Immune response of Lewis rats to peptide C1 (residues 68-88) of guinea pig and rat myelin basic proteins

The Short and Long-Term Effects of Pregnancy on Multiple Sclerosis and Experimental Autoimmune Encephalomyelitis

The role of pregnancy in multiple sclerosis (MS) is of importance because many patients with MS are young women in the childbearing age who require information to inform their reproductive decisions. Pregnancy is now well-known to be associated with fewer relapses of MS and reduced activity of autoimmune encephalomyelitis (EAE). However, in women with multiple sclerosis, this benefit is not always sufficient to protect against a rebound of disease activity if disease-modulating therapy is ceased for pregnancy. There is concern that use of assisted reproductive therapies can be associated with relapses of MS, but more data are required. It is thought that the beneficial effects of pregnancy are due to the pregnancy-associated changes in the maternal immune system. There is some evidence of this in human studies and studies of EAE. There is also evidence that having been pregnant leads to better long-term outcome of MS. The mechanism for this is not fully understood but it could result from epigenetic changes resulting from pregnancy or parenthood. Further studies of the mechanisms of the beneficial effects of pregnancy could provide information that might be used to produce new therapies.

Lewis Rat Model of Experimental Autoimmune Encephalomyelitis

In this unit, we describe in detail the most common methods used to break immunological tolerance for central myelin antigens and induce experimental autoimmune encephalomyelitis (EAE) in Lewis rats as an animal model of multiple sclerosis. The resulting disease course ranges from an acute monophasic disease to a chronic relapsing or chronic progressive course, which strongly resembles the human disease. These models enable the study of cellular and humoral autoimmunity against major antigenic epitopes of the myelin basic protein, myelin oligodendrocyte glycoprotein, or proteolipid protein. We provide an overview of common immunization protocols for induction of active and passive EAE, assessment and analysis of clinical score, preparation and purification of myelin basic protein, and derivation of neuroantigen-specific rat T cell lines. Finally, we describe the major clinical characteristics of these models. © 2017 by John Wiley & Sons, Inc.

Severely exacerbated neuromyelitis optica rat model with extensive astrocytopathy by high affinity anti-aquaporin-4 monoclonal antibody

Introduction

Neuromyelitis optica (NMO), an autoimmune astrocytopathic disease associated with anti-aquaporin-4 (AQP4) antibody, is characterized by extensive necrotic lesions preferentially involving the optic nerves and spinal cord. However, previous in-vivo experimental models injecting human anti-AQP4 antibodies only resulted in mild spinal cord lesions compared to NMO autopsied cases. Here, we investigated whether the formation of severe NMO-like lesions occurs in Lewis rats in the context of experimental autoimmune encephalomyelitis (EAE), intraperitoneally injecting incremental doses of purified human immunoglobulin-G from a NMO patient (hIgG_NMO) or a high affinity anti-AQP4 monoclonal antibody (E5415A), recognizing extracellular domain of AQP4 made by baculovirus display method.

Results

NMO-like lesions were observed in the spinal cord, brainstem, and optic chiasm of EAE-rats with injection of pathogenic IgG (hIgG_NMO and E5415A), but not in control EAE. Only in higher dose E5415A rats, there were acute and significantly severer clinical exacerbations (tetraparesis or moribund) compared with controls, within half day after the injection of pathogenic IgG. Loss of AQP4 was observed both in EAE rats receiving hIgG_NMO and E5415A in a dose dependent manner, but the ratio of AQP4 loss in spinal sections became significantly larger in those receiving high dose E5415A up to about 50 % than those receiving low-dose E5415A or hIgG_NMO less than 3 %. These lesions were also characterized by extensive loss of glial fibrillary acidic protein but relatively preserved myelin sheaths with perivascular deposition of IgG and C5b-9, which is compatible with post mortem NMO pathology. In high dose E5415A rats, massive neutrophil infiltration was observed especially at the lesion edge, and such lesions were highly vacuolated with partial demyelination and axonal damage. In contrast, such changes were absent in EAE rats receiving low-dose E5415A and hIgG_NMO.

Conclusions

In the present study, we established a severe experimental NMO rat model with highly clinical exacerbation and extensive tissue destructive lesions typically observed in NMO patients, which has not adequately been realized in in-vivo rodent models. Our data suggest that the pathogenic antibodies could induce immune mediated astrocytopathy with mobilized neutrophils, resulted in early lesion expansion of NMO lesion with vacuolation and other tissue damages. (350/350)

Electronic supplementary material

The online version of this article (doi:10.1186/s40478-015-0259-2) contains supplementary material, which is available to authorized users.

Multiple sclerosis-induced neuropathic pain: pharmacological management and pathophysiological insights from rodent EAE models

In patients with multiple sclerosis (MS), pain is a frequent and disabling symptom. The prevalence is in the range 29-86 % depending upon the assessment protocols utilised and the definition of pain applied. Neuropathic pain that develops secondary to demyelination, neuroinflammation and axonal damage in the central nervous system is the most distressing and difficult type of pain to treat. Although dysaesthetic extremity pain, L'hermitte's sign and trigeminal neuralgia are the most common neuropathic pain conditions reported by patients with MS, research directed at gaining insight into the complex mechanisms underpinning the pathobiology of MS-associated neuropathic pain is in its relative infancy. By contrast, there is a wealth of knowledge on the neurobiology of neuropathic pain induced by peripheral nerve injury. To date, the majority of research in the MS field has used rodent models of experimental autoimmune encephalomyelitis (EAE) as these models have many clinical and neuropathological features in common with those observed in patients with MS. However, it is only relatively recently that EAE-rodents have been utilised to investigate the mechanisms contributing to the development and maintenance of MS-associated central neuropathic pain. Importantly, EAE-rodent models exhibit pro-nociceptive behaviours predominantly in the lower extremities (tail and hindlimbs) as seen clinically in patients with MS-neuropathic pain. Herein, we review research to date on the pathophysiological mechanisms underpinning MS-associated neuropathic pain as well as the pharmacological management of this condition. We also identify knowledge gaps to guide future research in this important field.

