-derived basophils expressed high levels of ST2 receptor and responded to IL-33 by producing several pro-inflammatory cytokines including IL-1 beta, IL-4, IL-5, IL-6, IL-8, IL-13 and granulocyte macrophage colony-stimulating factor. Next, utilizing a human T(h)2-polarized T cell culture system derived from allergic donor blood cells, we found that IL-33 was able to enhance antigen-dependent and -independent T cell responses, including IL-5, IL-13 and IFN-gamma production. IL-33 activity was also tested on V alpha 24-positive human invariant NKT (iNKT) cells. In the presence of alpha-galactosylceramide antigen presentation, IL-33 dose dependently enhanced iNKT production of several cytokines, including both IL-4 and IFN-gamma. IL-33 also directly induced IFN-gamma production from both iNKT and human NK cells via cooperation with IL-12. Taken together, these results indicate that in addition to its activity on human mast cells, IL-33 is capable of activating human basophils, polarized T cells, iNKT and NK cells. Moreover, the nature of the responses elicited by IL-33 suggests that this axis may amplify both T(h)1- and T(h)2-oriented immune responses.

Molecular Mechanisms of Mast Cell Development

Mast cells are progeny of multipotential hematopoietic stem cells (MHSCs). MHSCs commit to the mast cell lineage in the bone marrow, and the mast cell-committed progenitors leave the bone marrow, migrate in blood, invade connective or mucosal tissue, and then proliferate and differentiate to connective tissue-type or mucosal mast cell. GATA-1, GATA-2, and PU.1 transcription factors seem to be involved i the commitment to mast cells, and MITF, a basic helix-loop-helix leucine zipper-type transcription factor, seems to be involved in the migration, phenotypic expression, and survival of mast cells. KIT ligand (KITL) is the most important cytoline for development of mast cells, and KIT is the receptor of KITL. Tissues of loss-of-function mutants of KIT, KITL, or MITF are deficient in mast cells.

T-helper type 2 cell-specific expression of the ST2 gene is regulated by transcription factor GATA-3

ST2 is a member of the interleukin-1 receptor family and is expressed in type-2 T helper (Th2) cells. Here, we have studied the molecular mechanism responsible for the transcriptional regulation of the ST2 gene in Th2 cells using a mouse thymoma cell line, EL-4. The ST2 gene has distal and proximal promoters. ST2 mRNA was produced from the distal promoter in EL-4 cells stimulated with both phorbol 12-myristate 13-acetate (PMA) and dibutyryl cAMP (Bt2cAMP). The region of approximately 100 bp upstream of transcription start site, containing two GATA consensus sites, was indispensable for the activation of the distal promoter in reporter gene analysis. An electrophoretic mobility shift assay showed that transcription factor GATA-3 bound one of the GATA consensus sites (from -84 to -79) with nuclear extracts from PMA plus Bt2cAMP-stimulated EL-4 cells. The overexpression of GATA-3 enhanced the activity of the distal promoter. On the other hand, mutations of the GATA consensus site canceled out the enhancement by GATA-3. These data suggest that GATA-3 is an important transcription factor for the expression of the ST2 gene in Th2 cells.

GATA-1 as a regulator of mast cell differentiation revealed by the phenotype of the GATA-1low mouse mutant

Here it is shown that the phenotype of adult mice lacking the first enhancer (DNA hypersensitive site I) and the distal promoter of the GATA-1 gene (neo Delta HS or GATA-1(low) mutants) reveals defects in mast cell development. These include the presence of morphologically abnormal alcian blue(+) mast cells and apoptotic metachromatic(-) mast cell precursors in connective tissues and peritoneal lavage and numerous (60-70% of all the progenitors) "unique" trilineage cells committed to erythroid, megakaryocytic, and mast pathways in the bone marrow and spleen. These abnormalities, which were mirrored by impaired mast differentiation in vitro, were reversed by retroviral-mediated expression of GATA-1 cDNA. These data indicate an essential role for GATA-1 in mast cell differentiation.

Characterization of signaling pathways activated by the interleukin 1 (IL-1) receptor homologue T1/ST2. A role for Jun N-terminal kinase in IL-4 induction

