Peptide-induced T cell regulation of experimental autoimmune encephalomyelitis: a role for IL-10

Tregs and allergic disease

Allergic diseases such as asthma, rhinitis, and eczema are increasing in prevalence and affect up to 15% of populations in Westernized countries. The description of Tregs as T cells that prevent development of autoimmune disease led to considerable interest in whether these Tregs were also normally involved in prevention of sensitization to allergens and whether it might be possible to manipulate Tregs for the therapy of allergic disease. Current data suggest that Th2 responses to allergens are normally suppressed by both CD4+CD25+ Tregs and IL-10 Tregs. Furthermore, suppression by these subsets is decreased in allergic individuals. In animal models, Tregs could be induced by high- or low-dose inhaled antigen, and prior induction of such Tregs prevented subsequent development of allergen sensitization and airway inflammation in inhaled challenge models. For many years, allergen-injection immunotherapy has been used for the therapy of allergic disease, and this treatment may induce IL-10 Tregs, leading to both suppression of Th2 responses and a switch from IgE to IgG4 antibody production. Improvements in allergen immunotherapy, such as peptide therapy, and greater understanding of the biology of Tregs hold great promise for the treatment and prevention of allergic disease.

Animal models of type I allergy using recombinant allergens

Various animal models including guinea pigs, monkeys, dogs, rats, and mice have been established in an attempt to provide insights into the complex immunological and pathophysiological mechanisms of human type I allergic diseases. The detailed knowledge of the murine genome, the various components of the murine immune system, and the generation of engineered mice has made the murine system the most attractive among all animal models. The availability of multitude technologies and reagents to characterize and manipulate immunological pathways and mediators adds to the outstanding opportunities to assess the pathology of allergic diseases and to develop novel therapeutic strategies in mice. Numerous sensitization protocols with food and aero-allergens are used to establish an allergic/asthma-like phenotype in mice. Requirements for an appropriate murine model include a close resemblance to the pathology of the disease in humans, the objective measurement of the physiologic parameters, as well as reliability and reproducibility of the experimental data. With respect to reproducible experimental conditions, it has been recognized that extract preparations from natural allergen sources can vary in their allergen-content and -composition. This might influence the degree of sensitization or the outcome of treatment strategies in dependence of the applied extract preparation. The use of recombinant allergens in experimental in vivo and in vitro systems can overcome these problems. Another aspect, that has become obvious from the experimental studies, is that allergens can differ in their immunogenicity as well as in their capacity to act as tolerogens. Therefore, it seems important that the efficacy of the different allergen-molecules to act as therapeutic agents is individually examined. In this review, examples of animal models are described, in which recombinant allergens have been used for sensitization and/or treatment of allergic responses and how they have been used to enhance our understanding of the pathology of allergic diseases.

Regulatory T cells and mechanisms of immune system control

The immune system evolved to protect the host against the attack of foreign, potentially pathogenic, microorganisms. It does so by recognizing antigens expressed by those microorganisms and mounting an immune response against all cells expressing them, with the ultimate aim of their elimination. Various mechanisms have been reported to control and regulate the immune system to prevent or minimize reactivity to self-antigens or an overexuberant response to a pathogen, both of which can result in damage to the host. Deletion of autoreactive cells during T- and B-cell development allows the immune system to be tolerant of most self-antigens. Peripheral tolerance to self was suggested several years ago to result from the induction of anergy in peripheral self-reactive lymphocytes. More recently, however, it has become clear that avoidance of damage to the host is also achieved by active suppression mediated by regulatory T (T(reg)) cell populations. We discuss here the varied mechanisms used by T(reg) cells to suppress the immune system.

Alteration of the tertiary structure of the major bee venom allergen Api m 1 by multiple mutations is concomitant with low IgE reactivity

We have engineered a recombinant form of the major bee venom allergen (Api m 1) with the final goal of reducing its IgE reactivity. This molecule (Api mut) contains 24 mutations and one deletion of 10 amino acids. The successive introduction of these sequence modifications led to a progressive loss of specific IgE and IgG reactivity and did not reveal any immunodominant epitopes. However, Api mut exhibited a clear loss of reactivity for Api m 1-specific IgE and IgG. Injection of Api mut into mice induced specific antibody production. This humoral response was as high as that induced by the Api m 1 but the cross-reactivity of the antibodies was weak. As inferred by far UV circular dichroism, this mutant was correctly folded. However, near UV circular dichroism and denaturation curves of Api mut showed that it exhibits a dynamic tertiary structure and that it is a highly flexible molecule. Finally, as all the sequence modifications have been introduced outside the human and murine T cell epitope regions, we investigated its T cell properties in mice. We showed that Api mut-specific T lymphocytes induced in vivo were stimulated in vitro by both proteins. These data provide new insights in the design of hypoallergenic molecules.

