In the present study we demonstrate that human monocytes activated by lipopolysaccharides (LPS) were able to produce high levels of interleukin 10 (IL-10), previously designated cytokine synthesis inhibitory factor (CSIF), in a dose dependent fashion. IL-10 was detectable 7 h after activation of the monocytes and maximal levels of IL-10 production were observed after 24-48 h. These kinetics indicated that the production of IL-10 by human monocytes was relatively late as compared to the production of IL-1 alpha, IL-1 beta, IL-6, IL-8, tumor necrosis factor alpha (TNF alpha), and granulocyte colony-stimulating factor (G-CSF), which were all secreted at high levels 4-8 h after activation. The production of IL-10 by LPS activated monocytes was, similar to that of IL-1 alpha, IL-1 beta, IL-6, IL-8, TNF alpha, granulocyte-macrophage colony-stimulating factor (GM-CSF), and G-CSF, inhibited by IL-4. Furthermore we demonstrate here that IL-10, added to monocytes, activated by interferon gamma (IFN-gamma), LPS, or combinations of LPS and IFN-gamma at the onset of the cultures, strongly inhibited the production of IL-1 alpha, IL-1 beta, IL-6, IL-8, TNF alpha, GM-CSF, and G-CSF at the transcriptional level. Viral-IL-10, which has similar biological activities on human cells, also inhibited the production of TNF alpha and GM-CSF by monocytes following LPS activation. Activation of monocytes by LPS in the presence of neutralizing anti-IL-10 monoclonal antibodies resulted in the production of higher amounts of cytokines relative to LPS treatment alone, indicating that endogenously produced IL-10 inhibited the production of IL-1 alpha, IL-1 beta, IL-6, IL-8, TNF alpha, GM-CSF, and G-CSF. In addition, IL-10 had autoregulatory effects since it strongly inhibited IL-10 mRNA synthesis in LPS activated monocytes. Furthermore, endogenously produced IL-10 was found to be responsible for the reduction in class II major histocompatibility complex (MHC) expression following activation of monocytes with LPS. Taken together our results indicate that IL-10 has important regulatory effects on immunological and inflammatory responses because of its capacity to downregulate class II MHC expression and to inhibit the production of proinflammatory cytokines by monocytes.

The type-I interferon (IFN-alpha/beta) response is critical to immunity against viruses and can be triggered in many cell types by cytosolic detection of viral infection, or in differentiated plasmacytoid dendritic cells by the Toll-like receptor 9 (TLR9) subfamily, which generates signals via the adaptor MyD88 to elicit robust IFN induction. Using mice deficient in the Irf7 gene (Irf7-/- mice), we show that the transcription factor IRF-7 is essential for the induction of IFN-alpha/beta genes via the virus-activated, MyD88-independent pathway and the TLR-activated, MyD88-dependent pathway. Viral induction of MyD88-independent IFN-alpha/beta genes is severely impaired in Irf7-/- fibroblasts. Consistently, Irf7-/- mice are more vulnerable than Myd88-/- mice to viral infection, and this correlates with a marked decrease in serum IFN levels, indicating the importance of the IRF-7-dependent induction of systemic IFN responses for innate antiviral immunity. Furthermore, robust induction of IFN production by activation of the TLR9 subfamily in plasmacytoid dendritic cells is entirely dependent on IRF-7, and this MyD88-IRF-7 pathway governs the induction of CD8+ T-cell responses. Thus, all elements of IFN responses, whether the systemic production of IFN in innate immunity or the local action of IFN from plasmacytoid dendritic cells in adaptive immunity, are under the control of IRF-7.

