How interferon-γ keeps autoimmune diseases in check

Positive and negative regulation of T cell responses by fibroblastic reticular cells within paracortical regions of lymph nodes

Fibroblastic reticular cells (FRC) form the structural backbone of the T cell rich zones in secondary lymphoid organs (SLO), but also actively influence the adaptive immune response. They provide a guidance path for immigrating T lymphocytes and dendritic cells (DC) and are the main local source of the cytokines CCL19, CCL21, and IL-7, all of which are thought to positively regulate T cell homeostasis and T cell interactions with DC. Recently, FRC in lymph nodes (LN) were also described to negatively regulate T cell responses in two distinct ways. During homeostasis they express and present a range of peripheral tissue antigens, thereby participating in peripheral tolerance induction of self-reactive CD8⁺ T cells. During acute inflammation T cells responding to foreign antigens presented on DC very quickly release pro-inflammatory cytokines such as interferon γ. These cytokines are sensed by FRC which transiently produce nitric oxide (NO) gas dampening the proliferation of neighboring T cells in a non-cognate fashion. In summary, we propose a model in which FRC engage in a bidirectional crosstalk with both DC and T cells to increase the efficiency of the T cell response. However, during an acute response, FRC limit excessive expansion and inflammatory activity of antigen-specific T cells. This negative feedback loop may help to maintain tissue integrity and function during rapid organ growth.

The Ifng gene is essential for Vdr gene expression and vitamin D₃-mediated reduction of the pathogenic T cell burden in the central nervous system in experimental autoimmune encephalomyelitis, a multiple sclerosis model

Compelling evidence suggests that vitamin D3 insufficiency may contribute causally to multiple sclerosis (MS) risk. Experimental autoimmune encephalomyelitis (EAE) research firmly supports this hypothesis. Vitamin D3 supports 1,25-dihydroxyvitamin D3 (1,25-[OH]2D3) synthesis in the CNS, initiating biological processes that reduce pathogenic CD4+ T cell longevity. MS is prevalent in Sardinia despite high ambient UV irradiation, challenging the vitamin D-MS hypothesis. Sardinian MS patients frequently carry a low Ifng expresser allele, suggesting that inadequate IFN-γ may undermine vitamin D3-mediated inhibition of demyelinating disease. Testing this hypothesis, we found vitamin D3 failed to inhibit EAE in female Ifng knockout (GKO) mice, unlike wild-type mice. The two strains did not differ in Cyp27b1 and Cyp24a1 gene expression, implying equivalent vitamin D3 metabolism in the CNS. The 1,25-(OH)2D3 inhibited EAE in both strains, but 2-fold more 1,25-(OH)2D3 was needed in GKO mice, causing hypercalcemic toxicity. Unexpectedly, GKO mice had very low Vdr gene expression in the CNS. Injecting IFN-γ intracranially into adult mice did not increase Vdr gene expression. Correlating with low Vdr expression, GKO mice had more numerous pathogenic Th1 and Th17 cells in the CNS, and 1,25-(OH)2D3 reduced these cells in GKO and wild-type mice without altering Foxp3+ regulatory T cells. Thus, the Ifng gene was needed for CNS Vdr gene expression and vitamin D3-dependent mechanisms that inhibit EAE. Individuals with inadequate Ifng expression may have increased MS risk despite high ambient UV irradiation because of low Vdr gene expression and a high encephalitogenic T cell burden in the CNS.

IFN-γ production by allogeneic Foxp3+ regulatory T cells is essential for preventing experimental graft-versus-host disease

It is emerging that CD4+Foxp3+ regulatory T (Treg) cells can produce the proinflammatory cytokine IFN-γ when stimulated in a Th1 cytokine environment. In this study, we report that Foxp3+ Treg cells readily produced IFN-γ in vivo in a highly inflammatory model of graft-versus-host disease (GVHD) and during a Th1-dominated immune response to intracellular bacteria. Moreover, stimulation in vitro via TCR in the presence of IL-12 alone was sufficient to induce IFN-γ production by Treg cells in a dose-dependent manner. Transfer of donor Treg cells can prevent lethal GVHD; therefore, we used this model as a robust readout for in vivo Treg function. Interestingly, >50% of allogeneic donor, but not residual recipient Foxp3+ Treg cells produced IFN-γ after transplantation, suggesting that this cytokine production was alloantigen specific. These IFN-γ producers were stable Foxp3+ Treg cells because methylation analysis of the Foxp3 gene locus of transferred and reisolated Treg cells during GVHD showed a fully demethylated Treg-specific-demethylated region. Next, we addressed whether IFN-γ production was supporting or rather impairing the immunosuppressive function of Treg cells during GVHD. Blocking of IFN-γ with specific mAb completely abolished the beneficial effect of donor Treg cells. We could further show that only wild-type Treg cells, but not Treg cells from IFN-γ-deficient donor mice, prevented GVHD. This indicated that Treg cell-intrinsic IFN-γ production was required for their protective function. In conclusion, our data show that IFN-γ produced by Foxp3+ Treg cells has essential immune-regulatory functions that are required for prevention of experimental GVHD.

IFN-γ signaling to astrocytes protects from autoimmune mediated neurological disability

Demyelination and axonal degeneration are determinants of progressive neurological disability in patients with multiple sclerosis (MS). Cells resident within the central nervous system (CNS) are active participants in development, progression and subsequent control of autoimmune disease; however, their individual contributions are not well understood. Astrocytes, the most abundant CNS cell type, are highly sensitive to environmental cues and are implicated in both detrimental and protective outcomes during autoimmune demyelination. Experimental autoimmune encephalomyelitis (EAE) was induced in transgenic mice expressing signaling defective dominant-negative interferon gamma (IFN-γ) receptors on astrocytes to determine the influence of inflammation on astrocyte activity. Inhibition of IFN-γ signaling to astrocytes did not influence disease incidence, onset, initial progression of symptoms, blood brain barrier (BBB) integrity or the composition of the acute CNS inflammatory response. Nevertheless, increased demyelination at peak acute disease in the absence of IFN-γ signaling to astrocytes correlated with sustained clinical symptoms. Following peak disease, diminished clinical remission, increased mortality and sustained astrocyte activation within the gray matter demonstrate a critical role of IFN-γ signaling to astrocytes in neuroprotection. Diminished disease remission was associated with escalating demyelination, axonal degeneration and sustained inflammation. The CNS infiltrating leukocyte composition was not altered; however, decreased IL-10 and IL-27 correlated with sustained disease. These data indicate that astrocytes play a critical role in limiting CNS autoimmune disease dependent upon a neuroprotective signaling pathway mediated by engagement of IFN-γ receptors.

