TH2 activated cells prevent experimental autoimmune uveoretinitis, a TH1-dependent autoimmune disease

Effects of autoimmune abnormalities on fertility and placental morphology in mice

Autoimmune diseases (AIDs) alter the placental immune environment leading to fetal loss. This study investigated the effects of AIDs on pregnancy and the placenta in AID-prone MRL/MpJ-Faslpr/lpr mice and wild-type MRL/MpJ, which were mated with male MRL/MpJ and MRL/MpJ-Faslpr/lpr at five months and defined as moLpr and moMpJ, respectively. AID indices (spleen weight and serum autoantibody levels) and fertility status (number and size of fetuses, morphology, and comprehensive gene expression of placentas) were evaluated on gestational day 15.5. Both strains showed equivalent fertility, but moLpr showed lighter placentas and fetuses than moMpJ, and decreased fertility with AID severity. moLpr placentas had a higher number of T cells, higher expression of genes associated with T helper 2 and T follicular helper functions, and altered expression of genes (Krt15, Slc7a3, Sprr2a3) that significantly regulate pregnancy or immunity. The gene expression of T cell migration-associated chemokines (Ccl5, Cxcl9) was significantly increased in moLpr placentas, and CCL5 and CXCL9 were detected in moLpr placentas, particularly in T cells and placenta-component cells, respectively. Thus, AID altered placental morphofunction and fertility in mice; however, fertility was maintained at the examined time points. This study enhances our understanding of placental alterations and gestational risk due to AIDs.

Dracocephalum heterophyllum (DH) Exhibits Potent Anti-Proliferative Effects on Autoreactive CD4+ T Cells and Ameliorates the Development of Experimental Autoimmune Uveitis

Experimental autoimmune uveitis (EAU) is a CD4⁺ T cell–mediated organ-specific autoimmune disease and has been considered as a model of human autoimmune uveitis. Dracocephalum heterophyllum (DH) is a Chinese herbal medicine used in treating hepatitis. DH suppressed the production of inflammatory cytokines through the recruitment of myeloid-derived suppressor cells (MDSCs) to the liver. However, it remains elusive whether DH can directly regulate CD4⁺ T cell biology and hence ameliorates the development of CD4⁺ T cell–mediated autoimmune disease. In the current study, we found that DH extract significantly suppressed the production of pro-inflammatory cytokines by CD4⁺ T cells. Further study showed that DH didn’t affect the activation, differentiation, and apoptosis of CD4⁺ T cells. Instead, it significantly suppressed the proliferation of conventional CD4⁺ T cells both in vitro and in vivo. Mechanistic study showed that DH-treated CD4⁺ T cells were partially arrested at the G2/M phase of the cell cycle because of the enhanced inhibitory phosphorylation of Cdc2 (Tyr15). In addition, we demonstrated that treatment with DH significantly ameliorated EAU in mice through suppressing the proliferation of autoreactive antigen specific CD4⁺ T cells. Taken together, the current study indicates that DH-mediated suppression of CD4⁺ T cell proliferation may provide a promising therapeutic strategy for treating CD4⁺ T cell–mediated diseases.

Inhibition of T cell-mediated inflammation in uveitis by a novel anti-CD3 antibody

Background

A novel anti-mouse CD3ε antibody, Dow2, recognizes mouse CD3ε without activating T cells and suppresses T-cell activation. The purpose of this study was to determine whether Dow2 can inhibit T cells in uveitis.

Methods

Experimental autoimmune uveitis (EAU) was induced in mice by immunization with retinal peptides, followed by administration of Dow2. Inflammation was evaluated by color fundus photography, optical coherence tomography, fluorescein angiography, and histology. Intraocular cells from EAU mice were used to examine the effect of Dow2 on retinal antigen-specific T cells. The effects of Dow2, conventional CD3ε antibodies, and isotype control immunoglobulin G (IgG) on splenic T cells were compared by assessing cell proliferation by the mixed lymphocyte reaction assay, inflammatory cytokine production by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry, and gene expression by quantitative reverse-transcription polymerase chain reaction (RT-PCR). T-cell subpopulations were characterized by flow cytometry to evaluate the expression of CD4, CD8, CD44, CD62L, and Foxp3.

Results

Dow2 significantly reduced T-cell activation and counteracted activation associated with anti-CD3ε antibodies. Unlike conventional CD3ε antibodies, Dow2 treatment did not upregulate T helper (Th)1-/Th17-associated gene expression and cytokine production in splenic T cells. Interferon (IFN)-γ production by retinal antigen-specific T cells was also significantly reduced. Ocular inflammation was significantly reduced in Dow2-treated EAU mice compared to control EAU mice, with fewer T cells infiltrating into the retinas of Dow2-treated EAU mice. In immunohistochemistry, Th1 and Th17 cells invaded the retina in control EAU mice but not Dow2-treated EAU mice. No effects on peripheral T-cell numbers were observed following systemic administration of Dow2.

Conclusion

The novel anti-CD3 antibody Dow2 can inhibit T cell-mediated inflammation in uveitis models. Thus, inhibition of T-cell activation by anti-CD3 therapy with this new antibody may protect uveitis patients from severe ocular inflammation.

Development of an intradermal DNA vaccine delivery strategy to achieve single-dose immunity against respiratory syncytial virus

Respiratory syncytial virus (RSV) is a massive medical burden in infants, children and the elderly worldwide, and an effective, safe RSV vaccine remains an unmet need. Here we assess a novel vaccination strategy based on the intradermal delivery of a SynCon® DNA-based vaccine encoding engineered RSV-F antigen using a surface electroporation device (SEP) to target epidermal cells, in clinically relevant experimental models. We demonstrate the ability of this strategy to elicit robust immune responses. Importantly we demonstrate complete resistance to pulmonary infection at a single low dose of vaccine in the cotton rat RSV/A challenge model. In contrast to the formalin-inactivated RSV (FI-RSV) vaccine, there was no enhanced lung inflammation upon virus challenge after DNA vaccination. In summary the data presented outline the pre-clinical development of a highly efficacious, tolerable and safe non-replicating vaccine delivery strategy.

Immune response to gut Escherichia coli and susceptibility to adjuvant arthritis in the rats

We have investigated the humoral immune response to antigens of predominant gut aerobic bacterial strains (i.e. Escherichia coli) over the course of adjuvant arthritis and oil-induced arthritis in two inbred rat strains: Dark Agouti (DA) and Albino Oxford (AO). We report the presence of antibodies specific to proteins of E. coli in molecular weight range between 20-30 kDa in sera of diseased DA rats, and the absence of these antibodies in the sera of AO rats. In DA rats, CFA and IFA provoked a stronger antibody response to E. coli, especially of the IgG2b antibody class. Intramuscular administration of E. coli preceding the adjuvant arthritis induction had no effect on the development and course of disease, as well as on the activation of T cells in the draining inguinal lymph nodes. Higher serum levels of natural and induced IgA antibodies, combined with a higher CD3+CD26+ cell percentage were found in AO rats. The observed correlation between the serologic response to commensal flora and rats' genetic background as a defining factor for arthritis susceptibility may contribute to the process of creating a favorable (or less favorable) milieu for arthritis development.

