The role of IL-12, IL-23 and IFN-gamma in immunity to viruses

Subversion and coercion: the art of redirecting tumor immune surveillance

Tumor immune surveillance and CD8+ T cells in particular appear capable of recognizing the antigenic properties of human tumor cells. However, those antigen specific T cells are often excluded from tumor tissue or are functionally limited in their cytotoxic capacity. Instead, the immune response provides proinflammatory cytokines and proteases promoting tumor growth and progression while subverting cytotoxic anti-tumor immunity. The cytokines and the inflammatory mechanisms driving tumor associated inflammation resemble tissue remodeling processes during wound healing and chronic inflammatory diseases. In this chapter, we summarize the current knowledge of how inflammatory cytokines may promote the deviation of anti-tumor immunity toward a tumor promoting, noncytotoxic inflammation.

IL-10 induction by Bordetella parapertussis limits a protective IFN-gamma response

Bordetella parapertussis causes the prolonged coughing illness known as pertussis or whooping cough, persisting for weeks within the respiratory tracts of infected hosts but inducing a very poor T cell response relative to that induced by Bordetella pertussis, the more common cause of pertussis. In this study, we examine the contributions of cytokines involved in the clearance of B. parapertussis and immunomodulation that delays effective clearance. The slow elimination of this pathogen from the respiratory tracts of mice coincides with the gradual accumulation of CD4(+) T cells in the lungs and B. parapertussis-responsive IFN-gamma-producing cells in the spleen. IFN-gamma-deficient mice were defective in the accumulation of leukocytes in lungs and in clearance of B. parapertussis from the lungs. In vitro B. parapertussis-stimulated macrophages produced IL-10, which inhibited the generation of the IFN-gamma response that is required for protection in vivo. As compared with wild-type mice, IL-10-deficient mice produced significantly higher levels of IFN-gamma, had higher numbers of leukocytes accumulated in the lungs, and cleared B. parapertussis more rapidly. Together, these data indicate that B. parapertussis induces the production of IL-10, which facilitates its persistence within infected hosts by limiting a protective IFN-gamma response.

Hyper-IgE syndrome

Hyper-IgE syndrome (HIES) is a complex primary immunodeficiency characterized by atopic dermatitis associated with extremely high serum IgE levels and susceptibility to infections with extracellular bacteria. Nonimmunological abnormalities, including a distinctive facial appearance, fracture following minor trauma, scoliosis, hyperextensive joints, and the retention of deciduous teeth are also observed in most patients. Recent studies have demonstrated that dominant-negative mutations in the signal transducer and activator of transcription 3 (STAT3) gene result in the classical multisystem form of HIES, whereas a null mutation in the tyrosine kinase 2 (TYK2) gene causes an autosomal recessive HIES associated with viral and mycobacterial infections. In both patients, signal transduction for multiple cytokines, including IL-6 and IL-23, was defective, resulting in impaired T(H)17 function. These findings suggest that the defect in cytokine signaling constitutes the molecular basis for the immunological and nonimmunological abnormalities observed in HIES.

Interleukin-12 (IL-12), but not IL-23, deficiency ameliorates viral encephalitis without affecting viral control

The relative contributions of interleukin-12 (IL-12) and IL-23 to viral pathogenesis have not been extensively studied. IL-12p40 mRNA rapidly increases after neurotropic coronavirus infection. Infection of mice defective in both IL-12 and IL-23 (p40(-/-)), in IL-12 alone (p35(-/-)), and in IL-23 alone (p19(-/-)) revealed that the symptoms of coronavirus-induced encephalitis are regulated by IL-12. IL-17-producing cells never exceeded background levels, supporting a redundant role of IL-23 in pathogenesis. Viral control, tropism, and demyelination were all similar in p35(-/-), p19(-/-), and wild-type mice. Reduced morbidity in infected IL-12 deficient mice was also not associated with altered recruitment or composition of inflammatory cells. However, gamma interferon (IFN-gamma) levels and virus-specific IFN-gamma-secreting CD4 and CD8 T cells were all reduced in the central nervous systems (CNS) of infected p35(-/-) mice. Transcription of the proinflammatory cytokines IL-1beta and IL-6, but not tumor necrosis factor, were initially reduced in infected p35(-/-) mice but increased to wild-type levels during peak inflammation. Furthermore, although transforming growth factor beta mRNA was not affected, IL-10 was increased in the CNS in the absence of IL-12. These data suggest that IL-12 does not contribute to antiviral function within the CNS but enhances morbidity associated with viral encephalitis by increasing the ratio of IFN-gamma to protective IL-10.

