In trans T cell tolerance diminishes autoantibody responses and exacerbates experimental allergic encephalomyelitis

A number of Ag-specific approaches have been developed that ameliorate experimental allergic encephalomyelitis (EAE), an animal model for the human autoimmune disease multiple sclerosis. Translation to humans, however, remains a consideration, justifying the search for more insight into the mechanism underlying restoration of self-tolerance. Ig-proteolipid protein (PLP) 1 and Ig-myelin oligodendrocyte glycoprotein (MOG) are Ig chimeras carrying the encephalitogenic PLP 139-151 and MOG 35-55 amino acid sequence, respectively. Ig-PLP1 ameliorates EAE in SJL/J (H-2(s)) mice while Ig-MOG modulates the disease in C57BL/6 (H-2(b)) animals. In this study, we asked whether the chimeras would suppress EAE in F(1) mice expressing both parental MHC alleles and representing a polymorphism with more relevance to human circumstances. The results show that Ig-MOG modulates both PLP1 and MOG peptide-induced EAE in the F(1) mice, whereas Ig-PLP1 counters PLP1 EAE but exacerbates MOG-induced disease. This in trans aggravation of MOG EAE by Ig-PLP1 operates through induction of PLP1-specific T cells producing IL-5 that sustained inhibition of MOG-specific Abs leading to exacerbation of EAE. Thus, in trans T cell tolerance, which should be operative in polymorphic systems, can aggravate rather than ameliorate autoimmunity. This phenomenon possibly takes place through interference with protective humoral immunity.     

T cell requirement for experimental allergic encephalomyelitis induction in the rat.

The question of whether a cell-mediated or a humoral mechanism initiates EAE in rats sensitized with BP-CFA was investigated. The requirement of T cells for EAE induction was manifested when Tx, irradiated rats were reconstituted with normal lymphoid cells treated with ATS and then injected with BP-CFA. Neither EAE nor antibody was produced, indicating the T cell dependency of BP specific antibody production. More precise information regarding the role of the T cell in the production of EAE was obtained by means of passive transfer of EAE with sensitized lymphocytes. Thus, transfer of lymphoid cells from rats previously sensitized to BP-CFA into Tx, irradiated rats elicited EAE and antibodies to BP. However, no EAE followed when the transferred cells were first depleted of T cells by treatment with ATS. Nevertheless, ATP pretreatment did not depress the levels of antibody to BP produced in the transfer recipients. The latter finding indicates that the cells from animals sensitized 9 days previously were already committed to the production of antibodies to BP. Therefore, a) T cells are absolutely necessary for induction of EAE and b) antibody detected by antigen-binding is not responsible for the pathogenesis of this disease.     

Passive induction of experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE) is a widely used animal model of the human demyelinating disease multiple sclerosis. EAE is initiated by immunization with myelin antigens in adjuvant or by adoptive transfer of myelin-specific T cells, resulting in inflammatory infiltrates and demyelination in the central nervous system. Induction of EAE in rodents typically results in ascending flaccid paralysis with inflammation primarily targeting the spinal cord. This protocol describes passive induction of EAE by adoptive transfer of T cells isolated from mice primed with myelin antigens into na?ve mice. The advantages of using this method versus active induction of EAE are discussed.     

Active induction of experimental allergic encephalomyelitis

This protocol details a method to actively induce experimental allergic encephalomyelitis (EAE), a widely used animal model for studies of multiple sclerosis. EAE is induced by stimulating T-cell-mediated immunity to myelin antigens. Active induction of EAE is accomplished by immunization with myelin antigens emulsified in adjuvant. This protocol focuses on induction of EAE in mice; however, the same principles apply to EAE induction in other species. EAE in rodents is manifested typically as ascending flaccid paralysis with inflammation targeting the spinal cord. However, more diverse clinical signs can occur in certain strain/antigen combinations in rodents and in other species, reflecting increased inflammation in the brain.     

Haplotype-specific suppression of experimental allergic encephalomyelitis with anti-IA antibodies

Treatment with monoclonal antibodies directed against the IA antigens of the MHC is known to alter the course and prevent a number of experimental autoimmune diseases. To determine whether the treatment in vivo with anti-IA antibodies is haplotype-specific, we studied the development of EAE in F1 (SJL/J X BALB/c) mice following anti-IA antibody therapy. We report that treatment of animals with monoclonal antibody directed against the high responder allele product, I-As, was successful in preventing disease when therapy was begun either at the time of immunization with antigen, or following passive transfer of MBP-sensitized T cells. Therapy with antibody directed to the low responder allele product (I-Ad), while effective when used at the time of immunization with antigen, was ineffective following passive transfer of MBP-sensitized lymphocytes.     

Niridazole suppression of experimental allergic encephalomyelitis in Lewis rats.

Administration of niridazole to Lewis rats beginning 2 days before sensitization with guinea pig spinal cord in combination with immunologic adjuvants exerted a dose related suppressive influence on development of experimental allergic encephalomyelitis (EAE). A daily dose of 75 mg/kg completely prevented clinical neurologic signs as well as markedly suppressed occurrence of immunohistopathologic manifestations of this autoimmune disease. A higher daily dose level of niridazole, i.e., 100 mg/k, also inhibited EAE but was associated with neurotoxic manifestations.     