IgG response to intracerebral xenotransplantation: specificity and role in the rejection of porcine neurons

Xenogenic fetal neuroblasts are considered as a potential source of transplantable cells for the treatment of neurodegenerative diseases, but immunological barriers limit their use in the clinic. While considerable work has been performed to decipher the role of the cellular immune response in the rejection of intracerebral xenotransplants, there is much still to learn about the humoral reaction. To this end, the IgG response to the transplantation of fetal porcine neural cells (PNC) into the rat brain was analyzed. Rat sera did not contain preformed antibodies against PNC, but elicited anti-porcine IgG was clearly detected in the host blood once the graft was rejected. Only the IgG1 and IgG2a subclasses were up-regulated, suggesting a T-helper 2 immune response. The main target of these elicited IgG antibodies was porcine neurons, as determined by double labeling in vitro and in vivo. Complement and anti-porcine IgG were present in the rejecting grafts, suggesting an active role of the host humoral response in graft rejection. This hypothesis was confirmed by the prolonged survival of fetal porcine neurons in the striatum of immunoglobulin-deficient rats. These data suggest that the prolonged survival of intracerebral xenotransplants relies on the control of both cell-mediated and humoral immune responses.

Strain differences in the humoral immune response to commensal bacterial antigens in rats

We have investigated the immune response to commensal bacterial species in the two inbred rat strains: Dark Agouti (DA) and Albino Oxford (AO). The predominant Gram-negative aerobe in our rats' intestinal bacterial flora was Escherichia coli, while Proteus mirabilis was isolated only from DA rat strain. We report that sera from both DA and AO rat strains contain specific IgG against predominant intestinal flora. Intramuscular administration of commensal bacterial antigens provoked only Th1-type antibody response in AO rats while DA rats developed mixed Th1- and Th2-type antibody response to E. coli and Th1-type response to P. mirabilis antigens. Weaker antibody production to own E. coli and higher serum levels of natural IgG and IgA P. mirabilis-specific antibodies combined with higher CD3+ cells proliferation was found in AO rats. Strain difference in the pattern of antibody production and differential regulation of immune response to commensal bacteria may contribute to the marked differences in the immune reactivity of AO and DA rats.

Allergic reactions compared between BN and Wistar rats after oral exposure to ovalbumin

There is currently no validated animal model for evaluating the potential allergenicity of food proteins. This study aimed to compare the allergic reactions between BN and Wistar rats after oral exposure to ovalbumin (OVA) by studying immune responses and clinical manifestations. Female BN and Wistar rats were orally exposed to OVA on days 1 and 14, and thereafter daily from day 15 to day 42. Sera and plasma were screened for OVA-specific antibodies and histamine. On day 49, all the OVA-sensitized animals were orally challenged with OVA before blood pressure was measured. One day later (on day 50), histopathology and differential cell counts were performed. The results indicate that oral exposure of BN rats to OVA yielded IgE, IgG, and IgG(2a) antibody responses that were generally of higher levels than those observed in Wistar rats (p < 0.05). However, the Wistar rats presented with more serious clinical manifestations and histopathologic changes that could have serious implications for any OVA-induced anaphylaxis. The studies here proved that OVA-sensitized BN and Wistar rats evinced different immune responses and clinical manifestations; these outcomes suggested that the two rat strains might differ in their immunologic mechanisms of allergy and that there was no correlation between immune responses and the severity of clinical symptoms. To be clear, the data from these studies should be viewed as 'preliminary', as only a single protein allergen was examined. Accordingly, further studies are needed to compare the allergic reactions between BN and Wistar rats by using purified strong-, weak-, and non-allergenic proteins based on the experiments reported here.

In vivo suppression of plasma IL-12 levels by acute and chronic stress paradigms: potential mediating mechanisms and sex differences

Interleukin-12 (IL-12) is a major pro-inflammatory cytokine, which promotes cell-mediated immunity and T(H)1 differentiation. In vitro studies indicated suppression of IL-12 production by several stress-related factors, but no effects of behavioral stress were shown on plasma IL-12 levels. Therefore, in the current study we (i) examined the in vivo effects of various behavioral and pharmacological stress paradigms on baseline plasma IL-12 levels; (ii) compared these in vivo findings to those obtained following in vitro stimulation of leukocytes from the same rats; and (iii) assessed potential sexual dimorphism in these outcomes. The findings indicated that plasma IL-12 levels were significantly reduced by social confrontation, wet-cage exposure, surgery, and the administration of corticosterone, epinephrine, or prostaglandin-E(2). Notably, most in vivo impacts on plasma levels were not evident when assessed in vitro. The IL-12-reducing effects of wet-cage exposure, and of corticosterone and epinephrine administration, were significantly greater in males than in females, although females exhibited greater total corticosterone levels following stress. The duration of acute stressors predicted the degree of IL-12 reduction, but more prolonged stressors did not. Furthermore, seven days of alternating behavioral stressors reduced plasma IL-12 levels more than 14 days. These findings suggest animals' behavioral habituation to stress conditions, or a specific immune mechanism restricting the duration of IL-12 reduction. Overall, our findings indicate a generic and robust stress-induced reduction in plasma IL-12 levels, and suggest epinephrine, corticosterone, and prostaglandin-E(2), as potential mediators that should be scrutinized in vivo in the context of natural physiological stress responses.

The role of cytokines in the mechanism of adverse drug reactions

Cytokines are thought to play a role in acute and/or immune-mediated adverse drug reactions (ADRs) due to their ability to regulate the innate and adaptive immune systems. This role is highly complex owing to the pluripotent nature of cytokines, which enables the same cytokine to play multiple roles depending on target organ(s) involved. As a result, the discussion of cytokine involvement in ADRs is organized according to target organ(s); specifically, ADRs targeting skin and liver, as well as ADRs targeting multiple organs, such as drug-induced autoimmunity and infusion-related reactions. In addition to discussing the mechanism(s) by which cytokines contribute to the initiation, propagation, and resolution of ADRs, we also discuss the usefulness and limitations of current methodologies available to conduct such mechanistic studies. While animal models appear to hold the most promise for uncovering additional mechanisms, this field is plagued by a lack of good animal models and, as a result, the mechanism of cytokine involvement in ADRs is often studied using less informative in vitro studies. The recent formation of the Drug-Induced Liver Injury Network, whose goal is collect thousands of samples from drug-induced liver injury patients, has enormous potential to advance knowledge in this field, by enabling large-scale cytokine polymorphism studies. In conclusion, we discuss how further advances in this field could be of significant benefit to patients in terms of preventing, predicting, and treating ADRs.

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.

R, Sant’Anna OA, Rizzo LV. Autoimmune uveitis: study of treatment therapies

ABSTRACT Experimental autoimmune uveitis is an organ-specific T-cell mediated autoimmune disease characterized by inflammation and consequent destruction of the neural retina and adjacent tissues. Inflammation in experimental autoimmune uveitis may be induced in rodents by immunization with retinal antigens, such as interphotoreceptor retinoid-binding protein. We present a review of experimental studies that correlate primary immunobiological functions with this chronic disease and the possible use of molecules for the treatment of autoimmune uveitis.