Reduction of human anti-tetanus toxoid antibody in hu-PBL-SCID mice by immunodominant peptides of tetanus toxoid

Immunotherapy of murine autoimmune and allergic diseases by administration of peptides corresponding to the dominant T cell epitope is a reality. However, problems remain in applying this therapy to reduce antibody responses in humans. To overcome these difficulties, a preclinical system was developed to test the effect of immunodominant peptides from a common antigen, tetanus toxoid (TT), on the long-term human anti-TT response. Individuals whose T cells proliferated against dominant TT peptides were identified. Peripheral blood leucocytes (PBL) from these donors were injected intraperitoneally (i.p.) into mice with severe combined immunodeficiency (SCID) that had been depleted of murine natural killer (NK) cells (hu-PBL-SCID mice). Peptides or PBS were injected i.p. before a further injection of PBL and immunization with TT. The concentration of human IgG and anti-TT in murine plasma was followed for 10 weeks. The total IgG was similar in both groups. By contrast, there was a statistically significant reduction in IgG anti-TT from eight weeks onwards. It is considered that the hu-PBL-SCID model system may provide a means by which the efficacy of peptide immunotherapy for reduction of pathological antibodies in humans can be examined.

Murine respiratory tract dendritic cells: isolation, phenotyping and functional studies

Respiratory tract dendritic cells (RTDC) form a contiguous subepithelial network within the nasorespiratory tract bridging innate and acquired immunity and have been implicated in nasal mucosal tolerance induction. Discrepancies exist between isolation techniques with respect to phenotype and function of RTDC. Therefore, the aim of this study was to modify previous methods to provide a consistent isolation method whilst maintaining good cell viability and enriched cell numbers so as to facilitate further phenotype and functional studies of murine RTDC. RTDCs isolated by enzyme digestion, Percoll density gradient centrifugation and overnight GM-CSF culture followed by MACS separation retain an archetypical immature dendritic cell phenotype, characterised by MHCII(low) CD40(neg) CD86(neg) CD80(neg) CD11c(low) cell surface expression. Splenic-derived DC (SDC) isolated conformed to a day 1 in vitro phenotype; MHCII(low) CD40(neg) CD86(low) CD80(neg) CD11c(low) but can further mature phenotypically in vitro. Both RTDC and SDC processed and presented antigen efficiently to T cells in vitro. Using such modified isolation procedures for RTDCs, we have developed a consistent method of RTDC enrichment, which maintains the immature phenotype and functional antigen presenting capability.

IL-10-Secreting Regulatory T Cells Do Not Express Foxp3 but Have Comparable Regulatory Function to Naturally Occurring CD4+CD25+ Regulatory T Cells

Regulatory T cells (T(Reg)) control immune responses to self and nonself Ags. The relationship between Ag-driven IL-10-secreting T(Reg) (IL-10-T(Reg)) and naturally occurring CD4(+)CD25(+) T(Reg) is as yet unclear. We show that mouse IL-10-T(Reg) obtained using either in vitro or in vivo regimens of antigenic stimulation did not express the CD4(+)CD25(+) T(Reg)-associated transcription factor Foxp3. However, despite the absence of Foxp3 expression, homogeneous populations of IL-10-T(Reg) inhibited the in vitro proliferation of CD4(+)CD25(-) T cells with a similar efficiency to that of CD4(+)CD25(+) T(Reg). This inhibition of T cell proliferation by IL-10-T(Reg) was achieved through an IL-10-independent mechanism as seen for CD4(+)CD25(+) T(Reg) and was overcome by exogenous IL-2. Both IL-10-T(Reg) and CD4(+)CD25(+) T(Reg) were similar in that they produced little to no IL-2. These data show that Foxp3 expression is not a prerequisite for IL-10-T(Reg) activity in vitro or in vivo, and suggest that IL-10-T(Reg) and naturally occurring CD4(+)CD25(+) T(Reg) may have distinct origins.

Gene therapy in a murine model for clinical application to multiple sclerosis

Female SJL/J mice, suffering from experimental autoimmune encephalomyelitis (EAE), were injected with 1 x 10(7) cells from a syngeneic fibroblast line transduced with a retroviral vector designed to encode proteolipid protein (101-157) targeted for secretion. A striking abrogation of both clinical and histological signs of disease resulted. The treatment was efficacious when given after the first or the third relapses, protected naive mice from challenge with spinal cord homogenate, and was dose dependent. This strategy was devised to provide a systemic, antigen-specific signal to pathogenic T cells in the absence of costimulation and, hence, render them anergic. Cytokine analyses of brain and spinal cord lymphocytes demonstrate that the treatment induces an antiinflammatory Th2 profile, indicating that this antigen-specific therapy acts by a cytokine-induced pathway. This study was designed for translation to the clinic. We envision using allogeneic transduced fibroblasts, encapsulated in a chamber, to deliver the antigen-specific signal. This will enable us to use one therapeutic cell line for all patients and to remove the device should the therapy exacerbate disease.

T cell and antibody responses in remitting–relapsing experimental autoimmune encephalomyelitis in (C57BL/6×SJL) F1 mice

To characterize T cell and antibody responses in remitting-relapsing experimental autoimmune encephalomyelitis (RR-EAE), we compared myelin oligodendrocyte glycoprotein (MOG)-induced RR-EAE in C57BL/6 (B6) x SJL (F1) mice and chronic-progressive EAE (CP-EAE) in B6 mice at week 8 p.i. when clinical scores were comparable. Although these two strains exhibited similar inflammation/demyelination pattern and MOG-induced T cell responses, RR-EAE mice produced significantly higher levels of anti-MOG IgG1/IgG2a antibodies. Further, lymphocytes of RR-EAE mice proliferated vigorously to the secondary epitope myelin basic protein (MBP) 1-11. These results support a potential involvement of anti-MOG antibodies and epitope spreading in T cell responses in the development of MOG-induced RR-EAE model.

