Preferential induction of IL-10 in APC correlates with a switch from Th1 to Th2 response following infection with a low pathogenic variant of Theiler's virus

Radiation-Detoxified Form of Endotoxin Effectively Activates Th1 Responses and Attenuates Ragweed-Induced Th2-Type Airway Inflammation in Mice

Urbanization with reduced microbial exposure is associated with an increased burden of asthma and atopic symptoms. Conversely, environmental exposure to endotoxins in childhood can protect against the development of allergies. Our study aimed to investigate whether the renaturation of the indoor environment with aerosolized radiation-detoxified lipopolysaccharide (RD-LPS) has a preventative effect against the development of ragweed-induced Th2-type airway inflammation. To explore this, cages of six-week-old BALB/c mice were treated daily with aerosolized native LPS (N-LPS) or RD-LPS. After a 10-week treatment period, mice were sensitized and challenged with ragweed pollen extract, and inflammatory cell infiltration into the airways was observed. As dendritic cells (DCs) play a crucial role in the polarization of T-cell responses, in our in vitro experiments, the effects of N-LPS and RD-LPS were compared on human monocyte-derived DCs (moDCs). Mice in RD-LPS-rich milieu developed significantly less allergic airway inflammation than mice in N-LPS-rich or common environments. The results of our in vitro experiments demonstrate that RD-LPS-exposed moDCs have a higher Th1-polarizing capacity than moDCs exposed to N-LPS. Consequently, we suppose that the aerosolized, non-toxic RD-LPS applied in early life for the renaturation of urban indoors may be suitable for the prevention of Th2-mediated allergies in childhood.

Alteration of Immunoregulatory Patterns and Survival Advantage of Key Cell Types in Food Allergic Children

All allergic responses to food indicate the failure of immunological tolerance, but it is unclear why cow's milk and egg (CME) allergies resolve more readily than reactivity to peanuts (PN). We sought to identify differences between PN and CME allergies through constitutive immune status and responses to cognate and non-cognate food antigens. Children with confirmed allergy to CME (n = 6) and PN (n = 18) and non-allergic (NA) (n = 8) controls were studied. Constitutive secretion of cytokines was tested in plasma and unstimulated mononuclear cell (PBMNC) cultures. Blood dendritic cell (DC) subsets were analyzed alongside changes in phenotypes and soluble molecules in allergen-stimulated MNC cultures with or without cytokine neutralization. We observed that in allergic children, constitutively high plasma levels IL-1β, IL-2, IL-4, IL-5 and IL-10 but less IL-12p70 than in non-allergic children was accompanied by the spontaneous secretion of sCD23, IL-1β, IL-2, IL-4, IL-5, IL-10, IL-12p70, IFN-γ and TNF-α in MNC cultures. Furthermore, blood DC subset counts differed in food allergy. Antigen-presenting cell phenotypic abnormalities were accompanied by higher B and T cell percentages with more Bcl-2 within CD69+ subsets. Cells were generally refractory to antigenic stimulation in vitro, but IL-4 neutralization led to CD152 downregulation by CD4+ T cells from PN allergic children responding to PN allergens. Canonical discriminant analyses segregated non-allergic and allergic children by their cytokine secretion patterns, revealing differences and areas of overlap between PN and CME allergies. Despite an absence of recent allergen exposure, indication of in vivo activation, in vitro responses independent of challenging antigen and the presence of unusual costimulatory molecules suggest dysregulated immunity in food allergy. Most importantly, higher Bcl-2 content within key effector cells implies survival advantage with the potential to mount abnormal responses that may give rise to the manifestations of allergy. Here, we put forward the hypothesis that the lack of apoptosis of key immune cell types might be central to the development of food allergic reactions.

Excessive Innate Immunity Steers Pathogenic Adaptive Immunity in the Development of Theiler's Virus-Induced Demyelinating Disease

Several virus-induced models were used to study the underlying mechanisms of multiple sclerosis (MS). The infection of susceptible mice with Theiler’s murine encephalomyelitis virus (TMEV) establishes persistent viral infections and induces chronic inflammatory demyelinating disease. In this review, the innate and adaptive immune responses to TMEV are discussed to better understand the pathogenic mechanisms of viral infections. Professional (dendritic cells (DCs), macrophages, and B cells) and non-professional (microglia, astrocytes, and oligodendrocytes) antigen-presenting cells (APCs) are the major cell populations permissive to viral infection and involved in cytokine production. The levels of viral loads and cytokine production in the APCs correspond to the degrees of susceptibility of the mice to the TMEV-induced demyelinating diseases. TMEV infection leads to the activation of cytokine production via TLRs and MDA-5 coupled with NF-κB activation, which is required for TMEV replication. These activation signals further amplify the cytokine production and viral loads, promote the differentiation of pathogenic Th17 responses, and prevent cellular apoptosis, enabling viral persistence. Among the many chemokines and cytokines induced after viral infection, IFN α/β plays an essential role in the downstream expression of costimulatory molecules in APCs. The excessive levels of cytokine production after viral infection facilitate the pathogenesis of TMEV-induced demyelinating disease. In particular, IL-6 and IL-1β play critical roles in the development of pathogenic Th17 responses to viral antigens and autoantigens. These cytokines, together with TLR2, may preferentially generate deficient FoxP3⁺CD25^- regulatory cells converting to Th17. These cytokines also inhibit the apoptosis of TMEV-infected cells and cytolytic function of CD8⁺ T lymphocytes (CTLs) and prolong the survival of B cells reactive to viral and self-antigens, which preferentially stimulate Th17 responses.