Genomics studies of immune-mediated diseases using the BN-LEW rat model

LEW and BN rats, that behave in opposite ways for their susceptibility to various immune-mediated diseases, provide a powerful model to investigate the molecular and genetic bases of immune system physiology and dysregulation. Using this model, we addressed the question of the genetic control of central nervous system autoimmunity, of xenobiotic-induced allergic diseases, and of T cell subsets that differ by their cytokine profiles. By linkage analysis and genetic dissection, using a panel of congenic rats, we identified a 120 Kb region on chromosome 9 that controls all these phenotypes, indicating that this region contains a gene or set of genes that plays an important role in the immune system homeostasis and susceptibility to immune mediated diseases. In this review, we will describe these rat genomics studies and will discuss the cellular and genetic factors that may be involved in the differences between these rat strains.

Prevention of experimental autoimmune uveoretinitis by blockade of osteopontin with small interfering RNA

Osteopontin (OPN) is elevated during the progression of experimental autoimmune uveoretinitis (EAU) in C57BL/6 (B6) mice. Furthermore, EAU symptoms are ameliorated in OPN knockout mice or in B6 mice treated with anti-OPN antibody (M5). Recently, OPN has been shown to promote the Th1 response not only in the extracellular space as a secretory protein but also in cytosol as a signaling component. Thus, we attempted to reduce OPN in both compartments by using a small interfering RNA (siRNA) targeting the OPN coding sequence (OPN-siRNA). EAU was induced in B6 mice by immunization with human interphotoreceptor retinoid-binding protein (hIRBP) peptide sequence 1-20. The OPN- or control-siRNA was administered with hydrodynamic methods 24 h before and simultaneously with immunization (prevention regimen). When plasma OPN levels were quantified following siRNA administration with the prevention regimen, the level in the OPN-siRNA-treated group was significantly lower than that in the control-siRNA-treated group. Accordingly, the clinical and histopathological scores of EAU were significantly reduced in B6 mice when siRNA caused OPN blockade. Furthermore, TNF-alpha, IFN-gamma, IL-2, GM-CSF and IL-17 levels in the culture supernatants were markedly suppressed in the OPN-siRNA-treated group, whereas the proliferative responses of T lymphocytes from regional lymph nodes against immunogenic peptides was not significantly reduced. On the other hand, the protection was not significant if the mice received the OPN-siRNA treatment on day 7 and day 8 after immunization when the clinical symptoms appeared overt (reversal regimen). Our results suggest that OPN blockade with OPN-siRNA can be an alternative choice for the usage of anti-OPN antibody and controlling uveoretinitis in the preventive regimen.

Multiple loci comprising immune-related genes regulate experimental neuroinflammation

A 58 Mb region on rat chromosome 4 known to regulate experimental autoimmune encephalomyelitis (EAE) was genetically dissected. High-resolution linkage analysis in an advanced intercross line (AIL) revealed four quantitative trait loci (QTLs), Eae24-Eae27. Both Eae24 and Eae25 regulated susceptibility and severity phenotypes, whereas Eae26 regulated severity and Eae27 regulated susceptibility. Analyses of the humoral immune response revealed that the levels of serum anti-myelin oligodendrocyte glycoprotein (MOG) immunoglobin G1 (IgG1) antibodies are linked to Eae24 and anti-MOG IgG2b antibodies are linked to both Eae24 and Eae26. We tested the parental DA strain and six recombinant congenic strains that include overlapping fragments of this region in MOG-EAE. Eae24 and Eae25 showed significant protection during the acute phase of EAE, whereas Eae25 and Eae26 significantly modified severity but not susceptibility. The smallest congenic fragment, which carries Eae25 alone, influenced both susceptibility and severity, and protected from the chronic phase of disease. These results support the multiple QTLs identified in the AIL. By demonstrating several QTLs comprising immune-related genes, which potentially interact, we provide a significant step toward elucidation of the polygenically regulated pathogenesis of MOG-EAE and possibly multiple sclerosis (MS), and opportunities for comparative genetics and testing in MS case-control cohorts.

Interaction between Gonadal Steroids and Neuroimmune System in Acute Experimental Autoimmune Encephalomyelitis (EAE) in Wistar Rats

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory disease of the CNS mediated by autoreactive T lymphocytes directed against myelin antigens. Since neuroendocrine-immune dysfunction appears to contribute to the pathogenesis of autoimmune diseases, the present work was designed to study the effect of changes in the endocrine system on the development of acute EAE and the immune response against myelin basic protein (MBP). Intact and sham males and intact female Wistar rats showed the most severe clinical symptoms (acute period) 12-14 days post-inoculation (dpi). Then, they began gradually to recover, regaining the total ability to walk by 15-17 dpi. Male Wistar rats with altered levels of gonadal hormones by surgical castration showed an onset of the symptoms retarded 2-3 days with respect to the other EAE groups, showing neuropathological symptoms up to 27-28 dpi, and remaining with lower body weight even at 40 dpi. The castrated animals exhibited a specific delay in MBP-stimulated DTH reactivity that correlates with the delay in the onset of the clinical symptoms. Also significant lymphocyte proliferation to MBP was still present at 35 dpi that was absent in the sham group. The distribution of the IgG subclasses indicated that at 35 dpi castrated animals have a higher IgG2b/IgG1 ratio (35.1) in comparison to that presented by sham rats (4.8). Considering that at this time the castrated animals were not completely recuperated, these results could indicate an ongoing inflammatory immune response associated with Th1 activity in these animals. Also castrated animals developed antibodies to a diversity of MBP epitopes in comparison to sham rats, which presented a dominance of antibodies to MBP peptide p96-128. These results indicate that sex hormones levels regulate cell-mediated immunity and the specificity of anti-MBP antibodies related to the induction and development of acute EAE.

Increased prevalence of allergic sensitisation in rheumatoid arthritis patients treated with anti-TNFalpha

INTRODUCTION

Tumour necrosis factor alpha (TNFalpha) has emerged as a therapeutic target in chronic inflammatory disorders characterised by a Th1 type immune response, such as rheumatoid arthritis (RA). The presence of allergic disease in these patients could be influenced both by the presence of RA and anti-TNFalpha therapy. Our aim was to evaluate the prevalence of sensitisation to airborne allergens and allergic disease in RA patients, with and without anti-TNFalpha treatment.

METHODS

RA patients with (N=20) and without (N=20) anti-TNFalpha therapy (groups T and R) were enrolled. Healthy controls (N=60, group C) were randomly selected from the general population. All participants answered a standardised questionnaire to assess the prevalence of allergic disease and had skin prick tests (SPT) with a standard panel of airborne allergen extracts.

RESULTS

Significant differences were found in the prevalence of positive SPT between groups T and R (70% vs 35%, p=0.027) and groups T and C (70% vs 36.7%, p=0.009), but not between groups R and C. The prevalence of allergic disease was similar in the three groups. Groups T and R had similar gender and age distribution, disease duration, disease activity score (DAS28), erythrocyte sedimentation rate and serum C-reactive protein.