Cytokine-based transformation of immune surveillance into tumor-promoting inflammation

During the last decade, it has become clear that the mammalian immune system is able to recognize and partially suppress nascent tumors. Human T cells specific to oncogenes and onco-fetal antigens are present in human cancer patients and their tumors. At the same time, molecular links between tumor-associated inflammation and tumor progression have been uncovered, providing an explanation for the long recognized epidemiological link between inflammation and cancer. The synopsis of these findings suggests a new interpretation of tumor immunity. It appears that antigen recognition or antigen-specific T-cell expansion at large is not as profoundly impaired in tumor patients as the correct polarization, the survival and the effector function of tumor-infiltrating T cells. This review will focus on pro-inflammatory cytokines likely to contribute to the deregulation of tumor-specific immunity and its consequences.

Generation of a protective T-cell response following coronavirus infection of the central nervous system is not dependent on IL-12/23 signaling

The functional role of IL-12 and IL-23 in host defense and disease following viral infection of the CNS was determined. Instillation of mouse hepatitis virus (MHV, a positive-strand RNA virus) into the CNS of mice results in acute encephalitis followed by a chronic immune-mediated demyelinating disease. Antibody-mediated blocking of either IL-23 (anti-IL-23p19) or IL-12 and IL-23 (anti-IL-12/23p40) signaling did not mute T-cell trafficking into the CNS or antiviral effector responses and mice were able to control viral replication within the brain. Therapeutic administration of either anti-IL-23p19 or anti-IL-12/23p40 to mice with viral-induced demyelination did not attenuate T-cell or macrophage infiltration into the CNS nor improve clinical disease or diminish white matter damage. In contrast, treatment of mice with anti-IL-12/23p40 or anti-IL-23p19 resulted in inhibition of the autoimmune model of demyelination, experimental autoimmune encephalomyelitis (EAE). These data indicate that (1) IL-12 and IL-23 signaling are dispensable in generating a protective T-cell response following CNS infection with MHV, and (2) IL-12 and IL-23 do not contribute to demyelination in a model independent of autoimmune T-cell-mediated pathology. Therefore, therapeutic targeting of IL-12 and/or IL-23 for the treatment of autoimmune diseases may offer unique advantages by reducing disease severity without muting protective responses following viral infection.

CD11c identifies a subset of murine liver natural killer cells that responds to adenoviral hepatitis

The liver contains a unique repertoire of immune cells and a particular abundance of NK cells. We have found that CD11c defines a distinct subset of NK cells (NK1.1(+)CD3(-)) in the murine liver whose function was currently unknown. In naïve animals, CD11c(+) liver NK cells displayed an activated phenotype and possessed enhanced effector functions when compared with CD11c(-) liver NK cells. During the innate response to adenovirus infection, CD11c(+) NK cells were the more common IFN-gamma-producing NK cells in the liver, demonstrated enhanced lytic capability, and gained a modest degree of APC function. The mechanism of IFN-gamma production in vivo depended on TLR9 ligation as well as IL-12 and -18. Taken together, our findings demonstrate that CD11c(+) NK cells are a unique subset of NK cells in the murine liver that contribute to the defense against adenoviral hepatitis.

