Signal transduction pathway of interleukin-4 and interleukin-13 in human B cells derived from X-linked severe combined immunodeficiency patients

Clinical, Immunological, and Molecular Features of Severe Combined Immune Deficiency: A Multi-Institutional Experience From India

Background

Severe Combined Immune Deficiency (SCID) is an inherited defect in lymphocyte development and function that results in life-threatening opportunistic infections in early infancy. Data on SCID from developing countries are scarce.

Objective

To describe clinical and laboratory features of SCID diagnosed at immunology centers across India.

Methods

A detailed case proforma in an Excel format was prepared by one of the authors (PV) and was sent to centers in India that care for patients with primary immunodeficiency diseases. We collated clinical, laboratory, and molecular details of patients with clinical profile suggestive of SCID and their outcomes. Twelve (12) centers provided necessary details which were then compiled and analyzed. Diagnosis of SCID/combined immune deficiency (CID) was based on 2018 European Society for Immunodeficiencies working definition for SCID.

Results

We obtained data on 277 children; 254 were categorized as SCID and 23 as CID. Male-female ratio was 196:81. Median (inter-quartile range) age of onset of clinical symptoms and diagnosis was 2.5 months (1, 5) and 5 months (3.5, 8), respectively. Molecular diagnosis was obtained in 162 patients - IL2RG (36), RAG1 (26), ADA (19), RAG2 (17), JAK3 (15), DCLRE1C (13), IL7RA (9), PNP (3), RFXAP (3), CIITA (2), RFXANK (2), NHEJ1 (2), CD3E (2), CD3D (2), RFX5 (2), ZAP70 (2), STK4 (1), CORO1A (1), STIM1 (1), PRKDC (1), AK2 (1), DOCK2 (1), and SP100 (1). Only 23 children (8.3%) received hematopoietic stem cell transplantation (HSCT). Of these, 11 are doing well post-HSCT. Mortality was recorded in 210 children (75.8%).

Conclusion

We document an exponential rise in number of cases diagnosed to have SCID over the last 10 years, probably as a result of increasing awareness and improvement in diagnostic facilities at various centers in India. We suspect that these numbers are just the tip of the iceberg. Majority of patients with SCID in India are probably not being recognized and diagnosed at present. Newborn screening for SCID is the need of the hour. Easy access to pediatric HSCT services would ensure that these patients are offered HSCT at an early age.

Progressive B Cell Loss in Revertant X-SCID

We report the case of a patient with X-linked severe combined immunodeficiency (X-SCID) who survived for over 20 years without hematopoietic stem cell transplantation (HSCT) because of a somatic reversion mutation. An important feature of this rare case included the strategy to validate the pathogenicity of a variant of the IL2RG gene when the T and B cell lineages comprised only revertant cells. We studied the X-inactivation of sorted T cells from the mother to show that the pathogenic variant was indeed the cause of his SCID. One interesting feature was a progressive loss of B cells over 20 years. CyTOF (cytometry time of flight) analysis of bone marrow offered a potential explanation of the B cell failure, with expansions of progenitor populations that suggest a developmental block. Another interesting feature was that the patient bore extensive granulomatous disease and skin cancers that contained T cells, despite severe T cell lymphopenia in the blood. Finally, the patient had a few hundred T cells on presentation but his TCRs comprised a very limited repertoire, supporting the important conclusion that repertoire size trumps numbers of T cells.

Mannose-binding lectin (MBL) and the lectin complement pathway play a role in cutaneous ischemia and reperfusion injury

Objectives

Cutaneous ischemia/reperfusion (CI/R) injury has shown to play a significant role in chronic wounds such as decubitus ulcers, diabetic foot ulcers, atherosclerotic lesions, and venous stasis wounds. CI/R also plays a role in free tissue transfer in reconstructive microsurgery and has been linked to clinical burn-depth progression after thermal injury. While the role of the complement system has been elucidated in multiple organ systems, evidence is lacking with respect to its role in the skin. Therefore, we evaluated the role of the complement system in CI/R injury.

Methods

Using a single pedicle skin flap mouse model of acute CI/R, we performed CI/R in wild-type (WT) mice and complement knock out (KO) mice, deficient in either C1q (C1q KO; classical pathway inhibition), mannose-binding lectin (MBL null; lectin pathway inhibition) or factor B (H2Bf KO; alternative pathway inhibition). Following 10 h ischemia and 7 days reperfusion, mice were sacrificed, flaps harvested and flap viability assessed via Image J software. The flap necrotic area was expressed as % total flap area. In another group, mice were sacrificed following CI/R with 10 h ischemia and 48 h reperfusion. Two cranial skin flap samples were taken for gene expression analysis of IL1b, IL6, TNFα, ICAM1, VCAM1, IL10, IL13 using real-time polymerase chain reaction (RT-PCR).

Results

Following CI/R, MBL null mice had a statistically significant smaller %necrotic flap area compared to WT mice (10.6 vs. 43.1%; p<0.05) suggesting protection from CI/R. A significantly reduced mean %necrotic flap area was not seen in either C1q KO or H2Bf KO mice relative to WT (22.9 and 31.3 vs. 43.1%; p=0.08 and p=0.244, respectively). There were no statistically significant differences between groups for markers of inflammation (TNFα, ICAM1, VCAM1, IL1b, IL6). In contrast, mRNA levels of IL10, a regulator of inflammation, were significantly increased in the MBL null group (p=0.047).

Conclusions

We demonstrated for the first time a significant role of MBL and the lectin complement pathway in ischemia/reperfusion injury of the skin and a potential role for IL10 in attenuating CI/R injury, as IL10 levels were significantly increased in the tissue from the CI/R-protected MBL null group.

Regulation of Filaggrin, Loricrin, and Involucrin by IL-4, IL-13, IL-17A, IL-22, AHR, and NRF2: Pathogenic Implications in Atopic Dermatitis

Atopic dermatitis (AD) is an eczematous, pruritic skin disorder with extensive barrier dysfunction and elevated interleukin (IL)-4 and IL-13 signatures. The barrier dysfunction correlates with the downregulation of barrier-related molecules such as filaggrin (FLG), loricrin (LOR), and involucrin (IVL). IL-4 and IL-13 potently inhibit the expression of these molecules by activating signal transducer and activator of transcription (STAT)6 and STAT3. In addition to IL-4 and IL-13, IL-22 and IL-17A are probably involved in the barrier dysfunction by inhibiting the expression of these barrier-related molecules. In contrast, natural or medicinal ligands for aryl hydrocarbon receptor (AHR) are potent upregulators of FLG, LOR, and IVL expression. As IL-4, IL-13, IL-22, and IL-17A are all capable of inducing oxidative stress, antioxidative AHR agonists such as coal tar, glyteer, and tapinarof exert particular therapeutic efficacy for AD. These antioxidative AHR ligands are known to activate an antioxidative transcription factor, nuclear factor E2-related factor 2 (NRF2). This article focuses on the mechanisms by which FLG, LOR, and IVL expression is regulated by IL-4, IL-13, IL-22, and IL-17A. The author also summarizes how AHR and NRF2 dual activators exert their beneficial effects in the treatment of AD.