Transgenic mouse models of multiple sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating disease affecting the central nervous system (CNS) and a frequent cause of neurological disability in young adults. Multifocal inflammatory lesions in the CNS white matter, demyelination, oligodendrocyte loss, axonal damage, as well as astrogliosis represent the histological hallmarks of the disease. These pathological features of MS can be mimicked, at least in part, using animal models. This review discusses the current concepts of the immune effector mechanisms driving CNS demyelination in murine models. It highlights the fundamental contribution of transgenesis in identifying the mediators and mechanisms involved in the pathophysiology of MS models.

EAE: an immunologist's magic eye

EAE comes in many shapes and colors. Individual variants of EAE present a baffling complexity of different aspects and traits, clinical, immunological, and structural. But, embedded in this seemingly chaotic image, the educated eye will discern patterns that retrace fundamental features of immune response, in particular, autoimmunity and self-tolerance. EAE and its variants thus can be likened to an autostereogram, i.e. they are an immunologist's magic eye.

Experimental autoimmune encephalomyelitis in the rat

There are several diverse rat models of experimental autoimmune encephalomyelitis (EAE) that can be used to investigate the pathogenesis and regulation of autoimmunity against CNS myelin. The disease course of these models ranges from an acute monophasic disease with limited demyelination to a chronic relapsing or chronic progressive course marked by severe demyelination. These models enable the study of encephalitogenic T cells and demyelinating antibody specific for major neuroantigens such as myelin basic protein (MBP), myelin oligodendrocyte glycoprotein (MOG), or proteolipid protein (PLP), among other important CNS autoantigens. Overall, this unit provides an overview of common methods for induction of active and passive EAE, assessment and analysis of clinical disease, preparation and purification of myelin basic protein, and derivation of neuroantigen-specific rat T cell lines. This unit also provides a brief discussion of the basic characteristics of these models.

The origin and application of experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a model of the neuroimmune system responding to priming with central nervous system (CNS)-restricted antigens. It is an excellent model of post-vaccinal encephalitis and a useful model of many aspects of multiple sclerosis. EAE has been established in numerous species and is induced by priming with a large number of CNS-derived antigens. As a consequence, the pathogenesis, pathology and clinical signs vary significantly between experimental protocols. As I describe in this Timeline article, the reductionist approach taken in some lines of investigation of EAE resulted in a reliance on results obtained under a narrow range of conditions. Although such studies made important contributions to our molecular understanding of inflammation, T-cell activation, and MHC restriction, they did not advance as effectively our knowledge of the polyantigenic responses that usually occur in CNS immunopathology and autoimmunity.

An experimental model of autoimmune pancreatitis in the rat

Autoimmune pancreatitis (AIP), a recently defined disease of unknown etiology, is characterized by inflammatory infiltrates in the pancreas with conspicuous involvement of the ducts. The disease clinically manifests in humans as epigastric pain, weight loss, and jaundice. This report describes the development of a novel animal model of this disease in the rat, which we have termed experimental autoimmune pancreatitis. Adoptive transfer of amylase-specific CD4(+) T cells was able to confer pancreatitis to naive syngeneic recipient animals. No treatments before the adoptive transfer of T cells were necessary for disease to ensue, and the severity of disease was proportional to the number of T cells administered. The pancreatic lesions of rats with experimental autoimmune pancreatitis were characterized histologically as overwhelmingly lymphocytic with occasional plasma cells, neutrophils, and mast cells. Acinar tissue destruction and ductular inflammation were common features, with less frequent involvement of larger ducts. Immunohistochemical analysis revealed the presence of CD4(+) T cells in large numbers as well as CD8(+) T cells, macrophages, and dendritic cells. Expression of MHC I and MHC II also increased at the site of the lesion. Clinically, the disease manifested as either failure to gain weight at a rate concomitant with control animals or as outright weight loss. Thus, administration of activated CD4(+) T cells specific for the pancreatic enzyme amylase can induce pancreatitis in the rat in a manner that is reminiscent of human AIP.

Homeostatic control of immunity by TCR peptide-specific Tregs

Regulation of the immune response is a multifaceted process involving lymphocytes that function to maintain both self tolerance as well as homeostasis following productive immunity against microbes. There are 2 broad categories of Tregs that function in different immunological settings depending upon the context of antigen exposure and the nature of the inflammatory response. During massive inflammatory conditions such as microbial exposure in the gut or tissue transplantation, regulatory CD4+CD25+ Tregs broadly suppress priming and/or expansion of polyclonal autoreactive responses nonspecifically. In other immune settings where initially a limited repertoire of antigen-reactive T cells is activated and expanded, TCR-specific negative feedback mechanisms are able to achieve a fine homeostatic balance. Here I will describe experimental evidence for the existence of a Treg population specific for determinants that are derived from the TCR and are expressed by expanding myelin basic protein-reactive T cells mediating experimental autoimmune encephalomyelitis, an animal prototype for multiple sclerosis. These mechanisms ensure induction of effective but appropriately limited responses against foreign antigens while preventing autoreactivity from inflicting escalating damage. In contrast to CD25+ Tregs, which are most efficient at suppressing priming or activation, these specific Tregs are most efficient in controlling T cells following their activation.