Multivariate analysis of cytokine profiles in pregnancy complications

PROBLEM

The immunoregulation to tolerate the semiallogeneic fetus during pregnancy includes a harmonious dynamic balance between anti- and pro-inflammatory cytokines. Several earlier studies reported significantly different levels and/or ratios of several cytokines in complicated pregnancy as compared to normal pregnancy. However, as cytokines operate in networks with potentially complex interactions, it is also interesting to compare groups with multi-cytokine data sets, with multivariate analysis. Such analysis will further examine how great the differences are, and which cytokines are more different than others.

METHODS

Various multivariate statistical tools, such as Cramer test, classification and regression trees, partial least squares regression figures, 2-dimensional Kolmogorov-Smirmov test, principal component analysis and gap statistic, were used to compare cytokine data of normal vs anomalous groups of different pregnancy complications.

RESULTS

Multivariate analysis assisted in examining if the groups were different, how strongly they differed, in what ways they differed and further reported evidence for subgroups in 1 group (pregnancy-induced hypertension), possibly indicating multiple causes for the complication.

CONCLUSION

This work contributes to a better understanding of cytokines interaction and may have important implications on targeting cytokine balance modulation or design of future medications or interventions that best direct management or prevention from an immunological approach.

Roles of regulatory T cells and IL-10 in virus-induced demyelination

Neurotropic viruses are important causes of morbidity and mortality in human populations. Some of these viruses preferentially infect oligodendrocytes in the white matter, causing either direct lysis of infected cells, or more commonly myelin damage as a consequence of the host immune response to the virus. Virus-induced demyelination has similarities to the human disease multiple sclerosis. To study this disease process in experimental animals, mice are infected, most commonly, with neurotropic strains of mouse hepatitis virus, a coronavirus or Theiler's murine encephalomyelitis, a picornavirus. While the diseases caused by these two viruses differ in some aspects, in both cases demyelination is a major consequence of the infection. As in autoimmune disease, therapeutic interventions that diminish an overactive immune response would be useful. However, unlike autoimmune disease, complete suppression would result in unchecked virus replication, generally leading to more severe disease. Here we discuss two approaches that dampen but do not fully suppress the host immune response. Regulatory T cells, especially those that are specific for antigens recognized by pathogenic T cells, and IL-10 are two anti-inflammatory/pro-resolution factors that demonstrate efficacy in experimental models of virus-induced demyelination and may be useful in patients infected with viruses that cause demyelination.

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MHV and TMEV are common causes of virus-induced demyelination in mice

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Virus-induced demyelination is often host cell-mediated.

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Virus-specific Treg dampen pathogenic T cells responding to cognate epitope

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IL-10 expressed by Tregs and Tr1 cells dampens pathogenic T cell responses

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Tregs and IL-10 suppress pathogenic T cells without broad immunosuppression

Viral mouse models of multiple sclerosis and epilepsy: Marked differences in neuropathogenesis following infection with two naturally occurring variants of Theiler's virus BeAn strain

Following intracerebral inoculation, the BeAn 8386 strain of Theiler's virus causes persistent infection and inflammatory demyelinating encephalomyelitis in the spinal cord of T-cell defective SJL/J mice, which is widely used as a model of multiple sclerosis. In contrast, C57BL/6 (B6) mice clear the virus and develop inflammation and lesions in the hippocampus, associated with acute and chronic seizures, representing a novel model of viral encephalitis-induced epilepsy. Here we characterize the geno- and phenotype of two naturally occurring variants of BeAn (BeAn-1 and BeAn-2) that can be used to further understand the viral and host factors involved in the neuropathogenesis in B6 and SJL/J mice. Next generation sequencing disclosed 15 single nucleotide differences between BeAn-1 and BeAn-2, of which 4 are coding changes and 3 are in the 5'-UTR (5'-untranslated region). The relatively minor variations in the nucleotide sequence of the two BeAn substrains led to marked differences in neurovirulence. In SJL/J mice, inflammatory demyelination in the spinal cord and its clinical consequences were significantly more marked following infection with BeAn-1 than with BeAn-2. Both BeAn substrains caused lymphocyte infiltration and increase of MAC3-positive cells in the hippocampus, but hippocampal damage and seizures were only observed in B6 mice. Seizures occurred in one third of BeAn-2 infected B6 mice, but not in BeAn-1 infected B6 mice. By comparing individual mice by receiver operating characteristic (ROC) curve analysis, the severity of hippocampal neurodegeneration and amount of MAC3-positive microglia/macrophages discriminated seizing from non-seizing B6 mice, whereas T-lymphocyte brain infiltration was not found to be a crucial factor. These data add novel evidence to the view that differential outcome of infection may be not invariably linked to a distinct viral burden but to a finely tuned balance between antiviral immune responses that although essential for host resistance can also contribute to immunopathology.