Polymorphism rs4787951 in IL-4R contributes to the increased risk of renal cell carcinoma in a Chinese population

OBJECTIVE

Interleukins are important molecules involved in tumor formation. In this study, the association between renal cell carcinoma (RCC) risk and single nucleotide polymorphisms (SNPs) on IL-4/IL-13/IL-4R was assessed.

METHODS

We recruited 620/623 cases/controls and conducted a case-control study. Five tagSNPs (i.e., IL-4R rs8832, IL-4R rs4787951, IL-13 rs1881457, IL-13 rs2066960 and IL-13 rs2069744) were selected. Odds ratios (ORs) with their 95% confidence intervals (CIs) were obtained to appraise the association between SNPs and RCC susceptibility. Luciferase report assay and EMSA were conducted to investigate whether SNPs could affect binding affinity of transcription factors to target genes.

RESULTS

IL-4R rs4787951T>C was significantly associated with RCC susceptibility. Individuals carrying CC genotypes had a significant increment in RCC risk compared with TT genotype carriers (adjusted OR = 1.57, 95% CI = 1.07-2.28, P = 0.020). By stratified analyses, more pronounced association was found in the female, diabetic or without smoking, drinking and hypertension group. Besides, SNP rs4787951 could influence the binding affinity of IL-4R to transcription factors. Sequence surrounding allele T was prone to bind transcription factor NFATc.

CONCLUSIONS

This study revealed that IL-4R rs4787951T>C was associated with susceptibility of RCC and could be a predictive biomarker for RCC risk.

In silico mutational analysis and identification of stability centers in human interleukin-4

Interleukin-4 (IL-4) is a multifunctional cytokine that plays a critical role in apoptosis, differentiation and proliferation. The intensity of IL4 response depends upon binding to its receptor, IL-4R. The therapeutic efficiency of interleukins can be increased by generating structural mutants having greater stability. In the present work, attempts were made to increase the stability of human IL-4 using in-silico site directed mutagenesis. Different orthologous sequences of IL4 from Pan troglodytes, Aotusnigriceps, Macacamulatta, Papiohamadryas, Chlorocebusaethiops, Vicugnapacos, Susscrofa and Homo sapiens were aligned using Clustal Omega that revealed the conserved and non-conserved positions. For each non-conserved position, possible favorable and stabilizing mutations were found using CUPSAT with predicted ΔΔG (kcal/mol). The one with highest ΔΔG (kcal/mol) among all possible mutations, for each non-conserved position was selected and introduced manually in human IL-4 sequence resulting in multiple mutants of IL-4. Mutant proteins were modeled using structure of IL4 (PDB ID: 2B8U) as a template by SWISS MODEL. The mutants A49L and Q106T were identified to have stability centre using SCide. Molecular dynamics and docking analysis also confirmed the mutants stability and binding respectively. Mutants A49L and Q106T had -7.580079 kcal/mol and -39.418124 kcal/mol respectively lesser energy value than the wild type IL4. The result suggested that, the stability of human IL-4 has been increased by mutation.

Extensive survey of STAT6 expression in a large series of mesenchymal tumors

OBJECTIVES

Expression of strong nuclear STAT6 is thought to be a specific marker for solitary fibrous tumors (SFTs). Little is known about subtle expression patterns in other mesenchymal lesions.

METHODS

We performed immunohistochemical studies against the C-terminus of STAT6 in tissue microarrays and whole sections, comprising 2366 mesenchymal lesions.

RESULTS

Strong nuclear STAT6 was expressed in 285 of 2,021 tumors, including 206 of 240 SFTs, 49 of 408 well-differentiated/dedifferentiated liposarcomas, eight of 65 unclassified sarcomas, and 14 of 184 desmoid tumors, among others. Expression in SFTs was predominately limited to the nucleus. Other positive tumors typically expressed both nuclear and cytoplasmic STAT6. Complete absence of STAT6 was most common in pleomorphic liposarcoma and alveolar soft part sarcoma (60% and 72% cases negative, respectively).

CONCLUSIONS

Strong nuclear STAT6 is largely specific for SFTs. Physiologic low-level cytoplasmic/nuclear expression is common in mesenchymal neoplasia and is of uncertain significance.

Review: Stem cells and gene therapy

Both stem cell and gene therapy research are currently the focus of intense research in institutions and companies around the world. Both approaches hold great promise by offering radical new and successful ways of treating debilitating and incurable diseases effectively. Gene therapy is an approach to treat, cure, or ultimately prevent disease by changing the pattern of gene expression. It is mostly experimental, but a number of clinical human trials have already been conducted. Gene therapy can be targeted to somatic or germ cells; the most common vectors are viruses. Scientists manipulate the viral genome and thus introduce therapeutic genes to the target organ. Viruses, in this context, can cause adverse events such as toxicity, immune and inflammatory responses, as well as gene control and targeting issues. Alternative modalities being considered are complexes of DNA with lipids and proteins. Stem cells are primitive cells that have the capacity to self renew as well as to differentiate into 1 or more mature cell types. Pluripotent embryonic stem cells derived from the inner cell mass can develop into more than 200 different cells and differentiate into cells of the 3 germ cell layers. Because of their capacity of unlimited expansion and pluripotency, they are useful in regenerative medicine. Tissue or adult stem cells produce cells specific to the tissue in which they are found. They are relatively unspecialized and predetermined to give rise to specific cell types when they differentiate. The current review provides a summary of our current knowledge of stem cells and gene therapy as well as their clinical implications and related therapeutic options.

IL-4/Stat6 activities correlate with apoptosis and metastasis in colon cancer cells

IL-4-induced Stat6 signaling is active in a variety of cell types and plays a role in cell proliferation/growth and resistance to apoptosis. Using EMSA, we identified differential IL-4/Stat6 activities in colorectal cancer cell lines, HT-29 being active Stat6(high) phenotype and Caco-2 being defective Stat6(null) phenotype, respectively. Active Stat6(high) HT-29 cells exhibited resistance to apoptosis by flowcytometry and aggressive metastasis by Transwell assay compared with defective Stat6(null) Caco-2 cells. Comparing one another using RT-PCR, Stat6(high) HT-29 cells expressed more mRNA of anti-apoptotic and pro-metastatic genes Survivin, MDM2, and TMPRSS4, while Stat6(null) Caco-2 cells expressed more mRNA of pro-apoptotic and anti-metastatic genes BAX, CAV1, and P53, respectively. This is the first study describing correlations of IL-4/Stat6 activities with apoptosis and metastasis in colon cancer. These findings, together with the observation of constitutive Stat6 activation in many human malignancies, suggest that Stat6 activities could be a biomarker for cancer cell's invasive/metastatic capability.