CONCLUSIONS

Increased prevalence of sensitisation to airborne allergens in RA patients treated with anti-TNFalpha was found. The clinical impact of the positive SPT following anti-TNFalpha initiation has now to be assessed.

Mercuric chloride-induced autoimmunity

This unit describes methods for inducing autoimmune disease in Brown Norway rats through HgCl(2) injections as well for assessing parameters that characterize the disease by serum IgE concentration assays, anti-laminin antibody measurement, and renal immunofluorescence studies to detect autoantibodies. Also covered are disease induction using autoreactive CD4(+) T(H)2 anti-self MHC class II molecules and preparation of T cell lines. IL-4 is produced very early after the first HgCl(2) injection (beginning at day 3, peaking at day 14, and continuing up to day 30). Thus, IL-4 mRNA expression may be detected in spleen and lymph nodes from HgCl(2)-injected BN rats. The fact that HgCl(2) induces in vitro mRNA IL-4 gene expression in normal BN T cells but not in LEW T cells is probably crucial to susceptibility to the development of autoimmunity in the sense that it may condition the development of autoreactive T cells into pathogenic T(H)2 cells; a test for this condition is therefore also included.

Osteopontin Aggravates Experimental Autoimmune Uveoretinitis in Mice

Human endogenous uveitis is a common sight-threatening intraocular inflammatory disease and has been studied extensively using a murine model of experimental autoimmune uveoretinitis (EAU). It is possibly mediated by Th1 immune responses. In the present study, we investigated the role of osteopontin (OPN), a protein with pleiotropic functions that contributes to the development of Th1 cell-mediated immunity. Accompanying EAU progression, OPN was elevated in wild-type (WT) mice that had been immunized with human interphotoreceptor retinoid-binding protein (hIRBP) peptide 1-20. OPN-deficient (OPN-/-) mice showed milder EAU progression in clinical and histopathological scores compared with those of WT mice. The T cells from hIRBP-immunized OPN-/- mice exhibited reduced Ag-specific proliferation and proinflammatory cytokine (TNF-alpha and IFN-gamma) production compared with those of WT T cells. When hIRBP-immunized WT mice were administered M5 Ab reacting to SLAYGLR sequence, a cryptic binding site to integrins within OPN, EAU development was significantly ameliorated. T cells from hIRBP-immunized WT mice showed significantly reduced proliferative responses and proinflammatory cytokine production upon stimulation with hIRBP peptide in the presence of M5 Ab in the culture. Our present results demonstrate that OPN may represent a novel therapeutic target to control uveoretinitis.

The role of the ICOS/B7RP-1 T cell costimulatory pathway in murine experimental autoimmune uveoretinitis

ICOS/B7RP-1 is a new member of the CD28/B7 family of costimulatory molecules and plays differential roles in autoimmune diseases. In this study, we examined the role of ICOS/B7RP-1 pathway in the pathogenesis of mouse experimental autoimmune uveoretinitis (EAU), an animal model of human autoimmune uveitis. ICOS expression was found on infiltrating CD4+ T cells in the region of the retina in EAU-induced mice. The anti-B7RP-1 monoclonal antibody (mAb)-treated or ICOS-deficient mice showed a substantial reduction of disease scores. Blockade of ICOS/B7RP-1 interaction during the effector phase ameliorated the disease, whereas its blockade during the induction phase exhibited no significant effect. Moreover, administration of anti-B7RP-1 mAb effectively ameliorated the disease induced by adoptive transfer of pathogenic T cells. The anti-B7RP-1 mAb treatment inhibited the expansion and/or effector function of pathogenic T cells, given that proliferative response and IFN-gamma production by lymph node cells were reduced upon restimulation with the antigen peptide in vitro. These results suggest that the ICOS/B7RP-1 interaction plays a critical role in the pathogenesis of uveitis. We also indicated that ICOS-mediated costimulation plays differential roles in EAU and experimental autoimmune encephalomyelitis, which is also a Th1 disease induced in the same manner as EAU.

In the rat, citrullinated autologous fibrinogen is immunogenic but the induced autoimmune response is not arthritogenic

Conversion of arginyl to citrullyl residues (citrullination) is essential for the formation of the epitopes recognized by rheumatoid arthritis (RA)-associated autoantibodies to citrullinated proteins (ACPA). ACPA are secreted by plasma cells of the rheumatoid synovial tissue where their major target, citrullinated fibrin, is abundant. Although numerous arguments suggest that ACPA play an important role in RA, their pathological relevance remains to be established. In the present study, we assessed the immunogenicity and arthritogenicity of complete Freund's adjuvant-emulsified autologous citrullinated (C-rFBG) or non-citrullinated (NC-rFBG) fibrinogen in Lewis (LEW) and Brown-Norway rats, which exhibit drastic differences in their susceptibility to induced autoimmune diseases. NC-rFBG induced no antibody response. In contrast, a single injection of C-rFBG induced an IgG response directed mainly to citrullinated determinants of rFBG. However, all rat strains remained devoid of clinical and histological signs of arthritis up to 3 months after C-rFBG inoculation. Next, in LEW rats, we tested whether autoimmunity to C-rFBG could aggravate acute ankle arthritis triggered by intra-articular injection of incomplete Freund's adjuvant (IFA). However, such arthritis evolved identically in the presence or absence of anti-C-rFBG autoantibodies. However, IFA-injected joints were devoid of citrullinated fibrin deposits. Therefore, citrullination allows breakdown of immunological tolerance but the autoimmune response developed is not spontaneously arthritogenic. Whether or not it can aggravate arthritis with citrullinated fibrin deposits remains to be evaluated.

The anti-IRBP IgG1 and IgG2a response does not correlate with susceptibility to experimental autoimmune uveitis

Susceptibility to experimental autoimmune uveitis (EAU) in inbred mice has been associated with a dominant Th1 response. Elevated anti-inter-photoreceptor retinoid-binding protein (anti-IRBP) IgG2a/IgG1 antibody ratios have been implicated as candidate markers to predict disease severity. In the present study, both the anti-IRBP antibody isotype and severity of EAU phenotypes were examined in 4 non-isogenic genetically selected mouse lines to determine if they can be used as general markers of disease. Mice between 8 and 12 weeks old selected for high (H(III)) or low (L(III)) antibody response and for maximum (AIR(MAX)) or minimum (AIR(MIN)) acute inflammatory reaction (AIR) were immunized with IRBP. Each experiment was performed with at least 5 mice per group. EAU was evaluated by histopathology 21 days after immunization and the minimal criterion was inflammatory cell infiltration of the ciliary body, choroid and retina. Serum IgG1- and IgG2a-specific antibodies were determined by ELISA. EAU was graded by histological examination of the enucleated eyes. The incidence of EAU was lower in AIR(MIN) mice whereas in the other strains approximately 40% of the animals developed the disease. Low responder animals did not produce anti-IRBP IgG2a antibodies or interferon-gamma. No correlation was observed between susceptibility to EAU and anti-IRBP isotype profiles. Susceptibility to EAU is related to the intrinsic capacity to mount higher inflammatory reactions and increased production of anti-IRBP IgG2a isotype is not necessarily a marker of this immunologic profile.

