Inconsistence between number and function of autoreactive T cells in the course of experimental autoimmune encephalomyelitis

Background: Mouse experimental autoimmune encephalomyelitis (EAE) is widely used model of multiple sclerosis (MS). The role of autoreactive CD4⁺ and CD8⁺ T cells in the development of mouse EAE has been demonstrated. However, little information is available about the relation between the frequency and reactivity of myelin antigen-reactive CD4⁺ and CD8⁺ T cells in secondary lymphoid organs and their relevance with the inflammation and pathological lesion of CNS during the course of EAE mouse model.

Methods: In this study, an EAE model with a clinical course containing acute onset, peak and chronic remission stages was established in C57BL/6J mice by myelin oligodendrocyte protein (MOG)_35–55 peptide immunization, and followed by the monitoring of clinical and pathological parameters and autoreactive T cells at different stages during the course.

Results: The dynamic changes of inflammatory infiltration, myelin loss, and astrocyte proliferation in brain and spinal cord were highly consistent with clinical severity observed in EAE course. However, the frequencies of both MOG-specific CD4⁺ and CD8⁺ T cells in secondary lymphoid organs presented different dynamic trends from the IFN-γ production by MOG-reactive T cells. Meanwhile, the IL-17 production by MOG-reactive CD4⁺ T cells was consistent with the proliferation of MOG-specific CD4⁺ T cells.

Conclusions: Both CD4⁺ and CD8⁺ T cells were most sensitive to MOG antigen stimulation for IFN-γ production during the early stage of EAE, but then rapidly lost the function despite their vigorous proliferation at the peak stage and later.     

Antigen-specific down-regulation of myelin basic protein-reactive T cells during spontaneous recovery from experimental autoimmune encephalomyelitis: further evidence of apoptotic deletion of autoreactive T cells in the central nervous system

Experimental autoimmune encephalomyelitis (EAE) was inducedin Lewis rats by the I.v. injection of 10⁷ cloned V_ß8.2⁺T cells specific for the 72–89 peptide of guinea pig myelinbasic protein(MBP). Some animals were injected simultaneouslywith 10⁷ cloned T cells specific for ovalbumin(OVA). Lymphocyteswere isolated from the spinal cord and from the peripheral lymphoidorgans of these rats and the frequencies of MBP-peptide-specificor OVA-specific proliferating cells were estimated by limitingdilution analysis at different times after cell transfer. Thefrequencies of cells specific for MBP_72–89 or OVA in thespinal cord were highest 5 days after cell transfer (MBP_72–89,1 in 1149; OVA, 1 in 1116). On day 7, when the rats were recovering,the frequency of cells specific for MBP_72–89 in the spinalcord fell dramatically to <1 in 10⁵, while that of OVA-specificcells decreased to a much lesser extent (1 in 7001). The frequenciesof MBP_72–89-specific cells in the peripheral lymphoidorgans during and after recovery were also much lower than thoseof OVA-specific cells. A similar pattern of down-regulationof the MBP-peptide-specific, but not the OVA-specific, T cellresponse was observed in the spleen and mesenteric lymph nodes(MLN) of rats 38 days after the active induction of EAE by immunizationwith equal amounts of MBP and OVA in adjuvants. In the passivelytransferred model, cells isolated from the spinal cord and MLNon day 7 did not regain responsiveness to MBP_72–89 afterincubation with high levels of IL-2, indicating that the unresponsivenesswas not due to T cell anergy. Thus this study demonstrates thatthere is a specific down-regulation of the MBP_72–89-specificT cell response during spontaneous recovery from EAE. This conclusionis consistent with our previous observation that V_ß8.2⁺T cells are selectively eliminated from the CNS by apoptosisduring recovery from EAE induced by the passive transfer ofV_ß8.2⁺ T cells reactive to this MBP peptide. In contrastto autoreactive T cells, the non-autoreactive T cells that accumulatein the CNS during EAE appear to recirculate to the peripherallymphoid organs.     