Kinetics and specificity of T and B cell responses in relapsing experimental allergic encephalomyelitis

T and B cell responses to myelin basic protein (MBP) and its relevant peptide fragments were examined throughout the course of MBP-induced relapsing experimental allergic encephalomyelitis (REAE) in (SJL X PL)F1 mice. T cell reactivity, measured by the antigen-driven proliferation of lymph node T cells in vitro, was directed predominantly against the encephalitogenic MBP-P2 peptide (amino acids 1 to 37) at all stages of disease. Levels of responsiveness did not correlate with disease expression, but declined over time to a relapse level that was four- to sixfold lower than that observed during peak acute stage reactivity. Relapse responses were further distinguished by the detection of host I-E restrictions on Lyt-1+ T cell recognition of P2, P2 recognition by acute-stage T cells occurring solely in the context of host I-A molecules. These data imply an increase in the heterogeneity of relapse T cell responses to MBP to include clones restricted by additional class II glycoproteins. A role for additional CNS autoantigens in the stimulation of relapse T cells is also considered. Serum antibody responses to MBP or the P2 fragment fluctuated randomly throughout R-EAE when total antibody activity (IgM plus IgG) was measured. However, analysis of individual isotypes of IgG immunoglobulins revealed an apparent correlation between peak antigen-binding activity and disease expression which may reflect either an effector or regulatory role for humoral immunity in recurrent EAE. Patterns of early antibody reactivity also distinguished F1 mice that developed or failed to develop disease signs after immunization, the latter exhibiting a consistent drop in antigen-binding activity 4 to 5 days before the usual onset of acute-stage paralysis. The results are considered with regard to possible mechanisms of chronic disease regulation in an environment of functional T cell suppression.     

Regulatory T cell induction during Plasmodium chabaudi infection modifies the clinical course of experimental autoimmune encephalomyelitis

Background

Experimental autoimmune encephalomyelitis (EAE) is used as an animal model for human multiple sclerosis (MS), which is an inflammatory demyelinating autoimmune disease of the central nervous system characterized by activation of Th1 and/or Th17 cells. Human autoimmune diseases can be either exacerbated or suppressed by infectious agents. Recent studies have shown that regulatory T cells play a crucial role in the escape mechanism of Plasmodium spp. both in humans and in experimental models. These cells suppress the Th1 response against the parasite and prevent its elimination. Regulatory T cells have been largely associated with protection or amelioration in several autoimmune diseases, mainly by their capacity to suppress proinflammatory response.

Methodology/Principal Findings

In this study, we verified that CD4⁺CD25⁺ regulatory T cells (T regs) generated during malaria infection (6 days after EAE induction) interfere with the evolution of EAE. We observed a positive correlation between the reduction of EAE clinical symptoms and an increase of parasitemia levels. Suppression of the disease was also accompanied by a decrease in the expression of IL-17 and IFN-γ and increases in the expression of IL-10 and TGF-β1 relative to EAE control mice. The adoptive transfer of CD4⁺CD25⁺ cells from P. chabaudi-infected mice reduced the clinical evolution of EAE, confirming the role of these T regs.

Conclusions/Significance

These data corroborate previous findings showing that infections interfere with the prevalence and evolution of autoimmune diseases by inducing regulatory T cells, which regulate EAE in an apparently non-specific manner.     

Antigen-specific T cell activation and proliferation during oral tolerance induction

One of several routes of achieving immunologic tolerance is through functional inactivation of Ag-specific T cells. Oral administration of Ag can allow survival of the Ag-specific T cells that are functionally anergic. The aim of this study was to investigate whether functional inactivation of Ag-specific T cells is directed through an activation process and to further define the differentiative pathways and functional characteristics of anergic T cells. Mice were transplanted with OVA-specific TCR-transgenic T cells and either fed OVA or immunized s.c. with the OVA peptide 323-339 in CFA. OVA-specific T cells from OVA-fed mice were unresponsive to restimulation in vitro within 48-72 h after treatment. In vivo, however, T cell proliferation was detected by 5, 6-carboxy-succinimidyl-fluoresceine-ester intensity changes in OVA-specific T cells. The mesenteric lymph nodes (LNs) from OVA-fed mice more frequently contained OVA-specific dividing cells in vivo than those in the peripheral LNs, and the reciprocal was observed following s.c. immunization of the OVA peptide in CFA. The induction of anergy in OVA-fed mice was accompanied by rapid up-regulation of CD69 and CTLA-4, later down-regulation of CD45RB on OVA-specific T cells, and a marked decrease in T cell secretion of IL-2, IL-10, and IFN-gamma after OVA restimulation in vitro. Results from this study indicate that the inductive phase of oral tolerance is preceded by Ag-specific T cell activation in vivo, proliferation in the regional draining LNs, and differentiation into a memory-like state. These results indicate that Ag-directed differentiation occurs as a part of T cell tolerance through anergy.     