Transplantation tolerance induced by intranasal administration of HY peptides

Induction of antigen-specific tolerance to transplantation antigens is desirable to control host-versus-graft and graft-versus-host reactions. Following molecular identification of a set of minor histocompatibility (H) antigens, we have used selected HY peptide epitopes for this purpose. Intranasal administration of individual major histocompatibility complex (MHC) class II-restricted HY peptides induces indefinite survival of syngeneic male skin grafts and allows engraftment of male bone marrow. Tolerance involves linked suppression to additional HY epitopes on test grafts. Long-term tolerance also requires suppression of emerging thymic emigrants. It does not involve deletion. HY peptide-specific CD4(+) and CD8(+) T cells expand on re-exposure to male antigen; these expansions are smaller in tolerant than control mice and fewer HY-specific cells from tolerant females secrete interferon gamma and interleukin 10 (IL-10). Significantly, CD4(+) cells from peptide-pretreated females fail to make IL-2 responses to cognate peptide, limiting expansion of the HY-specific CD8(+) populations that can cause graft rejection. Consistent with this, tolerance induction by HY peptide is abrogated by coadministration of lipopolysaccharide. IL-10 does not appear to be critically involved because tolerance is inducible in IL-10-deficient mice. Adoptive transfer of tolerance into naive neonatal recipients by splenocytes from long-term tolerant donors provides evidence for involvement of regulatory cells.

Vaccination and autoimmune disease: what is the evidence?

As many as one in 20 people in Europe and North America have some form of autoimmune disease. These diseases arise in genetically predisposed individuals but require an environmental trigger. Of the many potential environmental factors, infections are the most likely cause. Microbial antigens can induce cross-reactive immune responses against self-antigens, whereas infections can non-specifically enhance their presentation to the immune system. The immune system uses fail-safe mechanisms to suppress infection-associated tissue damage and thus limits autoimmune responses. The association between infection and autoimmune disease has, however, stimulated a debate as to whether such diseases might also be triggered by vaccines. Indeed there are numerous claims and counter claims relating to such a risk. Here we review the mechanisms involved in the induction of autoimmunity and assess the implications for vaccination in human beings.

Peptides containing a dominant T-cell epitope from red cell band 3 have in vivo immunomodulatory properties in NZB mice with autoimmune hemolytic anemia

The major target of the pathogenic red blood cell (RBC) autoantibodies in New Zealand black (NZB) mice is the anion channel protein band 3, and CD4+ T cells from NZB mice respond to band 3. Here, we demonstrate that a band 3 peptide 861-875, which is the predominant sequence recognized by NZB T cells in vitro, bears a dominant helper epitope able to modulate the autoimmune hemolyic anemia in vivo. The development of RBC-bound autoantibodies and anemia was accelerated in NZB mice injected with peptide 861-874, which is relatively insoluble, and inhalation of the peptide primed T cells for both peptide 861-874 and band 3 responses. By contrast, inhalation of a soluble analog (Glu861, Lys875) of peptide 861-874 deviated the autoimmune response toward a T helper-2 (Th2) profile, with marked increases in the ratio of interleukin-4 to interferon-gamma produced by splenic T cells responding in vitro to either peptide 861-874 or band 3. Moreover, in mice that had received such treatment, the proportion of RBC-bound immunoglobulin G (IgG) molecules that were of the Th2-associated IgG1 isotype was also increased, and anemia was less severe. It is concluded that NZB autoimmune hemolytic anemia is helper dependent and that nasal administration of different peptides containing the dominant T-cell epitope can have potentially detrimental or beneficial effects on the disease.

Induction of mucosal tolerance with recombinant Hev b 1 and recombinant Hev b 3 for prevention of latex allergy in BALB/c mice

The prevalence of type I allergy to Hevea brasiliensis latex is particularly high among individuals with frequent exposure to latex products, such as health-care workers (HCW) and patients with spina bifida (SB). Treatment of latex allergy seems problematic as preventive measures, such as allergen avoidance, are not always possible and conventional immunotherapy with standardized latex extracts is not performed routinely. Thus, the aim of the present study was to establish a mouse model of latex allergy using two major latex allergens for HCWs and SB patients, Hev b 1 and Hev b 3, for sensitization. Prophylactic measures on the basis of mucosal tolerance induction with the recombinant allergens were tested in this model. Female BALB/c mice immunized intraperitoneally with recombinant (r)Hev b 1 or rHev b 3 displayed strong immune responses in vivo and in vitro. Intranasal treatment with rHev b 1 and rHev b 3 prior to sensitization led to reduced allergen-specific IgG1/IgE levels and significantly suppressed allergen-induced basophil degranulation. Moreover, lymphocyte proliferation and cytokine production (IL-4, IL-5, IFN-gamma) in vitro were significantly suppressed after pretreatment with both allergens. Suppressive cytokines, such as interleukin (IL)-10 and transforming growth factor (TGF)-beta, remained unchanged after the intranasal pretreatment, indicating mechanism of anergy rather than active immunosuppression. Taken together, these results suggest that mucosal tolerance induction with recombinant allergens could present a promising prevention strategy against latex allergy.