Antigen presentation in autoimmunity and CNS inflammation: how T lymphocytes recognize the brain

The central nervous system (CNS) is traditionally viewed as an immune privileged site in which overzealous immune cells are prevented from doing irreparable damage. It was believed that immune responses occurring within the CNS could potentially do more damage than the initial pathogenic insult itself. However, virtually every aspect of CNS tissue damage, including degeneration, tumors, infection, and of course autoimmunity, involves a significant cellular inflammatory component. While the blood–brain barrier (BBB) inhibits diffusion of hydrophilic (immune) molecules across brain capillaries, activated lymphocytes readily pass the endothelial layer of postcapillary venules without difficulty. In classic neuro-immune diseases such as multiple sclerosis or acute disseminated encephalomyelitis, it is thought that neuroantigen-reactive lymphocytes, which have escaped immune tolerance, now invade the CNS and are responsible for tissue damage, demyelination, and axonal degeneration. The developed animal model for these disorders, experimental autoimmune encephalomyelitis (EAE), reflects many aspects of the human conditions. Studies in EAE proved that auto-reactive encephalitogenic T helper (Th) cells are responsible for the onset of the disease. Th cells recognize their cognate antigen (Ag) only when presented by professional Ag-presenting cells in the context of major histocompatibility complex class II molecules. The apparent target structures of EAE immunity are myelinating oligodendrocytes, which are not capable of presenting Ag to invading encephalitogenic T cells. A compulsory third party is thus required to mediate between the attacking T cells and the myelin-expressing target. This review will discuss the recent advances in this field of research and we will discuss the journey of an auto-reactive T cell from its site of activation into perivascular spaces and further into the target tissue.     

Pre‐existing central nervous system lesions negate cytokine requirements for regional experimental autoimmune encephalomyelitis development

In region‐specific forms of experimental autoimmune encephalomyelitis (EAE), lesion initiation is regulated by T‐cell‐produced interferon‐γ (IFN‐γ) resulting in spinal cord disease in the presence of IFN‐γ and cerebellar disease in the absence of IFN‐γ. Although this role for IFN‐γ in regional disease initiation is well defined, little is known about the consequences of previous tissue inflammation on subsequent regional disease, information vital to the development of therapeutics in established disease states. This study addressed the hypothesis that previous establishment of regional EAE would determine subsequent tissue localization of new T‐cell invasion and associated symptoms regardless of the presence or absence of IFN‐γ production. Serial transfer of optimal or suboptimal doses of encephalitogenic IFN‐γ‐sufficient or ‐deficient T‐cell lines was used to examine the development of new clinical responses associated with the spinal cord and cerebellum at various times after EAE initiation. Previous inflammation within either cerebellum or spinal cord allowed subsequent T‐cell driven inflammation within that tissue regardless of IFN‐γ presence. Further, T‐cell IFN‐γ production after initial lesion formation exacerbated disease within the cerebellum, suggesting that IFN‐γ plays different roles at different stages of cerebellar disease. For the spinal cord, IFN‐γ‐deficient cells (that are ordinarily cerebellum disease initiators) were capable of driving new spinal‐cord‐associated clinical symptoms more than 60 days after the initial acute EAE resolution. These data suggest that previous inflammation modulates the molecular requirements for new neuroinflammation development.     

