Biomedical subjects

Steven F Ziegler

Publications and source records attributed to Steven F Ziegler.

At least 19 recordsLinked to original sources

PubMed2007

Inducible expression of the proallergic cytokine thymic stromal lymphopoietin in airway epithelial cells is controlled by NFkappaB.

The epithelial-derived cytokine thymic stromal lymphopoietin (TSLP) is important for the initiation of allergic airway inflammation through a dendritic cell-mediated T helper 2 response. To identify the factors that control TSLP expression, we examined the ability of inflammatory mediators to regulate TSLP production in human airway epithelial cells. We found that both IL-1beta and TNF-alpha were capable of inducing rapid TSLP production in primary human bronchial airway epithelial cells. We further characterized the human TSLP gene promoter, using two human epithelial cell lines, 16HBEo(-) and A549, and showed that IL-1beta- and TNF-alpha-mediated human TSLP promoter activation in these cells was mediated by an upstream NFkappaB site. Mutation of this NFkappaB site abolished activation, as did overexpression of a dominant-negative version of IkappaB kinase (IKK)beta (a kinase acting on IkappaB, the inhibitor of NFkappaB). Interestingly, human TSLP mRNA levels were also increased after exposure to Toll-like receptor (TLR) 2, TLR8, and TLR9 ligands, further supporting an important role for NFkappaB in TSLP gene regulation. Similarly, analysis of the mouse TSLP gene promoter revealed the presence of a similarly situated NFkappaB site that was also critical for IL-1beta-inducible expression of mouse TSLP. Taken together, these results demonstrate that the inflammatory mediators IL-1beta and TNF-alpha regulate human TSLP gene expression in an NFkappaB-dependent manner.

Animals↗

PubMed2007

FOXP3: not just for regulatory T cells anymore.

The forkhead family transcription factor FOXP3 has been shown to be critical for the development and function of CD4+ CD25+ regulatory T cells. Recently, FOXP3 expression has been shown to be induced upon activation of human CD4+ T cells. A new report in this issue of the European Journal of Immunology shows that expression of FOXP3 in activated T cell leads to hyporesponsiveness, but not necessarily to acquisition of suppressor function. This finding suggests a new role for FOXP3 in human CD4+ T cells: down-modulating responses to TCR-mediated stimulation.

Animals↗

PubMed2007

TSLP: an epithelial cell cytokine that regulates T cell differentiation by conditioning dendritic cell maturation.

Dendritic cells (DCs) are professional antigen-presenting cells that have the ability to sense infection and tissue stress, sample and present antigen to T lymphocytes, and induce different forms of immunity and tolerance. The functional versatility of DCs depends on their remarkable ability to translate collectively the information from both the invading microbes and their resident tissue microenvironments and then make an appropriate immune response. Recent progress in understanding TLR biology has illuminated the mechanisms by which DCs link innate and adaptive antimicrobial immune responses. However, how tissue microenvironments shape the function of DCs has remained elusive. Recent studies of TSLP (thymic stromal lymphopoietin), an epithelial cell-derived cytokine that strongly activates DCs, provide evidence at a molecular level that epithelial cells/tissue microenvironments directly communicate with DCs. We review recent progress on how TSLP expressed within thymus and peripheral lymphoid and nonlymphoid tissues regulates DC-mediated central tolerance, peripheral T cell homeostasis, and inflammatory Th2 responses.

Animals↗

PubMed2006

Analysis of FOXP3 reveals multiple domains required for its function as a transcriptional repressor.