Decidual soluble factors, through modulation of dendritic cells functions, determine the immune response patterns at the feto-maternal interface

Dendritic cells (DCs) can acquire immunogenic or tolerogenic properties depending on intrinsic and tissue environmental factors. We aimed to determine the immunomodulatory effects of decidual soluble factors from abortion- and non-abortion-prone mice on DC functions. The decidual cell supernatants (DS) were obtained from abortion-prone and non-abortion-prone mice. Splenic DCs were treated with DS and conalbumin (as an antigen) and injected into the palms of the mice. After five days, regional lymph node cells were collected and cultured in the presence and absence of conalbumin. The proliferation of lymphocyte cells, the frequency of regulatory T cells (Tregs), and the production of IL-4 and IFN-γ were measured by [(3)H]thymidine incorporation, flow cytometry, and ELISA respectively. Our results indicated that DS from both abortion- and non-abortion-prone mice decreased the ability of DCs to induce lymphocyte proliferation and IFN-γ production, while enhanced their capacity to induce Tregs compared with non-treated DCs. Another important finding was that the immunosuppressive effects of DS from abortion-prone mice on DCs for inducing proliferative responses, developing Tregs, and producing IFN-γ by primed lymphocytes was less than DS from non-abortion-prone mice. We also found that only DS from non-abortion-prone mice could enhance the capacity of DCs to induce IL-4 production by primed lymphocytes. It can be concluded that decidua-secreted factors, by altering DC functions, can determine the pattern of immune responses at the fetomaternal interface and, subsequently, pregnancy outcome.

Cocaine alters cytokine profiles in HIV-1-infected African American individuals in the DrexelMed HIV/AIDS genetic analysis cohort

BACKGROUND

This study evaluated the relationship between illicit drug use and HIV-1 disease severity in HIV-1-infected patients enrolled in the DREXELMED HIV/AIDS Genetic Analysis Cohort. Because cocaine is known to have immunomodulatory effects, the cytokine profiles of preferential nonusers, cocaine users, and multidrug users were analyzed to understand the effects of cocaine on cytokine modulation and HIV-1 disease severity.

METHODS

Patients within the cohort were assessed approximately every 6 months for HIV-1 clinical markers and for history of illicit drug, alcohol, and tobacco use. The Luminex human cytokine 30-plex panel was used for cytokine quantitation. Analysis was performed using a newly developed biostatistical model.

RESULTS

Substance abuse was common within the cohort. Using the drug screens at the time of each visit, the subjects in the cohort were categorized as preferential nonusers, cocaine users, or multidrug users. The overall health of the nonuser population was better than that of the cocaine users, with peak and current viral loads in nonusers substantially lower than those in cocaine and multidrug users. Among the 30 cytokines investigated, differential levels were established within the 3 populations. The T-helper 2 cytokines, interleukin-4 and -10, known to play a critical role during HIV-1 infection, were positively associated with increasing cocaine use. Clinical parameters such as latest viral load, CD4 T-cell counts, and CD4:CD8 ratio were also significantly associated with cocaine use, depending on the statistical model used.

CONCLUSIONS

Based on these assessments, cocaine use seems to be associated with more severe HIV-1 disease.

MicroRNA profiling of activated and tolerogenic human dendritic cells

Dendritic cells (DCs) belong to the immune system and are particularly studied for their potential to direct either an activated or tolerogenic immune response. The roles of microRNAs (miRNAs) in posttranscriptional gene expression regulation are being increasingly investigated. This study's aim is to evaluate the miRNAs' expression changes in prepared human immature (iDCs), activated (aDCs), and tolerogenic dendritic cells (tDCs). The dendritic cells were prepared using GM-CSF and IL-4 (iDC) and subsequently maturated by adding LPS and IFN-γ (aDC) or IL-10 and TGF-β (tDC). Surface markers, cytokine profiles, and miRNA profiles were evaluated in iDC, tDC, and aDC at 6 h and 24 h of maturation. We identified 4 miRNAs (miR-7, miR-9, miR-155 and miR-182), which were consistently overexpressed in aDC after 6 h and 24 h of maturation and 3 miRNAs (miR-17, miR-133b, and miR-203) and miR-23b cluster solely expressed in tDC. We found 5 miRNAs (miR-10a, miR-203, miR-210, miR-30a, and miR-449b) upregulated and 3 miRNAs downregulated (miR-134, miR-145, and miR-149) in both tDC and aDC. These results indicate that miRNAs are specifically modulated in human DC types. This work may contribute to identifying specific modulating miRNAs for aDC and tDC, which could in the future serve as therapeutic targets in the treatment of cancer and autoimmune diseases.