Regulatory T cells in experimental allergic encephalomyelitis. I. Frequency and specificity analysis in normal and immune rats of a T cell subset that inhibits disease

We have shown previously that administration of myelin basic protein (MBP)-reactive T cells to naive Lewis rats induces not only autoimmune encephalomyelitis (EAE) but also a near total resistance to subsequent disease. By isolating the effector cells that are responsible for the resistance, we demonstrated that disease protection paralleled with increased numbers of a CD8+ regulatory T cell (RTC) subset and that co-injection of this RTC subset with encephalitogenic T cells aborted the pathogenic activity of the latter cells. Here, we show that a radio-sensitive splenic population of RTC also exists in naive rats that can be recruited and activated to inhibit the onset of secondary episodes of adoptive EAE. In co-transfer experiments, this protective RTC subpopulation can be isolated to neutralize the pathogenic activity of stimulatory MBP-reactive T cells in vivo. We show that the frequency of RTC with specificity for MBP-reactive T cells in naive rats is two orders of magnitude higher than the frequency of MBP-specific precursors, the activity of RTC increases substantially with age and RTC frequencies increase as a consequence of immunization with MBP-reactive cells lines. In specificity studies, we show that RTC isolated from naive rats and RTC from animals primed with one MBP-reactive cell line show cross-reactive responses to a variety of different MBP-reactive T cell lines. However, following repeated stimulation with a given MBP line, these RTC display a more limited, clonotypic response to the selecting line and assume a uniform CD8 phenotype. Finally, functional studies with RTC indicate that proliferative and lytic specificities do not necessarily correlate and that activated rat RTC are especially lytic for a Fas-sensitive murine cell line.     

The p38 mitogen‐activated protein kinase cascade modulates T helper type 17 differentiation and functionality in multiple sclerosis

The p38 mitogen‐activated protein kinase cascade is required for the induction of a T helper type 17 (Th17) ‐mediated autoimmune response, which underlies the development and progression of several autoimmune diseases, such as experimental autoimmune encephalomyelitis, the animal model of multiple sclerosis (MS). However, the contribution of p38 phosphorylation to human Th cell differentiation has not been clarified. Here we demonstrate that the p38 signalling pathway is implicated in the generation of Th17 lymphocytes from human CD4⁺ CD27⁺ CD45RA⁺ naive T cells, both in healthy donors and in patients affected by the relapsing–remitting form of MS. Our data also indicate that p38 activation is essential for interleukin‐17 release from central memory lymphocytes and committed Th17 cell clones. Furthermore, CD4⁺ T cells isolated from individuals with relapsing–remitting MS display an altered responsiveness of the p38 cascade, resulting in increased p38 phosphorylation upon stimulation. These findings suggest that the p38 signalling pathway, by modulating the Th17 differentiation and response, is involved in the pathogenesis of MS, and open new perspectives for the use of p38 inhibitors in the treatment of Th17‐mediated autoimmune diseases.     

The unwavering commitment of regulatory T cells in the suppression of autoimmune encephalomyelitis: another aspect of immune privilege in the CNS

FoxP3(+) regulatory T (Treg) cells accumulate in the central nervous system (CNS) during experimental autoimmune encephalomyelitis and have been shown to limit the extent of neuroinflammation and to facilitate clinical recovery. The recent demonstration that Treg cells lose FoxP3 expression and assume effector cell characteristics upon stimulation with proinflammatory cytokines has raised questions about their stability in the inflamed CNS. In this issue of the European Journal of Immunology, O'Connor et al. [Eur. J. Immunol. 2012. 42: 1164-1173] show that CNS-infiltrating Treg cells maintain their suppressor phenotype by downregulating the IL-6 receptor. This commentary discusses the finding particularly with relevance to therapy of multiple sclerosis.     

Analysis of T cell antigen receptors of myelin basic protein specific T cells in SJL/J mice demonstrates an {alpha} chain CDR3 motif associated with encephalitogenic T cells