Role for IL-10 in suppression mediated by peptide-induced regulatory T cells in vivo

Regulatory CD4(+) T cells were induced in the Tg4 TCR transgenic mouse specific for the N-terminal peptide (Ac1-9) of myelin basic protein by intranasal administration of a high-affinity MHC-binding analog (Ac1-9[4Y]). Peptide-induced tolerant cells (PItol) were anergic, failed to produce IL-2, but responded to Ag by secretion of IL-10. PItol cells were predominantly CD25(-) and CTLA-4(+) and their anergic state was reversed by addition of IL-2 in vitro. PItol cells suppressed the response of naive Tg4 cells both in vitro and in vivo. The in vitro suppression mediated by these cells was not reversed by cytokine neutralization and was cell-cell contact-dependent. However, suppression of proliferation and IL-2 production by PItol cells in vivo was abrogated by neutralization of IL-10. These results emphasize an important role for IL-10 in the function of peptide-induced regulatory T cells in vivo and highlight the caution required in extrapolating mechanisms of T regulatory cell function from in vitro studies.

Suppression of allergen reactive Th2 mediated responses and pulmonary eosinophilia by intranasal administration of an immunodominant peptide is linked to IL-10 production

The potential to induce systemic tolerance following exposure of the airway mucosa to soluble antigen, may be applied therapeutically for the treatment of allergic disease. Since the use of allergen can trigger IgE mediated inflammation, we investigated whether mucosal delivery of a peptide, containing an immunodominant epitope of the Der p1 allergen of house dust mite, can lead to CD4(+) Th2 cell tolerance and thus protect against airway inflammatory responses to inhalant allergen. The administration of microencapsulated peptide to the nasal mucosa of mice, protected against airway inflammation, with significant reductions in eosinophil infiltration into the airways following allergen challenge. Der p1 specific antibody levels in sera were not modulated. Allergen reactive CD4(+) T cells expressed a tolerized phenotype, with reduction in levels of the cytokines, IL-5, IL-13 and IFN-gamma although IL-10 levels were increased. The mucosal administration of a peptide containing an immunodominant region of an allergen can protect against the induction of systemic and local inflammatory responses to allergen challenge.

Interleukin-10-mediated regulatory T-cell responses to epitopes on a human red blood cell autoantigen

Regulatory T cells have been shown to control animal models of immune-mediated pathology by inhibitory cytokine production, but little is known about such cells in human disease. Here we characterize regulatory T-cell responses specific for a human red blood cell autoantigen in patients with warm-type autoimmune hemolytic anemia. Peripheral blood mononuclear cells from patients with autoimmune hemolytic anemia were found either to proliferate and produce interferon-gamma or to secrete the regulatory cytokine interleukin 10 when stimulated in vitro with a major red blood cell autoantigen, the RhD protein. Flow cytometric analysis confirmed that the majority of the responding cells were of the CD4(+) phenotype. Serial results from individual patients demonstrated that this bias toward proliferative or interleukin-10 responses was unstable over time and could reverse in subsequent samples. Epitope mapping studies identified peptides from the sequence of the autoantigen that preferentially induced interleukin-10 production, rather than proliferation, and demonstrated that many contain naturally processed epitopes. Responses to such peptides suppressed T-cell proliferation against the RhD protein, an inhibition that was mediated largely by interleukin 10 and dependent on cytotonic T lymphocyte-associated antigen (CTLA-4) costimulation. Antigenic peptides with the ability to stimulate specific regulatory cells may represent a new class of therapeutic agents for immune-mediated disease.

Kinetics and mode of peptide delivery via the respiratory mucosa determine the outcome of activation versus TH2 immunity in allergic inflammation of the airways

BACKGROUND

Specific immunotherapy involving systemic injection of allergen, though highly effective, can cause severe side effects due to IgE-mediated activation of effector cells. Allergen-derived peptides might provide a safer alternative. We have investigated the use of mucosally delivered peptide to induce CD4(+) T(H)2 cell tolerance and thus protect against allergen-induced airway inflammation.

OBJECTIVE

The purpose of this study was to investigate whether intranasal administration of an allergen-derived peptide, either alone or adsorbed to chitosan, can prevent the induction of T(H)2-mediated pulmonary inflammation after sensitization and challenge of the airways with allergen.

METHODS

Mice were given (intranasally) a peptide containing an immunodominant epitope of the Dermatophagoides pteronyssinus (Der p) 1 allergen, either as soluble antigen or adsorbed to chitosan, before sensitization and allergen challenge. Pulmonary inflammation, antigen-specific CD4(+) T-cell responses, and antibody levels in sera were then determined.

RESULTS

Mice given peptide adsorbed to chitosan had significant reductions in airway eosinophilia, which correlated with reduced levels of IL-4 and IL-5 in the bronchoalveolar lavage fluid. There was decreased recruitment of activated CD4(+) T cells into the airways after allergen challenge, which correlated with a loss of Der p 1-specific T-cell cytokine responses in the periphery and the localized production of IL-10 by antigen-specific T cells in bronchial lymph nodes. Induction of peripheral T-cell tolerance was preceded by transient T-cell activation and IFN-gamma production.

CONCLUSION

Our data demonstrate that suppression of airway inflammation by intranasal administration of peptide antigen adsorbed to chitosan is initiated by transient T-cell activation and maintained by the production of IL-10 by antigen-specific T cells in the draining lymph nodes.