Resistin-like molecule-beta is an allergen-induced cytokine with inflammatory and remodeling activity in the murine lung

Resistin-like molecule (RELM)-beta is a cysteine-rich cytokine implicated in insulin resistance and asthmatic responses, but its function remains an enigma. We now report that RELM-beta has a role in promoting airway inflammation and lung remodeling in the mouse lung. RELM-beta is strongly induced by diverse allergens and T helper type 2 (Th2) cytokines by an IL-13- and STAT6-dependent mechanism. To understand the in vivo role of RELM-beta, we delivered recombinant murine RELM-beta intratracheally to naïve mice. RELM-beta induced dose-dependent leukocyte accumulation (most prominently involving macrophages) and goblet cell hyperplasia. The most prominent effect induced by RELM-beta was increased perivascular and peribronchial collagen deposition. Mice genetically deficient in RELM-beta had reduced accumulation of collagen and goblet cell hyperplasia in an experimental model of allergic airway inflammation. In vitro experiments demonstrated that RELM-beta had fibroblast motogenic activity. These results identify RELM-beta as a Th2-associated cytokine with potent inflammatory and remodeling activity.

Screening for soluble expression constructs using cell-free protein synthesis

The SH2 domain of STAT6 was chosen to test the in vitro protein synthesis as a screening tool. Goal of the screening was to obtain constructs which produce soluble protein in E. coli. The expression of 70 different constructs using an E. coli based cell-free system revealed two constructs, which give partly soluble protein. The introduction of two mutations, which had been suggested by a structural based alignment of 20 different SH2 domains lead to increased solubility. The expression of both constructs in E. coli followed by an affinity and size exclusion chromatography resulted in milligram quantities of highly purified protein.

The squamous cell carcinoma antigens as relevant biomarkers of atopic dermatitis

BACKGROUND

Although it is thought that both Th1- and Th2-type inflammations are involved in the pathogenesis of atopic dermatitis (AD), it is controversial which immune response is more involved in regulating the clinical severity of AD. We recently found that the squamous cell carcinoma antigens 1 (SCCA1) and SCCA2 are novel biomarkers of bronchial asthma, downstream of IL-4 and IL-13.

OBJECTIVE

We examined whether SCCA1 and SCCA2 could also serve as biomarkers of AD, reflecting its Th2-type immune responses, and whether the expression level of SCCA was correlated with clinical severity of AD.

METHOD

We compared the expression of SCCA1 and SCCA2 at the mRNA and protein levels in both involved and uninvolved skin of AD patients and in normal control skin. We next analysed induction of SCCA by IL-4 or IL-13 in keratinocytes. Finally, we compared the serum level of SCCA with laboratory parameters reflecting Th2-type inflammation and clinical severity in AD patients.

RESULTS

SCCA1 and SCCA2 were highly expressed in involved skin of AD patients, compared with their uninvolved skin, at both mRNA and protein levels. SCCA protein was dominantly expressed in suprabasal keratinocytes in the epidermis of AD patients. Either IL-4 or IL-13, but not IFN-gamma or TNF, induced production of SCCA in keratinocytes. These result suggest that SCCA is induced in AD skin, probably due to direct actions of IL-4 and/or IL-13 on keratinocytes. Serum levels of SCCA were well correlated with eosinophil numbers and serum lactate dehydrogenase levels, and weakly with serum IgE levels, in AD patients. Furthermore, serum levels of SCCA were strongly correlated with clinical severity.

CONCLUSIONS

Th2-type inflammation dominantly regulates the clinical severity of AD, and SCCA is a relevant biomarker of AD, reflecting both Th2-type inflammation and clinical severity.

Induction and activation of the aryl hydrocarbon receptor by IL-4 in B cells

It is widely known that IL-4 and IL-13 act on various kinds of cells, including B cells, resulting in enhancement of proliferation, class switching to IgE and expression of several surface proteins. These functions are important for the recognition of the various antigens in B cells and are known to be involved in the pathogenesis of allergic diseases. However, it has not been known whether IL-4/IL-13 is involved in the metabolism of various kinds of xenobiotics including 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD), and it remains undetermined whether TCDD, an environmental pollutant, influences IgE production in B cells, exaggerating allergic reactions. We identified IL-4- or IL-13-inducible genes in a human Burkitt lymphoma cell line, DND-39, using microarray technology, in which the AHR gene was included. The AHR gene product, the aryl hydrocarbon receptor (AhR), was induced by IL-4 in both mouse and human B cells in a STAT6-dependent manner. IL-4 alone had the ability to translocate the induced AhR to the nuclei. TCDD, a ligand for AhR, rapidly degraded the induced AhR by the proteasomal pathway, although IL-4-activated AhR sustained its expression. AhR activated by IL-4 caused expression of a xenobiotic-metabolizing gene, CYP1A1, and TCDD synergistically acted on the induction of this gene by IL-4. However, the induction of AhR had no effect on IgE synthesis or CD23 expression. These results indicate that the metabolism of xenobiotics would be a novel biological function of IL-4 and IL-13 in B cells, whereas TCDD is not involved in IgE synthesis in B cells.

Characterization of the interaction between interleukin-13 and interleukin-13 receptors

Interleukin-13 (IL-13) possesses two types of receptor: the heterodimer, composed of the IL-13Ralpha1 chain (IL-13Ralpha1) and the IL-4Ralpha chain (IL-4Ralpha), transducing the IL-13 signals; and the IL-13Ralpha2 chain (IL-13Ralpha2), acting as a nonsignaling "decoy" receptor. Extracellular portions of both IL-13Ralpha1 and IL-13Ralpha2 are composed of three fibronectin type III domains, D1, D2, and D3, of which the last two comprise the cytokine receptor homology modules (CRHs), a common structure of the class I cytokine receptor superfamily. Thus far, there has been no information about the critical amino acids of the CRHs or the role of the D1 domains of IL-13Ralpha1 and IL-13Ralpha2 in binding to IL-13. In this study, we first built the homology modeling of the IL-13.hIL-13 receptor complexes and then predicted the amino acids involved in binding to IL-13. By incorporating mutations into these amino acids, we identified Tyr-207, Asp-271, Tyr-315, and Asp-318 in the CRH of human IL-13Ralpha2, and Leu-319 and Tyr-321 in the CRH of human IL-13Ralpha1, as critical residues for binding to IL-13. Tyr-315 in IL-13Ralpha2 and Leu-319 in IL-13Ralpha1 are positionally conserved hydrophobic amino acid residues. Furthermore, by using D1 domain-deleted mutants, we found that the D1 domain is needed for the expression of IL-13Ralpha2, but not IL-13Ralpha1, and that the D1 domain of IL-13Ralpha1 is important for binding to IL-13, but not to IL-4. These results provide the basis for a precise understanding of the interaction between IL-13 and its receptors.