Theiler's murine encephalomyelitis virus induced phenotype switch of microglia in vitro

The present in vitro study aimed to define the involvement of astrocytes and microglia in the initial inflammatory response of Theiler's murine encephalomyelitis (TME), a virus-induced mouse model of multiple sclerosis, and whether intralesional microglia exert pro- (M1) or anti-inflammatory (M2) effects following TME virus (TMEV) infection. Therefore astrocytes and microglia were purified from neonatal murine brains and inoculated either with TMEV or mock-solution. Gene expression of IL-1, IL-2, IL-10, IL-12, TNF, TNF receptors (TNFR1, TNFR2), TGFβ1, IFNγ and transcription factors NF-κB (p50, p65) and AP-1 (c-jun, c-fos) were quantified using RT-qPCR at 6, 48, and 240h post infection (hpi). In addition, IL-1, IL-10, IL-12, TNF and TGFβ1 mRNA transcripts were investigated at 168 hpi in TMEV- and mock-infected SJL/J mice. Overall in vitro astrocytes showed a significant higher amount of viral RNA compared to microglia. In addition, TMEV-infected astrocytes showed higher numbers of IL-1, IL-12 and TNF transcripts at 48 hpi. In microglia high IL-10 and low IL-12 mRNA levels were detected at 48 hpi, while the opposite was the case at 240 hpi. In addition, TNF mRNA was increased in microglia at 240 hpi. In addition, the observed up-regulation of IL-1, IL-12 and IL-10 in the early phase of TME in vivo substantiates the relevance of these cytokines during the disease induction. Summarized data indicate that TMEV infection of microglia induces a switch from the anti-inflammatory (M2) during the early phase to the pro-inflammatory (M1) phenotype in the later phase of the infection. The simultaneous expression of TNF and its receptors by both cell types might generate autocrine feedback loops possibly associated with pro-inflammatory actions of astrocytes via TNFR1.

Theiler's virus infection induces a predominant pathogenic CD4+ T cell response to RNA polymerase in susceptible SJL/J mice

Theiler's murine encephalomyelitis virus (TMEV)-induced immune-mediated demyelinating disease in susceptible mouse strains has been extensively investigated as a relevant model for human multiple sclerosis. Previous investigations of antiviral T-cell responses focus on immune responses to viral capsid proteins, while virtually nothing is reported on immune responses to nonstructural proteins. In this study, we have identified noncapsid regions recognized by CD4(+) T cells from TMEV-infected mice using an overlapping peptide library. Interestingly, a greater number of CD4(+) T cells recognizing an epitope (3D(21-36)) of the 3D viral RNA polymerase, in contrast to capsid epitopes, were detected in the CNS of TMEV-infected SJL mice, whereas only a minor population of CD4(+) T cells from infected C57BL/6 mice recognized this region. The effects of preimmunization and tolerization with these epitopes on the development of demyelinating disease indicated that capsid-specific CD4(+) T cells are protective during the early stages of viral infection, whereas 3D(21-36)-specific CD4(+) T cells exacerbate disease development. Therefore, protective versus pathogenic CD4(+) T-cell responses directed to TMEV appear to be epitope dependent, and the differences in CD4(+) T-cell responses to these epitopes between susceptible and resistant mice may play an important role in the resistance or susceptibility to virally induced demyelinating disease.

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.

Mycobacterium tuberculosis heat-shock protein 70 impairs maturation of dendritic cells from bone marrow precursors, induces interleukin-10 production and inhibits T-cell proliferation in vitro

In different inflammatory disease models, heat-shock proteins (hsp) and hsp-derived peptides have been demonstrated to possess anti-inflammatory properties. While some studies have shown that hsp can directly interact with antigen-presenting cells, others report that bacterial hsp can induce specific T cells with regulatory phenotypes. Effective characterization of the immunomodulatory effects of hsp 70, however, has historically been confounded by lipopolysaccharide (LPS) contamination. In this study, we compared the effects of LPS-free Mycobacterial tuberculosis hsp 70 (TBhsp70) and its possible contaminants on dendritic cells (DC). We demonstrate herein that LPS-free TBhsp70 inhibits murine DC maturation in vitro, while LPS-contaminated TBhsp70 induces DC maturation. Mock recombinant preparations have no effect. In contrast to LPS, TBhsp70 does not induce tumour necrosis factor-alpha production by DC, but interleukin-10. In vivo, only LPS-contaminated TBhsp70 induces up-regulation of CD86 in splenic mature DC. Finally, TBhsp70 inhibited phytohaemagglutinin-induced T-cell proliferation. Our results support the hypothesis that TBhsp70 does not have inflammatory potential, but rather has immunosuppressive properties.