3,3'-Diindolylmethane stimulates murine immune function in vitro and in vivo

3,3'-Diindolylmethane (DIM), a major condensation product of indole-3-carbinol, exhibits chemopreventive properties in animal models of cancer. Recent studies have shown that DIM stimulates interferon-gamma (IFN-gamma) production and potentiates the IFN-gamma signaling pathway in human breast cancer cells via a mechanism that includes increased expression of the IFN-gamma receptor. The goal of this study was to test the hypothesis that DIM modulates the murine immune function. Specifically, the effects of DIM were evaluated in a panel of murine immune function tests that included splenocyte proliferation, reactive oxygen species (ROS) generation, cytokine production and resistance to viral infection. DIM was found to induce proliferation of splenocytes as well as augment mitogen- and interleukin (IL)-2-induced splenocyte proliferation. DIM also stimulated the production of ROS by murine peritoneal macrophage cultures. Oral administration of DIM, but not intraperitoneal injection, induced elevation of serum cytokines in mice, including IL-6, granulocyte colony-stimulating factor (G-CSF), IL-12 and IFN-gamma. Finally, in a model of enteric virus infection, oral DIM administration to mice enhanced both clearance of reovirus from the GI tract and the subsequent mucosal IgA response. Thus, DIM is a potent stimulator of immune function. This property might contribute to the cancer inhibitory effects of this indole.

ATF3 regulates MCMV infection in mice by modulating IFN-gamma expression in natural killer cells

Activating transcription factor 3 (ATF3) is a negative regulator of proinflammatory cytokine expression in macrophages, and ATF3-deficient mice are more susceptible to endotoxic shock. Here, we demonstrate that ATF3 interacts with a cis-regulatory element of the IFN-gamma gene in natural killer (NK) cells, and that ATF3null NK cells show increased transcription and secretion of IFN-gamma. NK cell-derived IFN-gamma has previously been demonstrated to be protective against murine cytomegalovirus (MCMV) infection, and we show here that ATF3null mice exhibit decreased hepatic viral load and reduced liver histopathology upon challenge with MCMV. Reconstitution of NK-deficient mice with ATF3null NK cells more effectively controlled MCMV infection than mice reconstituted with WT cells, indicating that ATF3 acts within NK cells to regulate antiviral responses.

Modulation of the phagosome proteome by interferon-gamma

Macrophages are immune cells that function in the clearance of infectious particles. This process involves the engulfment of microbes into phagosomes where these particles are lysed and degraded. In the current study, we used a large scale quantitative proteomics approach to analyze the changes in protein abundance induced on phagosomes by interferon-gamma (IFN-gamma), an inflammatory cytokine that activates macrophages. Our analysis identified 167 IFN-gamma-modulated proteins on phagosomes of which more than 90% were up-regulated. The list of phagosomal proteins regulated by IFN-gamma includes proteins expected to alter phagosome maturation, enhance microbe degradation, trigger the macrophage immune response, and promote antigen loading on major histocompatibility complex (MHC) class I molecules. A dynamic analysis of IFN-gamma-sensitive proteins by Western blot indicated that newly formed phagosomes display a delayed proteolytic activity coupled to an increased recruitment of the MHC class I peptide-loading complex. These phagosomal conditions may favor antigen presentation by MHC class I molecules on IFN-gamma-activated macrophages.

Adjunctive treatment of disseminated Mycobacterium avium complex infection with interferon alpha-2b in a patient with complete interferon-gamma receptor R1 deficiency

We report adjunct treatment of (interferon) IFN-alpha2b (Intron-A) in a patient with complete interferon-gamma receptor R1 (IFNGR1) deficiency suffering from disseminated infection with Mycobacterium avium complex (MAC) resistant to multiple anti-mycobacterial agents. A low dose of IFN-alpha2b (3 x 10(6) units/m(2) three times weekly subcutaneously) successfully attenuated progressive hepatosplenomegaly and abdominal/retroperitoneal/pelvic lymphadenopathy, although the patient continued to be mycobacteremic. This is the first report of a complete IFNGR1 deficiency treated with adjuvant IFN-alpha2b for disseminated MAC infection.