Anti-S-nitrosocysteine antibodies are a predictive marker for demyelination in experimental autoimmune encephalomyelitis: implications for multiple sclerosis

Multiple sclerosis (MS) is characterized by inflammation within the CNS. This inflammatory response is associated with production of nitric oxide (NO) and NO-related species that nitrosylate thiols. We postulated that MS patients would exhibit an antibody (Ab) response directed against proteins containing S-nitrosocysteine (SNO-cysteine) and showed that anti-NO-cysteine Abs of the IgM isotype are in fact present in the sera of some MS patients (Boullerne et al., 1995). We report here the presence of a seemingly identical Ab response directed against SNO-cysteine in an acute model of MS, experimental autoimmune encephalomyelitis (EAE) induced in Lewis rats with the 68-84 peptide of guinea pig myelin basic protein (MBP(68-84)). Serum levels of anti-SNO-cysteine Abs peaked 1 week before the onset of clinical signs and well before the appearance of anti-MBP(68-84) Abs. The anti-SNO-cysteine Ab peak titer correlated with the extent of subsequent CNS demyelination, suggesting a link between Ab level and CNS lesion formation. In relapsing-remitting MS patients, we found elevated anti-SNO-cysteine Ab at times of relapse and normal values in most patients judged to be in remission. Two-thirds of patients with secondary progressive MS had elevated anti-SNO-cysteine Ab levels, including those receiving interferon beta-1b. The data show that a rise in circulating anti-SNO-cysteine Ab levels precedes onset of EAE. Anti-SNO-cysteine Abs are also elevated at times of MS attacks and in progressive disease, suggesting a possible role for these Abs, measurable in blood, as a biological marker for clinical activity.

Anti-S-nitrosocysteine antibodies are a predictive marker for demyelination in experimental autoimmune encephalomyelitis: implications for multiple sclerosis

Multiple sclerosis (MS) is characterized by inflammation within the CNS. This inflammatory response is associated with production of nitric oxide (NO) and NO-related species that nitrosylate thiols. We postulated that MS patients would exhibit an antibody (Ab) response directed against proteins containing S-nitrosocysteine (SNO-cysteine) and showed that anti-NO-cysteine Abs of the IgM isotype are in fact present in the sera of some MS patients (Boullerne et al., 1995). We report here the presence of a seemingly identical Ab response directed against SNO-cysteine in an acute model of MS, experimental autoimmune encephalomyelitis (EAE) induced in Lewis rats with the 68-84 peptide of guinea pig myelin basic protein (MBP(68-84)). Serum levels of anti-SNO-cysteine Abs peaked 1 week before the onset of clinical signs and well before the appearance of anti-MBP(68-84) Abs. The anti-SNO-cysteine Ab peak titer correlated with the extent of subsequent CNS demyelination, suggesting a link between Ab level and CNS lesion formation. In relapsing-remitting MS patients, we found elevated anti-SNO-cysteine Ab at times of relapse and normal values in most patients judged to be in remission. Two-thirds of patients with secondary progressive MS had elevated anti-SNO-cysteine Ab levels, including those receiving interferon beta-1b. The data show that a rise in circulating anti-SNO-cysteine Ab levels precedes onset of EAE. Anti-SNO-cysteine Abs are also elevated at times of MS attacks and in progressive disease, suggesting a possible role for these Abs, measurable in blood, as a biological marker for clinical activity.

MHC class-II-restricted antigen presentation by myelin basic protein-specific CD4+ T cells causes prolonged desensitization and outgrowth of CD4- responders

T cells express MHC class II glycoproteins under various conditions of activation or inflammation. To assess whether T cell APC (T-APC) activity had long-term tolerogenic consequences, myelin basic protein (MBP)-specific rat T cells were induced to acquire MBP-derived I-A complexes to promote reciprocal antigen presentation. T-T antigen presentation caused extensive cell death among T-APC and MBP-specific T responders and caused long-term desensitization of surviving responders. Addition of the anti-I-A mAb OX6 to activated I-A+ responders inhibited T-APC activity, accelerated recovery from postactivation refractoriness, and prevented long-term loss of reactivity in responder T cells. Antigenic activation of responder T cells with irradiated T-APC induced profound losses in reactivity that lasted for over 1 month of propagation in IL-2 and was associated with preferential outgrowth of CD4- T cells. Antigen-activated CD4- T cells exhibited more rapid IL-2-dependent growth that eventually normalized compared to CD4+ T cells 1-2 months after antigen exposure. In conclusion, expression of T-APC activity by activated T cells represents an important negative feedback pathway that depletes antigen-reactive T cells and causes long-term desensitization of surviving T cells. Hence, T cell APC may be an important mechanism of self-tolerance.

T cell recognition of rat myelin basic protein as a TCR antagonist inhibits reciprocal activation of antigen-presenting cells and engenders resistance to experimental autoimmune encephalomyelitis

The aim of this study was to assess whether T cell recognition of myelin basic protein (MBP) as a partially antagonistic self antigen regulates the reciprocal activation of professional antigen-presenting cells (APC). This study focused on the rat 3H3 T cell clone that recognized guinea pig (GP) MBP as a full agonist and self rat (R) MBP as a partial agonist. In cultures of 3H3 T cells and splenic APC, the agonist GPMBP elicited several responses by splenic APC, including production of nitric oxide, down-regulation of I-A, induction of B7.1 and B7.2, and prolongation of APC survival. RMBP stimulated a partial increase in production of nitric oxide, partially promoted survival of splenic APC, but did not alter expression of I-A, B7.1, or B7.2 on splenic APC. In the presence ofGPMBP, RMBP antagonized agonist-stimulated induction of B7 molecules, reversed the loss of I-A, and promoted the generation of I-A(+), costimulus-deficient APC. Furthermore, 3H3 T cells cultured with RMBP and irradiated splenocytes reduced the severity of EAE upon adoptive transfer into naive rat recipients subsequently challenged with an encephalitogenic dose of GPMBP/CFA. Overall, this study indicates that T cell receptor antagonism blocks T cell activation, inhibits feedback activation of splenic APC, and promotes T cell-dependent regulatory activities in EAE.