Effect of locally administered Syk siRNA on allergen-induced arthritis and asthma

New approaches for the treatment of inflammatory disorders such as rheumatic arthritis (RA) and inflammatory lung disease (asthma) are needed because a significant population of patients do not experience sustained relief with currently available therapies. The tyrosine kinase Syk plays a crucial role in inflammatory signaling pathways and has gained much attention as a potential target for treatment of inflammatory disorders. We have shown that our Syk siRNA injected directly into limb joints of arthritic mice, diminishes joint swelling and reduces levels of Syk kinase and inflammatory cytokines in joint tissue. Further, our Syk siRNA, administered via nasal instillation, inhibits recruitment of inflammatory cells to the bronchoalveolar fluid of allergen-sensitized mice. We propose that targeting Syk via localized application of Syk siRNA provides an opportunity for specific knockdown of Syk kinase with minimal potential for systemic effects.

IFN-γ protects from lethal IL-17 mediated viral encephalomyelitis independent of neutrophils

BACKGROUND

The interplay between IFN-γ, IL-17 and neutrophils during CNS inflammatory disease is complex due to cross-regulatory factors affecting both positive and negative feedback loops. These interactions have hindered the ability to distinguish the relative contributions of neutrophils, Th1 and Th17 cell-derived effector molecules from secondary mediators to tissue damage and morbidity.

METHODS

Encephalitis induced by a gliatropic murine coronavirus was used as a model to assess the direct contributions of neutrophils, IFN-γ and IL-17 to virus-induced mortality. CNS inflammatory conditions were selectively manipulated by adoptive transfer of virus-primed wild-type (WT) or IFN-γ deficient (GKO) memory CD4+ T cells into infected SCID mice, coupled with antibody-mediated neutrophil depletion and cytokine blockade.

RESULTS

Transfer of GKO memory CD4+ T cells into infected SCID mice induced rapid mortality compared to recipients of WT memory CD4+ T cells, despite similar virus control and demyelination. In contrast to recipients of WT CD4+ T cells, extensive neutrophil infiltration and IL-17 expression within the CNS in recipients of GKO CD4+ T cells provided a model to directly assess their contribution(s) to disease. Recipients of WT CD4+ T cells depleted of IFN-γ did not express IL-17 and were spared from mortality despite abundant CNS neutrophil infiltration, indicating that mortality was not mediated by excessive CNS neutrophil accumulation. By contrast, IL-17 depletion rescued recipients of GKO CD4+ T cells from rapid mortality without diminishing neutrophils or reducing GM-CSF, associated with pathogenic Th17 cells in CNS autoimmune models. Furthermore, co-transfer of WT and GKO CD4+ T cells prolonged survival in an IFN-γ dependent manner, although IL-17 transcription was not reduced.

CONCLUSIONS

These data demonstrate that IL-17 mediates detrimental clinical consequences in an IFN-γ-deprived environment, independent of extensive neutrophil accumulation or GM-CSF upregulation. The results also suggest that IFN-γ overrides the detrimental IL-17 effector responses via a mechanism downstream of transcriptional regulation.

A dried yeast fermentate prevents and reduces inflammation in two separate experimental immune models

Diverse and significant benefits against cold/flu symptoms and seasonal allergies have been observed with a dried fermentate (DF) derived from Saccharomyces cerevisiae (EpiCor) in multiple published randomized trials. To determine if DF may influence other immune conditions, two separate animal studies were conducted. Study 1 examined the ability of DF to prevent or reduce inflammation when given orally for 14 days to rats prior to receiving 1% carrageenan (localized inflammation model). DF significantly (P < 0.05) reduced swelling at all time points (1, 2, 3, 6, 12, and 24 hours) versus the control. Edema severity and PGE2 levels were reduced by approximately 50% and 25% (P < 0.05), respectively. Study 2 examined the ability of DF to treat established inflammation induced by type-2 collagen in mice over 4 weeks (autoimmune arthritis model). Significantly reduced arthritis scores, antibody response to type-2 collagen, and interferon-gamma levels were observed compared to controls (all parameters P < 0.05). DF favorably impacts multiple acute and potentially chronic immunologic inflammatory control mechanisms and should be further tested in clinical trials.

IFN-gamma signaling in the central nervous system controls the course of experimental autoimmune encephalomyelitis independently of the localization and composition of inflammatory foci

Background

Murine experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis, presents typically as ascending paralysis. However, in mice in which interferon-gamma (IFNγ) signaling is disrupted by genetic deletion, limb paralysis is accompanied by atypical deficits, including head tilt, postural imbalance, and circling, consistent with cerebellar/vestibular dysfunction. This was previously attributed to intense cerebellar and brainstem infiltration by peripheral immune cells and formation of neutrophil-rich foci within the CNS. However, the exact mechanism by which IFNγ signaling prohibits the development of vestibular deficits, and whether the distribution and composition of inflammatory foci within the CNS affects the course of atypical EAE remains elusive.

Methods

We induced EAE in IFNγ-/- mice and bone marrow chimeric mice in which IFNγR is not expressed in the CNS but is intact in the periphery (IFNγR^CNSKO) and vice versa (IFNγR^periKO). Blood-brain barrier permeability was determined by Evans blue intravenous administration at disease onset. Populations of immune cell subsets in the periphery and the CNS were quantified by flow cytometry. CNS tissues isolated at various time points after EAE induction, were analyzed by immunohistochemistry for composition of inflammatory foci and patterns of axonal degeneration.

Results

Incidence and severity of atypical EAE were more pronounced in IFNγR^CNSKO as compared to IFNγR^periKO mice. Contrary to what we anticipated, cerebella/brainstems of IFNγR^CNSKO mice were only minimally infiltrated, while the same areas of IFNγR^periKO mice were extensively populated by peripheral immune cells. Furthermore, the CNS of IFNγR^periKO mice was characterized by persistent neutrophil-rich foci as compared to IFNγR^CNSKO. Immunohistochemical analysis of the CNS of IFNγ-/- and IFNγR chimeric mice revealed that IFNγ protective actions are exerted through microglial STAT1.

Conclusions

Alterations in distribution and composition of CNS inflammatory foci are not sufficient for the onset of atypical EAE. IFNγ dictates the course of neuroinflammatory disorders mainly through actions exerted within the CNS. This study provides strong evidence that link microglial STAT1 inactivation to vestibular dysfunction.