Experimental autoimmune encephalomyelitis (EAE) is an animalautoimmune disease mediated by CD4⁺ T cells. Analysis of TCRexpression revealed that limited TCR elements (V^ß8.2,V2 or 4) were utilized by myelin basic protein (MBP) specificT cells In mice with H-2^U haplotype and Lewis rats. The usageof a particular ß chain complementarity determiningregion 3 (CDR3) motif has also been shown. However, It remainsunclear to what extent these observations can be extrapolated.Here we studied the TCR sequences of MBP 89–101/1-A^s specificT cell clones derived from SJL/J mice, using the polymerasechain reaction on reverse transcribed mRNA. Although the V_ßusage was less restricted than In H-2^U mice, they predominantlyutilized v_ß17a and expressed LGG or related motifsin the V_ß - D_ß - J_ß junctions.Furthermore, a single chain rearrangement between V1.1 andJBBM142 with no N region diversity was preferentially used.Concordantty, Immunization with a peptlde corresponding to the chain CDR3 was found to significantly alter the clinical courseof EAE. Comparison of the published TCR junctional regions demonstratesthat the CDR3 motifs (LGG in ß chain, CA*R*NY motifIn chains) are expressed by other encephalitogenic clones.Notably, the CA*R*NY was conserved in PL/J mice clones thatrecognize a distinct MBP–MHC determinant. It suggeststhat an antigen-independent mechanism may contribute to conservingthe a chain motif. The Implications of these observations arediscussed.     

Body fluid biomarkers in multiple sclerosis: how far we have come and how they could affect the clinic now and in the future

Multiple sclerosis (MS) is an autoimmune inflammatory disease of the central nervous system, which affects over 2.5 million people worldwide. Although MS has been extensively studied, many challenges still remain in regards to treatment, diagnosis and prognosis. Typically, prognosis and individual responses to treatment are evaluated by clinical tests such as the expanded disability status scale, MRI and presence of oligoclonal bands in the cerebrospinal fluid. However, none of these measures correlates strongly with treatment efficacy or disease progression across heterogeneous patient populations and subtypes of MS. Numerous studies over the past decades have attempted to identify sensitive and specific biomarkers for diagnosis, prognosis and treatment efficacy of MS. The objective of this article is to review and discuss the current literature on body fluid biomarkers in MS, including research on potential biomarker candidates in the areas of miRNA, mRNA, lipids and proteins.     

PDCD5 negatively regulates autoimmunity by upregulating FOXP3+ regulatory T cells and suppressing Th17 and Th1 responses

Maintenance of FOXP3 protein expression is crucial for differentiation and maturation of regulatory T (Treg) cells, which play important roles in immune homeostasis and immune tolerance. We demonstrate here that PDCD5 interacts with FOXP3, increases acetylation of FOXP3 in synergy with Tip60 and enhances the repressive function of FOXP3. In PDCD5 transgenic (PDCD5tg) mice, overexpression of PDCD5 enhanced the level of FOXP3 protein and percentage of CD4⁺CD25⁺FOXP3⁺ cells. Naïve CD4⁺ T cells from PDCD5tg mice were more sensitive to TGF-β-induced Treg polarization and expansion. These induced Tregs retained normal suppressive function in vitro. Severity of experimentally-induced autoimmune encephalomyelitis (EAE) in PDCD5tg mice was significantly reduced relative to that of wild-type mice. The beneficial effect of PDCD5 likely resulted from increases of Treg cell frequency, accompanied by a reduction of the predominant pathogenic Th17/Th1 response. Activation-induced cell death enhanced by PDCD5 was also linked to this process. This is the first report revealing that PDCD5 activity in T cells suppresses autoimmunity by modulating Tregs. This study suggests that PDCD5 serves as a guardian of immunological functions and that the PDCD5-FOXP3-Treg axis may be a therapeutic target for autoimmunity.     

Regulatory T cells play a role in T-cell receptor CDR2 peptide regulation of experimental autoimmune encephalomyelitis