Class II MHC/Peptide Complexes Are Released from APC and Are Acquired by T Cell Responders During Specific Antigen Recognition

T cell expression of class II MHC/peptide complexes may be important for maintenance of peripheral self-tolerance, but mechanisms underlying the genesis of class II MHC glycoproteins on T cells are not well resolved. T cell APC (T-APC) used herein were transformed IL-2-dependent clones that constitutively synthesized class II MHC glycoproteins. When pulsed with myelin basic protein (MBP) and injected into Lewis rats, these T-APC reduced the severity of experimental autoimmune encephalomyelitis, whereas unpulsed T-APC were without activity. Normal MBP-reactive clones cultured without APC did not express class II MHC even when activated with mitogens and exposed to IFN-γ. However, during a 4-h culture with T-APC or macrophage APC, recognition of MBP or mitogenic activation of responder T cells elicited high levels of I-A and I-E expression on responders. Acquisition of class II MHC glycoproteins by responders was resistant to the protein synthesis inhibitor cycloheximide, coincided with transfer of a PKH26 lipophilic dye from APC to responders, and resulted in the expression of syngeneic and allogeneic MHC glycoproteins on responders. Unlike rested I-A− T cell clones, rat thymic and splenic T cells expressed readily detectable levels of class II MHC glycoproteins. When preactivated with mitogens, naive T cells acquired APC-derived MHC class II molecules and other membrane-associated proteins when cultured with xenogeneic APC in the absence of Ag. In conclusion, this study provides evidence that APC donate membrane-bound peptide/MHC complexes to Ag-specific T cell responders by a mechanism associated with the induction of tolerance.

Citrullinated myelin basic protein induces experimental autoimmune encephalomyelitis in Lewis rats through a diverse T cell repertoire

An increased proportion of citrullinated MBP (MBP-C8) occurs in the brains of multiple sclerosis (MS) patients. In this study, MBP-C8 from guinea pig (GP) brains was isolated and found encephalitogenic in Lewis rats upon immunization. An encephalitogenic T cell line selected with MBP-C8 preferentially reacted with MBP-C8 over unmodified MBP. This T cell line responded weakly to the dominant encephalitogenic epitope, GP-MBP peptide 70-88, and did not display restricted TCR beta-chain usage (such as Vbeta88.2). The distinctive features of MBP-C8 were also demonstrated by its ability to reinduce active EAE in 70% of rats which had recovered from unmodified MBP induced EAE. These findings raise the possibility that citrullinated MBP may elicit a different pathogenic T cell repertoire for the recurrent phases of inflammatory demyelination.

Contrasting immunopathogenic properties of highly homologous peptides from rat and human thyroglobulin

The current lack of amino acid sequence data for mouse thyroglobulin (Tg) necessitates mapping of pathogenic T-cell epitopes on heterologous Tg in mouse experimental autoimmune thyroiditis (EAT). A prevailing assumption has been that epitopes sharing a high degree of amino acid homology among heterologous Tg are likely to exhibit the same immunopathogenic properties in the same host. In this report, we have examined this concept while working with the 18-mer rat(r)Tg(2695-13) peptide that was previously shown to elicit 'A'-restricted T cells and EAT in SJL mice. A major immunopathogenic T-cell epitope was localized within the 12-mer rTg(2695-06). It was found that the human 12-mer homologue that carries two Ser substitutions at Glu2703 and Thr2704 exhibited contrasting properties: it failed to activate Th1 cells in lymphokine and proliferation assays; it did not cross-react with rTg(2695-06) at the T-cell level; and it induced only focal thyroiditis following adoptive transfer of specific lymph node cells. These data highlight the caveat involved in extrapolating results of pathogenic T-cell epitope mapping across heterologous Tgs, even when such epitopes share a high degree of amino acid homology.

The myelin basic protein-specific T cell repertoire in (transgenic) Lewis rat/SCID mouse chimeras: preferential V beta 8.2 T cell receptor usage depends on an intact Lewis thymic microenvironment

In the Lewis rat, myelin basic protein (MBP)-specific, encephalitogenic T cells preferentially recognize sequence 68-88, and use the V beta 8.2 gene to encode their T cell receptors. To analyze the structural prerequisites for the development of the MBP-specific T cell repertoire, we reconstituted severe-combined immunodeficient (SCID) mice with fetal (embryonic day 15-16) Lewis rat lymphoid tissue, and then isolated MBP-specific T cell lines from the adult chimeras after immunization. Two types of chimera were constructed: SCID mice reconstituted with rat fetal liver cells only, allowing T cell maturation within a chimeric SCID thymus consisting of mouse thymic epithelium and rat interdigitating dendritic cells, and SCID mice reconstituted with rat fetal liver cells and rat fetal thymus grafts, allowing T cell maturation within the chimeric SCID and the intact Lewis rat thymic microenvironment. Without exception, the T cell lines isolated from MBP-immunized SCID chimeras were restricted by MHC class II of the Lewis rat (RT1.B1), and none by I-Ad of the SCID mouse. Most of the T cell lines recognized the immunodominant MBP epitope 68-88. In striking contrast to intact Lewis rats, in SCID mice reconstituted by rat fetal liver only, MBP-specific T cell clones used a seemingly random repertoire of V beta genes without a bias for V beta 8.2. In chimeras containing fetal Lewis liver plus fetal thymus grafted under the kidney capsule, however, dominant utilization of V beta 8.2 was restored. The migration of liver-derived stem cells through rat thymus grafts was documented by combining fetal tissues from wild-type and transgenic Lewis rats. The results confirm that the recognition of the immunodominant epitope 68-88 by MBP-specific encephalitogenic T cells is a genetically determined feature of the Lewis rat T cell repertoire. They further suggest that the formation of the repertoire requires T cell differentiation in a syngeneic thymic microenvironment.