Effect of cordycepin on interleukin-10 production of human peripheral blood mononuclear cells

Therapeutic options for controlling autoimmune diseases are still very limited. Interleukin-10 has been reported to be a promising approach to therapeutic intervention. In the search for a drug which results in the selective upregulation of interleukin-10, we investigated the immunoregulative effects of cordycepin. We have measured interleukin-10 and interleukin-2 secretion of human peripheral blood mononuclear cells that were incubated with cordycepin and assessed the influence of cordycepin on the expression of interleukin-10 mRNA, the proliferative response and the expression of surface markers on T lymphocytes. In addition, the subsets of interleukin-10-secreting cells, the influence of anti-interleukin-10 neutralizing antibody and cytotoxicity of cordycepin were evaluated. Our results suggest that cordycepin has a significantly upregulative effect on interleukin-10 production and interleukin-10 mRNA expression. Interleukin-10-producing cells included in CD4+, CD8+, CD19+, CD56+ and CD14+ cells. At the same time, cordycepin inhibited phytohaemagglutinin-induced interleukin-2 production and proliferation of peripheral blood mononuclear cells. A restricted T lymphocyte activation was also reflected by a reduced expression of the surface markers CD25, CD45RO, CD54, CD71 and HLA DR. Anti-interleukin-10 neutralizing antibody could not completely block the suppressive effect of cordycepin on production of interleukin-2. Cordycepin in the effective concentration presented slight cytotoxicity but did not increase apoptosis. These results indicate that cordycepin exerts immunoregulative effects. Further research on it may provide an approach for the development of novel immunomodulatory drugs which directly alter the secretion of cytokines.

Intranasal peptide-induced peripheral tolerance: the role of IL-10 in regulatory T cell function within the context of experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a T cell-mediated autoimmune disease commonly employed as a model for multiple sclerosis. Extensive studies have demonstrated that EAE may be prevented or ameliorated by the intranasal administration of soluble peptides representing encephalitogenic epitopes. There is increasing evidence that this peptide administration may function via the generation of regulatory cells. The mechanism of action of these cells remains controversial and it seems likely that it may vary between experimental models. At present the majority of work on regulatory cells has centred on characterising naturally occurring regulators, or those generated artificially ex vivo, and less is known about induced regulatory cells produced following peptide administration. This report aims to briefly outline the evidence for the existence of natural regulatory T cells and to introduce the sub-types of induced regulatory T cells now recognised. In several of these regulatory cell systems investigated to date, interleukin-10 (IL-10) has been shown to be important in cell function. This has not been directly investigated in a model employing peptide therapy to induce peripheral tolerance, hence the purpose of this study was to investigate the role of IL-10 in the generation of these regulatory cells. This work has employed both a TCR transgenic mouse system, for predominantly in vitro studies of cell function, and an IL-10 knock-out mouse strain to investigate in vivo disease protection. The results summarised in this report demonstrate that IL-10 is fundamentally important in the generation of disease protection following intranasal peptide therapy.

Tr1 cell-dependent active tolerance blunts the pathogenic effects of determinant spreading

Experimental autoimmune encephalomyelitis (EAE) is a T cell-mediated autoimmune disease of the CNS. The current study shows that even in an acute episode of disease the autoimmune response spreads from one determinant on myelin basic protein (MBP) to the other linked determinant and that this spread plays a functional role in the pathogenesis of disease. The soluble form of each determinant could be used to induce Ag-specific T cell tolerance and reverse an ongoing disease. We show that the rapid effect of soluble peptide therapy is due to repolarization of autoimmune T cells undergoing activation. We suggest that at least two different types of regulatory T cells participate in the induction of active tolerance. The first, yet to be fully characterized, functions in an IL-4-dependent manner. The second produces high levels of IL-10 and low levels of IL-4 (Tr1). We bring about completing evidence showing that these Tr1 cells play a pivotal role in the regulation of T cell tolerance during determinant spread and that soluble peptide therapy with the determinant to which the autoimmune response spreads amplifies a de novo regulatory mechanism aimed to reduce the pathological consequences of determinant spreading.

The role of IL-12 in the induction of intravenous tolerance in experimental autoimmune encephalomyelitis

Intravenous administration of autoantigen is an effective method to induce Ag-specific tolerance against experimental autoimmune encephalomyelitis (EAE). IL-12 is a potent Th1 stimulator and an essential cytokine in the induction of EAE. The role of IL-12 in the induction of i.v. tolerance is not clear. In this study, we induced tolerance by i.v. administering myelin basic protein (MBP) peptide Ac1-11 (MBP1-11) in EAE. We observed significant suppression of IL-12 production by the lymph node cells of MBP1-11-injected mice. To see whether the low level of IL-12 is the cause or effect of tolerance, we administered IL-12 to the EAE mice at the time of i.v. MBP1-11 injection. Exogenous IL-12 abrogated the suppression of clinical and pathological EAE by i.v. tolerance. IL-12 blocked the suppressive effect of i.v. tolerance on the proliferative response to MBP1-11 and MBP1-11-induced production of IL-12 and IFN-gamma. Furthermore, IL-12 completely blocked the i.v. tolerance-induced type 1 T regulatory cell response. These data suggest that i.v. administration of autoantigen results in the suppression of endogenous IL-12 and the consequent switching of the immune response from an immunogenic to a tolerogenic form.

CD4(+) regulatory T cells

There is now compelling evidence that CD4(+) T cells that specialize in the suppression of immune responses play a key role in the control of immune pathology. Recently, there have been a number of reports that have provided information on the generation of CD4(+) regulatory T cells in the thymus and in the periphery. These cells have also been identified in humans, paving the way for analysis of the function of CD4(+) regulatory T cells in immune-mediated disease.