Retinoid-related orphan receptor gamma t is a potential therapeutic target for controlling inflammatory autoimmunity

Retinoid-related orphan receptor gamma t (RORgamma t) is a member of the nuclear receptor family that is specifically expressed in T cell compartments. RORgamma t regulates the development of T cells in the thymus and the differentiation of effector T cells in the periphery. During T cell development, RORgamma t enhances CD4(+)CD8(+) double positive thymocyte survival by upregulating Bcl-x(L). In the periphery, RORgamma t regulates IL-17 production and dictates the differentiation of pro-inflammatory T helper 17 (T(H)17) cells that play a critical role in inflammatory conditions and autoimmunity. RORgamma t-deficient T cells fail to differentiate into T(H)17 cells, whereas forced expression of RORgamma t is sufficient to induce naive T cells to produce IL-17. T(H)17 cells are believed to be the major inflammatory cells in autoimmune diseases. Therefore, inhibition of RORgamma t activity could potentially alleviate the symptoms associated with the T(H)17-dependent inflammatory autoimmune diseases. RORgamma t is thus potentially an excellent therapeutic target for the intervention of inflammatory autoimmunity.

Interleukin 22 is a candidate gene for Tmevp3, a locus controlling Theiler's virus-induced neurological diseases

After intracerebral inoculation, Theiler's virus induces in its natural host, the mouse, an acute encephalomyelitis followed, in susceptible animals, by chronic inflammation and primary demyelination. Susceptibility to demyelination among strains of laboratory mice is explained by the capacity of the immune system to control viral load during persistence. Also, differences of susceptibility to viral load between the susceptible SJL strain and the resistant B10.S strain are mainly due to two loci, Tmevp2 and Tmevp3, located close to the Ifng locus on chromosome 10. In this article, we show that the Tmevp3 locus controls both mortality during the acute encephalomyelitis and viral load during persistence. Most probably, two genes located in the Tmevp3 interval control these two different phenotypes with efficiencies that depend on the age of the mouse at inoculation. Il22, a member of the IL-10 cytokine family, is a candidate gene for the control of mortality during the acute encephalomyelitis.

Discovery and biology of IL-23 and IL-27: related but functionally distinct regulators of inflammation

Long-term resistance to many infections depends on the innate ability of the immune system to coordinate the development of antigen-specific adaptive responses. Deficiencies in these events can result in increased susceptibility to pathogens, whereas an inability to regulate an appropriate response can lead to devastating pathological conditions. For over a decade, interleukin (IL)-12 has been recognized as the canonical cytokine that links innate and adaptive immunity, and with the discovery of IL-23 and IL-27 as cytokines related to IL-12, there has been a concerted effort to understand the relationship between these factors. The results emerging from these studies have provided fundamental new insights into the developmental pathways that promote the differentiation and function of CD4(+) T helper cells and offer a dramatically altered perspective on the cause and prevention of autoimmune disease. In this review, we aim to highlight the discoveries that have led to our current understanding of the biology of IL-23 and IL-27 in the context of their role in resistance to infection, immune-mediated inflammation, and cancer.

Inhibition of type I and type III interferons by a secreted glycoprotein from Yaba-like disease virus

Type I (IFN-alpha/beta) and type III (IFN-lambdas) IFNs are important components of the host antiviral response. Although type III IFNs possess intrinsic antiviral activity similar to that of type I IFNs, they signal through a specific unique receptor complex, and their functional importance for antiviral resistance is largely uncharacterized. Here, we report the first virus defense mechanism that directly targets type III IFNs. Y136 from Yaba-like disease virus, a yatapoxvirus, is a secreted glycoprotein related to protein B18 from Vaccinia virus, a known type I IFN-binding protein and a member of the Ig superfamily. Surprisingly, whereas B18 inhibits only type I IFNs, Y136 inhibits both type I and type III IFNs. Y136 inhibits IFN-induced signaling and suppresses IFN-mediated biological activities including up-regulation of MHC class I antigen expression and induction of the antiviral state. These data demonstrate that poxviruses have developed unique strategies to counteract IFN-mediated antiviral protection and highlight the importance of type III IFNs in antiviral defense. These results suggest that type III IFNs may be an effective treatment for some poxviral infections.