Influence of Interferon-γ Deficiency in Immune Tolerance Induced by Male Islet Transplantation

Background

Traditionally, interferon-γ (IFN-γ) was regarded as a pro-inflammatory cytokine, however, recent reports suggested role of IFN-γ in immune tolerance. In our previous report, we could induce tolerance to male antigen (HY) just by male islet transplantation in wild type C57BL/6 mice without any immunological intervention. We tried to investigate the influence of IFN-γ deficiency on tolerance induction by male islet transplantation.

Methods

To examine the immunogenicity of male tissue in the absence of IFN-γ, we transplanted male IFN-γ knock-out (KO) skin to female IFN-γ KO mice. Next, we analyzed male IFN-γ KO islet to streptozotocin-induced diabetic female IFN-γ KO mice. And, we checked the functionality of grafted islet by graft removal and insulin staining.

Results

As our previous results in wild type C57BL/6 mice, female IFN-γ KO mice rejected male IFN-γ KO skin within 29 days, and did not reject male IFN-γ KO islet. The maintenance of normal blood glucose level was dependent on the presence of grafted male islet. And the male islet recipient did not reject 2nd challenge of male islet graft also.

Conclusion

Deficiency of IFN-γ does not have influence on the result of male skin graft and male islet transplantation. Conclusively, male islet transplantation induced T cell tolerance is not dependent on the presence of IFN-γ.

Collagen-induced arthritis as an animal model for rheumatoid arthritis: focus on interferon-γ

Rheumatoid arthritis (RA), an autoimmune disease causing inflammation, destruction, and deformity of the joints, affects around 1% of the world population. It is a systemic disease as patients exhibit extra-articular manifestations as well. Collagen-induced arthritis (CIA) in DBA/1 mice is one of the many animal models used to study possible pathogenic mechanisms of RA. It involves immunizing mice with collagen type II in complete Freund's adjuvant. Here we briefly review the general characteristics of RA and CIA and present an overview of data obtained by studying CIA in several gene knockout mice. In particular, detailed analysis of CIA in interferon-gamma (IFN-γ) receptor-deficient mice has pin-pointed IFN-γ as an important cytokine in the pathogenesis and has exposed new functions of IFN-γ in immunological processes. Pilot trials with exogenous IFN-γ in RA have been indicative of a beneficial effect. That improvement of the disease symptoms by IFN-γ treatment was not spectacular may be explained by the fact that RA is a heterogeneous disease in which the severity of the autoimmune disease is strongly determined by environmental factors.

IFN-γ, IL-21, and IL-10 co-expression in evolving autoimmune vitiligo lesions of Smyth line chickens

The Smyth line (SL) of chicken is an excellent animal model for human autoimmune vitiligo. In SL vitiligo (SLV), postnatal loss of melanocytes in feathers appears to be due to cell-mediated immunity. In this study, leukocyte infiltration and associated expression (RNA) of immune function-related cytokines in growing feathers were investigated throughout SLV development and progression. Both leukocyte infiltration and cytokine expression levels started to increase near visible SLV onset (early SLV), reached peak levels during active SLV, and decreased to near pre-vitiligo levels after complete loss of melanocytes. Specifically, significant increases were noticed in relative proportions of T cells, B cells, and major histocompatibility complex (MHC) II-expressing cells during active SLV. Levels of T-cell infiltration were higher than those of B cells, with more CD8+ than CD4+ cells throughout SLV. Elevated leukocyte infiltration in early and active SLV was accompanied by increased levels of cytokine expression, especially in IFN-γ, IL-10, and IL-21. Low expression of IL-4 and IL-17 did not suggest important roles of Th2 and Th17 cells in SLV pathogenesis. Taken together, SLV appears to be a Th1-polarized autoimmune disease, whereby IFN-γ expression is strongly associated with parallel increases in IL-10 and IL-21, particularly during early and active stages of SLV.

Overlapping, additive and counterregulatory effects of type II and I interferons on myeloid dendritic cell functions

Dendritic cells (DCs) are central player in immunity by bridging the innate and adaptive arms of the immune system (IS). Interferons (IFNs) are one of the most important factors that regulate both innate and adaptive immunity too. Thus, the understanding of how type II and I IFNs modulate the immune-regulatory properties of DCs is a central issue in immunology. In this paper, we will address this point in the light of the most recent literature, also highlighting the controversial data reported in the field. According to the wide literature available, type II as well as type I IFNs appear, at the same time, to collaborate, to induce additive effects or overlapping functions, as well as to counterregulate each one's effects on DC biology and, in general, the immune response. The knowledge of these effects has important therapeutic implications in the treatment of infectious/autoimmune diseases and cancer and indicates strategies for using IFNs as vaccine adjuvants and in DC-based immune therapeutic approaches.

Inflammatory cytokines in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown origin affecting virtually all organ systems. Beyond genetic and environmental factors, cytokine imbalances contribute to immune dysfunction, trigger inflammation, and induce organ damage. The key cytokine that is involved in SLE pathogenesis is interferon alpha. Interferon secretion is induced by immune complexes and leads to upregulation of several inflammatory proteins, which account for the so-called IFN signature that can be found in the majority of SLE PBMCs. Additionally IL-6 and IFN-y as well as T-cell-derived cytokines like IL-17, IL-21, and IL-2 are dysregulated in SLE. The latter induce a T-cell phenotype that is characterized by enhanced B-cell help and enhanced secretion of proinflammatory cytokines but reduced induction of suppressive T cells and activation-induced cell death. This paper will focus on these cytokines and highlights pathophysiological approaches and therapeutic potential.

Oral administration of a probiotic Lactobacillus modulates cytokine production and TLR expression improving the immune response against Salmonella enterica serovar Typhimurium infection in mice

Background

Diarrheal infections caused by Salmonella, are one of the major causes of childhood morbidity and mortality in developing countries. Salmonella causes various diseases that range from mild gastroenteritis to enteric fever, depending on the serovar involved, infective dose, species, age and immune status of the host. Probiotics are proposed as an attractive alternative possibility in the prevention against this pathogen infection. Previously we demonstrated that continuous Lactobacillus casei CRL 431 administration to BALB/c mice before and after challenge with Salmonella enterica serovar Typhimurium (S. Typhimurium) decreased the severity of Salmonella infection. The aim of the present work was to deep into the knowledge about how this probiotic bacterium exerts its effect, by assessing its impact on the expression and secretion of pro-inflammatory (TNFα, IFNγ) and anti-inflammatory (IL-10) cytokines in the inductor and effector sites of the gut immune response, and analyzing toll-like receptor (TLR2, TLR4, TLR5 and TLR9) expressions in both healthy and infected mice.