Foxp3 has been shown to be both necessary and sufficient for the development and function of naturally arising CD4+ CD25+ regulatory T cells in mice. Mutation of Foxp3 in Scurfy mice and FOXP3 in humans with IPEX results in fatal, early onset autoimmune disease and demonstrates the critical role of FOXP3 in maintaining immune homeostasis. The FOXP3 protein encodes several functional domains, including a C2H2 zinc finger, a leucine zipper, and a winged-helix/forkhead (FKH) domain. We have shown previously that FOXP3 functions as a transcriptional repressor and inhibits activation-induced IL-2 gene transcription. To characterize the role of each predicted functional domain on the in vivo activity of FOXP3, we have evaluated the location of point mutations identified in a large cohort of patients with the immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome (IPEX) and found them to cluster primarily within the FKH domain and the leucine zipper, but also present within the poorly defined N-terminal portion of the protein. The molecular functions of each of the IPEX-targeted domains were investigated. We show that FOXP3 is constitutively localized to the nucleus and this localization requires sequences at both the amino and C-terminal ends of its FKH domain. Moreover, FOXP3 was found to homodimerize through its leucine zipper. We also identify a novel functional domain within the N-terminal half of FOXP3, which is required for FOXP3-mediated repression of transcription from both a constitutively active and a NF-AT-inducible promoter. Furthermore, we demonstrate that IPEX mutations in these domains correlate with deficiencies in FOXP3 repressor function, corroborating their in vivo relevance.

Active Transport, Cell Nucleus↗

PubMed2006

FOXP3 controls regulatory T cell function through cooperation with NFAT.

Antigen stimulation of immune cells activates the transcription factor NFAT, a key regulator of T cell activation and anergy. NFAT forms cooperative complexes with the AP-1 family of transcription factors and regulates T cell activation-associated genes. Here we show that regulatory T cell (Treg) function is mediated by an analogous cooperative complex of NFAT with the forkhead transcription factor FOXP3, a lineage specification factor for Tregs. The crystal structure of an NFAT:FOXP2:DNA complex reveals an extensive protein-protein interaction interface between NFAT and FOXP2. Structure-guided mutations of FOXP3, predicted to progressively disrupt its interaction with NFAT, interfere in a graded manner with the ability of FOXP3 to repress expression of the cytokine IL2, upregulate expression of the Treg markers CTLA4 and CD25, and confer suppressor function in a murine model of autoimmune diabetes. Thus by switching transcriptional partners, NFAT converts the acute T cell activation program into the suppressor program of Tregs.

Amino Acid Sequence↗

PubMed2006

CD127 expression inversely correlates with FoxP3 and suppressive function of human CD4+ T reg cells.

Regulatory T (T reg) cells are critical regulators of immune tolerance. Most T reg cells are defined based on expression of CD4, CD25, and the transcription factor, FoxP3. However, these markers have proven problematic for uniquely defining this specialized T cell subset in humans. We found that the IL-7 receptor (CD127) is down-regulated on a subset of CD4(+) T cells in peripheral blood. We demonstrate that the majority of these cells are FoxP3(+), including those that express low levels or no CD25. A combination of CD4, CD25, and CD127 resulted in a highly purified population of T reg cells accounting for significantly more cells that previously identified based on other cell surface markers. These cells were highly suppressive in functional suppressor assays. In fact, cells separated based solely on CD4 and CD127 expression were anergic and, although representing at least three times the number of cells (including both CD25(+)CD4(+) and CD25(-)CD4(+) T cell subsets), were as suppressive as the "classic" CD4(+)CD25(hi) T reg cell subset. Finally, we show that CD127 can be used to quantitate T reg cell subsets in individuals with type 1 diabetes supporting the use of CD127 as a biomarker for human T reg cells.

Adolescent↗

PubMed2006

Insights into transcriptional regulation by FOXP3.

FoxP3 recently entered the spotlight as a critical component of regulatory T cell development and function. Several groups are presently engaged in an effort to uncover the mechanistic details of its contribution to this critical T cell subset. Despite this, the mechanism of FoxP3-mediated transcriptional repression and the affected target genes are still largely unknown. First, we discuss insights from work on other Fox family members with an emphasis on those with known roles in the immune system. Second, we review recent data concerning the molecular mechanism of FoxP3 function and its role in human disease. Finally, we consider what is known about FoxP3 target genes and their effect on T cell physiology.

