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Angela M Thornton

Publications and source records attributed to Angela M Thornton.

10 recordsLinked to original sources
PubMed2006

Activated CD4+CD25+ T cells selectively kill B lymphocytes.

The suppressive capacity of naturally occurring mouse CD4+CD25+ T cells on T-cell activation has been well documented. The present study is focused on the interaction of CD4+CD25+ T cells and B cells. By coculturing preactivated CD4+CD25+ T cells with B cells in the presence of polyclonal B-cell activators, we found that B-cell proliferation was significantly suppressed. The suppression of B-cell proliferation was due to increased cell death caused by the CD4+CD25+ T cells in a cell-contact-dependent manner. The induction of B-cell death is not mediated by Fas-Fas ligand pathway, but surprisingly, depends on the up-regulation of perforin and granzymes in the CD4+CD25+ T cells. Furthermore, activated CD4+CD25+ T cells preferentially killed antigen-presenting but not bystander B cells. Our results demonstrate that CD4+CD25+ T cells can act directly on B cells and suggest that the prevention of autoimmunity by CD4+CD25+ T cells can be explained, at least in part, by the direct regulation of B-cell function.

Animals↗
PubMed2006

Signal transduction in CD4+CD25+ regulatory T cells: CD25 and IL-2.

IL-2 was originally identified as a growth factor critical for T cell proliferation in vitro. Although the early studies of IL-2 strongly implied an obligate role of IL-2 in T cell growth, it was later shown that mice deficient in IL-2 or in IL-2R developed an unexpected lymphocytic hyperproliferation and subsequent autoimmune disease. In separate studies of autoimmunity, it was observed that a population of CD4+ T cells suppressed the induction of autoimmunity in several in vivo models of autoimmune disease. It was not until the characterization of this subpopulation of CD4+ T cells demonstrated that they co-expressed the IL-2R-alpha chain (CD25) that the puzzling phenotype observed in IL-2 deficient mice began to be truly explained. The constitutive expression of the IL-2R-alpha chain on CD4+CD25+ T cells led to the obvious speculation that IL-2 signaling in CD4+CD25+ T cells was important to these cells. Recent studies have examined the role of IL-2 in the generation, the expansion, the survival and the effector function of CD4+CD25+ T cells. It is now evident that IL-2 is critical for the development of CD4+CD25+ T cells and the phenotype observed in IL-2 and IL-2R deficient mice is most readily explained by the absence of these potent suppressors.

Animals↗
PubMed2006

The lifestyle of naturally occurring CD4+ CD25+ Foxp3+ regulatory T cells.

Numerous studies over the past 10 years have demonstrated the importance of naturally occurring CD4+ CD25+ Foxp3+ regulatory T cells (nTregs) in immune regulation. We analyzed the mechanism of action of nTregs in a well-characterized model of autoimmune gastritis and demonstrated that nTregs act at an early stage of disease progression to inhibit the differentiation of naïve T cells to pathogenic T-helper 1 effectors. The effects of nTregs in this model are not antigen-specific but are mediated by activation of the nTregs by ubiquitous self-peptide major histocompatibility complex class II complexes together with cytokines released by activated effector cells. Studies in vitro confirmed that some nTregs exist in an activated state in vivo and can be activated to exert non-specific suppressor effector function by stimulation with interleukin-2 in the absence of engagement of their T-cell receptor. Natural Tregs can differentiate in vitro to exhibit potent granzyme B-dependent, partially perforin-independent cytotoxic cells that are capable of specifically killing antigen-presenting B cells. Natural Treg-mediated killing of antigen-presenting cells may represent one pathway by which they can induce long-lasting suppression of autoimmune disease.

Animals↗
PubMed2005

T regulatory cells.

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Forkhead Transcription Factors↗
PubMed2004

Cutting edge: IL-2 is critically required for the in vitro activation of CD4+CD25+ T cell suppressor function.

CD4(+)CD25(+) T cells are potent immunoregulatory cells that suppress TCR-induced proliferation of CD4 and CD8 T cells in vitro by a cell contact-dependent mechanism. Addition of IL-2 or anti-CD28 abrogates CD4(+)CD25(+)-mediated suppression of proliferation and has been assumed to "break suppression." We examined IL-2 mRNA by quantitative PCR in cocultures of mouse CD4(+)CD25(+) and CD4(+)CD25(-) T cells. Although IL-2 gene transcription was inhibited in the presence or absence of exogenous IL-2, the addition of anti-CD28 stimulated endogenous IL-2 production. Surprisingly, transcription of IL-2 mRNA was also restored in the cocultures in the presence of anti-IL-2. These results are most compatible with a model in which CD4(+)CD25(+) T cells do not suppress the initial activation of CD4(+)CD25(-) T cells, but mediate their suppressive effects following production of IL-2 by the responder cells resulting in both the expansion of the CD4(+)CD25(+) T cells and the induction of their suppressor function.

Animals↗
PubMed2004

Activation requirements for the induction of CD4+CD25+ T cell suppressor function.