Eliciting T-cell receptor (TCR) -specific responsiveness has been known to provide an effective autoregulatory mechanism for limiting inflammation mediated by T effector cells. Our previous use of TCR peptides derived from the CDR3 regions of a pathogenic TCR effectively reversed ongoing experimental autoimmune encephalomyelitis (EAE) in a humanized TCR transgenic model. In this study, we use the TCR BV8S2 CDR2 peptide in the non-transgenic C57BL/6 EAE model to down-regulate the heterogeneous TCR BV8S2(+) MOG-35-55-specific pathogenic T-cell population and demonstrate successful treatment of EAE after disease onset. Suppression of disease was associated with reduced MOG-35-55-specific and non-specific T-cell production of interleukin-17a and interferon-γ in the central nervous system, as well as reduced numbers of CD4(+) and Foxp3(+) T cells in the central nervous system. With the use of Foxp3-GFP and Foxp3 conditional knockout mice, we demonstrate that the TCR CDR2 peptide treatment effect is dependent on the presence of Foxp3(+) regulatory T cells and that regulatory T cell numbers are significantly expanded in the periphery of treated mice. Hence, TCR CDR2 peptide therapy is effective in regulating heterogeneous, pathogenic T-cell populations through the activity of the Foxp3(+) regulatory T cell population.     

Contrasting contributions of complementarity-determining region 2 and hypervariable region 4 of rat BV8S2+ (Vbeta8.2) TCR to the recognition of myelin basic protein and different types of bacterial superantigens

In experimental autoimmune encephalomyelitis (EAE) of LEW rats, BV8S2(+) (V(beta)8.2) T cells dominate the RT1B(l)-restricted response to guinea pig myelin basic protein (gpMBP), and respond to the superantigens (SAg) Staphylococcus enterotoxin C1 (SEC1), Mycoplasma arthritidis SAg (MAS) and Yersinia pseudotuberculosis mitogen (YPM). T cells expressing the closely related BV8S4 differ from BV8S2 T cells in their response to gpMBP, and the SAg SEC1 and MAS, but not in their response to YPM. The functional differences between BV8S2 and BV8S4, which vary in complementarity-determining/hypervariable region 4 (CDR4/HV4) and CDR2, were analyzed by cloning and mutating a TCR with features typical for gpMBP-specific BV8S2(+) TCR. The wild-type BV8S2 receptor and the BV8S4-like CDR2 + 4beta double mutant of BV8S2 showed the same differences in ligand specificity as polyclonal BV8S2(+) and BV8S4(+) lymphocyte populations. The CDR2beta mutant lost its reactivity for SEC1 and gpMBP(68-88), but the CDR4/HV4beta mutation abolished only activation by SEC1. Thus, CDR2 and HV4 contribute not only differently to recognition of peptide antigens, but also to recognition of different types of bacterial SAg.     

Down syndrome, autoimmunity and T regulatory cells

Autoimmune diseases are more represented in Down syndrome (DS) individuals compared to chromosomally normal people. Natural T regulatory cells (nT_reg) have been considered to be primary in the role of controlling the intensity and targets of the immune response. We have investigated the phenotypical and functional alteration of nT_reg in a group of DS people. The phenotypical characteristic of T_reg cells of 29 DS was analysed and compared with an age‐matched healthy control group. The inhibitory potential of CD4⁺CD25^highCD127^low T regulatory cells was evaluated on autologous CD4⁺CD25^‐ T cell proliferation in response to activation with a mytogenic pan‐stimulus (anti‐CD2, anti‐CD3 and anti‐CD28 antibodies). The CD4⁺CD25^high cells in the DS and control groups were 2·692 ± 0·3808%, n = 29 and 1·246 ± 0·119, n = 29%, respectively (P = 0.0007), with a percentage of forkhead box protein 3 (FoxP3)‐expressing cells of 79·21 ± 3·376%, n = 29 and 59·75 ± 4·496%, respectively (P = 0.0015). CD4⁺CD25⁺FoxP3⁺ cells were increased in peripheral blood from DS subjects (DS mean 5·231 ± 0·6065% n = 29, control mean 3·076 ± 0·3140% n = 29). The majority of CD4⁺CD25^high were CD127^low and expressed a high percentage of FoxP3 (natural T_reg phenotype). While the proliferative capacity of DS T cells was not altered significantly compared to normal individuals, a reduced inhibitory potential of T_reg compared to healthy controls was clearly observed (mean healthy control inhibition in T_eff : T_reg 1:1 co‐culture: 58·9% ± 4·157%, n = 10 versus mean DS inhibition in T_eff : T_reg 1:1 co‐culture: 39·8 ± 4·788%, n = 10, P = 0.0075; mean healthy control inhibition in T_eff : T_reg 1:0·5 co‐culture: 45·10 ± 5·858%, n = 10 versus DS inhibition in T_eff : T_reg 1:0·5 co‐culture: 24·10 ± 5·517%, n = 10, P = 0.0177). DS people present an over‐expressed peripheral nT_reg population with a defective inhibitory activity that may partially explain the increased frequency of autoimmune disease.     