Amino Acid Sequence↗

PubMed2006

Adaptive islet-specific regulatory CD4 T cells control autoimmune diabetes and mediate the disappearance of pathogenic Th1 cells in vivo.

Adaptive regulatory T cells that develop from naive CD4 cells in response to exposure to Ag can act as immunotherapeutic agents to control immune responses. We show that effectors generated from murine islet-specific CD4 cells by TCR stimulation with IL-2 and TGF-beta1 have potent suppressive activity. They prevent spontaneous development of type 1 diabetes in NOD mice and inhibit development of pancreatic infiltrates and disease onset orchestrated by Th1 effectors. These regulatory T cells do not require innate CD25+ regulatory cells for generation or function, nor do they share some characteristics typically associated with them, including expression of CD25. However, the adaptive population does acquire the X-linked forkhead/winged helix transcription factor, FoxP3, which is associated with regulatory T cell function and maintains expression in vivo. One mechanism by which they may inhibit Th1 cells is via FasL-dependent cytotoxicity, which occurs in vitro. In vivo, they eliminate Th1 cells in lymphoid tissues, where Fas/FasL interactions potentially play a role because Th1 cells persist when this pathway is blocked. The results suggest that adaptive regulatory CD4 cells may control diabetes in part by impairing the survival of islet-specific Th1 cells, and thereby inhibiting the localization and response of autoaggressive T cells in the pancreatic islets.

Adoptive Transfer↗

PubMed2006

Cutting Edge: Anti-CD25 monoclonal antibody injection results in the functional inactivation, not depletion, of CD4+CD25+ T regulatory cells.

CD4+CD25+ T regulatory (T(R)) cells are an important regulatory component of the adaptive immune system that limit autoreactive T cell responses in various models of autoimmunity. This knowledge was generated by previous studies from our lab and others using T(R) cell supplementation and depletion. Contrary to dogma, we report here that injection of anti-CD25 mAb results in the functional inactivation, not depletion, of T(R) cells, resulting in exacerbated autoimmune disease. Supporting this, mice receiving anti-CD25 mAb treatment display significantly lower numbers of CD4+CD25+ T cells but no change in the number of CD4+FoxP3+ T(R) cells. In addition, anti-CD25 mAb treatment fails to both reduce the number of Thy1.1+ congenic CD4+CD25+ T(R) cells or alter levels of CD25 mRNA expression in treatment recipients. Taken together, these findings have far-reaching implications for the interpretation of all previous studies forming conclusions about CD4+CD25+ T(R) cell depletion in vivo.

Animals↗

PubMed2006

Thymic stromal lymphopoietin in normal and pathogenic T cell development and function.

Thymic stromal lymphopoietin, a four helix-bundle cytokine, is expressed mainly by barrier epithelial cells and is a potent activator of several cell types, particularly myeloid dendritic cells. TSLP influences the outcome of interactions between dendritic cells and CD4+ thymocytes and T cells in many situations, such as the regulation of the positive selection of regulatory T cells, maintenance of peripheral CD4+ T cell homeostasis and induction of CD4+ T cell-mediated allergic inflammation.

Animals↗

PubMed2006

FOXP3: of mice and men.

The immune system has evolved mechanisms to recognize and eliminate threats, as well as to protect against self-destruction. Tolerance to self-antigens is generated through two fundamental mechanisms: (a) elimination of self-reactive cells in the thymus during selection and (b) generation of a variety of peripheral regulatory cells to control self-reactive cells that escape the thymus. It is becoming increasing apparent that a population of thymically derived CD4+ regulatory T cells, exemplified by the expression of the IL-2Ralpha chain, is essential for the maintenance of peripheral tolerance. Recent work has shown that the forkhead family transcription factor Foxp3 is critically important for the development and function of the regulatory T cells. Lack of Foxp3 leads to development of fatal autoimmune lymphoproliferative disease; furthermore, ectopic Foxp3 expression can phenotypically convert effector T cells to regulatory T cells. This review focuses on Foxp3 expression and function and highlights differences between humans and mice regarding Foxp3 regulation.