Results

Probiotic administration to healthy mice increased the expression of TLR2, TLR4 and TLR9 and improved the production and secretion of TNFα, IFNγ and IL-10 in the inductor sites of the gut immune response (Peyer's patches). Post infection, the continuous probiotic administration, before and after Salmonella challenge, protected the host by modulating the inflammatory response, mainly in the immune effector site of the gut, decreasing TNFα and increasing IFNγ, IL-6 and IL-10 production in the lamina propria of the small intestine.

Conclusions

The oral administration of L. casei CRL 431 induces variations in the cytokine profile and in the TLRs expression previous and also after the challenge with S. Typhimurium. These changes show some of the immune mechanisms implicated in the protective effect of this probiotic strain against S. Typhimurium, providing an alternative way to reduce the severity of the infection.

TNFRp55 modulates IL-6 and nitric oxide responses following Yersinia lipopolysaccharide stimulation in peritoneal macrophages

While cytokines are major regulators of macrophage activation following host-pathogen interactions, they also act to limit inflammation to avoid tissue damage. In previous studies we reported the development of progressive Yersinia enterocolitica-induced reactive arthritis (ReA) in mice lacking the tumor necrosis factor receptor p55 (TNFRp55). In this work, we analyzed the response of TNFRp55⁻/⁻ macrophages to Y. enterocolitica antigens. We found higher concentration of nitric oxide (NO) in TNFRp55⁻/⁻ compared to wild-type macrophages in response to heat-killed Yersinia (HKY) and Yersinia outer membranes (OM). Moreover, Toll-like receptor (TLR)4 expression was increased in OM-stimulated TNFRp55⁻/⁻ versus wild-type (WT) macrophages. Accordingly, NO production was inhibited in TLR4-deficient macrophages following stimulation with OM, suggesting that LPS may function as a major OM component implicated in these responses. Thus, augmented NO production together with enhanced expression of inducible nitric oxide synthase (iNOS) and higher IL-6 production, may provide a pro-inflammatory setting in Yersinia LPS-stimulated TNFRp55⁻/⁻ macrophages. Augmented synthesis of NO and IL-6 was prevented by treatment with Polymyxin B, or by exposure to a specific NF-κB p65 oligonucleotide antisense, indicating the involvement of TLR4-mediated NF-κB activation in the unleashed pro-inflammatory response triggered by TNFRp55 deficiency. Thus, TNFRp55 modulates macrophage functions in response to Yersinia LPS stimulation through mechanisms involving NO, IL-6 and NF-κB pathways, suggesting an essential regulatory role of TNF via TNFRp55 signaling.

The interactive effect of exercise and immunosuppressant cyclosporin A on immune function in mice

Cyclosporin A (CsA) is an effective immunosuppressive agent and exerts its actions by interfering with the activation of T cells. There is growing evidence that regular exercise improves immune function. However, the effects of exercise on immune functions in patients taking CsA are unclear. Here, we examine the interactive effects of CsA administration and regular exercise on immune function in mice. Forty-eight BALB/c mice were randomly assigned to one of six groups with eight mice per group: 0-Ex (no CsA/no exercise), 0 + Ex (no CsA + exercise), 10-Ex (10 mg kg(-1) day(-1) CsA/no exercise), 10 + Ex (10 mg kg(-1) day(-1) CsA + exercise), 20-Ex (20 mg kg(-1) day(-1) CsA/no exercise), and 20 + Ex (20 mg kg(-1) day(-1) CsA + exercise). The three exercise groups were trained for 8 weeks, three times a week, at approximately 75% maximum oxygen uptake (VO(2max)). Nitric oxide and interferon-gamma secretions by mitogen-activated macrophages and spleen cells, respectively, were higher in exercise groups than in non-exercise groups receiving the same doses of CsA. The results of this study indicate that regular exercise may enhance Type I helper T cell functions in mice receiving 10 or 20 mg kg(-1) day(-1) CsA. Our results demonstrate that moderate regular exercise modulates the immune function of CsA-treated mice. However, whether this exercise-induced immunomodulatory effect is beneficial or detrimental to CsA-treated patients needs to be clarified.

Ameliorated course of glucose-6-phosphate isomerase (G6PI)-induced arthritis in IFN-γ receptor knockout mice exposes an arthritis-promoting role of IFN-γ

The absence of IFN-γ signaling leads to an increased inflammatory response in many murine models of autoimmune diseases induced by a CFA-assisted immunization schedule. We investigated the role of endogenous IFN-γ in arthritis induced by immunization with glucose-6-phosphate isomerase (G6PI) in CFA in DBA/1 mice. Surprisingly, and in contrast to our previous findings in collagen-induced arthritis (CIA), G6PI-induced arthritis was found to be reduced in IFN-γ receptor-deficient (IFN-γR KO) mice, demonstrating a proinflammatory role for IFN-γ in this model. Milder disease in IFN-γR KO mice was associated with less vigorous innate and adaptive immune responses early (day 9) after immunization: less proliferation of myeloid cells in the spleen, less osteoclast formation, less G6PI-reactive Th cells (as measured by ex vivo stimulation and flow cytometry and by in vivo skin reactivity to G6PI) and lower G6PI-specific immunoglobulin serum levels. Surprisingly, on day 21, despite continued milder disease in IFN-γR KO mice, their Th cell responses were no longer diminished but augmented as compared to wild-type mice, and their numbers of immature myeloid splenocytes were also more increased. These data reveal that IFN-γ signaling is critical for the induction of the early immune responses which trigger G6PI-induced arthritis. The strikingly different clinical consequences of absent IFN-γ signaling in G6PI-induced arthritis compared with the very similarly induced CIA emphasize that the role of a single cytokine in experimentally induced arthritis depends critically on the very nature of the inciting (auto)antigen and in particular on the kinetics of the disease manifestation elicited by the antigen.

Immuno-modulatory Effect of IFN-gamma in AMD and its Role as a Possible Target for Therapy

Age-related macular degeneration (AMD) is a neurodegenerative disease characterized by retinal cell atrophy, and/or choroidal neovascularization in the macula and constitutes the most common cause of blindness among the elderly in industrialized countries. The management of AMD is constrained by our insufficient knowledge of its underlying mechanisms. Recent studies point towards an emerging involvement of interferon-gamma (IFN-γ), a soluble cytokine associated with innate and adaptive immunity. IFN-γ promotes proinflammatory responses by activating proinflammatory cytokines and chemokines, thereby recruiting immune cells such as macrophages and T cells. On the other hand, IFN-γ modulates inflammatory response by upregulating anti-inflammatory factors or inhibiting development of immune cells related to autoimmune response. The complex role of IFN-γ in AMD pathogenesis is intriguing and worth further investigation in terms of therapeutic development.