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.

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.

In healthy primates, circulating autoreactive T cells mediate autoimmune disease

A T cell response against myelin basic protein (MBP) is thought to contribute to the central nervous system (CNS) inflammation that occurs in the human demyelinating disease multiple sclerosis. To test whether MBP-reactive T cells that are normally retrieved from the circulation are capable of inducing CNS disease, MBP-reactive T cell clones were isolated from the peripheral blood of healthy, unimmunized Callithrix jacchus (C. jacchus) marmosets. This primate species is characterized by a natural chimerism of bone marrow elements between siblings that should make possible adoptive transfer of MBP-reactive T cells. We report that MBP-reactive T cell clones efficiently and reproducibly transfer CNS inflammatory disease between members of C. jacchus chimeric sets. The demyelination that is characteristic of experimental allergic encephalomyelitis induced in C. jacchus by immunization against human white matter did not occur after adoptive transfer of the MBP-reactive clones. It was noteworthy that encephalitogenic T cell clones were diverse in terms of their recognition of different epitopes of MBP, distinguishing the response in C. jacchus from that in some inbred rodents in which restricted recognition of MBP occurs. These findings are the first direct evidence that natural populations of circulating T cells directed against a CNS antigen can mediate an inflammatory autoimmune disease.

A pathogenic autoimmune process targeted at a surrogate epitope

Immunization with the retinal interphotoreceptor retinoid-binding protein (IRBP) induces in a variety of animals an inflammatory eye disease, experimental autoimmune uveoretinitis (EAU). We have previously shown that sequence 1181-1191 of bovine IRBP (BOV 1181-1191) is immunodominant and highly uveitogenic and immunogenic in Lewis rats. Sequence 1181-1191 of the rat IRBP (RAT 1181-1191) differs from BOV 1181-1191 by two residues, at positions 1188 and 1190, that are pivotal for the immunological activity of the bovine epitope. Here we show that, unlike its bovine homologue, RAT 1181-1191 did not induce EAU or an immune response in Lewis rats. The immunological inactivity of RAT 1181-1191 in Lewis rats is due at least in part to its poor affinity toward the antigen-presenting cells of these rats, as shown by its failure to compete with binding of BOV 1181-1191 to Lewis adherent spleen cells. Moreover, unlike all other known autologous homologues of immunopathogenic epitopes, RAT 1181-1191 was not recognized by lymphocytes sensitized against BOV 1181-1191 and failed to stimulate proliferation, uveitogenic capacity or signal transduction in these cells. These findings thus suggest that RAT 1181-1191 is not a likely target for lymphocytes sensitized against BOV 1181-1191 in the process in which these cells recognize IRBP in the rat eye and trigger the inflammatory reaction of EAU. Our data further suggest that the target for the disease-inducing lymphocytes is sequence 273-283 of the rat IRBP: (a) sequence 273-283 is highly conserved and is identical in the bovine and rat proteins; (b) determinant 273-283 is a "repeat" of 1181-1191 in the fourfold structure of IRBP and shares seven residues with BOV 1181-1191; (c) rat peptide 273-283 is recognized by lymphocytes sensitized against BOV 1181-1191 and stimulates them for proliferation and for acquisition of uveitogenicity; and (d) moreover, sequence 273-283 is superior to BOV 1181-1191 in its capacity to generate uveitogenicity in lymphocytes sensitized against this bovine peptide. The present study thus describes for the first time a system in which an autologous homologue of an immunopathogenic epitope is inactive and a "surrogate" determinant apparently serves as the target for lymphocytes sensitized against the immunopathogenic peptide.

Prevention strategies for multiple sclerosis

The design of effective prevention strategies for multiple sclerosis (MS) is hampered by ignorance of the basic pathophysiology of the disease. An understanding of specific immune mechanisms, the nature of genetic susceptibility, and environmental triggers will permit rational decision making from among the many proposed therapeutic directions available. It is reasonable to hypothesize that inhibition of central nervous system inflammation will be of benefit in MS, regardless of the trigger (autoantigen, exogenous antigen, or nonspecific trigger). Emerging concepts are reviewed to provide guideposts for the design of rational therapy for MS.