Human primary immunodeficiencies of type I interferons

Type I interferons (IFN-alpha/beta and related molecules) are essential for protective immunity to experimental infection by numerous viruses in the mouse model. In recent years, human primary immunodeficiencies affecting either the production of (UNC-93B deficiency) or the response to (STAT1 and TYK2 deficiencies) these IFNs have been reported. Affected patients are highly susceptible to certain viruses. Patients with STAT1 or TYK2 deficiency are susceptible to multiple viruses, including herpes simplex virus-1 (HSV-1), whereas UNC-93B-deficient patients present isolated HSV-1 encephalitis. However, these immunological defects are not limited to type I IFN-mediated immunity. Impaired type II IFN (IFN-gamma)-mediated immunity plays no more than a minor role in the pathogenesis of viral diseases in these patients, but the contribution of impaired type III IFN (IFN-lambda)-mediated immunity remains to be determined. These novel inherited disorders strongly suggest that type I IFN-mediated immunity is essential for protection against natural infections caused by several viruses in humans.

Dendritic cells and interferon-mediated autoimmunity

Dendritic cells (DCs) are central cells of the immune responses. They can be considered as the most influential antigen-presenting cells in the body because of their unique role in initiating immunity against most types of antigens. Recent studies have clearly established that the state of maturation of DC can be crucial for the ability of these antigen-presenting cells to inhibit or induce T-cell-mediated autoimmune diseases. Type I interferon has been shown to be produced at very high amounts by a specific type of DC (pDC). In recent years, the study of multiple autoimmune diseases has pointed to a central role for type I interferon (IFN-I) in disease pathogenesis, in particular through the IFN-molecular signature deciphered in some of these diseases. One hypothesis would be that IFN directly affects multiple actors of the immune reaction such as T cells and B cells and that it can induce the unabated activation of peripheral dendritic cells. On the other hand, type II IFN has been considered as pathogenic in multiple autoimmune diseases leading to the paradigm of TH-1 type autoimmune diseases. The discovery of the TH-17 type of cells and the protective role IFN-gamma can exert on particular phases of these diseases urge one to re-evaluate this assumption.

Keeping NK cells in highly regulated antiviral warfare

Natural killer (NK) cells use multiple mechanisms to defend against viral infections, and different stimuli can activate these antiviral effects. When engaged, receptors for innate cytokines produced during infections and for ligands on target cells can both induce NK cell cytotoxicity and the production of cytokines. These stimuli use different classes of intracellular signaling pathways to elicit the overlapping responses. What is the advantage of using different roads to the same ends? One answer might be in the nature of the alternative regulatory pathways that are in place to control the respective stimuli. A model of flexibility in accessing NK cell function, in the context of negative regulation of particular intracellular signaling pathways, is proposed here.

TC-PTP-deficient bone marrow stromal cells fail to support normal B lymphopoiesis due to abnormal secretion of interferon-{gamma}

The T-cell protein tyrosine phosphatase (TC-PTP) is a negative regulator of the Jak/Stat cytokine signaling pathway. Our study shows that the absence of TC-PTP leads to an early bone marrow B-cell deficiency characterized by hindered transition from the pre-B cell to immature B-cell stage. This phenotype is intrinsic to the B cells but most importantly due to bone marrow stroma abnormalities. We found that bone marrow stromal cells from TC-PTP(-/-) mice have the unique property of secreting 232-890 pg/mL IFN-gamma. These high levels of IFN-gamma result in 2-fold reduction in mitotic index on IL-7 stimulation of TC-PTP(-/-) pre-B cells and lower responsiveness of IL-7 receptor downstream Jak/Stat signaling molecules. Moreover, we noted constitutive phosphorylation of Stat1 in those pre-B cells and demonstrated that this was due to soluble IFN-gamma secreted by TC-PTP(-/-) bone marrow stromal cells. Interestingly, culturing murine early pre-B leukemic cells within a TC-PTP-deficient bone marrow stroma environment leads to a 40% increase in apoptosis in these malignant cells. Our results unraveled a new role for TC-PTP in normal B lymphopoiesis and suggest that modulation of bone marrow microenvironment is a potential therapeutic approach for selected B-cell leukemia.