Tremendous progress has been made in understanding the molecular basis of the antiviral actions of interferons (IFNs), as well as strategies evolved by viruses to antagonize the actions of IFNs. Furthermore, advances made while elucidating the IFN system have contributed significantly to our understanding in multiple areas of virology and molecular cell biology, ranging from pathways of signal transduction to the biochemical mechanisms of transcriptional and translational control to the molecular basis of viral pathogenesis. IFNs are approved therapeutics and have moved from the basic research laboratory to the clinic. Among the IFN-induced proteins important in the antiviral actions of IFNs are the RNA-dependent protein kinase (PKR), the 2',5'-oligoadenylate synthetase (OAS) and RNase L, and the Mx protein GTPases. Double-stranded RNA plays a central role in modulating protein phosphorylation and RNA degradation catalyzed by the IFN-inducible PKR kinase and the 2'-5'-oligoadenylate-dependent RNase L, respectively, and also in RNA editing by the IFN-inducible RNA-specific adenosine deaminase (ADAR1). IFN also induces a form of inducible nitric oxide synthase (iNOS2) and the major histocompatibility complex class I and II proteins, all of which play important roles in immune response to infections. Several additional genes whose expression profiles are altered in response to IFN treatment and virus infection have been identified by microarray analyses. The availability of cDNA and genomic clones for many of the components of the IFN system, including IFN-alpha, IFN-beta, and IFN-gamma, their receptors, Jak and Stat and IRF signal transduction components, and proteins such as PKR, 2',5'-OAS, Mx, and ADAR, whose expression is regulated by IFNs, has permitted the generation of mutant proteins, cells that overexpress different forms of the proteins, and animals in which their expression has been disrupted by targeted gene disruption. The use of these IFN system reagents, both in cell culture and in whole animals, continues to provide important contributions to our understanding of the virus-host interaction and cellular antiviral response.

The cause of fibrotic diseases, pathologies characterized by excessive production, deposition, and contraction of extracellular matrix, is unknown. To understand the molecular basis of fibrotic disease, it is essential to appreciate how matrix deposition is normally controlled and how this process is dysregulated in fibrogenesis. This review discusses the current state of knowledge concerning interactions among the profibrotic proteins transforming growth factor-beta (TGF-beta), connective tissue growth factor (CTGF, CCN2), and ED-A fibronectin (ED-A FN) and the antifibrotic proteins tumor necrosis factor-alpha (TNF-alpha) and gamma-interferon (IFN-gamma).

Interferons are cytokines that play a complex and central role in the resistance of mammalian hosts to pathogens. Type I interferon (IFN-alpha and IFN-beta) is secreted by virus-infected cells. Immune, type II, or gamma-interferon (IFN-gamma) is secreted by thymus-derived (T) cells under certain conditions of activation and by natural killer (NK) cells. Although originally defined as an agent with direct antiviral activity, the properties of IFN-gamma include regulation of several aspects of the immune response, stimulation of bactericidal activity of phagocytes, stimulation of antigen presentation through class I and class II major histocompatibility complex (MHC) molecules, orchestration of leukocyte-endothelium interactions, effects on cell proliferation and apoptosis, as well as the stimulation and repression of a variety of genes whose functional significance remains obscure. The implementation of such a variety of effects by a single cytokine is achieved by complex patterns of cell-specific gene regulation: Several IFN-gamma-regulated genes are themselves components of transcription factors. The IFN-gamma response is itself regulated by interaction with responses to other cytokines including IFN-alpha/beta, TNF-alpha, and IL-4. Over 200 genes are now known to be regulated by IFN-gamma and they are listed in a World Wide Web document that accompanies this review. However, much of the cellular response to IFN-gamma can be described in terms of a set of integrated molecular programs underlying well-defined physiological systems, for example the induction of efficient antigen processing for MHC-mediated antigen presentation, which play clearly defined roles in pathogen resistance. A promising approach to the complexity of the IFN-gamma response is to extend the analysis of the less understood IFN-gamma-regulated genes in terms of molecular programs functional in pathogen resistance.

The cellular innate immune system is essential for recognizing pathogen infection and for establishing effective host defence. But critical molecular determinants responsible for facilitating an appropriate immune response-following infection with DNA and RNA viruses, for example-remain to be identified. Here we report the identification, following expression cloning, of a molecule (STING; stimulator of interferon genes) that appears essential for effective innate immune signalling processes. It comprises five putative transmembrane regions, predominantly resides in the endoplasmic reticulum and is able to activate both NF-kappaB and IRF3 transcription pathways to induce expression of type I interferon (IFN-alpha and IFN-beta ) and exert a potent anti-viral state following expression. In contrast, loss of STING rendered murine embryonic fibroblasts extremely susceptible to negative-stranded virus infection, including vesicular stomatitis virus. Further, STING ablation abrogated the ability of intracellular B-form DNA, as well as members of the herpesvirus family, to induce IFN-beta, but did not significantly affect the Toll-like receptor (TLR) pathway. Yeast two-hybrid and co-immunoprecipitation studies indicated that STING interacts with RIG-I and with SSR2 (also known as TRAPbeta), which is a member of the translocon-associated protein (TRAP) complex required for protein translocation across the endoplasmic reticulum membrane following translation. Ablation by RNA interference of both TRAPbeta and translocon adaptor SEC61beta was subsequently found to inhibit STING's ability to stimulate expression of IFN-beta. Thus, as well as identifying a regulator of innate immune signalling, our results imply a potential role for the translocon in innate signalling pathways activated by select viruses as well as intracellular DNA.