Differential recognition of sequences within the encephalitogenic region of myelin basic protein capable of eliciting cell-mediated immune responses in experimental autoimmune encephalomyelitis

The fine specificity of myelin basic protein (MBP) epitopes capable of eliciting in vivo delayed-type hypersensitivity responses in Lewis rats with experimental autoimmune encephalomyelitis (EAE) was compared to those eliciting in vitro antigen-specific T cell proliferation and augmentation of disease transfer. Utilizing a panel of synthetic peptides with sequences representing the 68-86 region of guinea pig (GP-) or bovine myelin basic protein (B-MBP), animals were primed with one species of peptide and subsequently challenged with either the same peptide or peptides with truncations or substitutions representative of the other species of MBP. In regard to minimal length sequences capable of eliciting delayed-type hypersensitivity (DTH), rats primed with GP-MBP and complete Freund's adjuvant (CFA) exhibited a hierarchical pattern of responsiveness to challenge with a series of truncated peptides, ranking as follows: GP-68-86 > GP-72-86 > GP-68-84 > > GP-75-86 = no activity. This response pattern corresponds to that previously reported for T cell proliferation and activation for disease transfer. Furthermore, a comparison of these T cell-mediated immune parameters, as elicited by the substituted peptides, revealed the response patterns of DTH reactivity to be similar to that previously described for in vitro T cell proliferation with significant DTH responses generated only by the peptide species for which the animal was primed. In contrast, a cross-reactive pattern of recognition was observed in cells mediating disease transfer, with all four 68-86 sequences capable of augmenting activation for adoptive transfer of disease, regardless of the peptide species for which the animal was primed.(ABSTRACT TRUNCATED AT 250 WORDS)

T cell repertoire and autoimmune diseases

Self-reactivity and autoimmunity are processes related to the breakage of self-tolerance that can be distinguished by their different clinical outcome and are widely accepted cornerstones of immunology. The finding that several potentially autoaggressive cells contribute to the repertoire of healthy individuals has stimulated a great deal of experimental work aimed at understanding the mechanisms that prevent autoimmune pathology. In this review we will consider the basic principles, and our present knowledge of the rules that preside over the interplay of the immune system with self-components. One viewpoint stresses the importance of major histocompatibility complex (MHC) and non-MHC genes in determining genetic predisposition to develop autoimmune phenomena. At a different level there is a strong interest in understanding the mechanisms of processing and presentation of self antigens, especially during ontogeny. Another topic of major interest concerns the interaction between MHC genes and the T cell receptor (TcR) complex as well as the identification of TcR V genes that are preferentially expressed by autoimmune T cells. All of these aspects are evaluated in the context of tolerance based on deletion and anergy. Finally we will propose a general model of autoimmunity based on the most recent findings concerning the biological activity of exogenous superantigens.

Diverse T cell receptor beta chain usage by rat encephalitogenic T cells reactive to residues 68-88 of myelin basic protein

Encephalitogenic T cells not only cause experimental autoimmune encephalomyelitis (EAE), but they induce resistance against subsequent induction of the disease as well. The T cell receptor (TcR) of encephalitogenic T cells is believed to contribute to their vaccinating activity. Findings in support of this assumption include the apparent restricted use of particular TcR elements, such as V beta 8.2. However, results from other laboratories including ours do not support this idea. We previously showed that rat T cells reactive against the conserved encephalitogenic epitope of myelin basic protein [MBP (87-99)] use the TcR in a heterogeneous fashion (Sun, D. et al., Eur. J. Immunol. 1992. 22: 591). Here we show, in Lewis rats, that the TcR beta chain usage of T cells specific for the dominant MBP (68-88) epitope is not restricted to V beta 8.2. Not only did such cells rely on diverse V beta chains, but some non-V beta 8-bearing cells were highly encephalitogenic. We also show that antigen-presenting cells (APC) play an important role in determining the TcR usage of MBP-specific T cells. Stimulation of MBP (68-88)-specific T cell lines by cloned APC derived from different sources resulted in selection of encephalitogenic T cells bearing different TcR beta chains.

Suppression of experimental autoimmune encephalomyelitis by oral administration of myelin basic protein. V. Hierarchy of suppression by myelin basic protein from different species

We have been investigating the suppression of experimental autoimmune encephalomyelitis (EAE) by oral tolerization to autoantigens. In the present study the tolerizing effect of orally administered myelin basic protein (MBP) from different species was examined in the Lewis rat, Hartley guinea pig, and SJL/J mouse model of EAE. Animals were fed guinea pig, rat, bovine, human or mouse-MBP and then immunized with the homologous species of MBP or myelin: Lewis rats were immunized with rat MBP, Hartley guinea pigs with guinea pig-MBP, and SJL/J mice with mouse myelin. Clinical expression of EAE and delayed-type hypersensitivity (DTH) responses to MBP were assessed. In each species, suppression of disease and DTH responses were most pronounced by tolerization with the homologous species of MBP. In addition, cross-species tolerization was observed in each species and in general was less suppressive than homologous MBP although in some instances MBP from a heterologous species was as effective as tolerization with the homologous species. We also studied guinea pig-MBP induced EAE in the Lewis rat because it is a widely studied model of EAE and found that oral tolerization with guinea pig MBP was as suppressive as rat MBP. Of note is that oral tolerization with mouse MBP suppressed myelin-induced EAE in the SJL mouse in which autoimmunity to proteolipid protein appears to play a primary role, suggesting that antigen-driven bystander suppression following oral tolerization with autoantigens (Miller et al., 1991b) may be an important contributing mechanism for suppression of EAE following oral tolerization with MBP in this model.(ABSTRACT TRUNCATED AT 250 WORDS)

Mast cell proteases liberate stable encephalitogenic fragments from intact myelin

Protease-containing supernatants from activated rat mast cells were found to degrade purified rat myelin with a subsequent release of a stable encephalitogenic peptide. The two most abundant peptides were identified as residues 69-87 (GSLPQKSQRTQDENPVV) and residues 69-88 (GSLPQKSQRTQDENPVVH). While additional exposure to the mast cell supernatants removes the COOH terminal histamine from peptide 69-88 to yield peptide 69-87, additional proteolytic degradation of the 69-87 peptide was not detected. Immunization with this peptide emulsified in CFA caused the development of clinical experimental autoimmune encephalomyelitis (EAE) in Lewis rats. In addition this 69-87 sequence was found to activate resting encephalitogenic myelin basic protein-reactive T cell lines to adoptively transfer clinical EAE. The release of stable encephalitogenic peptides from the myelin sheath by mast cell proteases may play a role in activation of encephalitogen-specific T cells during the progression of EAE.