T1/ST2 is a member of the interleukin (IL)-1 receptor superfamily, possessing three immunoglobulin domains extracellularly and a Toll/IL1R (TIR) domain intracellularly. The ligand for T1/ST2 is not known. T1/ST2 is expressed on Type 2 T helper (Th2) cells, and its role appears to be in the regulation of Th2 cell function. Here, we have investigated T1/ST2 signal transduction, using either transient overexpression of T1/ST2 or a cross-linking monoclonal antibody to activate cells. We demonstrate that T1/ST2 does not activate the transcription factor NF-kappaB when overexpressed in murine thymoma EL4 cells, or in the mast cell line P815 treated with the anti-T1/ST2 antibody. However, a chimera comprising the extracellular domain of the type 1 IL-1 receptor and the intracellular domain of T1/ST2 activates NF-kappaB both by overexpression and in response to IL-1. This artificial activation requires the IL1RAcP recruited via the extracellular portion (IL1R1) of the chimera. T1/ST2 is, however, able to activate the transcription factor activator protein-1 (AP-1), increase phosphorylation of c-Jun, and activate the MAP kinases c-Jun N-terminal kinase (JNK), p42/p44 and p38. Anti-T1/ST2 also induces the selective expression of IL-4 but not IFN-gamma in naive T cells. Importantly, this effect is blocked by prior treatment with the JNK inhibitor SP600125 confirming that JNK as a key effector in T1/ST2 signaling. The lack of effect on NF-kappaB when T1/ST2 is homodimerized identifies T1/ST2 as the first member of the IL-1 receptor superfamily so far studied that is apparently unable to activate NF-kappaB, consistent with evidence indicating the lack of a role for NF-kappaB in Th2 cell function.

Regulation of ST2L expression on T helper (Th) type 2 cells

T1/ST2L, an IL-1 receptor homologue, is selectively expressed on murine Th2 cells and specific anti-ST2L antibodies can profoundly modulate the Th1/Th2 balance in vivo. Naive CD4+ T cells do not express ST2L but do so on activation with specific antigen in the presence of IL-4 or when stimulated with low doses of antigen in the absence of exogenously added IL-4. Similarly enhanced ST2L expression occurred after stimulation of Th2 cells with antigen or the mitogen ConA in the presence of APC. Restimulation of Th2 cells in the presence of IFN-gamma led to a decreased expression of ST2L to below basal levels. Conversely, Th2 cells cultured with IL-4 led to increased ST2L expression. The reduced expression of ST2L in response to high doses of antigen is also reversed by the neutralization of IFN-gamma. Using an ST2L promoter/luciferase reporter gene construct, we show that the distal but not proximal ST2L promoter is responsible for specific gene expression in Th2 cells. IL-4 enhances, whereas IFN-gamma suppresses ST2L expression via direct modulation of the distal promoter of the ST2L gene. These data provide a mechanistic explanation for the selective expression of ST2L on Th2 cells.

Enforced expression of GATA-3 in transgenic mice inhibits Th1 differentiation and induces the formation of a T1/ST2-expressing Th2-committed T cell compartment in vivo

The transcription factor GATA-3 is essential for early T cell development and differentiation of naive CD4(+) T cells into Th2 effector cells. To study the function of GATA-3 during T cell-mediated immune responses in vivo, we investigated CD2-GATA3-transgenic mice in which GATA-3 expression is driven by the CD2 locus control region. Both in the CD4(+) and the CD8(+) T cell population the proportion of cells exhibiting a CD44(high)CD45RB(low)CD62L(low) Ag-experienced phenotype was increased. In CD2-GATA3-transgenic mice, large fractions of peripheral CD4(+) T cells expressed the IL-1 receptor family member T1/ST2, indicative of advanced Th2 commitment. Upon in vitro T cell stimulation, the ability to produce IL-2 and IFN-gamma was decreased. Moreover, CD4(+) T cells manifested rapid secretion of the Th2 cytokines IL-4, IL-5, and IL-10, reminiscent of Th2 memory cells. In contrast to wild-type CD4(+) cells, which lost GATA-3 expression when cultured under Th1-polarizing conditions, CD2-GATA3-transgenic CD4(+) cells maintained expression of GATA-3 protein. Under Th1 conditions, cellular proliferation of CD2-GATA3-transgenic CD4(+) cells was severely hampered, IFN-gamma production was decreased and Th2 cytokine production was increased. Enforced GATA-3 expression inhibited Th1-mediated in vivo responses, such as Ag-specific IgG2a production or a delayed-type hypersensitivity response to keyhole limpet hemocyanin. Collectively, these observations indicate that enforced GATA-3 expression selectively inhibits Th1 differentiation and induces Th2 differentiation. The increased functional capacity to secrete Th2 cytokines, along with the increased expression of surface markers for Ag-experienced Th2-committed cells, would argue for a role of GATA-3 in Th2 memory formation.