Helminth regulation of host IL-4Ralpha/Stat6 signaling: mechanism underlying NOS-2 inhibition by Trichinella spiralis

Gastrointestinal nematode infection is known to alter host T cell activation and has been used to study immune and inflammatory reactions in which nitric oxide (NO) is a versatile player. We previously demonstrated that Trichinella spiralis infection inhibits host inducible NO synthase (NOS-2) expression. We now demonstrate that (i) an IL-4 receptor alpha-subunit (IL-4Ralpha)/Stat6-dependent but T cell-independent pathway is the key for the nematode-induced host NOS-2 inhibition; (ii) endogenous IL-4 and IL-13, the only known IL-4Ralpha ligands, are not required for activating the pathway; and (iii) treatment of RAW264.7 cells with parasite-cultured medium inhibits NOS-2 expression but not cyclooxygenase 2 expression. We propose that a yet-unidentified substance is released by the nematode during the host-parasite interaction.

Expression and regulation of small proline-rich protein 2 in allergic inflammation

Asthma is a complex inflammatory pulmonary disorder that is on the rise despite intense ongoing research. We aimed to elucidate novel pathways involved in the pathogenesis of asthma. Employing asthma models induced by different allergens (ovalbumin and Aspergillus fumigatus), we uncovered the involvement of two members of the small proline-rich protein (SPRR) family, SPRR2a and SPRR2b, known to be involved in epithelial differentiation but not allergic disease. In situ hybridization revealed induction of SPRR2 signal in a subset of bronchial epithelial cells and mononuclear cells associated with inflammation after allergen challenge. Allergen-induced SPRR2 mRNA accumulation in the lung occurred in a time-dependent manner, with peak expression 10-96 h after a second ovalbumin challenge. Transgenic overexpression of interleukin (IL)-13 in the lungs resulted in a marked increase of SPRR2 expression, and allergen-induced SPRR2 expression was significantly decreased in IL-13-deficient mice. Studies in gene-targeted mice revealed that allergen-induced SPRR2 was dependent upon STAT6. Finally, we aimed to determine if the induction of SPRR2 by allergen was tissue specific. Notably, SPRR2 was markedly increased in the small intestine after induction of allergic gastrointestinal inflammation. Thus, SPRR2 is an allergen- and IL-13-induced gene in experimental allergic responses that may be involved in disease pathophysiology.

Characterization of novel squamous cell carcinoma antigen-related molecules in mice

The squamous cell carcinoma antigen 1 (SCCA1) and SCCA2 are unique serpins that can inhibit cysteine proteinases. SQN-5, their mouse ortholog, has already been identified, and its inhibitory property has been characterized; however, its biological role has remained undefined. Furthermore, no other mouse homolog of SQN-5 has been known. We characterize three mouse members of SCCA-related molecules including SQN-5 in this article. Serpinb3a (SQN-5) and Serpinb3b, but not Serpinb3c, were functional, inhibiting both serine and cysteine proteinases with different inhibitory profiles due to the difference of two amino acids in their reactive site loops. Serpinb3a was ubiquitously expressed in most tissues, whereas expression of Serpinb3b was limited to keratinocytes. Keratinocytes secreted both SCCA-related proteins, Serpinb3a and Serpinb3b. These results indicate that Serpinb3a and Serpinb3b may play different roles by inhibiting intrinsic or extrinsic proteinases with different expression distributions and different inhibitory profiles.

Identification of a cooperative mechanism involving interleukin-13 and eotaxin-2 in experimental allergic lung inflammation

Pulmonary eosinophilia, a hallmark pathologic feature of allergic lung disease, is regulated by interleukin-13 (IL-13) as well as the eotaxin chemokines, but the specific role of these cytokines and their cooperative interaction are only partially understood. First, we elucidated the essential role of IL-13 in the induction of the eotaxins by comparing IL-13 gene-targeted mice with wild type control mice by using an ovalbumin-induced model of allergic airway inflammation. Notably, ovalbumin-induced expressions of eotaxin-1 and eotaxin-2 mRNA in the lungs were almost completely dependent upon IL-13. Second, in order to address the specific role of eotaxin-2 in IL-13-induced pulmonary eosinophilia, we generated eotaxin-2 gene-deficient mice by homologous recombination. Notably, in contrast to observations made in eotaxin-1-deficient mice, eotaxin-2-deficient mice had normal base-line eosinophil levels in the hematopoietic tissues and gastrointestinal tract. However, following intratracheal IL-13 administration, eotaxin-2-deficient mice showed a profound reduction in airway eosinophilia compared with wild type mice. Most interestingly, the level of peribronchial lung tissue eosinophils in IL-13-treated eotaxin-2-deficient mice was indistinguishable from wild type mice. Furthermore, IL-13 lung transgenic mice genetically engineered to be deficient in eotaxin-2 had a marked reduction of luminal eosinophils. Mechanistic analysis identified IL13-induced eotaxin-2 expression by macrophages in a distinct lung compartment (luminal inflammatory cells) compared with eotaxin-1, which was expressed solely in the tissue. Taken together, these results demonstrate a cooperative mechanism between IL-13 and eotaxin-2. In particular, IL-13 mediates allergen-induced eotaxin-2 expression, and eotaxin-2 mediates IL-13-induced airway eosinophilia.

Interleukin 13 Gene Transfer in Liver Ischemia and Reperfusion Injury: Role of Stat6 and TLR4 Pathways in Cytoprotection

Ischemia and reperfusion injury (IRI) represents the major problem in clinical liver transplantation. We have shown that transcription of signal transducer and activator of transcription 4 (Stat4) plays a key role in the mechanism of hepatic IRI, whereas local induction of interleukin 13 (IL-13) is cytoprotective. The disruption of innate Toll-like receptor 4 (TLR4) signaling prevents mouse livers from undergoing fulminant IRI. This study analyzes in vivo interplay between innate (TLR4) and adaptive (Stat6) immunity in Ad-IL-13 (recombinant adenovirus encoding IL-13) cytoprotection in hepatic IRI. Using a partial 90-min lobar warm ischemia model, groups of wild-type and Stat6-deficient knockout mice were assessed for the severity of hepatocellular damage at 6 hr postreperfusion. Unlike in wild-type mice, treatment of Stat6 knockout recipients with Ad-IL-13 failed to improve hepatic function/histology. The expression of mRNAs encoding tumor necrosis factor alpha/IL-1 beta and IL-2/interferon gamma remained depressed in the wild-type plus Ad-IL-13 group, but not in the Stat6 knockout plus Ad-IL-13 group. Ad-IL-13 increased antioxidant heme oxygenase 1 (HO-1) expression and prevented TLR4 activation in livers of Stat6-competent (wild-type) mice. In contrast, low HO-1 expression and enhanced TLR4 expression were recorded in Stat6 knockout recipients despite Ad-IL-13 therapy. Thus (1) Stat6 is required for Ad-IL-13 to prevent IRI, and (2) depression of TLR4 activation is Stat6 dependent. In conclusion, the Stat6 pathway operates as a key negative regulator in the hepatic inflammatory ischemia-reperfusion response. This study outlines requirements for Ad-IL-13 use to maximize the organ donor pool through the use of liver transplants despite prolonged ischemia.