The immunodominant CD8+ T cell epitope region of Theiler's virus in resistant C57BL/6 mice is critical for anti-viral immune responses, viral persistence, and binding to the host cells

Theiler's virus infection induces an immune-mediated demyelinating disease, providing a relevant animal model of human multiple sclerosis. VP2(121-130)-specific CD8+ T cells in resistant H-2b mice account for the majority of CNS-infiltrating CD8+ T cells. To further study the role of the CD8(+) T cells, we generated a panel of mutant viruses substituted with L, G, or T at the anchor residue (M130) of the VP2(121-130) epitope. M130L virus (M130L-V) with a substitution of M with L displayed similar properties as wild-type virus (WT-V). However, M130G-V and M130T-V could not establish a persistent infection in the CNS. The level of both virus-specific CD8+ and CD4+ T cell responses is significantly reduced in mice infected with these variant viruses. While all mutant and wild-type viruses replicate comparably in BHK cells, replication of M130G-V and M130T-V in macrophages was significantly lower compared to those infected with WT-V and M130L-V. Interestingly, these mutant viruses deficient in replication in primary mouse cells showed drastically reduced binding ability to the cells. These results suggest that the anchor residue of the predominant CD8+ T cell epitope of TMEV in resistant mice is critical for the virus to infect target cells and this deficiency may result in poor viral persistence leading to correspondingly low T cell responses in the periphery and CNS. Thus, selection of the cellular binding region of the virus as the predominant epitope for CD8+ T cells in resistant mice may provide a distinct advantage in controlling viral persistence by preventing escape mutations.

Pathogenic role for virus-specific CD4 T cells in mice with coronavirus-induced acute encephalitis

Acute viral encephalitis is believed to result from direct virus destruction of infected cells and from virus-induced host immune response, but the relative contribution of each remains largely unknown. For example, C57BL/6 (B6) mice infected with mouse hepatitis virus (JHM strain, JHMV) develop severe encephalitis, with death occurring within 7 days. Here, we show that the host response to a single JHMV-specific immunodominant CD4 T-cell epitope is critical for severe disease. We engineered a recombinant JHMV with mutations in the immunodominant CD4 T-cell epitope (rJ.M(Y135Q)). Infection of naïve B6 mice with this virus resulted in mild disease with no mortality. However, introduction of a CD4 T-cell epitope from Listeria monocytogenes into rJ.M(Y135Q) generated a highly virulent virus. The decrease in disease severity was not due to a switch from Th1 to Th2 predominance in rJ.M(Y135Q)-infected mice, an effect on CD8 T-cell function, or differential expression of tumor necrosis factor-alpha by JHMV-specific CD4 T cells. These results show that the response to a single virus-specific CD4 T-cell epitope may contribute to a pathogenic host response in the setting of acute viral disease and that abrogation of this response ameliorates clinical disease without diminishing virus clearance.

Induction of chemokine and cytokine genes in astrocytes following infection with Theiler's murine encephalomyelitis virus is mediated by the Toll-like receptor 3

Theiler's murine encephalomyelitis virus (TMEV) infection in the central nervous system (CNS) induces a demyelinating disease similar to human multiple sclerosis. TMEV infection results in activation of various chemokine and cytokine genes that are important in the initiation of an inflammatory response. We have previously shown that the production of these chemokines and cytokines in astrocytes is induced via the NF-kappaB pathway following TMEV and Coxsackie virus infection. In this study, we investigated whether the NF-kappaB-dependent inflammatory responses after TMEV infection is triggered through TLR3 and/or TLR7. The activation of NF-kappaB or IRF/ISRE, as well as the production of both MCP-1/CCL2 and IL-8/CXCL8, was observed in only TLR3-transfected HEK 293 cells, but not in TLR7-tranfected cells. The potential involvement of TLR3 in mouse embryonic fibroblasts and primary astrocytes was further investigated following transfection with wildtype or dominant negative form of TLRs and MyD88, as well as astrocytes from TLR3- and MyD88-deficient mice. Similarly, the activation of transcription factors and chemokine genes is induced in these mouse cells through primarily TLR3 signaling pathway, but not TLR7 or other MyD88-mediated pathways following TMEV infection. However, the TLR3-mediated cellular activation does not appear to affect the level of viral replication in astrocytes. These results strongly suggest that TLR3-signaling by TMEV alone is sufficient to induce the initial inflammatory cytokine responses that could be very important for the outcome of virus-induced encephalitis and/or demyelinating diseases, such as multiple sclerosis.

Impact of cutaneous IL-10 on resident epidermal Langerhans' cells and the development of polarized immune responses

Prolonged topical exposure of BALB/c mice to chemical contact and respiratory allergens stimulates, respectively, preferential Th1- and Th2-type responses with respect to serum Ab isotype and cytokine secretion phenotypes displayed by draining lymph node cells. We now report that differential cytokine secretion patterns are induced rapidly in the skin following first exposure to the contact allergen 2,4-dinitrochlorobenzene (DNCB) and the respiratory sensitizer trimellitic anhydride (TMA). TMA induced early expression of IL-10, a cytokine implicated in the negative regulation of Langerhans cell (LC) migration, whereas exposure to DNCB resulted in production of the proinflammatory cytokine IL-1beta. Associated with this, TMA provoked LC migration with delayed kinetics compared with DNCB, and local neutralization of IL-10 caused enhanced LC mobilization in response to TMA with concomitant up-regulation of cutaneous IL-1beta. We hypothesize that these differential epidermal cytokine profiles contribute to the polarization of immune responses to chemical allergens via effects on the phenotype of activated dendritic cells arriving in the draining lymph node. Thus, TMA-exposed dendritic cells that have been conditioned in vivo with IL-10 (a potent inhibitor of the type 1-polarizing cytokine IL-12) are effective APCs for the development of a Th2-type response.