The pleiotropic activities of interferons (IFNs) are mediated primarily through the transcriptional regulation of many downstream effector genes. The mRNA profiles from IFN-alpha, -beta, or -gamma treatments of the human fibrosarcoma cell line, HT1080, were determined by using oligonucleotide arrays with probe sets corresponding to more than 6,800 human genes. Among these were transcripts for known IFN-stimulated genes (ISGs), the expression of which were consistent with previous studies in which the particular ISG was characterized as responsive to either Type I (alpha, beta) or Type II (gamma) IFNs, or both. Importantly, many novel IFN-stimulated genes were identified that were diverse in their known biological functions. For instance, several novel ISGs were identified that are implicated in apoptosis (including RAP46/Bag-1, phospholipid scramblase, and hypoxia inducible factor-1alpha). Furthermore, several IFN-repressed genes also were identified. These results demonstrate the usefulness of oligonucleotide arrays in monitoring mammalian gene expression on a broad and unprecedented scale. In particular, these findings provide insights into the basic mechanisms of IFN actions and ultimately may contribute to better therapeutic uses for IFNs.

Unmethylated CpG motifs are prevalent in bacterial but not vertebrate genomic DNAs. Oligodeoxynucleotides (ODN) containing CpG motifs activate host defense mechanisms leading to innate and acquired immune responses. The recognition of CpG motifs requires Toll-like receptor (TLR) 9, which triggers alterations in cellular redox balance and the induction of cell signaling pathways including the mitogen activated protein kinases (MAPKs) and NF kappa B. Cells that express TLR-9, which include plasmacytoid dendritic cells (PDCs) and B cells, produce Th1-like proinflammatory cytokines, interferons, and chemokines. Certain CpG motifs (CpG-A) are especially potent at activating NK cells and inducing IFN-alpha production by PDCs, while other motifs (CpG-B) are especially potent B cell activators. CpG-induced activation of innate immunity protects against lethal challenge with a wide variety of pathogens, and has therapeutic activity in murine models of cancer and allergy. CpG ODN also enhance the development of acquired immune responses for prophylactic and therapeutic vaccination.

Natural killer (NK) cells are populations of lymphocytes that can be activated to mediate significant levels of cytotoxic activity and produce high levels of certain cytokines and chemokines. NK cells respond to and are important in defense against a number of different infectious agents. The first indications for this function came from the observations that virus-induced interferons alpha/beta (IFN-alpha and -beta) are potent inducers of NK cell-mediated cytotoxicity, and that NK cells are important contributors to innate defense against viral infections. In addition to IFN-alpha/beta, a wide range of other innate cytokines can mediate biological functions regulating the NK cell responses of cytotoxicity, proliferation, and gamma interferon (IFN-gamma) production. Certain, but not all, viral infections induce interleukin 12 (IL-12) to elicit NK cell IFN-gamma production and antiviral mechanisms. However, high levels of IFN-alpha/beta appear to be unique and/or uniquely dominant in the context of viral infections and act to regulate other innate responses, including induction of NK cell proliferation in vivo and overall negative regulation of IL-12 production. A detailed picture is developing of particular innate cytokines activating NK cell responses and their consorted effects in providing unique endogenous milieus promoting downstream adaptive responses, most beneficial in defense against viral infections.