The negative-feedback regulation of the IL-13 signal by the IL-13 receptor alpha2 chain in bronchial epithelial cells

Bronchial asthma is a complex disease characterized by airway inflammation involving Th2 cytokines. Among Th2 cytokines, the significance of IL-13 in the pathogenesis of bronchial asthma has recently emerged. Particularly, the direct action of IL-13 on bronchial epithelial cells (BECs) is critical for generation of airway hyperresponsiveness. IL-13 has two binding units; the IL-13 receptor alpha1 chain transduces the IL-13 signal comprising a heterodimer with the IL-4R alpha chain, whereas the IL-13 receptor alpha2 chain (IL-13Ralpha2) is thought to act as a decoy receptor. However, it remains obscure how expression of these molecules is regulated in each cell. In this article, we analyzed the expression of these components in BECs. Either IL-4 or IL-13 induced intracellular expression of IL-13Ralpha2 in BECs, which was STAT6-dependent and required de novo protein synthesis. IL-13Ralpha2 expressed on the cell surface as a monomer inhibited the STAT6-dependent IL-13 signal. Furthermore, expression of IL-13Ralpha2 was induced in lung tissues of ovalbumin-induced asthma model mice. Taken together, our results suggested the possibility that IL-13Ralpha2 induced by its ligand is transferred to the cell surface by an unknown mechanism, and it down-regulates the IL-13 signal in BECs, which functions as a unique negative-feedback system for the cytokine signal.

Expression and regulation of a disintegrin and metalloproteinase (ADAM) 8 in experimental asthma

Asthma, a complex chronic inflammatory pulmonary disorder, is on the rise despite intense ongoing research. To elucidate novel pathways involved in asthma pathogenesis, we used transcript expression profiling in a murine model of asthma. Employing asthma models induced by different allergens (ovalbumin and Aspergillus fumigatus) we uncovered the involvement of ADAM8, a member of a disintegrin and metalloproteinase (ADAM) family. In situ hybridization of mouse lungs revealed strong ADAM8 induction in peribronchial and perivascular inflammatory cells as well as in bronchiolar epithelial cells following allergen challenge. Sequence analysis of lung ADAM8 cDNA identified a novel splice variant of ADAM8 that contained an additional exon in juxtaposition to the transmembrane domain. Allergen-induced ADAM8 mRNA accumulation in the lung was dose- and time-dependent. Transgenic or pharmacologic delivery of interleukin (IL)-4 or IL-13 to the lungs resulted in a marked increase of ADAM8 expression. Gene-targeted mice studies revealed that ovalbumin-induced ADAM8 was largely dependent upon signal transducer and activator of transcription (STAT) 6 and the IL-4 receptor alpha-chain. Thus, ADAM8 is an allergen-, IL-4-, and IL-13-induced gene in the experimental asthmatic lung. Taken together with the role of ADAM33 in asthma, these results suggest that allergic lung responses involve the interplay of diverse members of the ADAM family.

Genetic control of interleukin-4-induced activation of the human signal transducer and activator of transcription 6 signaling pathway

The interleukin (IL)-4-induced Stat6 signaling pathway is active in a variety of cell types, including immune cells and cancer cells, and plays an important role in the regulation of gene expression, such as CD23 and major histocompatibility complex class II. Using a semiquantitative gel shift assay in which nuclear Stat6 activities were scored, three Stat6 activation phenotypes were defined as Stat6(high) (intense banding), Stat6(low) (medium intensity banding), and Stat6(null) (very low to no discernible banding). These Stat6 phenotypes correlated well with levels of CD23 expression, but not with those of human leukocyte antigen-DR cell-surface display. Pedigree analyses revealed a Mendelian inheritance pattern that can be explained by two STAT6 Pathway (STAT6P) activation genotypes, which we term A and a, where STAT6P*A determines an active Stat6 signaling and STAT6P*a determines an inactive Stat6 signaling, with incomplete dominance. Total Stat6 protein levels failed to correlate with the above Stat6 phenotypes allowing us to propose that IL-4-induced Stat6 signaling is a polygenic quantitative trait regulated by a collection of several contributing genetic loci that functionally interact. The Stat6(null) phenotype may result from a defect in Stat6 signaling, which has important implications with respect to the pathogenesis of cancer and Th1/Th2 cytokine imbalance in autoimmune diseases in general.

Gene therapy of X-linked severe combined immunodeficiency

Severe combined immunodeficiency (SCID) conditions appear to be the best possible candidates for a gene therapy approach. Transgene expression by lymphocyte precursors should confer to these cells a selective growth advantage that gives rise to long-lived T-lymphocytes. This rationale was used as a basis for a clinical trial of the SCID-X1 disorder caused by common gamma (gamma c) gene mutations. This trial consists of ex vivo retroviral-mediated (MFG-B2 gamma c vector) gammac gene transfer into marrow CD34+ cells in CH-296 fibronectin fragment-coated bags. Up to now, 9 patients with typical SCID-X1 diagnosed within the first year of life and lacking an HLA-identical donor have been enrolled. More than 2 years' assessment of 5 patients and more than 1 year for 7 patients provide evidence for full development of functional, mature T-cells in the absence of any adverse effects. Functional transduced natural killer cells are also detectable, although in low numbers. All but 1 patient with T-cell immunity have also developed immunoglobulin production, which has alleviated the need for intravenous immunoglobulin substitution despite a low detection frequency of transduced B-cells. These 8 patients are doing well and living in a normal environment. This yet successful gene therapy demonstrates that in a setting where transgene expression provides a selective advantage, a clinical benefit can be expected.

Signal transducer and activator of transcription 6 is frequently activated in Hodgkin and Reed-Sternberg cells of Hodgkin lymphoma

The unique clinicopathologic features of Hodgkin lymphoma (HL) are due to the multiple cytokines produced by its neoplastic cells, the Hodgkin and Reed-Sternberg (HRS) cells. Cytokine signaling is mediated through the signal transducer and activator of transcription (STAT) family of transcription factors. Immunoblotting and immunohistochemistry were used to examine cell lines and tissue sections derived from patients with HL and non-Hodgkin lymphoma (NHL) for expression of activated STAT proteins. Constitutive phosphorylation of STAT6 and STAT3 was common in HL. STAT6 was constitutively phosphorylated in 5 of 5 HL cell lines and in HRS cells from 25 of 32 (78%) classical HL cases. STAT3 was constitutively phosphorylated in 4 of 5 HL cell lines and in HRS cells from 27 of 31 (87%) classical HL cases. Only 4 of 24 NHL cases demonstrated constitutive STAT6 activation, whereas STAT3 activation was observed in 6 of 13 (46%) cases of B-cell NHL and 8 of 11 (73%) cases of T-cell NHL. Constitutive STAT5 phosphorylation was not a common feature of HL or NHL. STAT6 mediates signaling by interleukin 13 (IL-13), a cytokine frequently expressed by HRS cells. Antibody-mediated neutralization of IL-13 resulted in significant decreases in both cellular proliferation and levels of phosphorylated STAT6 of HL cell lines. In conclusion, constitutive STAT6 phosphorylation is a common and distinctive feature of HRS cells in classical HL, whereas STAT3 activation was regularly present in both HL and NHL. These results suggest that IL-13 signaling is largely responsible for the constitutive STAT6 activation observed in HRS cells and further implicate IL-13 as an important growth factor in classical HL.