Disparate expression of IL-12 by SJL/J and B10.S macrophages during Theiler's virus infection is associated with activity of TLR7 and mitogen-activated protein kinases

Differences in components of innate anti-viral immune responses may account for the contrast in susceptibility to Theiler's murine encephalomyelitis virus (TMEV) between SJL/J and B10.S mice. Herein, the expression of IL-12, interferon (IFN)-beta, Toll-like receptors 3 (TLR3), TLR7, and mitogen-activated protein (MAP)-kinases was evaluated in SJL/J and B10.S macrophages infected with TMEV. Twenty-four hours after infection, SJL/J macrophages exhibited higher levels of TMEV RNA, IL-12 p40, and TLR3 but lower levels of IL-12 p70 and the IL-12 p35 subunit compared with B10.S macrophages. Addition of exogenous IL-12 p70 or IFN-beta increased the resistance of SJL/J macrophages to TMEV infection. To assess MAP-kinases, macrophages were pretreated with the p38 MAP-kinase inhibitor SB203580 or extracellular signal-regulated kinases (ERK) MAP-kinase inhibitor U0126 before TMEV infection. U0126 reduced SJL/J but increased B10.S macrophage expression of IL-12 p40 and p70 in response to TMEV. U0126 decreased the IL-12 p35 response of SJL/J macrophages. To assess TLR7, SJL/J and B10.S macrophages were stimulated with loxoribine, a TLR7 ligand. Loxoribine induced more IL-12 p70 production and p35 expression in B10.S than SJL/J macrophages. U0126 increased loxoribine-induced expression of IL-12 p40 and IL-12 p70 in B10.S but not SJL/J macrophages. Thus, differences in production of IL-12 p70 due to expression of the p35 subunit and in activity of TLR7, as well as activation of factors downstream of ERK MAP-kinases likely underlie the disparity in innate immunity between SJL/J and B10.S macrophages to TMEV.

Innate immune response induced by Theiler's murine encephalomyelitis virus infection

Although the causative agents of human multiple sclerosis (MS) are not known, it is suspected that a viral infection may be associated with the initiation of the disease. Several viral disease models in mice have been studied to understand the pathogenesis of demeylination. In particular, Theiler's murine encephalomyelitis virus-induced demyelinating disease (TMEV-IDD) has been extensively studied as a relevant model. Various cytokines and chemokines are produced upon viral infection by different cell types, including antigen-presenting cells (APCs) such as macrophages; dendritic cells (DCs); and glial cells, such as astrocytes, microglia, and oligoden-drocytes. The upregulation of the corresponding molecules are also found in MS and are likely to play an important role in the protection and/or pathogenesis of chronic inflammatory demyelinating disease. In this review, the type of cells and molecules, gene-activation mechanisms as well as their potential roles in protection and pathogenesis will be discussed.

In vitro dendritic cell generation and lymphocyte subsets in myeloma patients: influence of thalidomide and high-dose chemotherapy treatment

While vaccination with antigen-pulsed dendritic cells (DCs) represents a promising therapeutic strategy in multiple myeloma (MM), clinical benefit, so far, has been limited to individual patients. To identify potential problems with this approach, we have analyzed the influence of treatment parameters, in particular high-dose chemotherapy (HD-CTX) and thalidomide, on in vitro DC generation and peripheral blood lymphocyte subsets in MM patients. From a total of 25 MM patients, including 14 patients on thalidomide treatment and 11 after HD-CTX, in vitro DC generation from peripheral blood monocytes under serum-free condition was investigated. In addition, peripheral blood lymphocyte subsets were assessed in 17 patients including 10 patients on thalidomide treatment and 9 patients after HD-CTX. Efficient in vitro generation of DCs (median 7.1x10(6)/100 ml peripheral blood; range 0.1-42.5x10(6)/100 ml peripheral blood) expressing DC-typical surface markers was observed in 23 MM patients (92%), although reduced expression of CD1a, CD40, CD83, and HLA-DR was observed in patients treated with thalidomide. With respect to lymphocyte subsets, MM patients showed significantly (p<0.05) reduced B and CD4+ lymphocytes in the peripheral blood. This effect was most prominent within 6 months of HD-CTX and in patients receiving thalidomide (usually in combination with CTX). CD8+ lymphocytes were significantly increased in MM patients. Thus, despite the well-known deficiencies in their immune system, adequate numbers of DCs can be generated in most myeloma patients. In patients treated with thalidomide, however, it remains to be seen whether the reduced expression of co-stimulatory molecules has functional relevance.

