Longman Essential Activator Pdf Free Download English

[Aili Peal]

Thankyou for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

It has been thought that chronic intestinal inflammation is driven by the pro-inflammatory cytokine interleukin-12 (IL-12), but new research now shows that the related cytokine IL-23, and not IL-12, is essential for the induction of intestinal inflammation. The authors used two models to examine the role of these cytokines in inflammatory bowel disease (IBD): a T-cell-dependent model, and a T-cell-independent model that involves infection with Helicobacter hepaticus. Blockade or genetic ablation of IL-23 resulted in attenuated intestinal pathology and decreased production of pro-inflammatory mediators in both models but had little impact on systemic T-cell responses. Therefore, IL-23 is an inducer of local innate and adaptive immune pathology in the intestine, indicating that selective targeting of IL-23 might be an effective therapy for human IBD.

Type I interferons (IFNs) have been shown to have contrasting roles in the immune response to viral infection. Longman et al. show that immature dendritic cells (DCs) exposed to type I IFNs are impaired in their ability to activate CD8+ T cells by cross-presentation of antigen. By contrast, stimulation of mature DCs with type I IFNs increased their capacity to activate T cells. Examining the STAT (signal transducer and activator of transcription) proteins showed that engagement of the type I IFN receptor on immature DCs activated STAT1, whereas in mature DCs, STAT4 was activated. Activation of STAT1 inhibited CD40-ligand-induced production of interleukin-12, thereby reducing activation of CD8+ T cells. So the effect of type I IFNs on cross-presentation is intrinsically linked to the maturation status of the DC, providing a mechanism by which the DC can differentially respond to cytokine signals from the surrounding environment.

Defective signalling by the GTPase RAS has been associated with T-cell anergy, but technical limitations have resulted in a lack of mechanistic data. Therefore, Zha et al. developed a system in which adenoviral transduction of quiescent cells is possible. Constitutive activation of RAS in anergic T cells restored production of interleukin-2 and activation of mitogen-activated-protein-kinase signalling. The expression of diacylglycerol kinases (DGKs), which are negative regulators of RAS, was found to be upregulated by anergic T cells, and inhibition of these kinases restored interleukin-2 production. So these data indicate that DGKs are anergy-associated molecules that negatively regulate RAS in anergic T cells.

3a8082e126