Inhibition of mucosal and systemic T(h)2-type immune responses by intranasal peptides containing a dominant T cell epitope of the allergen Der p 1

Although the intranasal administration of peptides containing T cell epitopes has been shown to be a potent method of inhibiting responses to the allergen Der p 1, the experiments to date have concentrated on their ability to regulate immune responses to the injection of antigen in a T(h)1-type adjuvant. Their ability to regulate responses to a T(h)2-type immunization and to sensitization via the respiratory mucosa has not been examined. Here it is shown that peptide used in doses required to block delayed-type hypersensitivity can also readily inhibit IgE responses to Der p 1 injected in alum. To examine responses induced in the respiratory mucosa, mice pretreated with intranasal peptide were sensitized with an intranasal dose of Der p 1 in conjunction with a mutated enterotoxin adjuvant. Intranasal peptide even in very high doses did not reduce IgE titers, but the ability of cells from the draining lymph nodes to release IL-4 and IL-13 but not IL-2, IL-5, IL-10 or IFN-gamma was reduced. These are the first reports on the effect of intranasal peptides containing T cell epitopes on IgE in T(h)2 immunization and on responses to respiratory immunization. Thus the effect of the peptide-induced mucosal tolerance differs depending on the type of immunization used for sensitization, but the potential to inhibit T(h)2 responses and responses to respiratory sensitization as well as T(h)1 responses has been demonstrated.

Importance of dose of type II collagen in suppression of collagen-induced arthritis by nasal tolerance

OBJECTIVE

To determine the influence of the dose of collagen given nasally on the induction of specific mucosal tolerance in collagen-induced arthritis.

METHODS

The severity of clinical arthritis induced in DBA/1 mice was studied after the nasal administration (before disease induction) of 1 of 4 doses (across a 2-log range) of bovine type II collagen (CII). Parameters of immunity included lymphocyte proliferation and cytokine production in vitro in response to antigen stimulation, and the production of anticollagen IgG antibody subclasses.

RESULTS

The 3 highest doses (20, 80, and 320 microg) ameliorated disease severity, whereas the lowest dose (5 microg) aggravated disease. These findings correlated well with antigen-specific T cell proliferation and cytokine and antibody production. T cell proliferation was suppressed by the higher doses of CII, whereas the low dose enhanced T cell proliferation, indicating it primed the T cells. Suppression of T cell proliferation could be overcome by the addition of exogenous interleukin-2 (IL-2) to these cultures. Decreased T cell proliferation was associated with suppression of both Th1 (interferon-gamma [IFNgamma]) and Th2 (IL-4) cytokines and all the subclasses of anticollagen IgG in mice receiving 20, 80, or 320 microg of collagen. Overall, the highest dose of collagen (320 microg) was less effective at suppressing the immune response and disease than the 20-microg or 80-microg doses. There was an increased production of antibodies of all IgG isotypes, and of the Th1-associated cytokines IFNgamma and IL-2, in animals that had received the lowest dose of 5 microg collagen nasally.

CONCLUSION

Nasal administration of antigens is effective in inducing tolerance and reducing disease severity, but the effects are dose dependent. Low doses can prime the immune system and aggravate disease; high doses may not suppress disease. Suppression of the immune response, which correlates with suppression of disease, is not obviously associated with a type I to type II T cell switch, but rather with an overall suppression of both forms of T cell response, with a potential role for anergy of T cells in this process.

Single dose intranasal administration of retinal autoantigen generates a rapid accumulation and cell activation in draining lymph node and spleen: implications for tolerance therapy

BACKGROUND/AIMS

A single intranasal delivery of retinal autoantigen suppresses effectively experimental autoimmune uveoretinitis (EAU). To further unravel underlying mechanisms the authors wished to determine, firstly, the kinetics of antigen delivery and, secondly, the early cellular responses involved in the initial stages of nasal mucosal tolerance induction.

METHODS

Flow cytometry, cell proliferation assays, and microscopy were used to track antigen following a single, intranasal dose of Alexa-488 labelled retinal antigen.

RESULTS

A rapid accumulation of antigen within both superficial cervical lymph nodes (SCLN) and spleen was observed after 30 minutes. Significant proliferative responses to IRBP were elicited by 48 hours indicating that systemic priming of naive T cells to retinal antigen had occurred. Cell activation was further confirmed by immunoprecipitation studies, which demonstrated phosphorylation of STAT4 but not STAT6 in both lymph nodes and spleen. However, at 24 hours, STAT4 heterodimerisation with STAT 3 was only observed in spleen.

CONCLUSIONS

The results provide novel evidence that following a single intranasal application rapid transfer of antigen occurs. Resulting T cell proliferation develops consequent to differential cell signalling in SCLN and spleen. Further understanding of these underlying cellular mechanisms, in particular as is inferred by the results the contribution of local versus systemic tolerance induction, may assist in strategies to clinically apply mucosal tolerance therapy successfully.

Total dose and frequency of administration critically affect success of nasal mucosal tolerance induction

AIMS

Nasal tolerance induction with autoantigens can effectively protect against a variety of experimental models of autoimmune disease. The aims of this study were to characterise the dosage and kinetics of inhibition of experimental autoimmune uveoretinitis (EAU) via intranasal administration of the uveitogenic antigen interphotoreceptor retinal binding protein (IRBP) in the murine model of IRBP induced EAU.