The in vivo differentiation/survival of CD4(+)CD25(+) T suppressor cells is dependent on IL-2 and CD28-mediated costimulatory signals. To determine the cytokine and costimulatory requirements for CD25(+) T cells in vitro, we established a two-stage culture system where CD25(+) T cells were activated in a primary culture. In the subsequent culture, activated CD4(+)CD25(+) cells were then mixed with responders in order to assess their suppressor function. Pre-culture of CD25(+) T cells with anti-CD3 alone resulted in poor survival and minimal induction of suppressor activity. Pre-culture in the presence of anti-CD3 and IL-2 or IL-4, but not IL-6, IL-7, IL-9, IL-10 or IL-15, resulted in proliferation of the CD25(+) cells and induction of potent suppressor function. Inhibition of the interaction of CD28 or cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) with CD80/CD86 in the pre-culture of CD4(+)CD25(+) cells did not prevent the induction of suppressor function. Furthermore, the inhibition of costimulatory signals did not inhibit the ability of fresh CD25(+) T cells to inhibit CD8(+) responders under conditions where activation of the responders was independent of CD80/CD86. These studies support the view that activation of CD25(+) T cells requires IL-2/IL-4 for their survival/differentiation into effector cells, but is independent of CD28/CTLA-4-mediated costimulation.

Animals↗
PubMed2003

Control of T cell activation by CD4+CD25+ suppressor T cells.

Although the concept of a separate lineage of T cells specifically equipped to suppress immune responses was initially proposed more than 30 years ago, progress in this area of immunoregulation has been hampered by the lack of solid biochemical and molecular data to support the existence of the soluble products of these purported suppressor T cells. Studies over the past 5-10 years have identified a distinct lineage of CD4+CD25+ regulatory or suppressor T cells that control autoreactive effector cells and prevent autoimmunity. The mechanism by which CD4+CD25+ T cells inhibit T cell activation in vivo or in vitro is still poorly defined. While autoreactive effector T cells undergo massive proliferation and expansion following injection into immunocompromised recipients, CD4+CD25+ T cells do not inhibit this lymphopaenia-induced proliferation and act later in the activation process at the site of immune damage in the target organ. The development of in vitro models that partially mimic the in vivo properties of the CD4+CD25+ regulatory T cells has facilitated their characterization. A member of the tumour necrosis receptor family, the GITR is expressed on CD4+CD25+ T cells and after interaction with its ligand down-regulates suppressor activity. Multiple methods of manipulating both the numbers of CD4+CD25+ suppressor T cells and their activation status are now available and will rapidly be applied to therapy of autoimmune, infectious and malignant diseases.

Animals↗
PubMed2002

CD4(+)CD25(+) regulatory T cells can mediate suppressor function in the absence of transforming growth factor beta1 production and responsiveness.

CD4(+)CD25(+) regulatory T cells inhibit organ-specific autoimmune diseases induced by CD4(+)CD25(-) T cells and are potent suppressors of T cell activation in vitro. Their mechanism of suppression remains unknown, but most in vitro studies suggest that it is cell contact-dependent and cytokine independent. The role of TGF-beta1 in CD4(+)CD25(+) suppressor function remains unclear. While most studies have failed to reverse suppression with anti-transforming growth factor (TGF)-beta1 in vitro, one recent study has reported that CD4(+)CD25(+) T cells express cell surface TGF-beta1 and that suppression can be completely abrogated by high concentrations of anti-TGF-beta suggesting that cell-associated TGF-beta1 was the primary effector of CD4(+)CD25(+)-mediated suppression. Here, we have reevaluated the role of TGF-beta1 in CD4(+)CD25(+)-mediated suppression. Neutralization of TGF-beta1 with either monoclonal antibody (mAb) or soluble TGF-betaRII-Fc did not reverse in vitro suppression mediated by resting or activated CD4(+)CD25(+) T cells. Responder T cells from Smad3(-/-) or dominant-negative TGF-beta type RII transgenic (DNRIITg) mice, that are both unresponsive to TGF-beta1-induced growth arrest, were as susceptible to CD4(+)CD25(+)-mediated suppression as T cells from wild-type mice. Furthermore, CD4(+)CD25(+) T cells from neonatal TGF-beta1(-/-) mice were as suppressive as CD4(+)CD25(+) from TGF-beta1(+/+) mice. Collectively, these results demonstrate that CD4(+)CD25(+) suppressor function can occur independently of TGF-beta1.

Animals↗
PubMed2002

Subtractive cloning: new genes for studying inflammatory disorders.

Understanding of the biology of interaction between pathogens and host is the central question in studying inflammatory disorders. Subtractive DNA cloning is one of the most efficient and comprehensive methods available for identifying eukaryotic genes regulated under specific physiological conditions, including inflammation and host response. Here we explore the utility of subtractive DNA cloning and describe suppression subtractive hybridization (SSH), a polymerase chain reaction (PCR)-based DNA subtraction method that has been developed and evolved in our labs over several years. The SSH method possesses a number of advantages as compared to other subtractive cloning techniques, making it one of the most adventitious methods for cloning differentially expressed genes. Besides isolation of differentially expressed eukaryotic mRNAs, subtractive DNA cloning can be used to identify genes that are differentially expressed between diverse bacterial species. These genes can be of great interest, as some may encode strain-specific traits such as drug resistance, or bacterial surface proteins involved in determining the virulence of a particular strain. Other genes may be useful as markers for epidemiological or evolutionary studies. To demonstrate the potential of the SSH technique, we describe here the comprehensive characterization of 2 SSH subtracted libraries constructed in our laboratories. One library was created using eukaryotic cDNA subtraction and is specific for mRNAs up-regulated in CD25 positive cells from mouse lymph nodes as compared to CD25 negative cells. The second subtracted library is specific for a methicillin-resistant Staphylococcus aureus bacterial strain, but not in a methicillin-sensitive strain. The bacterial genomes of these 2 strains have been completely sequenced and this second library provides an excellent reference for testing the ability of SSH to recover all strain-specific gene content. The analysis of these 2 subtracted libraries serves as the basis for a discussion of the strength and limitations of the SSH technique. We will also compare and contrast subtractive DNA cloning to other current technologies used to isolate differentially expressed genes.

Animals↗