The role of cytokines in Guillain-Barré syndrome

Cytokines play an important role in the pathogenesis of autoimmune diseases including Guillain-Barré syndrome (GBS) and its animal model experimental autoimmune neuritis (EAN). In this article, we reviewed the current knowledge of the role of cytokines such as TNF-α, IFN-γ, IL-1β, IL-6, IL-12, IL-18, IL-23, IL-17, IL-10, IL-4 and chemokines in GBS and EAN as unraveled by studies both in the clinic and the laboratory. However, these studies occasionally yield conflicting results, highlighting the complex role that cytokines play in the disease process. Efforts to modulate cytokine function in GBS and other autoimmune disease have shown efficiency indicating that cytokines are important therapeutic targets.

Effector and regulatory T-cell subsets in autoimmunity and tissue inflammation

Many autoimmune diseases are driven by self-reactive T helper cells. Until recently, organ-specific autoimmune diseases were primarily associated with Th1 cells but not Th2 cells. However, the discovery of a number of new effector T-cell subsets, like Th17 and Th9 cells, and regulatory T cells, like Tregs and Tr1 cells, has changed the way we view and understand autoimmunity at cellular and molecular levels. In recent years, IL-17-producing Th17 cells have emerged as major players in autoimmunity. The complicated relationship between Th1 and Th17 cells, as well as the intricate balance between Tregs and Th17 cells, provides a basis for understanding the immunological mechanisms that induce and regulate autoimmunity. Here, we give an overview of the interplay between different effector T-cell subsets and regulatory T-cell subsets, and how they contribute to the development of autoimmunity and tissue inflammation.

Mechanisms of IFNγ regulation of autoimmune myocarditis

A protective effect of interferon-gamma (IFNγ) has been described in a number of models of autoimmune disease, including experimental autoimmune myocarditis (EAM). Some reports have suggested that regulation of apoptosis in autoreactive lymphocytes mediate these protective functions. We examined the potential of IFNγ to regulate apoptotic mechanisms in detail, both in vitro and in vivo in EAM. We observed multiple apoptotic defects in caspase activity, and the expression of TNF superfamily members on CD4(+) T cells. In addition, we observed selective defects in CD4(+) T cell activation in response to antigenic stimulation. These activation and apoptotic defects were CD4(+) cell autonomous, independent of the genotype of APCs. Inhibition of nitric oxide production in vivo did not reproduce the severe form of EAM of IFNγ-deficient mice, indicating that this pathway does not mediate the protective effect of IFNγ. Crosswise adoptive transfer of wild type, IFNγ(-/-), and IFNγR(-/-)EAM demonstrated that IFNγ signaling was critical in CD4(+) cells, but that non-CD4(+) sources of IFNγ production were also involved in the control of disease. Together, these data indicate multiple mechanisms of autonomous and non-autonomous CD4(+) T cell regulation mediated by IFNγ in the control of autoimmune heart disease.

Association of CCR2-CCR5 haplotypes and CCL3L1 copy number with Kawasaki Disease, coronary artery lesions, and IVIG responses in Japanese children

Background

The etiology of Kawasaki Disease (KD) is enigmatic, although an infectious cause is suspected. Polymorphisms in CC chemokine receptor 5 (CCR5) and/or its potent ligand CCL3L1 influence KD susceptibility in US, European and Korean populations. However, the influence of these variations on KD susceptibility, coronary artery lesions (CAL) and response to intravenous immunoglobulin (IVIG) in Japanese children, who have the highest incidence of KD, is unknown.

Methodology/Principal Findings

We used unconditional logistic regression analyses to determine the associations of the copy number of the CCL3L1 gene-containing duplication and CCR2-CCR5 haplotypes in 133 Japanese KD cases [33 with CAL and 25 with resistance to IVIG] and 312 Japanese controls without a history of KD. We observed that the deviation from the population average of four CCL3L1 copies (i.e., < or > four copies) was associated with an increased risk of KD and IVIG resistance (adjusted odds ratio (OR)  = 2.25, p = 0.004 and OR = 6.26, p = 0.089, respectively). Heterozygosity for the CCR5 HHF*2 haplotype was associated with a reduced risk of both IVIG resistance (OR = 0.21, p = 0.026) and CAL development (OR = 0.44, p = 0.071).

Conclusions/Significance

The CCL3L1-CCR5 axis may play an important role in KD pathogenesis. In addition to clinical and laboratory parameters, genetic markers may also predict risk of CAL and resistance to IVIG.

Regulation of interleukin-1beta by interferon-gamma is species specific, limited by suppressor of cytokine signalling 1 and influences interleukin-17 production

Reports describing the effect of interferon-gamma (IFNgamma) on interleukin-1beta (IL-1beta) production are conflicting. We resolve this controversy by showing that IFNgamma potentiates IL-1beta release from human cells, but transiently inhibits the production of IL-1beta from mouse cells. Release from this inhibition is dependent on suppressor of cytokine signalling 1. IL-1beta and Th17 cells are pathogenic in mouse models for autoimmune disease, which use Mycobacterium tuberculosis (MTB), in which IFNgamma and IFNbeta are anti-inflammatory. We observed that these cytokines suppress IL-1beta production in response to MTB, resulting in a reduced number of IL-17-producing cells. In human cells, IFNgamma increased IL-1beta production, and this might explain why IFNgamma is detrimental for multiple sclerosis. In mice, IFNgamma decreased IL-1beta and subsequently IL-17, indicating that the adaptive immune response can provide a systemic, but transient, signal to limit inflammation.

Indoleamine 2,3-dioxygenase in human hematopoietic stem cell transplantation

In recent years tryptophan metabolism and its rate limiting enzyme indoleamine 2,3-dioxygenase (IDO) have attracted increasing attention for their potential to modulate immune responses including the regulation of transplantation tolerance. The focus of this review is to discuss some features of IDO activity which particularly relate to hematopoietic stem cell transplantation (HSCT). HSCT invariably involves the establishment of some degree of a donor-derived immune system in the recipient. Thus, the outstanding feature of tolerance in HSCT is that in this type of transplantation it is not rejection, which causes the most severe problems to HSCT recipients, but the reverse, graft-versus-host (GvH) directed immune responses. We will discuss the peculiar role of IDO activity and accelerated tryptophan metabolism at the interface between immune activation and immune suppression and delineate from theoretical and experimental evidence the potential significance of IDO in mediating tolerance in HSCT. Finally, we will examine therapeutic options for exploitation of IDO activity in the generation of allo-antigen-specific tolerance, i.e. avoiding allo-reactivity while maintaining immunocompetence, in HSCT.