Activation, coactivation, and costimulation of resting human natural killer cells

Natural killer (NK) cells possess potent perforin- and interferon-gamma-dependent effector functions that are tightly regulated. Inhibitory receptors for major histocompatibility complex class I display variegated expression among NK cells, which confers specificity to individual NK cells. Specificity is also provided by engagement of an array of NK cell activation receptors. Target cells may express ligands for a multitude of activation receptors, many of which signal through different pathways. How inhibitory receptors intersect different signaling cascades is not fully understood. This review focuses on advances in understanding how activation receptors cooperate to induce cytotoxicity in resting NK cells. The role of activating receptors in determining specificity and providing redundancy of target cell recognition is discussed. Using Drosophila insect cells as targets, we have examined the contribution of individual receptors. Interestingly, the strength of activation is not determined simply by additive effects of parallel activation pathways. Combinations of signals from different receptors can have different outcomes: synergy, no enhancement over individual signals, or additive effects. Cytotoxicity requires combined signals for granule polarization and degranulation. The integrin leukocyte function-associated antigen-1 contributes a signal for polarization but not for degranulation. Conversely, CD16 alone or in synergistic combinations, such as NKG2D and 2B4, signals for phospholipase-C-gamma- and phosphatidylinositol-3-kinase-dependent degranulation.

Inborn errors of IL-12/23- and IFN-γ-mediated immunity: molecular, cellular, and clinical features

Mendelian susceptibility to mycobacterial diseases confers predisposition to clinical disease caused by weakly virulent mycobacterial species in otherwise healthy individuals. Since 1996, disease-causing mutations have been found in five autosomal genes (IFNGR1, IFNGR2, STAT1, IL12B, IL12BR1) and one X-linked gene (NEMO). These genes display a high degree of allelic heterogeneity, defining at least 13 disorders. Although genetically different, these conditions are immunologically related, as all result in impaired IL-12/23-IFN-gamma-mediated immunity. These disorders were initially thought to be rare, but have now been diagnosed in over 220 patients from over 43 countries worldwide. We review here the molecular, cellular, and clinical features of patients with inborn errors of the IL-12/23-IFN-gamma circuit.

TLR-ligand stimulated interleukin-23 subunit expression and assembly is regulated differentially in murine plasmacytoid and myeloid dendritic cells

Interleukin-23 (IL-23) is a heterodimeric cytokine composed of the p40 and p19 subunits, the first of which is also part of the IL-12 heterodimer. IL-23 induces a unique T helper cell subset to produce IL-17, which plays a critical and IL-12/IFN-gamma-independent role in autoimmunity. Plasmacytoid dendritic cells (pDC), as opposed to myeloid DC (mDC) and the closely related epidermal Langerhans cells (LC), exhibit a specific and broad range of pro-inflammatory cytokine secretion, with type I interferons representing a typical difference to classical mDC and LC. In this study we show that upon treatment with a selection of ligands for Toll-like receptor (TLR) 3, 4, 7, and 9, only mDC and LC but not pDC secreted IL-23. While pDC produced both mRNA and protein of the p40 subunit, the lack of bioactive heterodimeric IL-23 protein release was related to the fact that in these cells only the p19 mRNA was expressed which was not translated into protein. In addition to these differential findings in both DC subsets a novel p19 splice variant was identified. This analysis of transcriptional and/or post-transcriptional regulation of the IL-23 subunits p40 and p19 may help to understand the complex regulation of heterodimeric cytokines and the overlapping but distinct functions of IL-12 and IL-23. It supports the hypothesis of a coordinated adaptive immune response based on a finely tuned contribution of these cytokines by different mouse DC subsets.

Rationale and safety of anti-interleukin-23 and anti-interleukin-17A therapy

PURPOSE OF REVIEW

Interleukin-12 is a heterodimeric cytokine and an important mediator of the cellular immune response. The recent discovery of the novel cytokine interleukin-23 has led to a re-evaluation of interleukin-12 biology, as both cytokines use a common p40 subunit. This review discusses understanding of what distinguishes these related cytokines and the infection risks associated with targeting these cytokine pathways during treatment of inflammatory diseases.