METHODS

B10RIII mice were tolerised by intranasal administration of IRBP either with a long term multiple low dose or a short term/high dosing regimen before subcutaneous immunisation with IRBP in complete Freund's adjuvant (CFA). On day 15 post-immunisation, mice were killed and eyes were removed for histological examination and quantification of inflammatory cell infiltration and degree of target organ (rod outer segment, ROS) destruction.

RESULTS

Nasal administration of multiple low doses of IRBP (1 microg or 3 microg IRBP per mouse per day for 10 days) significantly protected mice from IRBP induced EAU. Short term/high dose regimens were only effective when given either as a single or, at most, as two consecutive doses (40 microg per dose). Multiple doses in the range of 45-120 microg over 3 days afforded no protection.

CONCLUSIONS

These results indicate that both dose and frequency of intranasal antigen administration are pivotal to tolerance induction and subsequent suppression of T cell mediated autoimmune disease.

Interleukin-10 and apoptotic death of circulating lymphocytes in surgical/anesthesia trauma

OBJECTIVE

To examine the relationship between circulating interleukin-10 (IL-10) and the occurrence of lymphocyte apoptosis after surgical/anesthesia trauma.

METHODS

Data were collected prospectively on 18 adult patients undergoing elective major surgery. Blood sampling for assessment of lymphocyte apoptosis and IL-10 levels was performed on the day before surgery (t(0)) and at 24 and 96 hours after operation (t(1) and t(2), respectively). After lymphocyte isolation, quantification of apoptosis was made by staining apoptotic cells with 7-amino-actinomycin D. Plasma IL-10 concentrations were measured using enzyme-linked immunosorbent assay.

RESULTS

A significantly increased frequency of apoptotic CD4(+) and CD8(+) cells (p < 0.05) was observed at t1 measurement (8.10% +/- 0.58% and 12.21% +/- 1.47% for CD4(+) and CD8(+), respectively) compared with preoperative values (1.53% +/- 0.38% and 1.32% +/- 0.45% for CD4(+) and CD8(+), respectively). Plasma IL-10 levels showed a significant elevation at both t(1) and t(2) times, peaking at t(1). At t(1), IL-10 levels were correlated with the frequency of CD4(+) and CD8(+) apoptotic lymphocytes (r = 0.78, p = 0.0005 for IL-10 vs. apoptotic CD4(+); r = 0.71, p = 0.003 for IL-10 vs. apoptotic CD8(+)).

CONCLUSION

Surgical trauma is associated with a significant but transient increase in lymphocyte commitment to apoptosis and IL-10 production. The exact relationship linking the overproduction of IL-10 with lymphocyte apoptosis after a surgical operation is still elusive and requires further investigation.

Interferon beta1a treatment modulates TH1 expression in gammadelta + T cells from relapsing-remitting multiple sclerosis patients

A paradigm exists that multiple sclerosis is causally related to dysregulation of TH1 inflammatory cytokines and TH2 antiinflammatory cytokines. The cytokine source(s) that initiate the imbalances are unknown. In this study, gammadelta, CD4, and CD8 T cell receptor-positive (TCR+) cells were isolated from the blood of 26 definitive relapsing-remitting multiple sclerosis patients prior to interferon beta-1a (IFNbeta1a) therapy and following 8-10 weeks of this therapy. The bioactivities of interferon gamma (IFNgamma), interleukin 10 (IL10), and interleukin 12 (IL12) were determined. The concentrations of IFN-gamma, IL10, and IL12 from each cell type did not change significantly with IFNbeta1a treatment. The IL10 secreted by gammadelta TCR+ cells strongly correlated with the IL12 secreted by the same gammadelta TCR+ cells, supporting the paradigm. Furthermore, IFNbeta1a therapy decreased the gammadelta TCR+ cell secretion of TH1 cytokines after 8-10 weeks of therapy.

Chemokine receptor expression and function in CD4+ T lymphocytes with regulatory activity

We have investigated the chemokine receptor expression and migratory behavior of a new subset of nickel-specific skin-homing regulatory CD4(+) T cells (Th(IL-10)) releasing high levels of IL-10, low IFN-gamma, and undetectable IL-4. These cells inhibit in a IL-10-dependent manner the capacity of dendritic cells to activate nickel-specific Tc1 and Th1 lymphocytes. RNase protection assay and FACS analysis revealed the expression of a vast repertoire of chemokine receptors on resting Th(IL-10), including the Th1-associated CXCR3 and CCR5, and the Th2-associated CCR3, CCR4, and CCR8, the latter at higher levels compared with Th2 cells. The most active chemokines for resting Th(IL-10), in terms of calcium mobilization and in vitro migration, were in order of potency: CCL2 (monocyte chemoattractant protein-1, CCR2 ligand), CCL4 (macrophage-inflammatory protein-1beta, CCR5 ligand), CCL3 (macrophage-inflammatory protein-1alpha, CCR1/5 ligand), CCL17 (thymus and activation-regulated chemokine, CCR4 ligand), CCL1 (I-309, CCR8 ligand), CXCL12 (stromal-derived factor-1, CXCR4), and CCL11 (eotaxin, CCR3 ligand). Consistent with receptor expression down-regulation, activated Th(IL-10) exhibited a reduced or absent response to most chemokines, but retained a significant migratory capacity to I-309, monocyte chemoattractant protein-1, and thymus and activation-regulated chemokine. I-309, which was ineffective on Th1 lymphocytes, attracted more efficiently Th(IL-10) than Th2 cells. I-309 and CCR8 mRNAs were not detected in unaffected skin and were up-regulated at the skin site of nickel-allergic reaction, with an earlier expression kinetics compared with IL-10 and IL-4. Results indicate that skin-homing regulatory Th(IL-10) lymphocytes coexpress functional Th1- and Th2-associated chemokine receptors, and that CCR8/I-309-driven recruitment of both resting and activated Th(IL-10) cells may be critically involved in the regulation of Th1-mediated skin allergic disorders.