Th1 and Th17 cells: adversaries and collaborators

Autoreactive effector CD4+ T cells have been associated with the pathogenesis of autoimmune disorders. Early studies implicated the interferon (IFN)-gamma-producing T helper (Th)1 subset of CD4+ cells as the causal agents in the pathogenesis of autoimmunity. However, further studies have suggested a more complex story. In models thought to be driven by Th1 cells, mice lacking the hallmark Th1 cytokine IFN-gamma were not protected but tended to have enhanced susceptibility to disease. Identification of the IL-17-producing CD4+ effector cell lineage (Th17) has helped shed light on this issue. Th17 effector cells are induced in parallel to Th1, and, like Th1, polarized Th17 cells have the capacity to cause inflammation and autoimmune disease. This, together with the finding that deficiency of the Th17-related cytokine IL-23 but not the Th1-related cytokine IL-12 causes resistance, led to the notion that Th17 cells are the chief contributors to autoimmune tissue inflammation. Nevertheless, mice lacking IL-17 are not protected from disease and display elevated numbers of IFN-gamma-producing CD4+ T cells, and, in some cases, lack of IFN-gamma does confer resistance. Recent studies report overlapping as well as differential roles of these cells in tissue inflammation, which suggests the existence of a more complex relationship between these two effector T-cell subsets than has hitherto been suspected. This review will attempt to bring together current information regarding interaction, balance, and collaborative potential between the Th1 and Th17 effector lineages.

Discrepancy between the in vitro and in vivo effects of murine mesenchymal stem cells on T-cell proliferation and collagen-induced arthritis

INTRODUCTION

The goal of this study is to analyze the potential immunosuppressive properties of mesenchymal stem cells (MSC) on T cell proliferation and in collagen-induced arthritis (CIA). An additional aim is to investigate the role of interferon-gamma (IFN-gamma) in these processes.

METHODS

MSC were isolated from bone marrow of DBA/1 wild type and IFN-gamma receptor knock-out (IFN-gammaR KO) mice and expanded in vitro. Proliferation of anti-CD3-stimulated CD4+ T cells in the presence or absence of MSC was evaluated by thymidine incorporation. CIA was induced in DBA/1 mice and animals were treated with MSC by intravenous or intraperitoneal injections of wild type or IFN-gammaR KO MSC.

RESULTS

Purity of enriched MSC cultures was evaluated by flow cytometry and their ability to differentiate into osteoblasts and adipocytes. In vitro, wild type MSC dose-dependently suppressed anti-CD3-induced T cell proliferation whereas IFN-gammaR KO MSC had a significantly lower inhibitory potential. A role for inducible nitric oxide (iNOS), programmed death ligand-1 (PD-L1) and prostaglandin E2 (PGE2), but not indoleamine 2,3-dioxigenase (IDO), in the T cell inhibition was demonstrated. In vivo, neither wild type nor IFN-gammaR KO MSC were able to reduce the severity of CIA or the humoral or cellular immune response toward collagen type II.

CONCLUSIONS

Whereas MSC inhibit anti-CD3-induced proliferation of T cells in vitro, an effect partially mediated by IFN-gamma, MSC do not influence in vivo T cell proliferation nor the disease course of CIA. Thus there is a clear discrepancy between the in vitro and in vivo effects of MSC on T cell proliferation and CIA.

CXCR2-positive neutrophils are essential for cuprizone-induced demyelination: relevance to multiple sclerosis

Multiple sclerosis is an inflammatory demyelinating disorder of the CNS. Recent studies have suggested diverse mechanisms as underlying demyelination, including a subset of lesions induced by an interaction between metabolic insult to oligodendrocytes and inflammatory mediators. For mice of susceptible strains, cuprizone feeding results in oligodendrocyte cell loss and demyelination of the corpus callosum. Remyelination ensues and has been extensively studied. Cuprizone-induced demyelination remains incompletely characterized. We found that mice lacking the type 2 CXC chemokine receptor (CXCR2) were relatively resistant to cuprizone-induced demyelination and that circulating CXCR2-positive neutrophils were important for cuprizone-induced demyelination. Our findings support a two-hit process of cuprizone-induced demyelination, supporting the idea that multiple sclerosis pathogenesis features extensive oligodendrocyte cell loss. These data suggest that cuprizone-induced demyelination is useful for modeling certain aspects of multiple sclerosis pathogenesis.

Establishment of an IFN-gamma specific reporter cell line in fish

An interferon (IFN)-gamma responsive stable cell line RTG-3F7 has been developed for rainbow trout by modifying the RTG-2 cell line through transfection with a plasmid construct (pGL4.14[luc2/hygro]-PrTAP2) containing a promoter element from the IFN-gamma responsive gene TAP2 linked to a luciferase reporter gene and a hygromycin resistance gene. Following transfection single clones were selected in 96 well plates using hygromycin B, and those showing specific activation after rIFN-gamma stimulation were maintained. Five clones that showed the highest reporter activity to rIFN-gamma were incubated with different stimuli to examine specificity. No significant induction of luciferase was observed following exposure to recombinant type I IFN, LPS, PHA or poly I:C. The cell line was responsive to rIFN-gamma at concentrations between 150 pg and 20 ng ml(-1). Supernatants of primary cultures of head kidney leucocytes stimulated with PHA, known to induce IFN-gamma gene expression, were also used to assess the reporter activity of the stable cell line. A dose-dependent induction of the promoter activity was observed with these supernatants indicating the presence of IFN-gamma. These results indicate that the stable cell line RTG-3F7 is an excellent tool for monitoring the presence of trout IFN-gamma in biological samples, and in addition, enables the study of intracellular signalling pathways of IFNs, their receptor interactions, and other closely related signalling networks.

Mice with a selective impairment of IFN-gamma signaling in macrophage lineage cells demonstrate the critical role of IFN-gamma-activated macrophages for the control of protozoan parasitic infections in vivo

IFN-gamma has long been recognized as a cytokine with potent and varied effects in the immune response. Although its effects on specific cell types have been well studied in vitro, its in vivo effects are less clearly understood because of its diverse actions on many different cell types. Although control of multiple protozoan parasites is thought to depend critically on the direct action of IFN-gamma on macrophages, this premise has never been directly proven in vivo. To more directly examine the effects of IFN-gamma on cells of the macrophage lineage in vivo, we generated mice called the "macrophages insensitive to IFN-gamma" (MIIG) mice, which express a dominant negative mutant IFN-gamma receptor in CD68+ cells: monocytes, macrophages, dendritic cells, and mast cells. Macrophage lineage cells and mast cells from these mice are unable to respond to IFN-gamma, whereas other cells are able to produce and respond to this cytokine normally. When challenged in vitro, macrophages from MIIG mice were unable produce NO or kill Trypanosoma cruzi or Leishmania major after priming with IFN-gamma. Furthermore, MIIG mice demonstrated impaired parasite control and heightened mortality after T. cruzi, L. major, and Toxoplasma gondii infection, despite an appropriate IFN-gamma response. In contrast, MIIG mice displayed normal control of lymphocytic choriomeningitis virus, despite persistent insensitivity of macrophages to IFN-gamma. Thus, the MIIG mouse formally demonstrates for the first time in vivo, the specific importance of direct, IFN-gamma mediated activation of macrophages for controlling infection with multiple protozoan parasites.