Vasoactive Intestinal Polypeptide Suppressed Experimental Autoimmune Encephalomyelitis by Inhibiting T Helper 1 Responses

Vasoactive intestinal peptide (VIP) has been found to act as a potent anti-inflammatory factor through regulating the production of both anti- and pro-inflammatory mediators and promoting Th2-type responses. In this study, we used myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis (EAE) model in C57BL/6 mice to investigate the potential effects of VIP on multiple sclerosis. Our results showed that in vivo treatment of EAE-induced mice with VIP had great protective benefit at both clinical and histological levels. Disease suppression was associated with the inhibition of T cells proliferation, shifting of the immune response toward a Th2-type response and influencing the expression of pro-inflammatory cytokines including IFN-γ, IL-6 and IL-2 as well as chemotactic factors such as RANTES. In conclusion, the study provides evidence that VIP had great protective effect on EAE through its inhibition actions on pathogenic T cells and through a specific effect on the Th1 response.Haiyan Li and Yunhua Mei contributed equally to this work     

Autoimmune syndrome after induction of neonatal tolerance to alloantigens: analysis of the role of donor T cells in the induction of autoimmunity.

The injection of (C57BL/6 x BALB/c) F1 spleen cells into BALB/c newborn mice leads to activation of persisting F1 donor B cells and development of a lupus-like syndrome in tolerized BALB/c mice. This syndrome is characterized by hypergammaglobulinaemia, high levels of anti-DNA and anti-Sm antibodies, circulating immune complexes and deposits of immunoglobulin in renal glomeruli. The role of donor T cells in this model was investigated by injecting the newborn mice with F1 cells depleted in different T cell subsets by using specific monoclonal antibodies (MoAbs). Tolerance, as shown by an absence of H-2b-specific CTL alloreactivity and persistence of immunoglobulin bearing the donor allotype were observed in mice injected with F1 cells previously depleted in the CD4+ and/or CD8+ T cell subsets as well as in those which received Thy-1+-depleted F1 spleen cells. In these mice, a typical autoimmune syndrome was found, including splenomegaly and lymphadenopathy, anti-ssDNA and anti-aortic myosin IgG antibodies and renal deposition of immunoglobulin. However, some quantitative changes were seen: the levels of anti-aortic myosin antibodies were lower in mice tolerized with CD4+-depleted F1 cells than in those receiving untreated F1 cells. Conversely, higher levels of these autoantibodies were observed in mice tolerized with CD8+-depleted F1 cells. These results suggest that mature donor T cells are not necessary neither for the establishment of neonatal tolerance to alloantigens nor for the activation of F1 donor B cells in the production of the autoimmune syndrome in tolerant mice, but they may contribute in the regulation of the expression of autoreactive B cell clones.     

Activation-induced cell death in T cells and autoimmunity

Activation-induced cell death (AICD), which results from the interaction between Fas and Fas ligand, is responsible for maintaining tolerance to self-antigen. A defect in AICD may lead to development of autoimmunity. During the last several years, much progress has been made in understanding the mechanism(s) of AICD and its potential role in the pathogenesis of autoimmune diseases. In this review, we summarize the most recent progress on the regulation of the susceptibility of T cells to AICD and its possible involvement in autoimmune diseases.     