Type 1 interferon-(alpha, beta, omega)-producing cells (IPCs), also known as plasmacytoid dendritic cell precursors (pDCs), represent 0.2%-0.8% of peripheral blood mononuclear cells in both humans and mice. IPCs display plasma cell morphology, selectively express Toll-like receptor (TLR)-7 and TLR9, and are specialized in rapidly secreting massive amounts of type 1 interferon following viral stimulation. IPCs can promote the function of natural killer cells, B cells, T cells, and myeloid DCs through type 1 interferons during an antiviral immune response. At a later stage of viral infection, IPCs differentiate into a unique type of mature dendritic cell, which directly regulates the function of T cells and thus links innate and adaptive immune responses. After more than two decades of effort by researchers, IPCs finally claim their place in the hematopoietic chart as the most important cell type in antiviral innate immunity. Understanding IPC biology holds future promise for developing cures for infectious diseases, cancer, and autoimmune diseases.

Members of the nuclear factor kappa B (NF-kappaB) family of dimeric transcription factors (TFs) regulate expression of a large number of genes involved in immune responses, inflammation, cell survival, and cancer. NF-kappaB TFs are rapidly activated in response to various stimuli, including cytokines, infectious agents, and radiation-induced DNA double-strand breaks. In nonstimulated cells, some NF-kappaB TFs are bound to inhibitory IkappaB proteins and are thereby sequestered in the cytoplasm. Activation leads to phosphorylation of IkappaB proteins and their subsequent recognition by ubiquitinating enzymes. The resulting proteasomal degradation of IkappaB proteins liberates IkappaB-bound NF-kappaB TFs, which translocate to the nucleus to drive expression of target genes. Two protein kinases with a high degree of sequence similarity, IKKalpha and IKKbeta, mediate phosphorylation of IkappaB proteins and represent a convergence point for most signal transduction pathways leading to NF-kappaB activation. Most of the IKKalpha and IKKbeta molecules in the cell are part of IKK complexes that also contain a regulatory subunit called IKKgamma or NEMO. Despite extensive sequence similarity, IKKalpha and IKKbeta have largely distinct functions, due to their different substrate specificities and modes of regulation. IKKbeta (and IKKgamma) are essential for rapid NF-kappaB activation by proinflammatory signaling cascades, such as those triggered by tumor necrosis factor alpha (TNFalpha) or lipopolysaccharide (LPS). In contrast, IKKalpha functions in the activation of a specific form of NF-kappaB in response to a subset of TNF family members and may also serve to attenuate IKKbeta-driven NF-kappaB activation. Moreover, IKKalpha is involved in keratinocyte differentiation, but this function is independent of its kinase activity. Several years ago, two protein kinases, one called IKKepsilon or IKK-i and one variously named TBK1 (TANK-binding kinase), NAK (NF-kappaB-activated kinase), or T2K (TRAF2-associated kinase), were identified that exhibit structural similarity to IKKalpha and IKKbeta. These protein kinases are important for the activation of interferon response factor 3 (IRF3) and IRF7, TFs that play key roles in the induction of type I interferon (IFN-I). Together, the IKKs and IKK-related kinases are instrumental for activation of the host defense system. This Review focuses on the functions of IKK and IKK-related kinases and the molecular mechanisms that regulate their activities.

Induction of the interferon (IFN)-alpha/beta gene transcription in virus-infected cells is an event central to innate immunity. Mice lacking the transcription factor IRF-3 are more vulnerable to virus infection. In embryonic fibroblasts, virus-induced IFN-alpha/beta gene expression levels are reduced and the spectrum of the IFN-alpha mRNA subspecies altered. Furthermore, cells additionally defective in IRF-7 expression totally fail to induce these genes in response to infections by any of the virus types tested. In these cells, a normal profile of IFN-alpha/beta mRNA induction can be achieved by coexpressing both IRF-3 and IRF-7. These results demonstrate the essential and distinct roles of thetwo factors, which together ensure the transcriptional efficiency and diversity of IFN-alpha/beta genes for the antiviral response.

The significance of type I interferons (IFN-alpha/beta) in biology and medicine renders research on their activities continuously relevant to our understanding of normal and abnormal (auto) immune responses. This relevance is bolstered by discoveries that unambiguously establish IFN-alpha/beta, among the multitude of cytokines, as dominant in defining qualitative and quantitative characteristics of innate and adaptive immune processes. Recent advances elucidating the biology of these key cytokines include better definition of their complex signaling pathways, determination of their importance in modifying the effects of other cytokines, the role of Toll-like receptors in their induction, their major cellular producers, and their broad and diverse impact on both cellular and humoral immune responses. Consequently, the role of IFN-alpha/beta in the pathogenesis of autoimmunity remains at the forefront of scientific inquiry and has begun to illuminate the mechanisms by which these molecules promote or inhibit systemic and organ-specific autoimmune diseases.