IL-10-dependent suppression of experimental allergic encephalomyelitis by Th2-differentiated, anti-TCR redirected T lymphocytes

We previously showed that transgenically expressed chimeric Ag-MHC-zeta receptors can Ag-specifically redirect T cells against other T cells. When the receptor's extracellular Ag-MHC domain engages cognate TCR on an Ag-specific T cell, its cytoplasmic zeta-chain stimulates the chimeric receptor-modified T cell (RMTC). This induces effector functions such as cytolysis and cytokine release. RMTC expressing a myelin basic protein (MBP) 89-101-IAs-zeta receptor can be used therapeutically, Ag-specifically treating murine experimental allergic encephalomyelitis (EAE) mediated by MBP89-101-specific T cells. In initial studies, isolated CD8+ RMTC were therapeutically effective whereas CD4+ RMTC were not. We re-examine here the therapeutic potential of CD4+ RMTC. We demonstrate that Th2-differentiated, though not Th1-differentiated, CD4+ MBP89-101-IAs-zeta RMTC prevent actively induced or adoptively transferred EAE, and treat EAE even after antigenic diversification of the pathologic T cell response. The Th2 RMTC both Th2-deviate autoreactive T cells and suppress autoantigen-specific T cell proliferation. IL-10 is critical for the suppressive effects. Anti-IL-10R blocks RMTC-mediated modulation of EAE and suppression of autoantigen proliferation, as well as the induction of IL-10 production by autoreactive T cells. In contrast to IL-10, IL-4 is required for IL-4 production by, and hence Th2 deviation of autoreactive T cells, but not the therapeutic activity of the RMTC. These results therefore demonstrate a novel immunotherapeutic approach for the Ag-specific treatment of autoimmune disease with RMTC. They further identify an essential role for IL-10, rather than Th2-deviation itself, in the therapeutic effectiveness of these redirected Th2 T cells.     

Antigen-stimulated rosette formation by T lymphocytes in experimental allergic encephalomyelitis

Peripheral blood lymphocytes form rosettes in the presence of heterologous etythrocytes. Spontaneous or active rosette formation has been reported to be a measure of circulating and immunologically functional thymus-dependent lymphocytes. The present study utilizes the rosette assay to measure changes in the circulating T cells of guinea pigs sensitized with encephalitogenic myelin basic protein (BP) or with nonencephalitogenic peptide S42 known to induce cellular transformation in experimental allergic encephalomyelitis, a cell-mediated disorder of the central nervous system. The results show a significant depression in the number of active but not in the total number of rosette-forming T lymphocytes from the peripheral blood of antigen-sensitized animals. This reduction, which was not related to the encephalitogenic property of the BP, was readiiy reversible by incubating lymphocytes with the sensitizing antigen but not with histone. Under these conditions, lymphocytes from unsensitized control animals were unresponsive to stimulation by any of the antigens used. The antigenstimulated rosette assay described in this report provides a specific assay for sensitization to basic protein in BP-related demyelinating diseases.     

Biochemical and physico-chemical changes in albumin in dynamics of experimental allergic encephalomyelitis

The experiments on guinea pig with experimental allergic encephalomyelitis (EAE) have shown that the most significant changes in the content, binding ability and thermodynamic characteristics of serum albumin are found at the early stages preceding the appearance of neurological characters. The plasma perfusion through granulated carbon-activated sorbents increases the binding ability and decreases the temperature denaturation of albumin down to the normal level.     

Characterization of a T suppressor cell line that downgrades experimental allergic encephalomyelitis in mice.

A T-suppressor (Ts) cell line of CD8 phenotype was isolated from spleens of SJL/J mice that had recovered from experimental allergic encephalomyelitis (EAE) induced by injection of MBP-activated T cells. The Ts cell line inhibited the proliferation of MBP-sensitized T cells in vitro. Addition of recombinant IL-2 enhanced the Ts-mediated suppression. Adoptively transferred Ts line was able to downgrade EAE in mice subsequently challenged with MBP-activated T cells. The mechanism of suppression appeared to involve neither direct cytolysis of the effector T cells nor the production of a soluble suppressor factor. The findings suggest an in vivo role for suppressor T cells in the regulation of EAE.     

Structural specificity of synthetic peptide adjuvant for induction of experimental allergic encephalomyelitis

The peptide N-acetylmuramyl-l-alanyl-d-isoglutamine (MDP), which has adjuvant activities, and 17 of its derivatives and analogs were synthesized and assayed to elucidate the structure necessary for adjuvant activity in induction of experimental allergic encephalomyelitis (EAE) in guinea pigs. The results revealed the importance of the d configuration and the α-carboxamide group of the isoglutaminyl residue of MDP for adjuvant activity. Replacement of the l-alanyl residue of MDP by d-alanine, but not by l-serine or glycine, resulted in a marked decrease in the activity. The β-methyl glycoside of MDP was found to be more active than the α-methyl derivative. 6-O-Stearoyl-N-acetylmuramyl-l-alanyl-d-isoglutamme showed activity.