Heterogeneity of rat encephalitogenic T cells elicited by variants of the myelin basic protein (68–86) peptide

By immunizing Lewis rats with myelin basic protein (MBP) peptide variants derived from the major encephalitogenic epitope of guinea pig (MBP(68–88) and then isolating encephalitogenic T cells from these animals, we demonstrated that the variant peptides do not elicit the same encephalitogenic T cell subsets as those induced by the wild-type peptide or by intact MBP. Rather, the pathogenic T cells differed in clonal composition as reflected by their heterogeneous responses to a panel of variant peptides and by their T cell receptor usage. Thus, molecules mimicking the MBP(68–88) autoantigen can elicit pathogenic T cell subsets without necessarily cross-reacting with T cells specific for the original autoantigen. This suggests that a more clonally diverse group of pathogenic T cells might be involved in EAE than has been apparent from studies with intact MBP or its unaltered peptides.     

Proinsulin multi-peptide immunotherapy induces antigen-specific regulatory T cells and limits autoimmunity in a humanized model

Peptide immunotherapy (PIT) is a targeted therapeutic approach, involving administration of disease-associated peptides, with the aim of restoring antigen-specific immunological tolerance without generalized immunosuppression. In type 1 diabetes, proinsulin is a primary antigen targeted by the autoimmune response, and is therefore a strong candidate for exploitation via PIT in this setting. To elucidate the optimal conditions for proinsulin-based PIT and explore mechanisms of action, we developed a preclinical model of proinsulin autoimmunity in a humanized HLA-DRB1*0401 transgenic HLA-DR4 Tg mouse. Once proinsulin-specific tolerance is broken, HLA-DR4 Tg mice develop autoinflammatory responses, including proinsulin-specific T cell proliferation, interferon (IFN)-γ and autoantibody production. These are preventable and quenchable by pre- and post-induction treatment, respectively, using intradermal proinsulin-PIT injections. Intradermal proinsulin-PIT enhances proliferation of regulatory [forkhead box protein 3 (FoxP3⁺)CD25^high] CD4 T cells, including those capable of proinsulin-specific regulation, suggesting this as its main mode of action. In contrast, peptide delivered intradermally on the surface of vitamin D3-modulated (tolerogenic) dendritic cells, controls autoimmunity in association with proinsulin-specific IL-10 production, but no change in regulatory CD4 T cells. These studies define a humanized, translational model for in vivo optimization of PIT to control autoimmunity in type 1 diabetes and indicate that dominant mechanisms of action differ according to mode of peptide delivery.     

The clonal composition of myelin basic protein-reactive encephalitogenic T cell populations is influenced both by the structure of relevant antigens and the nature of antigen-presenting cells

Studies of experimental autoimmune encephalomyelitis (EAE) in rodents have revealed that encephalitogenic T cell lines reactive with myelin basic protein (BP) are frequently dominated by clones expressing a restricted T cell receptor repertoire. Using the rat EAE model, we have begun to examine the basis for clonal dominance within BP-reactive T cell lines. We find that variations introduced into the standard protocol of periodic antigen stimulation produce marked shifts in the representation of different clones within encephalitogenic T cell populations. For example, altering the source of antigen-presenting cells (APC), while holding antigen (BP) constant, and substituting BP from guinea pig (GPBP) for that of the rat antigen (RBP) with constant APC, both cause shifts in the composition of the dominant clones within BP-reactive T cell lines. Our results suggest that: (i) adherence to an invariant protocol of antigen challenge may lead to an underestimation of the diversity of BP-reactive encephalitogenic T cell populations; and (ii) the minor structural differences between GPBP and RBP not only cause the weak immunogenicity of RBP but also result in the alteration of different T cell subsets. These observations indicate that apparent restrictions upon the repertoire of autoimmune T cells should be interpreted with caution when such cells are elicited by immunization with foreign antigens.