IFN-gamma regulates the requirement for IL-17 in proteoglycan-induced arthritis

The contribution of the proinflammatory cytokines IFN-gamma and IL-17 to the pathogenesis of experimental arthritis is controversial. In proteoglycan (PG)-induced arthritis (PGIA), severe arthritis is dependent on the production of IFN-gamma, whereas IL-17 is dispensable. In collagen-induced arthritis and Ag-induced arthritis, although high levels of IFN-gamma are secreted, disease is exacerbated in IFN-gamma or IFN-gamma receptor-deficient mice due to the ability of IFN-gamma to suppress IL-17 expression. In the current study, we investigated the effect of IFN-gamma on the IL-17 response and its consequences in PGIA. In PG-immunized IFN-gamma(-/-) mice, despite reduction in arthritis, the PG-specific CD4(+) T cell IL-17 response was significantly increased. Elevated IL-17 contributed to development of arthritis, as disease in IFN-gamma/IL-17(-/-) was significantly reduced in comparison with either IFN-gamma(-/-) or IL-17(-/-) mice. A contribution of IFN-gamma and IL-17 to the development of arthritis was also identified in T-bet(-/-) mice. PG-specific CD4(+) T cells from T-bet(-/-) mice produced reduced IFN-gamma and elevated concentrations of IL-17. Both IFN-gamma and IL-17 contribute to arthritis, as T-bet(-/-) mice lacking IL-17 (T-bet/IL-17(-/-)) were resistant, whereas wild-type, T-bet(-/-), and IL-17(-/-) mice were susceptible to PGIA. T cell proliferation and autoantibody production did not correlate with development of disease; however, expression of cytokines and chemokines in joint tissues demonstrate that IFN-gamma and IL-17 cooperatively contribute to inflammation. These results demonstrate that both IFN-gamma and IL-17 have the potential to induce PGIA, but it is the strength of the IFN-gamma response that regulates the contribution of each of these Th effector cytokines to disease.

Transcriptional regulation of Foxp3 gene: multiple signal pathways on the road

Foxp3, forkhead/winged helix transcription factor 3, is a master transcription factor for the development and function of regulatory T cells. Foxp3 has been proved to be associated with immunoregulation, autoimmune diseases, infections, and tumor immune evasion/escape. Foxp3 regulates other critical gene transcriptions. However, the mechanism how the transcription of Foxp3 itself is regulated remains partly clear. In this article, we provided an overview of the current understanding of the transcriptional regulation of Foxp3 gene, including signaling pathways initiated by TCR, IL-2R/STAT pathway, TGF-beta/Smad pathway, PI3K/Akt/mTOR axis, Notch signal pathway, IFN/IRF and IFN/nitric oxide axis, and epigenetic mechanisms. Some therapeutic agents on Foxp3 regulation were also reviewed. Points for attention in further study of Foxp3 transcription regulation, such as the combinations/cross-talks, the bi-directional functions, and species specificity of these pathways, were discussed as well.

Cross-regulation of signaling pathways by interferon-gamma: implications for immune responses and autoimmune diseases

Interferon-gamma (IFN-gamma) is an important mediator of immunity and inflammation that utilizes the JAK-STAT signaling pathway to activate the STAT1 transcription factor. Many functions of IFN-gamma have been ascribed to direct STAT1-mediated induction of immune effector genes, but recently it has become clear that key IFN-gamma functions are mediated by cross-regulation of cellular responses to other cytokines and inflammatory factors. Here, we review mechanisms by which IFN-gamma and STAT1 regulate signaling by Toll-like receptors, inflammatory factors, tissue-destructive cytokines, anti-inflammatory cytokines, and cytokines that activate opposing STATs. These signaling mechanisms reveal insights about how IFN-gamma regulates macrophage activation, inflammation, tissue remodeling, and helper and regulatory T cell differentiation and how Th1 and Th17 cell responses are integrated in autoimmune diseases.

Endotoxin tolerance: new mechanisms, molecules and clinical significance

Prior exposure of innate immune cells like monocytes/macrophages to minute amounts of endotoxin cause them to become refractory to subsequent endotoxin challenge, a phenomenon called "endotoxin tolerance". Clinically, this state is associated with monocytes/macrophages in sepsis patients where they contribute to "immunosuppression" and mortality. The molecular mechanisms underlying endotoxin tolerance remain elusive. The recent appreciation of inflammation as a self-regulating process, the relative contribution of MyD88 versus TRIF signaling pathways in inducing activation or tolerance, plasticity of NF-kappaB function and the role of chromatin modification and microRNAs in LPS-induced gene reprogramming urges a re-evaluation of endotoxin tolerance. This review integrates these new findings into an up-to-date account of endotoxin tolerance, its molecular basis and clinical implications in different pathologies.

Donor reactive regulatory T cells

PURPOSE OF REVIEW

Donor reactive regulatory T cells (Treg) play an important role in tolerance induction and maintenance in experimental transplant models. In this review we focus on the formation of the donor reactive Treg pool and explore the potential of these cells for therapeutic application in clinical transplantation.

RECENT FINDINGS

Donor reactive Treg can arise by both conversion of alloreactive nonregulatory cells and expansion of naturally occurring Treg (nTreg) cross-reactive with donor alloantigen but the quantitative contribution of each of these pathways is at present unclear. However, the fact that donor reactive Treg can be driven both in vivo and ex vivo by alloantigen challenge of nonregulatory precursors is encouraging as it demonstrates that the functional potential of these cells for use in clinical transplantation will not be limited by fortuitous cross-reactivity between nTreg and donor alloantigens. Treg can be generated in vivo by transplantation or alloantigen challenge in combination with Treg-permissive immunosuppression, or ex vivo by phenotypic selection or by polyclonal or antigen-specific stimulation. A number of ex-vivo protocols exist for the enrichment of Treg in the laboratory and in many cases these cells have demonstrable function both in vitro and in relevant graft-versus-host disease (GVHD) or organ transplant models. The challenge now is to understand the clinical opportunities and limitations that these populations present.

