Large CD3- cells were analyzed (as shown in gate represented in bottom left dot-plot) to exclude T cells, and results show staining above isotype control (bottom right dot-plot), being expressed as percentages of CD1a+ cells expressing IFN-. IL-1, like IL-1, co-induced IL-12 secretion whereas IL-18 did not. Conversely, the inhibitor IL-1Ra, produced endogenously by DC curtailed IL-12 production in response to CD40L. Conclusions IL-1 and Rabbit Polyclonal to GPR156 IL-1Ra play a biologically-relevant role in the positive and negative regulation of DC activation. In conjunction with CD40L, IL-1 sends a powerful activation transmission to DC that could be distinguished from other modes of activation. This transmission enables the production of pro-inflammatory cytokines by DC, and enhances the differentiation of na?ve T cells into effectors of type-1 cellular immune responses. but is usually a central event that enables DC to primary effective MHC class I-restricted CD8+ T cell responses [5-7]. IL-12 is usually a pivotal factor for the initiation of cellular immunity (examined in [8]). IL-12 promotes the polarization of Th1 T cell development, increases the differentiation and activation of cytolytic T cells and in concert with IL-18, induces IFN- production by T cells and NK cells. The mechanisms regulating IL-12 production are complex as IL-12 is composed of two chains IL-12 (IL-12p35) and IL-12 (IL-12p40) with impartial transcriptional regulation. The two chains assemble as a disulfide-linked heterodimer which is usually glycosylated and secreted as a biologically active pro-inflammatory and immune mediator [9,10]. CD40L is known to induce the production of high levels of IL-12 in human monocyte-derived DC [11]. Yet, signalling through CD40 alone is not sufficient to induce the secretion of substantial amounts of IL-12 heterodimer. We as well as others have shown that a second transmission, provided by a microbial product (lipopolysaccharide=LPS) or by immune mediators such as IFN- or IL-1, is required to induce the secretion of high levels of IL-12 by DC in the presence of CD40L [12-15]. IL-1 is usually major pro-inflammatory cytokine with multiple activities in the regulation of immune, inflammatory, endocrine and neuronal systems (examined in [16]). The IL-1 family comprises several structurally-related ligands and the most extensively characterized include IL-1, IL-1, the inhibitory IL-1 receptor antagonist (IL-1Ra) and IL-18 (IL-1). These ligands bind to users of a family of receptors characterized by immunoglobulin folds in the extracellular portion and Toll/IL-1R (TIR) motif in the intra-cytoplasmic portion [17]. Whereas ligands of Toll-like receptors such HDM201 as LPS and other microbial products have recently gained a lot of attention as regulators of immune responses in general (reviewed by [18]) and of DC activation in particular [19], HDM201 ligands of IL-1R family have not been as extensively examined under this angle. On its own, IL-1 is HDM201 known to be a weak maturing agent for DC [4]. However, we have recently shown that when combined with CD40L, IL-1 sends a powerful cooperative signal to monocyte-derived DC, inducing the secretion of high levels of IL-12 [14]. This was recently confirmed and extended to show that IL-1 and CD40L also induce the secretion of high levels of IL-12 in CD34+ cell-derived DC [15] and A. Wesa, unpublished observation), and that this mode of activation also triggers the production of high levels of IL-6 and the production of IL-1. The effects of IL-1 can be explained at least at the transcriptional level, as CD40L up-regulates IL-12 mRNA and IL-1 complements this effect by up-regulating IL-12 mRNA [14]. Our own results suggest that CD40L co-activation with IL-1 yields high amounts of IL-12 but little IL-10 whereas LPS induces IL-12 but also more IL-10 [14]. As DC encounter various innate, microbial or immune stimuli that engage distinct intracellular signaling pathways, it seems likely that various combinations of these modes of activation might not produce equivalent APCs. The immuno-stimulatory properties of DC activated with IL-1 and C40L have not been well-defined and it is not clear that these cells which produce high amounts of IL-12 will be able to prime and activate naive.