The mouse L-histidine decarboxylase gene: structure and transcriptional regulation by CpG methylation in the promoter region

To investigate the regulation of mouse L-histidine decarboxylase (HDC) gene expression, we isolated genomic DNA clones encoding HDC. Structural analysis revealed that the mouse HDC gene was composed of 12 exons, spanning approximately 24 kb. Northern blotting analysis indicated that, among the cell lines examined, a high level of HDC gene expression was restricted to mature mast cell lines and an erythroblastic cell line. The gene was induced strongly in the mouse immature mast cell line P815 after incubation in the peritoneal cavity of BDF1 mice. We observed that the promoter region was demethylated in the HDC-expressing cell lines and in induced P815 cells. Interestingly, forced demethylation by 5-azacytidine (5-azaC) treatment induced high expression of HDC mRNA in P815 cells. The activity of a mouse HDC promoter-reporter construct stably transfected in P815 cells was repressed by in vitro patch-methylation. This low promoter activity of the patch-methylated reporter construct was restored after 5-azaC treatment, which demethylated the patch-methylated promoter. These results indicate that DNA methylation state of the promoter region controls HDC gene expression.

Construction of ELISA system to quantify human ST2 protein in sera of patients

The human ST2 gene can be specifically induced by growth stimulation in fibroblastic cells, and can also be induced by antigen stimulation in Th2 cells. The gene encodes a soluble secreted protein, ST2, and a transmembrane protein, ST2L, which are closely related to the interleukin-1 receptor. To gain insight into the biological roles of the ST2 gene, three monoclonal antibodies (MAbs) against human ST2 gene products were obtained. To obtain these antibodies, immunization was carried out using two different immunogens: purified soluble human ST2 protein (hST2), and COS7 cells, which express the extracellular portion of human ST2L. 2A5 and FB9 MAbs were derived from the immunization with soluble hST2, and HB12 was derived from the COS7 cell immunization. All three antibodies were shown to detect native forms of the human ST2 gene products by immunoprecipitation, flow cytometry, and enzyme-linked immunosorbent assay (ELISA). In the competitive ELISA using biotinylated and nonlabelled MAbs, neither FB9 nor HB12 affected the binding of 2A5 to ST2 gene products. Based on this result, we constructed a sandwich ELISA system using 2A5 and FB9 to measure the concentration of soluble hST2 in sera. The ELISA, combined with the flow cytometry using these antibodies, will be a useful tool for elucidating the functions of human ST2 gene products in individuals.

T1/ST2-deficient mice demonstrate the importance of T1/ST2 in developing primary T helper cell type 2 responses

We have generated mice with a deficiency in T1/ST2 expression to clarify the roles of T1/ST2 in T helper cell type 2 (Th2) responses. Using immunological challenges normally characterized by a Th2-like response, we have compared the responses of T1/ST2-deficient mice with those generated by wild-type mice. Using a primary pulmonary granuloma model, induced with Schistosoma mansoni eggs, we demonstrate that granuloma formation, characterized by eosinophil infiltration, is abrogated in T1/ST2-deficient mice. Furthermore, we clearly demonstrate that in the absence of T1/ST2 expression, the levels of Th2 cytokine production are severely impaired after immunization. Thus, in a secondary pulmonary granuloma model, draining lymph node cells from the T1/ST2-deficient animals produced significantly reduced levels of IL-4 and IL-5, despite developing granulomas of a magnitude similar to those of wild-type mice and comparable antigen-specific immunoglobulin isotype production. These data clearly demonstrate that T1/ST2 expression plays a role in the development of Th2-like cytokine responses and indicate that effector functions are inhibited in its absence.

Different promoter usage and multiple transcription initiation sites of the interleukin-1 receptor-related human ST2 gene in UT-7 and TM12 cells

The ST2 gene encodes receptor-like molecules that are very similar to the type I interleukin-1 receptor. Two distinct types of the ST2 gene products, ST2 (a soluble secreted form) and ST2L (a transmembrane form) are produced by alternative splicing. Here we demonstrate that the human ST2 gene has two alternative promoters followed by distinct noncoding first exons, which are located more than 8 kb apart and are spliced to the common exon 2 containing the translation initiation site. Within 1001 bp upstream of the transcription initiation site of the cloned distal promoter, there are four GATA-1. The main promoter used for the expression of the ST2 gene in UT-7, a human leukaemic cell line, is distinct from that in TM12, a human fibroblastic cell line. Although UT-7 cells use both distal and proximal promoters, the distal promoter is used dominantly for expression of both ST2 and ST2L mRNA. On the other hand, almost all transcription in TM12 cells starts from the proximal promoter. These results contrast with those of former studies on the rat system, in which ST2 and ST2L mRNA were generated by use of the proximal and distal promoters, respectively. Furthermore, UT-7 cells use multiple transcription initiation sites in both the proximal and distal promoters, whereas the transcription of the ST2 gene in TM12 cells starts at a unique site. Intriguingly, these results suggest that ST2 and ST2L proteins have distinct functions in different cells within different biological systems, such as those of growth control, differentiation and immunological responses.