Recombinant interferon-alpha (IFN-alpha) was approved by regulatory agencies in many countries in 1986. As the first biotherapeutic approved, IFN-alpha paved the way for the development of many other cytokines and growth factors. Nevertheless, understanding the functions of the multitude of human IFNs and IFN-like cytokines has just touched the surface. This review summarizes the history of the purification of human IFNs and the key aspects of our current state of knowledge of human IFN genes, proteins, and receptors. All the known IFNs and IFN-like cytokines are described [IFN-alpha, IFN-beta, IFN-epsilon, IFN-kappa, IFN-omega, IFN-delta, IFN-tau, IFN-gamma, limitin, interleukin-28A (IL-28A), IL-28B, and IL-29] as well as their receptors and signal transduction pathways. The biological activities and clinical applications of the proteins are discussed. An extensive section on the evolution of these molecules provides some new insights into the development of these proteins as major elements of innate immunity. The overall structure of the IFNs is put into perspective in relation to their receptors and functions.

Interleukin 10 (IL-10) and viral IL-10 (v-IL-10) strongly reduced antigen-specific proliferation of human T cells and CD4+ T cell clones when monocytes were used as antigen-presenting cells. In contrast, IL-10 and v-IL-10 did not affect the proliferative responses to antigens presented by autologous Epstein-Barr virus-lymphoblastoid cell line (EBV-LCL). Inhibition of antigen-specific T cell responses was associated with downregulation of constitutive, as well as interferon gamma- or IL-4-induced, class II MHC expression on monocytes by IL-10 and v-IL-10, resulting in the reduction in antigen-presenting capacity of these cells. In contrast, IL-10 and v-IL-10 had no effect on class II major histocompatibility complex (MHC) expression on EBV-LCL. The reduced antigen-presenting capacity of monocytes correlated with a decreased capacity to mobilize intracellular Ca2+ in the responder T cell clones. The diminished antigen-presenting capacities of monocytes were not due to inhibitory effects of IL-10 and v-IL-10 on antigen processing, since the proliferative T cell responses to antigenic peptides, which did not require processing, were equally well inhibited. Furthermore, the inhibitory effects of IL-10 and v-IL-10 on antigen-specific proliferative T cell responses could not be neutralized by exogenous IL-2 or IL-4. Although IL-10 and v-IL-10 suppressed IL-1 alpha, IL-1 beta, tumor necrosis factor alpha (TNF-alpha), and IL-6 production by monocytes, it was excluded that these cytokines played a role in antigen-specific T cell proliferation, since normal antigen-specific responses were observed in the presence of neutralizing anti-IL-1, -IL-6, and -TNF-alpha mAbs. Furthermore, addition of saturating concentrations of IL-1 alpha, IL-1 beta, IL-6, and TNF-alpha to the cultures had no effect on the reduced proliferative T cell responses in the presence of IL-10, or v-IL-10. Collectively, our data indicate that IL-10 and v-IL-10 can completely prevent antigen-specific T cell proliferation by inhibition of the antigen-presenting capacity of monocytes through downregulation of class II MHC antigens on monocytes.

Maintenance of the blood system is dependent on dormant haematopoietic stem cells (HSCs) with long-term self-renewal capacity. After injury these cells are induced to proliferate to quickly re-establish homeostasis. The signalling molecules promoting the exit of HSCs out of the dormant stage remain largely unknown. Here we show that in response to treatment of mice with interferon-alpha (IFNalpha), HSCs efficiently exit G(0) and enter an active cell cycle. HSCs respond to IFNalpha treatment by the increased phosphorylation of STAT1 and PKB/Akt (also known as AKT1), the expression of IFNalpha target genes, and the upregulation of stem cell antigen-1 (Sca-1, also known as LY6A). HSCs lacking the IFNalpha/beta receptor (IFNAR), STAT1 (ref. 3) or Sca-1 (ref. 4) are insensitive to IFNalpha stimulation, demonstrating that STAT1 and Sca-1 mediate IFNalpha-induced HSC proliferation. Although dormant HSCs are resistant to the anti-proliferative chemotherapeutic agent 5-fluoro-uracil, HSCs pre-treated (primed) with IFNalpha and thus induced to proliferate are efficiently eliminated by 5-fluoro-uracil exposure in vivo. Conversely, HSCs chronically activated by IFNalpha are functionally compromised and are rapidly out-competed by non-activatable Ifnar(-/-) cells in competitive repopulation assays. Whereas chronic activation of the IFNalpha pathway in HSCs impairs their function, acute IFNalpha treatment promotes the proliferation of dormant HSCs in vivo. These data may help to clarify the so far unexplained clinical effects of IFNalpha on leukaemic cells, and raise the possibility for new applications of type I interferons to target cancer stem cells.