Differential effect of IL-4 and IL-13 on CD44 expression in the Burkitt's lymphoma B cell line BL30/B95-8 and in Epstein-Barr virus (EBV) transformed human B cells: loss of IL-13 receptors on Burkitt's lymphoma B cells

IL-4 and IL-13, cytokines with similar biological effects may influence growth and progression of B-cell tumors through regulation of key cell surface molecules important in intercellular communications. In this study, we demonstrate that IL-4 and IL-13 exhibited differential effects on CD23 and CD44 expression and binding to hyaluronan in BL30/B95-8, a Burkitt's lymphoma (BL), and MK3.31, an Epstein-Barr virus transformed normal human B cell line (B-LCL). Studies conducted to understand the molecular mechanisms underlying this differential effect show that IL-4 induced phosphorylation of JAK1, JAK3, and STAT6 in BL30/B95-8 cells and of JAK3 and STAT6 in MK 3.31 cells. In contrast, IL-13 failed to induce the phosphorylation of JAK kinases or STAT6 proteins in these cell lines. The inability of BL30/B95-8 cells to respond to IL-13 was attributed to the loss of expression of IL-13R subunits alpha1 and alpha2, a finding confirmed for a number of other BL cell lines examined.

Localization of human interleukin 13 receptor in non-haematopoietic cells

Although the functional roles of interleukin (IL-)13 in haematopoietic cells are well investigated, those in non-haematopoietic cells remain to be addressed. IL-13 exerts its actions by binding to the IL-13 receptor (IL-13R) on target cells, which is composed of IL-13Ralpha1 and the IL-4 receptor alpha chain (IL-4Ralpha). However, there has been no study of localization of IL-13R in each tissue. To address this question, we generated monoclonal anti-IL-13Ralpha1 antibody, and performed immunohistochemistry using this antibody and anti-IL-4Ralpha antibody. Distribution of these two components was the same in all examined tissues. Staining was positive in keratinocytes, hair follicles, and sebaceous and sweat glands in skin; in ciliated respiratory epithelial cells in nasal tissue; in heart muscle cells; in foveola cells, gastric glands, and the smooth muscle layer in stomach; and in hepatocytes in liver. However, staining was undetectable in brain and bone marrow. Fibroblasts and endothelial cells were stained in some tissues. These results provide clues to elucidate the known pathological roles of IL-13 in atopic dermatitis and allergic rhinitis, as well as its unknown physiological roles.

Characterization of IL-4 and IL-13 signals dependent on the human IL-13 receptor alpha chain 1: redundancy of requirement of tyrosine residue for STAT3 activation

IL-4 and IL-13 are pleiotropic cytokines whose biological activities overlap with each other. IL-13 receptor alpha chain 1 (IL-13R alpha 1) is necessary for binding to IL-13, and the heterodimer composed of IL-13R alpha 1 and IL-4R alpha chain transduces IL-13 and IL-4 signals; however, the functional mapping of the intracellular domain of IL-13R alpha 1 is not fully understood. In this study, we constructed wild and mutated types of human IL-13R alpha 1, and analyzed IL-4 and IL-13 signals using an IL-13R alpha 1-transfected human B cell line. Expression of IL-13R alpha 1 evoked STAT3 activation by IL-4 and IL-13, and in stimulated human B cells, on which IL-13R alpha 1 was highly expressed, IL-4 and IL-13 induced STAT3 activation. Replacement of the two tyrosine residues completely abolished STAT3 activation, although replacing either tyrosine residue alone retained it. Furthermore, we found that the Box1 region and the C-terminal tail of IL-13R alpha 1 were critical for binding to Tyk2, and activation of Jak1, Tyk2, the insulin receptor substrate-1 and STAT6 respectively. These results suggest that STAT3 activation is involved with IL-4 and IL-13 signals in human B cells along with the activation of STAT6, and that there is a unique sequence in IL-13R alpha 1 to activate STAT3.

Augmentation of signal transducer and activation of transcription (STAT)6 and STAT3 expression in stimulated B and T cells

Signal transducer and activation of transcription (STAT)6 has a central role in the signal transduction of interleukin (IL)-4 and IL-13. It has recently been revealed that STAT3 is also involved. STAT6 and STAT3 are expressed ubiquitously; however, it remains unknown how STAT6 and STAT3 expression is regulated. In this study, we found that STAT6 expression was augmented at the transcription level in B and T cells stimulated with anti-IgM antibody and anti-CD40 antibody or PMA and ionomycin, respectively, and that STAT3 expression was similarly augmented in the stimulated B cells. The stimulated B and T cells showed enhancement of STAT6 activation and CD23 expression induced by IL-4 and IL-13. Augmentation of STAT6 and STAT3 would be a mechanism of the amplification of the IL-4 and IL-13 signals in stimulated B and T cells.

Atopy and the human IL-4 receptor alpha chain

BACKGROUND

Atopy is a common inherited disorder characterized by increased IgE responsiveness, but no functional analysis of the candidate genes related to atopy has been performed. IL-4 is important for B-cell production of IgE, and the human IL-4 receptor alpha chain (hIL-4Ralpha) is crucial for the binding and signal transduction of IL-4, so hIL-4Ralpha may be a candidate gene related to atopy.

OBJECTIVE

We examined the relationship between the variation at amino acid 50 of hIL-4Ralpha and atopic asthma.

METHODS

We performed a genetic study to investigate the relationship between the variation of amino acid 50 (isoleucine [Ile(50)] or valine [Val(50)]) and atopic asthma in a Japanese population and a functional study with the use of transfectants that expressed hIL4Ralpha bearing either Ile(50) or Val(50). Furthermore, we analyzed CD23 expression and IgE synthesis after IL-4 stimulation of peripheral blood mononuclear cells bearing either Ile(50) or Val(50).

RESULTS

The prevalence of Ile(50) was higher than that of Val(50) in individuals with atopic asthma, especially during childhood. In transfectants, germline epsilon transcription activity and Stat6 activity were upregulated by the Ile(50) variant, compared with Val(50), but receptor affinity for IL-4 was similar between the two. CD23 expression and IgE synthesis in response to IL-4 were augmented in Ile(50)-expressing peripheral mononuclear blood cells compared to cells expressing Val(50).

CONCLUSION

The Ile(50) variant of hIL-4Ralpha may be related to atopic asthma, particularly in children.