Animals↗

PubMed2006

Defective regulatory and effector T cell functions in patients with FOXP3 mutations.

The autoimmune disease immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) is caused by mutations in the forkhead box protein P3 (FOXP3) gene. In the mouse model of FOXP3 deficiency, the lack of CD4+ CD25+ Tregs is responsible for lethal autoimmunity, indicating that FOXP3 is required for the differentiation of this Treg subset. We show that the number and phenotype of CD4+ CD25+ T cells from IPEX patients are comparable to those of normal donors. CD4+ CD25high T cells from IPEX patients who express FOXP3 protein suppressed the in vitro proliferation of effector T cells from normal donors, when activated by "weak" TCR stimuli. In contrast, the suppressive function of CD4+ CD25high T cells from IPEX patients who do not express FOXP3 protein was profoundly impaired. Importantly, CD4+ CD25high T cells from either FOXP3+ or FOXP3- IPEX patients showed altered suppression toward autologous effector T cells. Interestingly, IL-2 and IFN-gamma production by PBMCs from IPEX patients was significantly decreased. These findings indicate that FOXP3 mutations in IPEX patients result in heterogeneous biological abnormalities, leading not necessarily to a lack of differentiation of CD4+ CD25high Tregs but rather to a dysfunction in these cells and in effector T cells.

Animals↗

PubMed2005

The role of 2 FOXP3 isoforms in the generation of human CD4+ Tregs.

Little is known about the molecules that control the development and function of CD4+ CD25+ Tregs. Recently, it was shown that the transcription factor FOXP3 is necessary and sufficient for the generation of CD4+ CD25+ Tregs in mice. We investigated the capacity of FOXP3 to drive the generation of suppressive CD4+ CD25+ Tregs in humans. Surprisingly, although ectopic expression of FOXP3 in human CD4+ T cells resulted in induction of hyporesponsiveness and suppression of IL-2 production, it did not lead to acquisition of significant suppressor activity in vitro. Similarly, ectopic expression of FOXP3delta2, an isoform found in human CD4+ CD25+ Tregs that lacks exon 2, also failed to induce the development of suppressor T cells. Moreover, when FOXP3 and FOXP3delta2 were simultaneously overexpressed, although the expression of several Treg-associated cell surface markers was significantly increased, only a modest suppressive activity was induced. These data indicate that in humans, overexpression of FOXP3 alone or together with FOXP3delta2 is not an effective method to generate potent suppressor T cells in vitro and suggest that factors in addition to FOXP3 are required during the process of activation and/or differentiation for the development of bona fide Tregs.

Cell Differentiation↗

PubMed2005

Thymic stromal lymphopoietin as a key initiator of allergic airway inflammation in mice.

The cytokine thymic stromal lymphopoietin (TSLP) has been linked to human allergic inflammatory diseases. We show here that TSLP expression was increased in the lungs of mice with antigen-induced asthma, whereas TSLP receptor-deficient mice had considerably attenuated disease. Lung-specific expression of a Tslp transgene induced airway inflammation and hyperreactivity characterized by T helper type 2 cytokines and increased immunoglobulin E. The lungs of Tslp-transgenic mice showed massive infiltration of leukocytes, goblet cell hyperplasia and subepithelial fibrosis. TSLP was capable of activating bone marrow-derived dendritic cells to upregulate costimulatory molecules and produce the T helper type 2 cell-attracting chemokine CCL17. These findings suggest that TSLP is an important factor necessary and sufficient for the initiation of allergic airway inflammation.

Allergens↗

PubMed2005

Spontaneous atopic dermatitis in mice expressing an inducible thymic stromal lymphopoietin transgene specifically in the skin.