Type 1 and type 2 diabetes are characterized by progressive beta-cell failure. Apoptosis is probably the main form of beta-cell death in both forms of the disease. It has been suggested that the mechanisms leading to nutrient- and cytokine-induced beta-cell death in type 2 and type 1 diabetes, respectively, share the activation of a final common pathway involving interleukin (IL)-1beta, nuclear factor (NF)-kappaB, and Fas. We review herein the similarities and differences between the mechanisms of beta-cell death in type 1 and type 2 diabetes. In the insulitis lesion in type 1 diabetes, invading immune cells produce cytokines, such as IL-1beta, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma. IL-1beta and/or TNF-alpha plus IFN-gamma induce beta-cell apoptosis via the activation of beta-cell gene networks under the control of the transcription factors NF-kappaB and STAT-1. NF-kappaB activation leads to production of nitric oxide (NO) and chemokines and depletion of endoplasmic reticulum (ER) calcium. The execution of beta-cell death occurs through activation of mitogen-activated protein kinases, via triggering of ER stress and by the release of mitochondrial death signals. Chronic exposure to elevated levels of glucose and free fatty acids (FFAs) causes beta-cell dysfunction and may induce beta-cell apoptosis in type 2 diabetes. Exposure to high glucose has dual effects, triggering initially "glucose hypersensitization" and later apoptosis, via different mechanisms. High glucose, however, does not induce or activate IL-1beta, NF-kappaB, or inducible nitric oxide synthase in rat or human beta-cells in vitro or in vivo in Psammomys obesus. FFAs may cause beta-cell apoptosis via ER stress, which is NF-kappaB and NO independent. Thus, cytokines and nutrients trigger beta-cell death by fundamentally different mechanisms, namely an NF-kappaB-dependent mechanism that culminates in caspase-3 activation for cytokines and an NF-kappaB-independent mechanism for nutrients. This argues against a unifying hypothesis for the mechanisms of beta-cell death in type 1 and type 2 diabetes and suggests that different approaches will be required to prevent beta-cell death in type 1 and type 2 diabetes.

The brain and the immune system are the two major adaptive systems of the body. During an immune response the brain and the immune system "talk to each other" and this process is essential for maintaining homeostasis. Two major pathway systems are involved in this cross-talk: the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system (SNS). This overview focuses on the role of SNS in neuroimmune interactions, an area that has received much less attention than the role of HPA axis. Evidence accumulated over the last 20 years suggests that norepinephrine (NE) fulfills the criteria for neurotransmitter/neuromodulator in lymphoid organs. Thus, primary and secondary lymphoid organs receive extensive sympathetic/noradrenergic innervation. Under stimulation, NE is released from the sympathetic nerve terminals in these organs, and the target immune cells express adrenoreceptors. Through stimulation of these receptors, locally released NE, or circulating catecholamines such as epinephrine, affect lymphocyte traffic, circulation, and proliferation, and modulate cytokine production and the functional activity of different lymphoid cells. Although there exists substantial sympathetic innervation in the bone marrow, and particularly in the thymus and mucosal tissues, our knowledge about the effect of the sympathetic neural input on hematopoiesis, thymocyte development, and mucosal immunity is extremely modest. In addition, recent evidence is discussed that NE and epinephrine, through stimulation of the beta(2)-adrenoreceptor-cAMP-protein kinase A pathway, inhibit the production of type 1/proinflammatory cytokines, such as interleukin (IL-12), tumor necrosis factor-alpha, and interferon-gamma by antigen-presenting cells and T helper (Th) 1 cells, whereas they stimulate the production of type 2/anti-inflammatory cytokines such as IL-10 and transforming growth factor-beta. Through this mechanism, systemically, endogenous catecholamines may cause a selective suppression of Th1 responses and cellular immunity, and a Th2 shift toward dominance of humoral immunity. On the other hand, in certain local responses, and under certain conditions, catecholamines may actually boost regional immune responses, through induction of IL-1, tumor necrosis factor-alpha, and primarily IL-8 production. Thus, the activation of SNS during an immune response might be aimed to localize the inflammatory response, through induction of neutrophil accumulation and stimulation of more specific humoral immune responses, although systemically it may suppress Th1 responses, and, thus protect the organism from the detrimental effects of proinflammatory cytokines and other products of activated macrophages. The above-mentioned immunomodulatory effects of catecholamines and the role of SNS are also discussed in the context of their clinical implication in certain infections, major injury and sepsis, autoimmunity, chronic pain and fatigue syndromes, and tumor growth. Finally, the pharmacological manipulation of the sympathetic-immune interface is reviewed with focus on new therapeutic strategies using selective alpha(2)- and beta(2)-adrenoreceptor agonists and antagonists and inhibitors of phosphodiesterase type IV in the treatment of experimental models of autoimmune diseases, fibromyalgia, and chronic fatigue syndrome.