B-cell function in canine X-linked severe combined immunodeficiency

Canine X-linked severe combined immunodeficiency (XSCID) is due to mutations in the common gamma (gammac) subunit of the IL-2, IL-4, IL-7, IL-9 and IL-15 receptors and has a similar clinical phenotype to human XSCID. We have previously shown that the block in T-cell development is more profound in XSCID dogs than in genetically engineered gamma c-deficient mice. In this study we evaluated the B-cell function in XSCID dogs. In contrast to the marked decrease in peripheral B-cells in gamma c-deficient mice, XSCID dogs have increased proportions and numbers of peripheral B-cells as observed in XSCID boys. Canine XSCID B-cells do not proliferate following stimulation with the T-cell-dependent B-cell mitogen, pokeweed mitogen (PWM); however, they proliferate normally in response to the T-cell-independent B-cell mitogen, formalin-fixed, heat-killed Staphylococcus aureus. Canine XSCID B-cells are capable of producing IgM but are incapable of normal class-switching to IgG antibody production as demonstrated by in vitro stimulation with PWM and immunization with the T-cell-dependent antigen, bacteriophage PhiX174. Similar results have been reported for XSCID boys. Thus, it appears that gamma c-dependent cytokines have differing roles in human and canine B-cell development than in the mouse making the XSCID dog a valuable model for studying the role of these cytokines in B-cell development and function.

Efficient detection of thirty-seven new IL2RG mutations in human X-linked severe combined immunodeficiency

X-linked severe combined immunodeficiency (XSCID) is a rare and potentially fatal disease caused by mutations of IL2RG, the gene encoding the interleukin-2 receptor gamma chain, a component of multiple cytokine receptors that are essential for lymphocyte development and function. To date, over 100 different mutations of IL2RG resulting in XSCID have been published. Using nonradioactive, direct DNA sequencing of a single PCR amplicon containing the whole IL2RG gene, we found IL2RG mutations in 78 previously unpublished unrelated cases of XSCID. We report 37 newly identified mutations of IL2RG, including 23 point mutations, 10 small deletions, 3 instances of the same single nucleotide insertion, 1 large deletion, and 2 complex mutations. More than half of the mutations (22 of 37) were predicted to result in unstable IL2RG mRNA. The remaining 14 mutations disrupted conserved functional motifs common to all cytokine receptor family members; changed protein conformation, charge, or hydrophobicity; or altered the intracellular portion of the protein, which is critical for proper interaction with signal-transducing molecules including Janus family tyrosine kinase 3.

Lipopolysaccharide increases cyclo-oxygenase-2 expression in a colon carcinoma cell line through nuclear factor-kappa B activation

Both nonneoplastic colon epithelium and colon carcinoma cells in situ are continuously exposed to lipopolysaccharide (LPS). Few reports have addressed possible direct effects of LPS in promotion of colon carcinoma and underlying mechanisms. We found evidence that LPS directly stimulated growth of the human colon carcinoma cell line CE-1 through an increase in the production of prostaglandin E2 (PGE2) as a result of cyclo-oxygenase-2 (COX-2) expression. LPS induced significant increases in PGE2 production in CE-1 cells, which were found to express a high-affinity LPS receptor, CD14. Positive correlations were found between PGE2 production and activation of nuclear factor (NF)-kappa B as well as expression of both COX-2 mRNA and protein in LPS-stimulated CE-1 cells. When CE-1 cells were exposed to exogenous PGE2, DNA synthesis increased. These results indicate that LPS may stimulate DNA synthesis in certain colon carcinoma cells as a result of PGE2 production involving increased COX-2 expression that might result in turn from activation of NF-kappa B by LPS. Further investigation of the pathways mediating LPS-induced stimulation of colon carcinoma cells may provide insights into LPS effects in in vivo tumor biology.

Molecular mechanisms of IgE regulation

IgE antibody plays an important role in allergic diseases. IgE synthesis by B cells requires two signals. The first signal is delivered by the cytokines IL-4 or IL-13, which target the Cepsilon gene for switch recombination. The second signal is delivered by interaction of the B cell surface antigen CD40 with its ligand (CD40L) expressed on activated T cells. This activates deletional switch recombination. We review the molecular mechanisms of IL-4 and CD40 signaling that lead to IgE isotype switching and discuss the implications for intervening to abort or suppress the IgE antibody response.

Epstein-barr virus transformation: involvement of latent membrane protein 1-mediated activation of NF-kappaB

Epstein-Barr virus (EBV) transforms resting primary human B lymphocytes into indefinitely proliferating lymphoblastoid cell lines in vitro and is associated with several human malignancies in vivo. Recombinant EBV genetic analyses combined with in vitro B lymphocyte transformation assays demonstrate that latent infection membrane protein 1 (LMP1) is essential for EBV-mediated lymphocyte transformation. LMP1 has no intrinsic enzymatic activity but instead aggregates cellular proteins of the tumor necrosis factor receptor signaling pathway to activate transcription factor NF-kappaB. Mutants rendering LMP1 defective in these protein interactions are impaired in their abilities to activate NF-kappaB in reporter gene assays. Concordantly, EBV recombinants with LMP1 mutations that are compromised for NF-kappaB activation are impaired for growth transformation. Thus, EBV-mediated growth transformation is genetically and biochemically linked to LMP1-mediated activation of NF-kappaB.

Long-Term Chimerism and B-Cell Function After Bone Marrow Transplantation in Patients With Severe Combined Immunodeficiency With B Cells: A Single-Center Study of 22 Patients

We retrospectively analyzed the B-cell function and leukocyte chimerism of 22 patients with severe combined immunodeficiency with B cells (B+ SCID) who survived more than 2 years after bone marrow transplantation (BMT) to determine the possible consequences of BMT procedures, leukocyte chimerism, and SCID molecular deficit on B-cell function outcome. Circulating T cells were of donor origin in all patients. In recipients of HLA-identical BMT (n = 5), monocytes were of host origin in 5 and B cells were of host origin in 4 and of mixed origin in 1. In recipients of HLA haploidentical T-cell–depleted BMT (n = 17), B cells and monocytes were of host origin in 14 and of donor origin in 3. Engraftment of B cells was found to be associated with normal B-cell function. In contrast, 10 of 18 patients with host B cells still require Ig substitution. Conditioning regimen (ie, 8 mg/kg busulfan and 200 mg/kg cyclophosphamide) was shown neither to promote B-cell and monocyte engraftment nor to affect B-cell function. Eight patients with B cells of host origin had normal B-cell function. Evidence for functional host B cells was further provided in 3 informative cases by Ig allotype determination and by the detection, in 5 studied cases, of host CD27+ memory B cells as in age-matched controls. These results strongly suggest that, in some transplanted patients, host B cells can cooperate with donor T cells to fully mature in Ig-producing cells.