RECENT FINDINGS

Recent work has shown that interleukin-23 stimulates the development of a distinct subset of effector T cells that produce interleukin-17A. These interleukin-17A-producing cells are critical mediators of the inflammatory response in several mouse models of autoimmunity. Although it is well established that interleukin-12 is a critical mediator of host defense, the role of the interleukin-23/interleukin-17A axis during infections has only recently been evaluated.

SUMMARY

Interleukin-12 and interleukin-23 have distinct roles in mediating host defense and autoimmune inflammation. Although targeting interleukin-12 and interleukin-23 simultaneously against the common p40 subunit is efficacious in clinical trials for human autoimmune diseases, targeting of interleukin-23 alone or the downstream effector cytokine interleukin-17A may be an effective treatment strategy for organ-specific autoimmune diseases. It is likely that targeting interleukin-23 or interleukin-17A alone, as opposed to targeting interleukin-12 and interleukin-23 together, will reduce the patients' risk of developing treatment-related infections.

IL-23: changing the verdict on IL-12 function in inflammation and autoimmunity

IL-12 and IL-23 are molecules mainly produced by activated accessory and antigen-presenting cells. The tools for studying the biology of IL-12 in man and laboratory rodents have greatly advanced our appreciation of the central role of this molecule in cell-mediated immunity and inflammation. In particular, IL-12 is thought to be the prime-regulator of TH1 development. Targeting what was thought to be IL-12 function in vivo, resulted in drastic amelioration of inflammation and autoimmunity firmly linking TH1 polarisation to autoimmune development. Upon discovery of IL-23 and the fact that the large subunit of IL-23 is shared by IL-12, the research community only begins to grasp that the features attributed to IL-12 and TH1 development in inflammation are, in fact, dependent on IL-23 and not on IL-12. Hence, the perception of IL-12 biology is, to a large extent, based on a mistaken identity. In this review, the authors provide an overview of their current understanding of IL-12 and IL-23 biology in inflammation and autoimmunity, and how this viewpoint has been readjusted over the past 15 years.

Characterization of the mouse IFN-lambda ligand-receptor system: IFN-lambdas exhibit antitumor activity against B16 melanoma

Recently discovered type III IFNs (IFN-lambda) exert their antiviral and immunomodulatory activities through a unique receptor complex composed of IFN-lambdaR1 and interleukin-10 receptor 2. To further study type III IFNs, we cloned and characterized mouse IFN-lambda ligand-receptor system. We showed that, similar to their human orthologues, mIFN-lambda2 and mIFN-lambda3 signal through the IFN-lambda receptor complex, activate IFN stimulated gene factor 3, and are capable of inducing antiviral protection and MHC class I antigen expression in several cell types including B16 melanoma cells. We then used the murine B16 melanoma model to investigate the potential antitumor activities of IFN-lambdas. We developed B16 cells constitutively expressing murine IFN-lambda2 (B16.IFN-lambda2 cells) and evaluated their tumorigenicity in syngeneic C57BL/6 mice. Although constitutive expression of mIFN-lambda2 in melanoma cells did not affect their proliferation in vitro, the growth of B16.IFN-lambda2 cells, when injected s.c. into mice, was either retarded or completely prevented. We found that rejection of the modified tumor cells correlated with their level of IFN-lambda2 expression. We then developed IFN-lambda-resistant B16.IFN-lambda2 cells (B16.IFN-lambda2Res cells) and showed that their tumorigenicity was also highly impaired or completely abolished similar to B16.IFN-lambda2 cells, suggesting that IFN-lambdas engage host mechanisms to inhibit melanoma growth. These in vivo experiments show the antitumor activities of IFN-lambdas and suggest their strong therapeutic potential.