Galectin-1 Suppresses Autoimmune Retinal Disease by Promoting Concomitant Th2- and T Regulatory-Mediated Anti-Inflammatory Responses

Intraocular inflammatory diseases are a common cause of severe visual impairment and blindness. In this study, we investigated the immunoregulatory role of galectin-1 (Gal-1), an endogenous lectin found at sites of T cell activation and immune privilege, in experimental autoimmune uveitis (EAU), a Th1-mediated model of retinal disease. Treatment with rGal-1 either early or late during the course of interphotoreceptor retinoid-binding protein-induced EAU was sufficient to suppress ocular pathology, inhibit leukocyte infiltration, and counteract pathogenic Th1 cells. Administration of rGal-1 at the early or late phases of EAU ameliorated disease by skewing the uveitogenic response toward nonpathogenic Th2 or T regulatory-mediated anti-inflammatory responses. Consistently, adoptive transfer of CD4(+) regulatory T cells obtained from rGal-1-treated mice prevented the development of active EAU in syngeneic recipients. In addition, increased levels of apoptosis were detected in lymph nodes from mice treated with rGal-1 during the efferent phase of the disease. Our results underscore the ability of Gal-1 to counteract Th1-mediated responses through different, but potentially overlapping anti-inflammatory mechanisms and suggest a possible therapeutic use of this protein for the treatment of human uveitic diseases of autoimmune etiology.

The role of cytokine mRNA stability in the pathogenesis of autoimmune disease

Inflammatory cytokines such as interferon (IFN)-gamma, interleukin (IL)-2, tumor-necrosis factor (TNF)-alpha and IL-17 play an important role in the pathogenesis of cell-mediated autoimmune diseases. Cytokine gene expression is tightly regulated at the post-transcriptional level. Cytokine mRNA decay is dependent not only upon cis-elements in the RNA but also upon trans-acting factors such as the RNA binding proteins TTP, HuR, AUF-1, Nucleolin and YB-1. Physiologic signals, for instance signaling through the CD28 receptor on T cells, can modulate the half-life of a select subset of cytokine mRNAs, such as IL-2. Distinct cis- and trans-acting elements in human and mouse IL-2 mRNA may account for the different pattern of CD28-mediated mRNA stabilization in these two species. TTP-deficient mice or mice with a deletion of the TNF-alpha mRNA ARE element develop a complex inflammatory syndrome that is associated with a prolonged TNF-alpha mRNA half-life and elevated levels of circulating TNF-alpha. This syndrome can be prevented by treatment with TNF-alpha blocking antibodies. Evidence from mice with altered cytokine mRNA stability, along with human data, suggests that imbalance between the stability and decay of inflammatory cytokine mRNAs could represent a basic mechanism leading to autoimmunity.

Induction of suppressors of cytokine signaling (SOCS) in the retina during experimental autoimmune uveitis (EAU): potential neuroprotective role of SOCS proteins

Suppressors of cytokine signaling (SOCS) are implicated in immunopathogenic mechanisms of autoimmune diseases. We show here that SOCS expression in retina is temporarily correlated with progression of experimental autoimmune uveitis (EAU), an organ-specific autoimmune disease that serves as model of human uveitis. Peak of EAU correlates with highest SOCS genes expression while disease resolution coincides with their down-regulation. Surprisingly, SOCS5 is constitutively expressed in retina. SOCS5 expression increases significantly during EAU and remains elevated even after disease resolution. Our data suggest that cytokine-inducible SOCS members may be involved in negative regulation of inflammatory cytokines activities during EAU, while constitutively expressed SOCS5 may have neuroprotective functions.

Peripheral expression of rod photoreceptor arrestin induces an epitope-specific, protective response against experimental autoimmune uveoretinitis

PURPOSE

To examine the immunological basis for reduced susceptibility to experimental autoimmune uveoretinitis (EAU) in rats expressing retinal photoreceptor cell arrestin in the periphery.

METHODS

Peripheral expression of arrestin in Lewis rats was achieved by engraftment of syngeneic bone marrow (BM) transduced with retroviruses encoding wild-type arrestin or a mutant arrestin lacking the immunodominant epitope Arr(273 - 289) (Delta273-Arr). EAU was induced by immunization with arrestin peptides Arr(273-289) or Arr(343-362). Cultured splenocytes and/or lymphocytes from immunized rats were assayed for antigen-induced proliferation, antibody production, and cytokines.

RESULTS

Rats expressing Delta273-Arr were not protected from Arr(273 - 289)-induced EAU, showing that protection was epitope specific. Proliferation assays found little difference in the ability of draining lymph node cells from arrestin-transduced rats to proliferate in response to the antigen, indicating that antigen-responsive T cells were not deleted in BM recipients. Only rats immunized with Arr(343 - 362) elicited antibodies, but no difference in titer was found between transduced and control animals. Higher levels of IFN-gamma mRNA were made by Arr(273 - 289)-immunized rats than Arr(343 - 366)-immunized rats, but in either case, the levels did not correlate with chimeric status or EAU susceptibility. Arr(273 - 289)-immunized rats had higher levels of IL-10 mRNA than Arr(343 - 362)-immunized rats, and those levels were decreased in arrestin chimeric rats. Overall, immunization with the more potently uveitogenic Arr(343 - 362) induced lower levels of IL-10 and IFN-gamma than the less uveitogenic Arr(273 - 289). A strong correlation was found between the ability of lymphocytes to make IL-4 in the arrestin-chimeric animals and inhibition of EAU.

CONCLUSIONS

Peripheral expression of arrestin in a regenerating immune system induces an epitope-specific protective response to EAU induced by arrestin peptides. Although IL-4 and IL-10 levels were altered in arrestin-chimeric mice, the outcome was not consistently T(H)2-like. Only IL-4 production was clearly associated with reduced susceptibility to EAU.

PyNTTTTGT prototype oligonucleotide IMT504 is a potent adjuvant for the recombinant hepatitis B vaccine that enhances the Th1 response

PyNTTTTGT oligodeoxinucleotides (ODNs) cause activation, proliferation and immunoglobulin secretion on B cells, and the expression of co-stimulatory molecules on plasmacytoid dendritic cells of primates. It has now been discovered that these ODNs are also active on rat cells. This fact allowed us to investigate the adjuvant properties of PyNTTTTGT ODNs in a human Hepatitis B vaccine using this animal model. A very significant increment, as compared with the antigen alone, was observed in the antibody production induced by vaccination with the recombinant Hepatitis B surface antigen adjuvated with the PyNTTTTGT prototype IMT504 ODN. Analysis of the IgG subclass distribution in the sera of vaccinated animals indicated that, although an increase was observed in the titer of all the IgG subclasses, the increase on the Th1-associated IgG2b subclass was clearly more pronounced. Remarkably, this effect on the IgG2b titer was observed even if alum, a Th2 promoting adjuvant, was present together with IMT504 in the vaccine formulation. The increase in the Th1 response induced by IMT504 was also suggested by in vitro gamma interferon secretion assays. Monkeys of the species Cebus apella immunized with the recombinant Hepatitis B surface antigen plus alum and IMT504 also showed titers of antibodies against the antigen several times superior to the titers observed in control animals immunized with the antigen plus alum without ODN. Since rat and monkey cells are significantly less immunostimulated "in vitro" by PyNTTTTGT ODNs than human cells, the present results reasonably predict a very good performance of these ODNs as adjuvants in human vaccination.