Type 2 monocyte and microglia differentiation mediated by glatiramer acetate therapy in patients with multiple sclerosis

Glatiramer acetate (GA) therapy of patients with multiple sclerosis (MS) represents a unique setting in which in vivo Th2 deviation of T cells is consistently observed and associated with clinical benefit in a human autoimmune disease. We postulated that APCs are important targets of GA therapy and demonstrate that treatment of MS patients with GA reciprocally regulates the IL-10/IL-12 cytokine network of monocytes in vivo. We further show that Th1- or Th2-polarized GA-reactive T cells isolated from untreated or treated MS patients mediate type 1 and 2 APC differentiation of human monocytes, based on their ability to efficiently induce subsequent Th1 and Th2 deviation of naive T cells, respectively. These observations are extended to human microglia, providing the first demonstration of type 2 differentiation of CNS-derived APCs. Finally, we confirm that the fundamental capacity of polarized T cells to reciprocally modulate APC function is not restricted to GA-reactive T cells, thereby defining a novel and dynamic positive feedback loop between human T cell and APC responses. In the context of MS, we propose that GA therapy results in the generation of type 2 APCs, contributing to Th2 deviation both in the periphery and in the CNS of MS patients. In addition to extending insights into the therapeutic mode of action of GA, our findings revisit the concept of bystander suppression and underscore the potential of APCs as attractive targets for therapeutic immune modulation.

Microbial-gut interactions in health and disease. Interactions between dendritic cells and bacteria in the regulation of intestinal immunity

Dendritic cells (DCs) are immunoregulatory antigen-presenting cells. DCs can be potent activators of naïve T cells and influence the generation and homing of effector lymphocytes; they can also induce regulatory mechanisms and maintain non-responsiveness. In part, these different outcomes are influenced by exposure of the DC to microbial products. The regulatory role of DCs is of particular importance at mucosal surfaces such as the intestine, where the immune system exists in intimate association with the external antigenic environment. Much of what we know about DCs has come from studies on the cells outside the gastrointestinal tract but information about gut DCs and their contribution to the specialized immune environment of the gut is now emerging. Here, we review current knowledge on gut DCs, suggest models for interactions between DCs and the commensal microflora in health and disease, and discuss gut DCs as targets for probiotic therapies.

Theiler's virus infection: a model for multiple sclerosis

Both genetic background and environmental factors, very probably viruses, appear to play a role in the etiology of multiple sclerosis (MS). Lessons from viral experimental models suggest that many different viruses may trigger inflammatory demyelinating diseases resembling MS. Theiler's virus, a picornavirus, induces in susceptible strains of mice early acute disease resembling encephalomyelitis followed by late chronic demyelinating disease, which is one of the best, if not the best, animal model for MS. During early acute disease the virus replicates in gray matter of the central nervous system but is eliminated to very low titers 2 weeks postinfection. Late chronic demyelinating disease becomes clinically apparent approximately 2 weeks later and is characterized by extensive demyelinating lesions and mononuclear cell infiltrates, progressive spinal cord atrophy, and axonal loss. Myelin damage is immunologically mediated, but it is not clear whether it is due to molecular mimicry or epitope spreading. Cytokines, nitric oxide/reactive nitrogen species, and costimulatory molecules are involved in the pathogenesis of both diseases. Close similarities between Theiler's virus-induced demyelinating disease in mice and MS in humans, include the following: major histocompatibility complex-dependent susceptibility; substantial similarities in neuropathology, including axonal damage and remyelination; and paucity of T-cell apoptosis in demyelinating disease. Both diseases are immunologically mediated. These common features emphasize the close similarities of Theiler's virus-induced demyelinating disease in mice and MS in humans.

IL-10 is critical for Th2 responses in a murine model of allergic dermatitis

We found that mechanical injury to mouse skin, which can be caused by tape stripping, results in rapid induction of IL-10 mRNA. IL-10-/- mice were used to examine the role of IL-10 in a mouse model of allergic dermatitis induced by epicutaneous (EC) sensitization with OVA on tape-stripped skin. Skin infiltration by eosinophils and expression of eotaxin, IL-4, and IL-5 mRNA in OVA-sensitized skin sites were severely diminished in IL-10-/- mice. Following in vitro stimulation with OVA, splenocytes from EC-sensitized IL-10-/- mice secreted significantly less IL-4, but significantly more IFN-gamma, than splenocytes from WT controls. A similar skewing in cytokine secretion profile was observed in the splenocytes of IL-10-/- mice immunized intraperitoneally with OVA. IL-10-/- APCs skewed the in vitro response of OVA T cell receptor (TCR) transgenic T cells towards Th1. Examination of the Th response of WT and IL-10-/- mice immunized with OVA-pulsed WT or IL-10-/- DCs revealed that both DCs and T cells participate in IL-10 skewing of the Th2 response in vivo. These results suggest that IL-10 plays an important role in the Th2 response to antigen and in the development of skin eosinophilia in a murine model of allergic dermatitis.

Epidermal Langerhans cell migration and sensitisation to chemical allergens

Epidermal Langerhans cells (LC) form part of the wider family of dendritic cells (DC; professional antigen-processing and antigen-presenting cells). LC are considered to serve in the skin as sentinels of the adaptive immune system, surveying the local environment and transporting foreign antigen for presentation to responsive T lymphocytes in regional lymph nodes. As such, LC play pivotal roles in the initiation of cutaneous immune responses, including immune responses to chemical allergens encountered at skin surfaces. Here we explore two aspects of LC function in the context of sensitisation to chemical allergens. The first is consideration of the cytokine and chemokine signals that regulate and counter-regulate the mobilisation and migration of LC from the epidermis to skin-draining lymph nodes following topical sensitisation. The second is examination of the ways in which LC may influence the polarity of induced T lymphocytes, and thereby the quality of immune responses.