Interaction of T lymphocytes with cerebral endothelial cells in vitro

As a prerequisite of inflammatory lesion formation in (auto-)immune disease of the central nervous system, lymphocytes have to interact with brain endothelia. In recent years much progress has been made towards a better understanding of mechanisms and factors involved in organ specific homing of lymphocytes. Many lines of evidence indicate that T lymphocytes recognizing antigens which are exclusively beyond the blood-brain barrier cross this barrier only when they are in an activated state, irrespective of their antigen specificity. Antigen presentation by blood-brain barrier endothelia, however, may play a role in later stages of florid inflammation.

DNA length polymorphism 5' to the myelin basic protein gene is associated with multiple sclerosis

A site of DNA polymorphism linked to the myelin basic protein gene, identified as restriction fragment length polymorphism, was analyzed in a population-based study comparing patients with clinically definite multiple sclerosis (MS) and population-matched control subjects. A 0.9-kilobase (kb) genomic DNA fragment (EcoG) encompassing the first exon of the human myelin basic protein gene, located on the long arm of chromosome 18, identified ten alleles arising from a region of DNA, 1.5 kb 5' to the myelin basic protein gene first exon coding region. Produced by RsaI digests and ranging in length from 2.05 to 2.15 kb, these alleles vary in size by up to 100 base pairs due to insertion or deletion, or both, from a 1-kb length of repetitive DNA. Allele frequencies among 65 patients with MS were compared with those of 63 control subjects. Chi square for these data was significant (p less than 0.001), largely due to a preponderance in the patients with MS of alleles in the 2.14- to 2.15-kb range. Comparison of the numbers of patients with MS and control subjects bearing specific alleles showed that 45% of the patients carried at least one allele of 2.14 to 2.15 kb as opposed to 19% of control subjects (p less than 0.005). These data, while preliminary, suggest that patients with MS differ from population-matched control subjects with respect to DNA polymorphism linked to the myelin basic protein gene. Although no pathogenic relationship between this polymorphism and MS can be presupposed, this finding raises the possibility that the myelin basic protein gene or some other myelin basic protein-linked locus may be a factor in susceptibility to MS.

Antibody to peptides of human myelin basic protein in post-rabies vaccine encephalomyelitis sera

Development of neurologic complications after Semple rabies vaccine is closely linked to development of antibody to myelin basic protein (MBP). The portions of MBP against which the antibodies are directed were analyzed by enzyme immunoassay in sera and cerebrospinal fluid from 27 patients with vaccine complications. Most of the antibody was directed to regions of MBP peptides 45-89 and 90-170. There was no apparent correlation between antibody specificity for MBP peptides 1-44, 45-89 and 90-170 and the type of post-vaccinal neurologic complication. We conclude that the immunoglobulin repertoire in human B lymphocytes for responding to human MBP favors the portion of the MBP molecule containing residues 45-170.

Limiting-dilution analysis of the frequency of myelin basic protein-reactive T cells in Lewis, PVG/c and BN rats. Implication for susceptibility to autoimmune encephalomyelitis

Susceptibility to experimental autoimmune encephalomyelitis (EAE), which is an autoimmune disease inducible by immunization with a brain-specific antigen in complete Freund's adjuvant (CFA), is different among strains. In an attempt to resolve the immune mechanisms by which the difference in susceptibility to EAE is regulated, we re-estimated susceptibility of several strains of rats, and the frequency of antigen-reactive T cells in each strain was determined by limiting-dilution analysis. EAE was induced in Lewis (LEW), PVG/c and BN rats using four different methods: (i) active immunization with guinea-pig myelin basic protein (GPBP) in CFA; (ii) immunization with GPBP in CFA that had been further supplemented with Mycobacterium tuberculosis H37Ra (supplemented CFA); (iii) adoptive transfer of GPBP-activated spleen cells into syngeneic rats; and (iv) transfer of a GPBP-specific T-cell line. The LEW strain was susceptible to all four methods. The PVG/c strain was resistant to immunization with GPBP in conventional CFA (GPBP/conv. CFA), but was susceptible to immunization with GPBP in supplemented CFA (GPBP/suppl. CFA) and to transfer of activated spleen cells. The BN strain was resistant to all methods. Limiting-dilution analysis using T cells from LEW, PVG/c or BN rats has revealed that each strain of rat displays a different pattern of frequencies of GPBP-reactive or the 68-88 sequence (GP68-88)-reactive T cells. LEW rats showed relatively high frequencies of GPBP-reactive and GP68-88-reactive T cells after immunization with either GPBP/conv. CFA or GPBP/suppl. CFA, symptomatic rats showing higher values than asymptomatic rats. In asymptomatic PVG/c rats, the frequency of GP68-88-reactive T cells was lower than that of GPBP-reactive T cells. In PVG/c rats with clinical EAE, however, GP68-88-reactive T cells increased in frequency and were almost the same as GPBP-reactive T cells. BN rats, on the other hand, responded very poorly not only to the GP68-88 sequence but also to the whole GPBP molecule, even after immunization with GPBP/suppl. CFA. These findings, obtained by limiting-dilution analysis, strongly suggest that the development of EAE in LEW, PVG/c and BN rats is closely related to the frequency of GPBP-reactive T cells. Furthermore, it is shown that resistance to EAE found in PVG/c and BN rats may be generated by different immune mechanisms.