Mice lacking the IFN-gamma receptor or fyn develop severe experimental autoimmune uveoretinitis characterized by different immune responses

Endogenous interferon (IFN)-gamma negatively regulates experimental autoimmune uveoretinitis (EAU), a Th1-mediated disease. Although it is well known that IFN-gamma exerts its effects by binding to the IFN-gamma receptor (IFN-gammaR), the role that IFN-gammaR plays in the development of EAU has not been investigated. Fyn has been reported to inhibit Th2 differentiation. We aimed to investigate how endogenous IFN-gammaR and fyn, which influence Th1/Th2 differentiation, participate in the development of EAU. Sex-matched 6- to 10-week-old C57BL/6 wild-type (WT), IFN-gammaR knockout (GRKO) and fyn knockout (fyn KO) mice were compared. Mice were immunized subcutaneously with human interphotoreceptor retinoid-binding protein peptide 1-20 emulsified in Freund's complete adjuvant together with an intraperitoneal injection of Bordetella pertussis toxin. Three weeks later, mice were sacrificed, and their eyes and spleens were harvested for histopathologic analyses and examination of cellular immune responses, respectively. Cellular immune responses were evaluated by measuring the proliferative responses and cytokine production [interleukin (IL)-4, IL-5, IL-6, IL-13, IFN-gamma and tumor necrosis factor (TNF)-alpha] of splenocytes. The incidence of EAU was 40.0% in WT mice, 59.3% in GRKO mice and 78.6% in fyn KO mice. The average EAU score was 0.294 in WT mice, 0.917 in GRKO mice and 1.063 in fyn KO mice. Upon EAU induction, significant infiltration of eosinophils into the eyes was observed in GRKO and fyn KO mice compared to WT mice. Splenocytes from GRKO mice proliferated against the antigen and a mitogen more vigorously than those from WT and fyn KO mice. Stimulation of splenocytes with the antigen induced a higher production of IL-4, IL-6, IL-13 and IFN-gamma in GRKO mice compared to WT and fyn KO mice. In contrast, IL-5 and TNF-alpha were most abundantly produced by splenocytes from fyn KO mice compared to WT and GRKO mice. The incidence and mean severity of EAU were significantly higher in GRKO and fyn KO mice than in WT mice, suggesting that endogenous IFN-gammaR and fyn negatively regulate the development of EAU. The different cytokine production patterns by the GRKO and fyn KO mice indicate that the negative regulatory mechanism mediated by IFN-gammaR and fyn may differ.

The immunomodulatory actions of E-type prostaglandins

Prostaglandins (PGs) have been recognised as modulators of immune responses. This has been proved by both in vitro studies and from observations in animals and humans. Administration of prostaglandins for therapeutic purposes, however, has been hampered by their limited bioavailability and their pleiotropic effects, with resultant toxicological profile. Despite this, some success has been demonstrated in the clinic for the control of graft rejection, especially when used as part of a broader immunosuppressant regimen. Full realisation of the therapeutic potential of prostaglandins will depend on a better understanding of their mechanism of action at the cellular level. Recently, it has been appreciated that prostaglandins do not merely inhibit T-cell function, but appear to modulate the profile of lymphocyte sub-populations through regulation of cytokine synthesis and release. Recent efforts have also begun to focus on identifying prostaglandin receptor subtypes important for immune regulation and offer a means, together with targeted delivery, of utilising the immunosuppressant/anti-inflammatory effects of E-type prostaglandins in a safe and effective manner.

COX-2 Inhibitors at The 8th International Conference of the Inflammation Research Association

An intensive search is underway for novel selective inhibitors of cyclo-oxygenase (COX)-2. These compounds promise to be potent anti-inflammatory agents with little gastrointestinal intolerance. Meloxicam, with some selectivity for COX-2, is already marketed, and at least two companies are carrying out clinical studies with selective inhibitors. A variety of potential successor compounds were presented at the 8th International Conference of the Inflammation Research Association (IRA) in Hershey, PA on 27-31 October 1996.

Age-related changes in the development of experimental autoimmune encephalomyelitis

A prominent feature of multiple sclerosis is its high incidence of onset in the third decade of life and its relatively rare onset in persons older than 50 years. In order to study age-related restriction of clinical expression, a comparative biochemical, immunological and histological study was undertaken during development of experimental autoimmune encephalomyelitis (EAE) in young (7 weeks) and middle-aged (15 months) Wistar rats. Young rats showed characteristic clinical signs 12-16 days postinduction, and then they spontaneously recuperated. In middle-aged rats, the incidence of clinical signs was significantly reduced, with a later onset of the disease. Similar biochemical and histological alterations were detected in both age groups, but they were present in a later stage in middle-aged animals. However, cellular and humoral immune responses to myelin basic protein (MBP) were observed 15 days postinduction in all EAE animals. The study of anti-MBP IgG isotype pattern in 7-week-old animals indicated a predominant Th1-type immune response during the acute stage of EAE, with antibodies predominantly recognizing the MBP 96-128 peptide. In contrast, 15-month-old animals showed a less prominent Th1 response, without any epitope dominance. The changes in immune function found in middle-aged animals may account for the different susceptibility and expression of EAE, and may also be relevant to the different clinical expression observed in multiple sclerosis with maturation.

[Pathogenic mechanisms of autoimmune diseases]

BACKGROUND

Auto-immune diseases are a fascinating but poorly understood group of diseases.

MAJOR POINTS

In this review, we will consider genetic susceptibility to auto-immune diseases, initiation of autoreactivity and changes in pathologic processes. Recent physiopathological hypotheses are detailed with clinical examples.

PERSPECTIVES

A better knowledge of the physiopathological mechanisms would allow the development of more efficacious treatments.

Peritoneal Exudate Cells Treated with Calcitonin Gene-Related Peptide Suppress Murine Experimental Autoimmune Uveoretinitis via IL-10

Immunization with retinal Ag induces experimental autoimmune uveoretinitis (EAU) in mice. We investigated the suppression of murine EAU by peritoneal exudate cells (PEC) cultured with calcitonin gene-related peptide (CGRP). PEC derived from mice were treated with CGRP and residues 1-20 of human interphotoreceptor retinoid-binding protein (hIRBP 1-20). The hIRBP 1-20-immunized mice were injected i.v. with PEC treated with CGRP and hIRBP 1-20. After immunization, Ag-specific delayed hypersensitivity (DH) was measured and EAU was assessed histopathologically. Both EAU- and Ag-specific DH were suppressed by injection of PEC treated with CGRP (100 ng/ml) and hIRBP 1-20. However, hIRBP 1-20-mediated EAU was not suppressed by injection of PEC treated with CGRP and BSA. Both EAU- and Ag-specific DH were not suppressed by injection of PEC treated with CGRP and hIRBP 1-20 into splenectomized mice. In mice adoptively transferred spleen cells from hIRBP 1-20-immunized mice, EAU was also suppressed by injection of CGRP-treated PEC. EAU was markedly inhibited in hIRBP 1-20-immunized mice adoptively transferred T cells obtained from mice injected with hIRBP 1-20-pulsed, CGRP-treated PEC. Furthermore, EAU- and Ag-specific DH were not suppressed by injection of PEC treated with CGRP and hIRBP 1-20 when the recipient mice were given anti-IL-10 Ab i.p., or when the PEC were derived from IL-10 knockout mice. The present results indicate that PEC treated with CGRP suppress murine EAU in an Ag-specific manner, even in the efferent phase, and IL-10 secreted from PEC might play an important role in the CGRP-mediated suppression of murine EAU.