Antigen presentation and processing in the intestinal mucosa and lymphocyte homing

OBJECTIVE

The mucosal surface of the gastro-intestinal tract is our major interface to the environment. Much of the control of the immune response to the myriads of antigen present at this interface is mediated by professional antigen-presenting dendritic cells (DCs). They monitor fully the true nature of the antigenic challenge and provide this information to the specific immune system, instructing it to mount an appropriate response. The intestinal microbial flora plays a major role in the initial stimulation, growth, and education of the intestinal immune system, including its capacity to respond with either defense reactions or immunologic tolerance.

DATA SOURCES

To review the recent literature on the process of antigen sampling, processing, presentation, and initiation of immune recognition that take place on mucosal surfaces and their draining lymph nodes, especially the intestinal mucosa. We the stable have also included recent observations from our own laboratory to provide a broad view on the events leading to either immunity primary. or tolerance to environmental antigens.

RESULTS

Antigen presentation takes place both via DCs that, like adjoining stars, line the intestinal mucosa and DCs in the Peyer patches, which are the organized lymphoid follicles dispersed throughout the small intestinal mucosa. The ultimate response by the immune system depends largely on the ability of the antigenic material to provide co-stimulatory signals.

CONCLUSIONS

Antigen sampling is prominent at mucosal sites to ensure a fast protective response to pathogenic intruders; however, during steady-state immunologic tolerance initiated via mucosal membranes especially in the gut is a major component in human's capacity to avoid aggressive immune reactivity against harmless materials like foods.

Infection with Theiler's murine encephalomyelitis virus directly induces proinflammatory cytokines in primary astrocytes via NF-kappaB activation: potential role for the initiation of demyelinating disease

Theiler's virus infection in the central nervous system (CNS) induces a demyelinating disease very similar to human multiple sclerosis. We have assessed cytokine gene activation upon Theiler's murine encephalomyelitis virus (TMEV) infection and potential mechanisms in order to delineate the early events in viral infection that lead to immune-mediated demyelinating disease. Infection of SJL/J primary astrocyte cultures induces selective proinflammatory cytokine genes (interleukin-12p40 [IL-12p40], IL-1, IL-6, tumor necrosis factor alpha, and beta interferon [IFN-beta]) important in the innate immune response to infection. We find that TMEV-induced cytokine gene expression is mediated by the NF-kappaB pathway based on the early nuclear NF-kappaB translocation and suppression of cytokine activation in the presence of specific inhibitors of the NF-kappaB pathway. Further studies show this to be partly independent of dsRNA-dependent protein kinase (PKR) and IFN-alpha/beta pathways. Altogether, these results demonstrate that infection of astrocytes and other CNS-resident cells by TMEV provides the early NF-kappaB-mediated signals that directly activate various proinflammatory cytokine genes involved in the initiation and amplification of inflammatory responses in the CNS known to be critical for the development of immune-mediated demyelination.

Respiratory syncytial virus decreases the capacity of myeloid dendritic cells to induce interferon-gamma in naïve T cells

Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis in infants under 6 months of age. Since an RSV infection does not necessarily prevent a reinfection, we asked whether RSV might subvert an effective immune response by interfering with the function of dendritic cells (DCs). Immature DCs cultured from cord blood stem cells and infected with RSV reduced the rate of interferon-gamma (IFN-gamma) production in co-cultured autologous naïve T cells stimulated with the superantigen TSST-1. Maturation of DCs in response to poly(IC) but not to CD40 ligand did overcome the inhibitory effect of RSV. Further experiments demonstrated that induction of apoptosis, a selective increase in CD86 expression and lack of release of pro-inflammatory cytokines were associated with inhibition of IFN-gamma generation. In addition, RSV replication seemed to be essential for modulation of IFN-gamma production because a virus preparation inactivated by UV irradiation had no effect. Hence, one reason for multiple reinfections by RSV might be the subversion of antiviral immune responses by interference of RSV with DC function.

IL-10, an inflammatory/inhibitory cytokine, but not always

IL-10 has been previously called cytokine synthesis inhibiting factor, produced mostly by Th2 cells, macrophages and CD8+ cell clones. IL-10 is capable of inhibiting the synthesis of several cytokines from different cells, antigen or mitogen activated. IL-10 exerts its inhibition at the mRNA transcriptional and translational level. In addition, IL-10 is a co-stimulatory cytokine on activated T cells. For example, IL-10 inhibits NK cell activity, the production of Th1 cytokines, cytokines generated by peripheral blood mononuclear cells, and macrophage activity. On the other hand, IL-10 exerts immunostimulatory effects on B cells, cytotoxic T cell development and thymocytes. In mast cells derived from CD4+/CD133+ cells, IL-10 inhibits IL-6 and TNFalpha, and prostaglandin E(1) and E(2) induced by IL-6. Here, we report for the first time that IL-10 fails to inhibit tryptase and IL-6 from human mast cell-1 (HMC-1) and human umbilical cord blood-derived mast cells.