SUMMARY

Combined with appropriate immunosuppression, Treg generated/expanded in vivo or ex vivo may hold the final key to operational tolerance in clinical setting.

Effector mechanisms of interleukin-17 in collagen-induced arthritis in the absence of interferon-gamma and counteraction by interferon-gamma

INTRODUCTION

Interleukin (IL)-17 is a pro-inflammatory cytokine in rheumatoid arthritis (RA) and collagen-induced arthritis (CIA). Since interferon (IFN)-gamma inhibits Th17 cell development, IFN-gamma receptor knockout (IFN-gammaR KO) mice develop CIA more readily. We took advantage of this model to analyse the mechanisms of action of IL-17 in arthritis. The role of IFN-gamma on the effector mechanisms of IL-17 in an in vitro system was also investigated.

METHODS

IFN-gammaR KO mice induced for CIA were treated with anti-IL-17 or control antibody. The collagen type II (CII)-specific humoral and cellular autoimmune responses, myelopoiesis, osteoclastogenesis, and systemic cytokine production were determined. Mouse embryo fibroblasts (MEF) were stimulated with IL-17, tumor necrosis factor (TNF)-alpha and the expression of cytokines and chemokines were determined.

RESULTS

A preventive anti-IL-17 antibody treatment inhibited CIA in IFNgammaR KO mice. In the joints of anti-IL-17-treated mice, neutrophil influx and bone destruction were absent. Treatment reduced the cellular autoimmune response as well as the splenic expansion of CD11b+ cells, and production of myelopoietic cytokines such as granulocyte macrophage colony-stimulating factor (GM-CSF) and IL-6. IL-17 and TNF-alpha synergistically induced granulocyte chemotactic protein-2 (GCP-2), IL-6 and receptor activator of NFkappaB ligand (RANKL) in MEF. This induction was profoundly inhibited by IFN-gamma in a STAT-1 (signal transducer and activator of transcription-1)-dependent way.

CONCLUSIONS

In the absence of IFN-gamma, IL-17 mediates its pro-inflammatory effects mainly through stimulatory effects on granulopoiesis, neutrophil infiltration and bone destruction. In vitro IFN-gamma profoundly inhibits the effector function of IL-17. Thus, aside from the well-known inhibition of the development of Th17 cells by IFN-gamma, this may be an additional mechanism through which IFN-gamma attenuates autoimmune diseases.

Eosinophil-derived IFN-gamma induces airway hyperresponsiveness and lung inflammation in the absence of lymphocytes

BACKGROUND

Eosinophils are key players in T(H)2-driven pathologies, such as allergic lung inflammation. After IL-5- and eotaxin-mediated tissue recruitment, they release several cytotoxic and inflammatory mediators. However, their exact contribution to asthma remains controversial. Indeed, in human subjects anti-IL-5 treatment inhibits eosinophilia but not antigen-induced airway hyperresponsiveness (AHR). Likewise, lung fibrosis is abrogated in 2 strains of eosinophil-deficient mice, whereas AHR is inhibited in only one of them. Finally, eosinophils have been shown to attract T(H)2 lymphocytes at the inflammatory site.

OBJECTIVE

The ability of eosinophils to promote AHR and lung inflammation independently of lymphocytes was investigated.

METHODS

Adoptive transfers of resting or activated eosinophils from IL-5 transgenic mice were performed into naive BALB/c mice, mice with severe combined immunodeficiency, and IFN-gamma-deficient BALB/c recipients.

RESULTS

Adoptively transferred eosinophils induced lung inflammation, fibrosis, collagen deposition, and AHR not only in BALB/c mice but also in recipient mice with severe combined immunodeficiency. Surprisingly, IFN-gamma expression was increased in lungs from eosinophil-transferred animals. Furthermore, IFN-gamma neutralization in recipients partially inhibited eosinophil-induced AHR. Moreover, IFN-gamma-deficient eosinophils or eosinophils treated with a blocking anti-IFN-gamma receptor antibody failed to induce AHR in IFN-gamma-deficient recipients. Finally, in vitro and at low concentrations, IFN-gamma increased eosinophil peroxidase release, potentiated chemotaxis, and prolonged survival, suggesting the existence of an autocrine mechanism.

CONCLUSIONS

These results support the important and previously unsuspected contribution of eosinophils to lung inflammation independently of lymphocytes through production of IFN-gamma, the prototypical T(H)1 cytokine.

Interferon-gamma treatment accelerates and aggravates autoimmune pancreatitis in the MRL/Mp-mouse

BACKGROUND

T helper 1 cell-released pro-inflammatory cytokines have been implicated in the pathogenesis of autoimmune pancreatitis (AIP), but the experimental database is small. Here, we have directly tested the effects of interferon-gamma (IFN-gamma) by applying it to AIP-prone MRL/Mp mice.

METHODS

MRL/Mp-mice were treated for 4 weeks with IFN-gamma. Severity of AIP was assessed by histopathology, laboratory findings and gene expression analysis.

RESULTS

Using a histopathological score from 0 (healthy pancreas) to 4 (severe AIP), we found that IFN-gamma treatment strongly increased severity of pancreatic lesions. IFN-gamma also caused pancreatic accumulation of CD4-, CD8-, C11b- and CD138-positive cells, and enhanced pancreatic mRNA expression of interleukin (IL)-1 beta, transforming growth factor-beta and IFN-gamma itself. In the serum of IFN-gamma-treated mice, higher lipase activities but normal glucose levels were observed.

DISCUSSION

IFN-gamma accelerates and aggravates AIP in MRL/Mp mice. IFN-gamma-enhanced AIP of MRL/Mp mice may serve to study pathophysiology, and to test diagnostic/therapeutic approaches.

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.

Interferon-gamma: a historical perspective

This article reviews the main lines of thinking and exploration that have led to our current conception of the role of IFN-gamma in immune defense and autoimmunity. In 1965 the first report appeared describing production of an interferon-like virus inhibitor in cultured human leukocytes following exposure to the mitogen phytohemagglutinin. In the early 1970s the active principle became recognized as being distinct from classical virus-induced interferons, leading to its designation as immune interferon or Type II interferon, and eventually IFN-gamma. Up to that point interest in the factor had come almost exclusively from virologists, in particular those among them who were believers in interferon. Evidence first coming forward in the 1980s that IFN-gamma is indistinguishable from macrophage-activating factor (MAF), then a prototype lymphokine, was the signal for immunologists at large to become interested. Today IFN-gamma ranks among the most important endogenous regulators of immune responses.