Activation of purified murine CD4<sup>+</sup> T cells enhanced expression of the Notch target gene <i>hes1</i> and induced differential expression of Notch receptors and ligands compared to unstimulated cells. Surface staining for Notch 1 revealed that unstimulated cells expressed this receptor at the membrane. Activation of T cells induced capping of Notch1, which was found to co-localise with CD4. Capping of surface Notch and co-localisation with CD4 upon T cell activation was reminiscent of immunological synapse formation, suggesting that Notch may interact directly with T cell receptor signalling. Notch signalling was attenuated in CD4<sup>+ </sup>T cells using a γ-secretase inhibitor, allowing assessment of Notch function in determining effector function. Notch signal inhibition in the context of anti-CD3-Ab stimulation, resulted in inhibition of TNFα, IFNγ, IL-4 and IL-10 secretion. Blockade of Notch signalling where cells were stimulated with anti-CD3/28-Ab did not down-regulate TNFα, IFNγ or IL-4 secretion, but IL-10 was inhibited. Notch signalling may thus be important as a co-stimulator when CD28 signalling is limiting. Naturally occurring CD25<sup>+</sup> CD4<sup>+</sup> T regulatory cells and <i>in vitro </i>generated TrI cells were examined for expression of Notch pathway components to ascertain if Notch may be involved in mediating regulatory function. Both populations were found to express higher levels of the Notch ligand Delta 1 than non-regulatory CD4<sup>+</sup> T cells. Inhibition of Notch signalling did not affect the ability of CD25<sup>+</sup> CD4<sup>+</sup> T cells to regulate proliferation of CD4<sup>+</sup> CD25<sup>+</sup> T cells, but did reduce secretion of IL-10. These findings indicate that Notch receptors and ligands are expressed by CD4<sup>+</sup> T cells. Notch may also be a component of the immune synapse and potentially modulates CD4<sup>+</sup> T cell effector function through regulation of cytokine secretion, particularly IL-10.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:641538 |
| Date | January 2004 |
| Creators | Benson, Robert A. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/25108 |
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