IL-13 activates STAT6 and inhibits liver injury induced by ischemia/reperfusion

Hepatic ischemia/reperfusion injury is initiated by the activation of Kupffer cells and their subsequent release of proinflammatory mediators, including tumor necrosis factor-alpha (TNFalpha). These mediators stimulate a cascade of events including up-regulation of CXC chemokines and vascular endothelial adhesion molecules, leading to hepatic neutrophil recruitment and tissue injury. Interleukin-13 (IL-13) is a cytokine that has been shown to suppress macrophage production of proinflammatory mediators. The objective of the current study was to determine whether IL-13 could regulate the liver inflammatory injury induced by ischemia and reperfusion. C57BL/6 mice underwent 90 minutes of partial hepatic ischemia followed by reperfusion with or without intravenous administration of recombinant murine IL-13. Hepatic ischemia/reperfusion increased expression of TNFalpha and macrophage inflammatory protein-2 (MIP-2), leading to hepatic neutrophil recruitment, hepatocellular injury, and liver edema. Administration of IL-13 reduced the production of TNFalpha and MIP-2 mRNA and protein. IL-13 suppressed liver neutrophil recruitment by up to 72% and hepatocellular injury and liver edema were each reduced by >60%. Administration of IL-13 had no effect on liver NFkappaB activation, but greatly increased the activation of STAT6. The data suggest that the hepatoprotective effects of IL-13 may be a result of STAT6 activation.

BCL-6-Deficient Mice Reveal an IL-4-Independent, STAT6-Dependent Pathway That Controls Susceptibility to Infection by Leishmania major

The BCL-6 gene negatively regulates Th2 responses as shown by the finding that BCL-6-deficient (BCL-6−/−) mice develop a lethal Th2-type inflammatory disease. The response of inbred mouse strains to infection with Leishmania major is under genetic control; BALB/c mice are susceptible and develop a progressive parasite burden, whereas most other common laboratory strains of mice are resistant to infection. We found that BCL-6−/− mice on a resistant genetic background (C57BL/6 × 129 intercrossed mice) were highly susceptible to L. major infection; they resembled BALB/c mice in terms of lesion size, parasite load, and the production of Th2 cytokines. BCL-6−/−IL-4−/− double-mutant mice were also susceptible to L. major infection and produced 10-fold higher levels of the Th2 cytokine IL-13 than IL-4−/− littermate controls. By contrast, BCL-6−/−STAT6−/− double-mutant mice were resistant to L. major infection despite also producing elevated levels of IL-13. These results show that STAT6 is required for susceptibility to L. major infection and suggest that IL-13 signaling through STAT6 may contribute to a nonhealing, exacerbated L. major infection.

Signalling through the JAK-STAT pathway in the developing brain

The JAK -STAT (Janus kinase-signal transducer and activator of transcription) signalling pathway that is stimulated by cytokines has been much investigated in haematopoietic cells, but recent data indicate that this pathway is also present and active during neuronal and glial differentiation. Furthermore, it is now clear that growth factors other than the classical cytokines can act through this pathway and that physiological inhibitors of this signalling cascade exist. Thus, the JAKs, the STATs and their specific inhibitors could be molecules with important roles in the CNS.

Janus kinases and their role in growth and disease

Janus kinases (JAK) play a crucial role in the initial steps of cytokine signaling. Each of the four members (JAK1, JAK2, JAK3, TYK2) of this non-receptor tyrosine kinase family is indispensable for the effects of distinct cytokines. Moreover, recent reports have added to our knowledge on their highly specific functions: JAK3 knockout mice and JAK3 deficient patients cannot signal through the interleukin-2,4,7,9, or 15 receptors and suffer from severe combined immunodeficiency (SCID). JAK1 and JAK2 knockout mice do not survive, their cells again showing distinct patterns of cytokine signaling deficits. At the other end of the spectrum, JAK fusion proteins have been shown to play a role in leukemias. In addition, a new class of JAK-specific inhibitors was described by several groups, the CIS/SOCS/Jab family. This review on the rapidly growing field focuses on JAK function and regulation, and on their emerging role in development and human disease.

Selective DNA-binding activity of interleukin-10-stimulated STAT molecules in human monocytes

It has been demonstrated that interferon-gamma (IFN-gamma) and interleukin-10 (IL-10) have various reverse effects on macrophages; however, the molecular mechanism of this difference has not been fully understood. In this study, we analyzed the binding activity of IL-10- and IFN-gamma-activated STAT molecules to two kinds of GAS-motif sequences. IL-10-activated STAT1 could bind to the GAS-motif sequence in the promoter region of the Fcgamma receptor, but not to that in the promoter region of the COX-2 gene, whereas IFN-gamma-activated STAT1 and STAT5 could bind to both sequences. IL-10 inhibited IFN-gamma-induced STAT activation without newly synthesized protein. We further demonstrated that aspirin, but not dexamethasone, suppressed IFN-gamma-induced STAT activation. Taken together, these results suggest that IL-10-activated STAT1 has a specificity in binding to the GAS-motif sequences, whereas IFN-gamma-activated STAT1 and STAT5 have a broader spectrum in binding to the GAS-motif sequences. This may explain the difference between IL-10 and IFN-gamma in biological activity, and the inhibitory effect of IL-10 on IFN-gamma activities.

Interleukin-4 (IL-4) and IL-13 Enhance the Effect of IL-1β on Production of IL-1 Receptor Antagonist by Human Primary Hepatocytes and Hepatoma HepG2 Cells: Differential Effect on C-Reactive Protein Production

Interleukin-1 receptor antagonist (IL-1Ra) is produced by hepatocytes with characteristics of an acute-phase protein. To examine the role of IL-4 and IL-13 in production of IL-1Ra, human primary hepatocytes and HepG2 human hepatoma cells were cultured in the presence of IL-4 or IL-13 in combination with IL-1β and/or IL-6. The results indicated that both IL-4 and IL-13 amplified the stimulatory effect of IL-1β on production of IL-1Ra protein and messenger RNA (mRNA) by both human primary hepatocytes and HepG2 cells. IL-1Ra refers to three different peptides, one secreted (sIL-1Ra) and two intracellular (icIL-1RaI and icIL-1RaII), derived from the same gene. sIL-1Ra and icIL-1RaI are the products of two different mRNA, whereas icIL-1RaII is synthesized by alternative translation initiation mainly from sIL-1Ra mRNA. Our results show that both sIL-1Ra and icIL-1RaII, but not icIL-1RaI, are produced by HepG2 cells and human hepatocytes. Transient transfection experiments as well as mRNA stability studies indicated that IL-4 stimulated sIL-1Ra production primarly at the level of transcription. Gel retardation assays showed that IL-4 induced the formation of a STAT6-DNA complex with a STAT6 binding element within the sIL-1Ra promoter, but had no effect on IL-1–induced NF-κB binding activity. In contrast to IL-1Ra, production of C-reactive protein by human primary hepatocytes was stimulated by IL-6 and decreased by the addition of IL-4.