Recruitment of IFN-gamma-producing (Th1-like) cells into the inflamed retina in vivo is preferentially regulated by P-selectin glycoprotein ligand 1:P/E-selectin interactions

Although there is evidence that altering the Th1/Th2 balance toward Th2 cells may be important in the resolution of Th1-type autoimmune disease, adoptive transfer of Th2 cells is not effective in protecting against Th1-type disease and may cause disease. Therefore, we examined the recruitment of Th1- and Th2-like cells into the retina in the murine autoimmune disease experimental autoimmune uveoretinitis. CD4 T cells were polarized in vitro to IFN-gamma-producing Th1-like cells and non-IFN-gamma-producing Th2-like cells, labeled, and adoptively transferred. Trafficking to the retina in vivo was evaluated by scanning laser ophthalmoscopy and infiltration by confocal microscopy. There were more rolling and adherent Th1-like cells and they rolled more slowly than did Th2-like cells. Th1-like cells were preferentially recruited into the retinal parenchyma at both initiation and resolution. Surface P-selectin glycoprotein ligand 1 (PSGL-1) and LFA-1 were up-regulated on both populations but were expressed at higher levels on Th1-like cells. Up-regulation of CD44 expression was higher on Th2-like cells. P-selectin, E-selectin, and ICAM-1 are up-regulated on postcapillary venules in the retina. Pretreatment of Th1-like cells with anti-PSGL-1 inhibited rolling and infiltration of Th1-like cells but not Th2-like cells, providing direct in vivo evidence for the inability of Th2 to respond to P/E-selectin despite increased expression of PSGL-1. Anti-LFA-1 pretreatment inhibited infiltration of both Th1- and Th2-like cells, but more so Th-1. We suggest that random trafficking of activated T cells (both Th1 and Th2) across the blood-retina barrier is mediated by CD44:CD44R and LFA-1:ICAM-1, whereas preferential recruitment of Th1 cells is mediated by PSGL-1:P/E-selectin.

Neuronal antigens modulate the immune response associated with experimental autoimmune encephalomyelitis

Rats primed with bovine myelin (BM) in complete Freunds adjuvant, develop acute experimental autoimmune encephalomyelitis (EAE). We have previously described that intraperitoneal administration prior to the active induction of the disease of a bovine synaptosomal fraction (BSF) and BM were effective ways of suppressing EAE. We found that both treatments diminish the incidence of the disease and reduced biochemical and histological alterations of the central nervous system (CNS). To characterize this suppression process, in this study we examined the antigen-specific immune response in animals protected from EAE. Lymph node mononuclear cells derived from sick EAE rats, as well as from those protected by BM and BSF, showed strong myelin basic protein (MBP) proliferation. Analysis of the humoral response against MBP showed a significant diminution of IgG2b anti-MBP titres in protected BM and BSF rats in contrast to sick EAE rats whose condition could be related to a diminished anti-MBP Th1 response. Finally, cells from rats protected by BSF and BM reduced the incidence of EAE when they were adoptively transferred into animals prior to active induction of the disease. These results suggest that a mechanism based on the generation of regulatory cells and immune deviation could account for the EAE suppression mediated by myelin as well as synaptosomal antigens.

Polarity of helper T cell subsets represents disease nature and clinical course of experimental autoimmune myocarditis in rats

The mechanisms of progression, remission and relapse of myocarditis remain unclear. To clarify these mechanisms, we focused on T helper-1 (Th1)/T helper-2 (Th2) subsets balance of peripheral lymphocytes and serum cytokine levels during disease progression in rats with experimental autoimmune myocarditis (EAM). Lewis rats were immunized with cardiac myosin on day 0. Blood samples were collected on days 0, 7, 15, 18, 21, 28, 35, 42, 49 and 56 following immunization. We examined percentages of interferon (IFN)-gamma and/or interleukin (IL)-4 producing cells in stimulated peripheral CD4-positive lymphocytes using flow cytometry analysis. Serum IFN-gamma, IL-2, IL-6 and IL-10 levels were measured by enzyme-linked immunosorbent assay (ELISA). The percentage of Th1/Th2 subsets in EAM on days 0, 15, 28 and 56 were 2.5 +/- 0.5/0.5 +/- 0.1%, 19.4 +/- 3.2/1.6 +/- 0.3%, 2.0 +/- 0.5/22.1 +/- 5.7% and 3.0 +/- 0.4/1.7 +/- 0.3%, respectively. Serum levels of Th1 cytokines, IFN-gamma and IL-2 significantly increased in the acute phase (from day 15-18) and immediately decreased in the early recovery phase. On the other hand, serum levels of Th2 cytokine, IL-10 significantly increased in the early recovery phase (from day 24-30). These results suggest that induction of acute myocarditis might be associated with systemic Th1 dominance, while recovery is related to systemic Th2 polarity. Thus, analysis of Th1/Th2 balance in peripheral T cells may be useful in disease monitoring in patients with myocarditis and postmyocarditic dilated cardiomyopathy.

Allograft inflammatory factor-1 regulates trinitrobenzene sulphonic acid-induced colitis

The expression of allograft inflammatory factor-1 (AIF-1) in 2,4,6-trinitrobenzene sulphonic acid (TNBS)-induced colitis, a model for T helper 1 (Th1) type disease, was investigated in BALB/c mice. The AIF-1 expression was significantly increased in the colitis lesion compared to that in the normal colon. We then prepared AIF-1 transgenic mice (Tgm) with the BALB/c background that express high levels of AIF-1 in lymphoid tissues and the colon. When AIF-1 Tgm were administrated TNBS, the TNBS-induced colitis was ameliorated compared with that in non-transgenic littermates. The amelioration of colitis was associated with the low expression of interleukin-1beta in the colon. The present findings suggest that AIF-1 regulates Th1-type inflammatory responses.

