Toll-like receptor 2 (TLR2) agonists induce a subset of TLR4-inducible proinflammatory genes, which suggests the use of differential signaling pathways. Murine macrophages stimulated with the TLR4 agonist Escherichia coli lipopolysaccharide (LPS), but not with TLR2 agonists, induced phosphorylation of signal transducer and activator of transcription 1alpha (STAT1alpha) and STAT1beta, which was blocked by antibodies to interferon beta (IFN-beta) but not IFN-alpha. All TLR2 agonists poorly induced IFN-beta, which is encoded by an immediate early LPS-inducible gene. Thus, the failure of TLR2 agonists to induce STAT1-dependent genes resulted, in part, from their inability to express IFN-beta. TLR4-induced IFN-beta mRNA was MyD88- and PKR (double-stranded RNA-dependent protein kinase)-independent, but TIRAP (Toll-interleukin 1 receptor domain-containing adapter protein)-dependent. Together, these findings provide the first mechanistic basis for differential patterns of gene expression activated by TLR4 and TLR2 agonists.

Overproduction of inflammatory mediators by macrophages in response to Gram-negative LPS has been implicated in septic shock. Recent reports indicate that three membrane-associated proteins, CD14, CD11b/CD18, and Toll-like receptor (TLR) 4, may serve as LPS recognition and/or signaling receptors in murine macrophages. Therefore, the relative contribution of these proteins in the induction of cyclooxygenase 2 (COX-2), IL-12 p35, IL-12 p40, TNF-α, IFN-inducible protein (IP)-10, and IFN consensus sequence binding protein (ICSBP) genes in response to LPS or the LPS-mimetic, Taxol, was examined using macrophages derived from mice deficient for these membrane-associated proteins. The panel of genes selected reflects diverse macrophage effector functions that contribute to the pathogenesis of septic shock. Induction of the entire panel of genes in response to low concentrations of LPS or Taxol requires the participation of both CD14 and TLR4, whereas high concentrations of LPS or Taxol elicit the expression of a subset of LPS-inducible genes in the absence of CD14. In contrast, for optimal induction of COX-2, IL-12 p35, and IL-12 p40 genes by low concentrations of LPS or by all concentrations of Taxol, CD11b/CD18 was also required. Mitigated induction of COX-2, IL-12 p35, and IL-12 p40 gene expression by CD11b/CD18-deficient macrophages correlated with a marked inhibition of NF-κB nuclear translocation and mitogen-activated protein kinase (MAPK) activation in response to Taxol and of NF-κB nuclear translocation in response to LPS. These findings suggest that for expression of a full repertoire of LPS-/Taxol-inducible genes, CD14, TLR4, and CD11b/CD18 must be coordinately engaged to deliver optimal signaling to the macrophage.

Vascular disrupting agents (VDAs) represent a novel approach to the treatment of cancer, resulting in the collapse of tumor vasculature and tumor death. 5,6-dimethylxanthenone-4-acetic acid (DMXAA) is a VDA currently in advanced phase II clinical trials, yet its precise mechanism of action is unknown despite extensive preclinical and clinical investigations. Our data demonstrate that DMXAA is a novel and specific activator of the TANK-binding kinase 1 (TBK1)–interferon (IFN) regulatory factor 3 (IRF-3) signaling pathway. DMXAA treatment of primary mouse macrophages resulted in robust IRF-3 activation and ∼750-fold increase in IFN-β mRNA, and in contrast to the potent Toll-like receptor 4 (TLR4) agonist lipopolysaccharide (LPS), signaling was independent of mitogen-activated protein kinase (MAPK) activation and elicited minimal nuclear factor κB–dependent gene expression. DMXAA-induced signaling was critically dependent on the IRF-3 kinase, TBK1, and IRF-3 but was myeloid differentiation factor 88–, Toll–interleukin 1 receptor domain–containing adaptor inducing IFN-β–, IFN promoter-stimulator 1–, and inhibitor of κB kinase–independent, thus excluding all known TLRs and cytosolic helicase receptors. DMXAA pretreatment of mouse macrophages induced a state of tolerance to LPS and vice versa. In contrast to LPS stimulation, DMXAA-induced IRF-3 dimerization and IFN-β expression were inhibited by salicylic acid. These findings detail a novel pathway for TBK1-mediated IRF-3 activation and provide new insights into the mechanism of this new class of chemotherapeutic drugs.

Interleukin-15 (IL-15) is a pleiotropic cytokine with a broad range of biological functions in many diverse cell types. It plays a major role in the development of inflammatory and protective immune responses to microbial invaders and parasites by modulating immune cells of both the innate and adaptive immune systems. This review provides an overview of the mechanisms by which IL-15 modulates the host response to infectious agents and its utility as a cytokine adjuvant in vaccines against infectious pathogens.

autoimmunity ͉ celiac disease ͉ immunotherapy ͉ interleukine 15 receptor C eliac disease (CD) is an immune-mediated enteropathy triggered by the consumption of gluten-containing cereals by genetically susceptible individuals carrying the HLA class II DQ alleles that encode DQ2 or DQ8 molecules (1, 2). Gluten peptides resulting from partial digestion of dietary cerealderived prolamines are presented by the antigen-presenting cells in the lamina propria bearing HLA-DQ2 or HLA-DQ8 class II molecules to cognate gluten-specific CD4 ϩ