Negative selection during the peripheral immune response to antigen

Thymic selection depends on positive and negative selective mechanisms based on the avidity of T cell interaction with antigen-major histocompatibility complex complexes. However, peripheral mechanisms for the recruitment and clonal expansion of the responding T cell repertoire remain obscure. Here we provide evidence for an avidity-based model of peripheral T cell clonal expansion in response to antigenic challenge. We have used the encephalitogenic, H-2 A(u)-restricted, acetylated NH(2)-terminal nonameric peptide (Ac1-9) epitope from myelin basic protein as our model antigen. Peptide analogues were generated that varied in antigenic strength (as assessed by in vitro assay) based on differences in their binding affinity for A(u). In vivo, these analogues elicited distinct repertoires of T cells that displayed marked differences in antigen sensitivity. Immunization with the weakest (wild-type) antigen expanded the high affinity T cells required to induce encephalomyelitis. In contrast, immunization with strongly antigenic analogues led to the elimination of T cells bearing high affinity T cell receptors by apoptosis, thereby preventing disease development. Moreover, the T cell repertoire was consistently tuned to respond to the immunizing antigen with the same activation threshold. This tuning mechanism provides a peripheral control against the expansion of autoreactive T cells and has implications for immunotherapy and vaccine design.

The role of different subsets of T regulatory cells in controlling autoimmunity

T regulatory cells-in addition to clonal deletion and anergy-are essential for the downregulation of T cell responses to both foreign and self antigens, and for the prevention of autoimmunity. Recent progress has been made in characterising the different subsets of T regulatory cells, the factors that drive their differentiation, and their mode of action. The resolution of these mechanisms will make it possible to use T regulatory cells therapeutically in human autoimmune diseases.

Antigen-specific therapy for autoimmune disease

The application of self-antigens as therapeutic tools is validated in inbred animal models of autoimmune disease. Mechanisms of antigen-induced tolerance (apoptosis, anergy, regulatory T cells and immune deviation) are being clarified in relation to the properties of antigens and the modes and routes of their delivery. Mucosa-mediated tolerance remains the predominant mode of antigen-specific therapy but awaits demonstration of clinical efficacy in human autoimmune disease.

Control of experimental inflammatory bowel disease by regulatory T cells

A helper T cell type 1-mediated colitis driven by enteric bacteria develops in severe combined immunodeficient mice after transfer of CD45RB(high)CD4(+) T cells. Development of disease can be prevented by cotransfer of the reciprocal CD45RB(low) subset. Analysis of the mechanism of immune suppression transferred by CD45RB(low)CD4(+) cells revealed essential roles for both IL-10 and TGF-beta. These data indicate that a functionally specialized population of regulatory T (Treg) cells exists in normal mice and that these can prevent the development of pathogenic responses toward commensal bacteria. The role of Treg cells in the control of the immune response is discussed.

Immunological tolerance to inhaled antigen

Regulatory mechanisms exist in the immune system to limit the induction of pathogenic responses to antigens encountered within the respiratory tract. The development of allergic disease is thought to arise as a result of the breakdown in these regulatory processes. In this review we examine the nature of immune responses generated to inhaled protein antigens and the mechanisms used to establish tolerance to inhaled antigens.

The potential use of peptides and vaccination to treat systemic lupus erythematosus

Studies in humans and mice with systemic lupus erythematosus (SLE) suggest that the development of autoantibodies and disease is dependent on T helper (Th) cells. This review highlights recent efforts to identify the antigens that activate such autoreactive Th cells. Various laboratories are using different approaches to identify the autoantigenic epitopes, which appear to be derived from diverse sources such as nucleosome core histones, ribonucleoproteins, and immunoglobulin variable regions. Identification of the putative autoantigenic epitopes has raised the possibility of peptide-specific vaccination as therapy for SLE. Indeed, vaccination of prenephritic lupus-susceptible mice with such peptides delays the development of autoantibodies and nephritis, and prolongs survival. Recent data suggest that peptide treatment can also influence established disease in older lupus mice. These studies offer new hope for a similar treatment approach in patients with SLE. Studies have begun to identify T cell epitopes in human disease.

T-cell regulation of peripheral tolerance and immunity: the potential role for Notch signalling

Recognition of antigen by T cells in the periphery may lead either to the generation of productive immunity or the induction of tolerance. These two functional outcomes are a consequence of distinct pathways of T-cell differentiation. T cells are selected to become regulatory cells and their function is to maintain homeostasis with the immune system. In this review we discuss the cell-fate decisions that T cells might make allowing them to promote immunity or induce tolerance in the context of the role that Notch signalling may play in this process.