The cytokine thymic stromal lymphopoietin (TSLP) has recently been implicated in the pathogenesis of atopic dermatitis (AD) and other allergic diseases in humans. To further characterize its role in this disease process, transgenic mice were generated that express a keratinocyte-specific, tetracycline-inducible TSLP transgene. Skin-specific overexpression of TSLP resulted in an AD-like phenotype, with the development of eczematous lesions containing inflammatory dermal cellular infiltrates, a dramatic increase in Th2 CD4+ T cells expressing cutaneous homing receptors, and elevated serum levels of IgE. These transgenic mice demonstrate that TSLP can initiate a cascade of allergic inflammation in the skin and provide a valuable animal model for future study of this common disease.

Animals↗

PubMed2005

Functional avidity directs T-cell fate in autoreactive CD4+ T cells.

Major histocompatibility complex class II tetramer staining and activation analysis identified 2 distinct types of antigen-specific CD4+ T cells in the peripheral blood of humans with type 1 (autoimmune) diabetes. T cells with low-avidity recognition of peptide-MHC ligands had low sensitivity to activation and inefficient activation-induced apoptosis. In contrast, high-avidity T cells were highly sensitive to antigen-induced cell death through apoptotic mechanisms, and both apoptosis-resistant high- and low-avidity T cells that survived prolonged tetramer treatment were rendered anergic to restimulation by antigen. In addition, however, apoptosis-resistant high-avidity T cells acquired regulatory features, being able to suppress both antigen-specific and nonspecific CD4+ T-cell responses. This suppression was contact-dependent and correlated with the down-regulation of HLA class II and costimulatory molecules on antigen-presenting cells, including B cells and dendritic cells. T cells face a variety of fates following antigen exposure, including the paradoxic maintenance of high-avidity autoreactive T cells in the peripheral circulation, perhaps due to this capability of acquiring anergic and suppressive properties. Regulation via down-modulation of antigen-presenting cell function, a form of cell-to-cell licensing for suppression, also offers possibilities for the application of peptide-MHC therapeutics.

Adolescent↗

PubMed2005

Decreased FOXP3 levels in multiple sclerosis patients.

Autoimmune diseases such as multiple sclerosis (MS) may result from the failure of tolerance mechanisms to prevent expansion of pathogenic T cells. Our study is the first to establish that MS patients have abnormalities in FOXP3 message and protein expression levels in peripheral CD4+ CD25+ T cells (Tregs) that are quantitatively related to a reduction in functional suppression induced during suboptimal T-cell receptor (TCR) ligation. Of importance, this observation links a defect in functional peripheral immunoregulation to an established genetic marker that has been unequivocally shown to be involved in maintaining immune tolerance and preventing autoimmune diseases. Diminished FOXP3 levels thus indicate impaired immunoregulation by Tregs that may contribute to MS. Future studies will evaluate the effects of therapies known to influence Treg cell function and FOXP3 expression, including TCR peptide vaccination and supplemental estrogen.

Adult↗

PubMed2005

De novo generation of antigen-specific CD4+CD25+ regulatory T cells from human CD4+CD25- cells.

Antigen-specificity is a hallmark of adaptive T cell-mediated immune responses. CD4+CD25+FOXP3+ regulatory T cells (T(R)) also require activation through the T cell receptor for function. Although these cells require antigen-specific activation, they are generally able to suppress bystander T cell responses once activated. This raises the possibility that antigen-specific T(R) may be useful therapeutically by localizing generalized suppressive activity to tissues expressing select target antigens. Here, we demonstrate that T(R) specific for particular peptide-MHC complexes can be generated from human CD4+CD25- T cells in vitro and isolated by using HLA class II tetramers. Influenza hemagglutinin epitopes were used to generate hemagglutinin-specific T(R), which required cognate antigen for activation but which subsequently suppressed noncognate bystander T cell responses as well. These findings have implications for the generation of therapeutic regulatory T cells in disease, and also suggest an important mechanism by which T cells may be regulated at the site of inflammation.

CD4-Positive T-Lymphocytes↗