IFNgammaR2 trafficking tunes IFNgamma-STAT1 signaling in T lymphocytes

Ligand-dependent downregulation of the interferon gamma receptor signaling chain (IFNgammaR2) has always been seen as a key mechanism for shielding T lymphocytes from the antiproliferative effects of the IFNgamma-signal transducer and activator of transcription 1 (STAT1) pathway. Now, however, a ligand-independent mechanism of IFNgammaR2 internalization is emerging as a more general way of limiting IFNgamma-STAT1 signaling in T cells, with insulin-like growth factor-1 (IGF-1) and iron as the main players. Here, we review the array of immunomodulatory effects exerted by these two factors on different cell types involved in the immune response; these effects suggest that an inflammatory environment generates signals that favor IFNgammaR2 cell-surface accumulation and IFNgamma-induced apoptosis in T cells, whereas an anti-inflammatory environment promotes IFNgammaR2 internalization and induces T cell unresponsiveness to IFNgamma signaling.

Marked differences in human melanoma antigen-specific T cell responsiveness after vaccination using a functional microarray

BACKGROUND

In contrast to many animal model studies, immunotherapeutic trials in humans suffering from cancer invariably result in a broad range of outcomes, from long-lasting remissions to no discernable effect.

METHODS AND FINDINGS

In order to study the T cell responses in patients undergoing a melanoma-associated peptide vaccine trial, we have developed a high-throughput method using arrays of peptide-major histocompatibility complexes (pMHC) together with antibodies against secreted factors. T cells were specifically immobilized and activated by binding to particular pMHCs. The antibodies, spotted together with the pMHC, specifically capture cytokines secreted by the T cells. This technique allows rapid, simultaneous isolation and multiparametric functional characterization of antigen-specific T cells present in clinical samples. Analysis of CD8+ lymphocytes from ten melanoma patients after peptide vaccination revealed a diverse set of patient- and antigen-specific profiles of cytokine secretion, indicating surprising differences in their responsiveness. Four out of four patients who showed moderate or greater secretion of both interferon-gamma (IFNgamma) and tumor necrosis factor-alpha (TNFalpha) in response to a gp100 antigen remained free of melanoma recurrence, whereas only two of six patients who showed discordant secretion of IFNgamma and TNFalpha did so.

CONCLUSION

Such multiparametric analysis of T cell antigen specificity and function provides a valuable tool with which to dissect the molecular underpinnings of immune responsiveness and how this information correlates with clinical outcome.

Macrophages and cytokines in the early defence against herpes simplex virus

Herpes simplex virus (HSV) type 1 and 2 are old viruses, with a history of evolution shared with humans. Thus, it is generally well-adapted viruses, infecting many of us without doing much harm, and with the capacity to hide in our neurons for life. In rare situations, however, the primary infection becomes generalized or involves the brain. Normally, the primary HSV infection is asymptomatic, and a crucial element in the early restriction of virus replication and thus avoidance of symptoms from the infection is the concerted action of different arms of the innate immune response. An early and light struggle inhibiting some HSV replication will spare the host from the real war against huge amounts of virus later in infection. As far as such a war will jeopardize the life of the host, it will be in both interests, including the virus, to settle the conflict amicably. Some important weapons of the unspecific defence and the early strikes and beginning battle during the first days of a HSV infection are discussed in this review. Generally, macrophages are orchestrating a multitude of anti-herpetic actions during the first hours of the attack. In a first wave of responses, cytokines, primarily type I interferons (IFN) and tumour necrosis factor are produced and exert a direct antiviral effect and activate the macrophages themselves. In the next wave, interleukin (IL)-12 together with the above and other cytokines induce production of IFN-gamma in mainly NK cells. Many positive feed-back mechanisms and synergistic interactions intensify these systems and give rise to heavy antiviral weapons such as reactive oxygen species and nitric oxide. This results in the generation of an alliance against the viral enemy. However, these heavy weapons have to be controlled to avoid too much harm to the host. By IL-4 and others, these reactions are hampered, but they are still allowed in foci of HSV replication, thus focusing the activity to only relevant sites. So, no hero does it alone. Rather, an alliance of cytokines, macrophages and other cells seems to play a central role. Implications of this for future treatment modalities are shortly considered.