A major challenge in vaccinology is to prospectively determine vaccine efficacy. Here we have used a systems biology approach to identify early gene 'signatures' that predicted immune responses in humans vaccinated with yellow fever vaccine YF-17D. Vaccination induced genes that regulate virus innate sensing and type I interferon production. Computational analyses identified a gene signature, including complement protein C1qB and eukaryotic translation initiation factor 2 alpha kinase 4-an orchestrator of the integrated stress response-that correlated with and predicted YF-17D CD8(+) T cell responses with up to 90% accuracy in an independent, blinded trial. A distinct signature, including B cell growth factor TNFRS17, predicted the neutralizing antibody response with up to 100% accuracy. These data highlight the utility of systems biology approaches in predicting vaccine efficacy.

Naive lymphocytes continually enter and exit lymphoid organs in a recirculation process that is essential for immune surveillance. During immune responses, the egress process can be shut down transiently. When this occurs locally it increases lymphocyte numbers in the responding lymphoid organ; when it occurs systemically it can lead to immunosuppression as a result of the depletion of recirculating lymphocytes. Several mediators of the innate immune system are known to cause shutdown, including interferon alpha/beta (IFN-alpha/beta) and tumour necrosis factor, but the mechanism has been unclear. Here we show that treatment with the IFN-alpha/beta inducer polyinosine polycytidylic acid (hereafter 'poly(I:C)') inhibited egress by a mechanism that was partly lymphocyte-intrinsic. The transmembrane C-type lectin CD69 was rapidly induced and CD69-/- cells were poorly retained in lymphoid tissues after treatment with poly(I:C) or infection with lymphocytic choriomeningitis virus. Lymphocyte egress requires sphingosine 1-phosphate receptor-1 (S1P1), and IFN-alpha/beta was found to inhibit lymphocyte responsiveness to S1P. By contrast, CD69-/- cells retained S1P1 function after exposure to IFN-alpha/beta. In coexpression experiments, CD69 inhibited S1P1 chemotactic function and led to downmodulation of S1P1. In a reporter assay, S1P1 crosslinking led to co-crosslinking and activation of a CD69-CD3zeta chimaera. CD69 co-immunoprecipitated with S1P1 but not the related receptor, S1P3. These observations indicate that CD69 forms a complex with and negatively regulates S1P1 and that it functions downstream of IFN-alpha/beta, and possibly other activating stimuli, to promote lymphocyte retention in lymphoid organs.

Immunoglobulin (Ig) class-switch DNA recombination (CSR) is thought to be highly dependent upon engagement of CD40 on B cells by CD40 ligand on T cells. We show here that dendritic cells up-regulate BLyS and APRIL upon exposure to interferon-alpha, interferon-gamma or CD40 ligand. In the presence of interleukin 10 (IL-10) or transforming growth factor-beta, BLyS and APRIL induce CSR from C(mu) to C(gamma) and/or C(alpha) genes in B cells, whereas CSR to C(epsilon) requires IL-4. Secretion of class-switched antibodies requires additional stimulation by B cell antigen receptor engagement and IL-15. By eliciting CD40-independent Ig class switching and plasmacytoid differentiation, BLyS and APRIL critically link the innate and adaptive immune responses.