Analysis of immunoregulatory T-helper cell subsets in patients with multiple sclerosis: relapsing-progressive course correlates with enhanced T H1, relapsing-remitting course with enhanced T H0 reactivity

In this study, we analysed the recall antigen-induced cytokine production by peripheral blood mononuclear cells (PBMC) from 31 patients with multiple sclerosis (MS) with a relapsing-remitting (rr) and a relapsing-progressive (rp) course and from 40 healthy controls. Cells were stimulated with purified protein derivative (PPD; type 1 response) and tetanus toxoid (TT; type 2 response). Cytokines were determined in the supernatants by ELISA. One of the interesting findings was that healthy controls showed more frequently an IL-5 production after incubation with TT than MS-patients (68% vs.37%; p<0.01), while the type 1 reactivity was only slightly enhanced in MS patients as compared to the controls. However, within the MS patients, there was a significant difference in the incidence of the type 1 reactivity comparing patients with an rp and an rr course (60% vs. 24%; p<0.05). Furthermore, the frequency of a type 0 profile (simultaneous PPD-induced IFN-gamma and TT-induced IL-5 production) was fourfold higher in rr than in the rp patients (43% vs. 10%, p<0.05). In vitro analysis of cytokine profiles in MS could therefore be an interesting approach to evaluate the prognosis of MS (rr vs. rp) already at the beginning of the disease. Thus, it seems that the presence of a type 0 profile is a valid indicator for a favorable course, while a type 1 profile is rather associated with rp MS.

Immunization with cathepsin L proteinases CL1 and CL2 secreted by Fasciola hepatica elicit a preferential type 1 response based on IgG2a antibodies in rats

Cathepsin L proteinases (CL1 and CL2), the major components of Fasciola hepatica excretion/secretion products (E/S) are considered potential antigens of a vaccine against fascioliasis. The humoral response elicited by CL1 and CL2 in rats either immunized with the enzymes or infected with F. hepatica has been analysed, examining specific IgE and IgG subclass dynamics. The experiment was continued for 10 weeks and peripheral blood eosinophilia was also determined. Infected rats presented peaks of eosinophilia at weeks 3 and 7 post-infection, while those immunized with CL1 and CL2 were no different from controls. Total IgE in infected rats increased up to week 5, reaching 30 microg(-1) in some cases, then decreased slowly and rising again towards the end of the experiment. Determination of specific IgE, carried out in sera previously absorbed with Protein G-Sepharose, reached a peak in infected rats between weeks 2 and 5, depending on the individual. In immunized rats both total and specific IgE levels remained around the pre-immunization values. With regard to the IgG subclass responses to E/S products, in infected rats IgG1 predominated over IgG2a, and the reverse was true in rats immunized with CL1 and CL2 and tested against the respective antigens. In all cases an increase in IgG1 and IgG2a antibody titres was seen, with maximum levels being reached later (weeks 6-7) in infected rats than in immunized ones (weeks 4-5). No IgG2b or IgG2c responses were detected in any of the groups studied.

Attenuation of experimental allergic encephalomyelitis in complement component 6-deficient rats is associated with reduced complement C9 deposition, P-selectin expression, and cellular infiltrate in spinal cords

The role of Ab deposition and complement activation, especially the membrane attack complex (MAC), in the mediation of injury in experimental allergic encephalomyelitis (EAE) is not resolved. The course of active EAE in normal PVG rats was compared with that in PVG rats deficient in the C6 component of complement (PVG/C6(-)) that are unable to form MAC. Following immunization with myelin basic protein, PVG/C6(-) rats developed significantly milder EAE than PVG/C rats. The anti-myelin basic protein response was similar in both strains, as was deposition of C3 in spinal cord. C9 was detected in PVG/C rats but not in PVG/C6(-), consistent with their lack of C6 and inability to form MAC. In PVG/C6(-) rats, the T cell and macrophage infiltrate in the spinal cord was also significantly less than in normal PVG/C rats. There was also reduced expression of P-selectin on endothelial cells, which may have contributed to the reduced cellular infiltrate by limiting migration from the circulation. Assay of cytokine mRNA by RT-PCR in the spinal cords showed no differences in the profile of Th1 or Th2 cytokines between PVG/C and PVG/C6(-) rats. PVG/C rats also had a greater increase in peripheral blood white blood cell, neutrophil, and basophil counts than was observed in the PVG/C6(-). These findings suggest that the MAC may have a role in the pathogenesis of EAE, not only by Ig-activated MAC injury but also via induction of P-selectin on vascular endothelium to promote infiltration of T cells and macrophages into the spinal cord.

Th1 and Th2 responses in pathogenesis and regulation of experimental autoimmune uveoretinitis

Experimental autoimmune uveoretinitis (EAU) in animals can be induced by immunization with retinal antigens or their fragments and represents human uveitis of putative autoimmune origin. The pathogenesis of EAU, and likely also of human uveitis, involves cell-mediated destruction of retinal tissues that is dependent on retinal antigen-specific T cells. Because in most cases a Th1-type response has been implicated in pathogenesis, the prevailing consensus has been that immunoregulatory manipulations designed to enhance the Th2 response at the expense of the Th1 response will be beneficial in clinical treatment of uveitis. This assumption may not always be correct. The present review will summarize the evidence that, despite a central role for Th1 response in uveitis, an unopposed Th2-like response can be equally or more destructive to the retinal tissues. Furthermore, the Th1 response itself triggers regulatory circuits that feed back and dampen further recruitment of antigen-specific T cells into the Th1 effector pool. Thus, although the Th1 effector response can and does result in retinal pathology, immunoregulatory strategies must take into account that immune deviation therapies designed to replace the Th1 with a Th2 response might result in exchanging one type of pathology for another rather than in achieving the desired therapeutic effect.

Self major histocompatibility complex class-II-specific regulatory CD4 T cells prevent both Th1- and Th2-mediated autoimmune diseases in the rat

It is clear that functional heterogeneity of T cells may be explained by differential cytokine production. The aim of this paper was to review evidence for regulatory cells, generated after HgCl(2)-exposure. They differ from classical Th1 and Th2 cells, produce transforming growth factor-beta and interleukin-10 and exert their regulatory functions in a Th1/Th2-unrestricted fashion.

Analysis of mercury-induced immune activation in nonobese diabetic (NOD) mice

In susceptible mice, the heavy metal ion mercury is able to induce a strong immune activation, which resembles a T helper 2 (Th2) type of immune response and is characterized by a polyclonal B cell activation, formation of high levels of IgG1 and IgE antibodies, production of autoantibodies of different specificities and development of renal IgG deposits. In the present study, we analysed the in vivo effects of mercury in nonobese diabetic (NOD) mice, which is believed to develop a spontaneous Th1 cell-mediated autoimmune diabetes similar to type 1 diabetes in humans. Three weeks of treatment with mercury induced a strong Th2 like immune/autoimmune response in NOD mice. This response was characterized by an intensive increase in splenic IgG1 antibody secreting cells, a marked elevation in serum IgE levels, a substantial increase in splenic IL-4 mRNA, but a significant decrease in splenic IFN-gamma mRNA. Mercury-induced IgG1 antibodies were mainly against ssDNA, TNP and thyroglobulin, but not against nucleolar antigen. Moreover, mercury-injected NOD mice developed high titres of IgG1 deposits in the kidney glomeruli. We further tested if the generated Th2 response could interfere with the development of insulitis and diabetes in NOD mice. We found that three weeks of treatment with mercury was also able to significantly suppress the development of insulitis and postpone the onset of diabetes in these mice. Thus, mercury-induced immune activation can counter-regulate the Th1 cell-mediated autoimmune responses and confer a partial protection against autoimmune diabetes in NOD mice.