Alpha/beta interferon immune defenses are essential for resistance to viruses and can be triggered through the actions of the cytoplasmic helicases retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5). Signaling by each is initiated by the recognition of viral products such as RNA and occurs through downstream interaction with the IPS-1 adaptor protein. We directly compared the innate immune signaling requirements of representative viruses of the Flaviviridae, Orthomyxoviridae, Paramyxoviridae, and Reoviridae for RIG-I, MDA5, and interferon promoter-stimulating factor 1 (IPS-1). In cultured fibroblasts, IPS-1 was essential for innate immune signaling of downstream interferon regulatory factor 3 activation and interferon-stimulated gene expression, but the requirements for RIG-I and MDA5 were variable. Each was individually dispensable for signaling triggered by reovirus and dengue virus, whereas RIG-I was essential for signaling by influenza A virus, influenza B virus, and human respiratory syncytial virus. Functional genomics analyses identified cellular genes triggered during influenza A virus infection whose expression was strictly dependent on RIG-I and which are involved in processes of innate or adaptive immunity, apoptosis, cytokine signaling, and inflammation associated with the host response to contemporary and pandemic strains of influenza virus. These results define IPS-1-dependent signaling as an essential feature of host immunity to RNA virus infection. Our observations further demonstrate differential and redundant roles for RIG-I and MDA5 in pathogen recognition and innate immune signaling that may reflect unique and shared biologic properties of RNA viruses whose differential triggering and control of gene expression may impact pathogenesis and infection.

Approximately 5% of the world population is infected by the hepatitis B virus (HBV) that causes a necroinflammatory liver disease of variable duration and severity. Chronically infected patients with active liver disease carry a high risk of developing cirrhosis and hepatocellular carcinoma. The immune response to HBV-encoded antigens is responsible both for viral clearance and for disease pathogenesis during this infection. While the humoral antibody response to viral envelope antigens contributes to the clearance of circulating virus particles, the cellular immune response to the envelope, nucleocapsid, and polymerase antigens eliminates infected cells. The class I- and class II-restricted T cell responses to the virus are vigorous, polyclonal, and multispecific in acutely infected patients who successfully clear the virus, and the responses are relatively weak and more narrowly focused in chronically infected patients who do not. The pathogenetic and antiviral potential of the cytotoxic T lymphocyte (CTL) response to HBV has been demonstrated by the induction of a severe necroinflammatory liver disease following the adoptive transfer of HBsAg-specific CTL into HBV transgenic mice, and by the noncytolytic suppression of viral gene expression and replication in the same animals by a posttranscriptional mechanism mediated by interferon gamma, tumor necrosis factor alpha, and interleukin 2. The dominant cause of viral persistence during HBV infection is the development of a weak antiviral immune response to the viral antigens. While neonatal tolerance probably plays an important role in viral persistence in patients infected at birth, the basis for poor responsiveness in adult-onset infection is not well understood and requires further analysis. Viral evasion by epitope inactivation and T cell receptor antagonism may contribute to the worsening of viral persistence in the setting of an ineffective immune response, as can the incomplete downregulation of viral gene expression and the infection of immunologically privileged tissues. Chronic liver cell injury and the attendant inflammatory and regenerative responses create the mutagenic and mitogenic stimuli for the development of DNA damage that can cause hepatocellular carcinoma. Elucidation of the immunological and virological basis for HBV persistence may yield immunotherapeutic and antiviral strategies to terminate chronic HBV infection and reduce the risk of its life-threatening sequellae.

Dendritic cells (DCs) are important in regulating both immunity and tolerance. Hence, we hypothesized that systemic lupus erythematosus (SLE), an autoimmune disease characterized by autoreactive B and T cells, may be caused by alterations in the functions of DCs. Consistent with this, monocytes from SLE patients' blood were found to function as antigen-presenting cells, in vitro. Furthermore, serum from SLE patients induced normal monocytes to differentiate into DCs. These DCs could capture antigens from dying cells and present them to CD4-positive T cells. The capacity of SLE patients' serum to induce DC differentiation correlated with disease activity and depended on the actions of interferon-alpha (IFN-alpha). Thus, unabated induction of DCs by IFN-alpha may drive the autoimmune response in SLE.