T lymphocytes can recognize determinants unique to neuropeptides of guinea pig myelin basic protein containing a single D-isomer amino acid substitution

The present studies were undertaken to examine how the substitution of racemized forms of selected amino acids in synthetic peptides of guinea pig myelin basic protein (GPMBP) would alter the host's immunological ability to recognize such molecules. Using peptides from the 69-84 sequence of GPMBP containing a D-serine at position 70 or 75 (69-84[D-ser70 or D-ser75]) or D-aspartate at position 82 (69-84[D-asp82]), the findings demonstrated that the position of the diastereomer substitution on these neuropeptides was critical with respect to the ability of the immune system to recognize the molecule. Thus substitution of D-asp at position 82 or D-ser at position 75 abrogated the ability of these peptides to induce experimental autoimmune encephalitis and proliferation of host T cells. In contrast, a peptide containing a D-ser70 residue was capable of inducing clinical disease in rats, as well as stimulating T lymphocytes from 69-84-(D-ser70)-injected animals. Moreover, although this D-peptide was shown to share at least some determinant(s) with the 69-84 peptide, the use of 69-84(D-ser70)-stimulated cell lines demonstrated that some epitope(s) unique to this molecule could stimulate CD4+ syngeneic T cells.

Clonotypic heterogeneity of Lewis rat T cells specific for the encephalitogenic 68-86 region of myelin basic protein

Experimental autoimmune encephalomyelitis was induced in a Lewis rat by sensitization with synthetic peptide GP68-86, representing the 68-86 sequence of guinea pig myelin basic protein (GPMBP). To delineate T cell determinants of GP68-86, lymph node cells from this rat were activated in culture with GP68-86 and were fused with cells of the mouse thymoma BW5147. The resultant hybrids were cloned by limiting dilution and screened for GP68-86-evoked secretion of IL2 in the presence of rat splenocytes. Twelve T cell hybrids derived in this manner were tested for reactivity to different heterologous species of MBP as well as to substituted or truncated analogs of GP68-86. The hybrids generally exhibited potent reactivity to GPMBP but differed markedly in their reactivity to autologous rat MBP (RMBP). A few exceptional hybrids exhibited crossreactivity with peptides in which native serine75 or serine80 residues of GPMBP were substituted with either alanine75 (A75) or proline80 (P80) residues. These cross-reactive hybrids also possessed high levels of anti-RMBP reactivity. The remaining hybrids were unresponsive to the A75 and P80 substituted peptides and, with one exception, had relatively low levels of anti-RMBP reactivity. Unique reactivity patterns were also revealed by hybrid responses to peptides having modified C-terminal 84-86 residues. In summary, the contrasting fine specificities of different hybrids indicated that several distinct clones of T cells mediate the immune response of Lewis rats against the 68-86 region of GPMBP. Furthermore, heterogeneity in the hybrid response to "self" RMBP may reflect substantial differences in encephalitogenic potency of the T cell clones from which these hybrids were derived.

Neurological autoimmune disease and the trimolecular complex of T-lymphocytes

T-lymphocytes recognize antigen in a trimolecular complex: The T-cell receptor binds to a processed fragment of antigen that itself is bound to a major histocompatibility complex (MHC) molecule on the surface of an antigen-presenting cell. The trimolecular complex controls antigen-specific T-cell activation in normal and abnormal immune reactions. Recent progress in myasthenia gravis (MG) and experimental autoimmune encephalomyelitis (EAE) exemplifies this, leading to the following conclusions: (1) Autoimmune T cells may act by interfering with immunoregulation (as in MG) or by directly mediating autoimmune damage (as in EAE), or both. (2) In both diseases, the autoimmune T cells are clonally heterogeneous but recognize only a limited number of epitopes on the autoantigen (acetylcholine receptor in MG; myelin basic protein in EAE). Many of these epitopes can be defined as short peptide fragments of antigen, bound to a particular type of MHC molecule. (3) The MHC determines which peptides are recognized by autoimmune T cells in a given patient or inbred animal strain. (4) The discovery of the limited repertoire of autoimmune T cells has allowed considerable progress in the immunotherapy of EAE, using either monoclonal antibodies or cytotoxic T cells directed against clonotypic determinants on the autoaggressive T cells. (5) One obstacle to this approach in human disease is the polymorphism of the MHC in the species and the commensurate heterogeneity of autoimmune T cells.

Identification of an immunodominant and highly immunopathogenic determinant in the retinal interphotoreceptor retinoid-binding protein (IRBP)

Interphotoreceptor retinoid-binding protein (IRBP), a glycoprotein specific for the retina and pineal gland, induces inflammatory changes in these two organs in immunized animals. We report here on the identification of an immunodominant determinant of bovine IRBP that is highly immunogenic and immunopathogenic in the Lewis rat. The peptide, which comprises the sequence 1169-1191 of bovine IRBP, was shown to be immunodominant by its capacity to stimulate lymphocytes sensitized against whole IRBP. A comparison was made between peptide 1169-1191 and another peptide, 1158-1180, which is nondominant but is immunogenic and immunopathogenic in the Lewis rat. Peptide 1169-1191 was found to be superior in its immunological capacities; the minimal dose of 1169-1191 needed to induce cellular immune response or disease in Lewis rats (0.02-0.1 nmol/rat) is congruent to 1,000 times smaller than that of 1158-1180. In addition, unlike the ocular disease induced by 1158-1180, the disease produced by 1169-1191 resembled that induced by whole IRBP in its kinetics and histopathological features. The immunological activity of 1169-1191 in the Lewis rat was localized to the 10 residues at the COOH terminus; no such activity was exhibited by the truncated peptide 1169-1188, which comprises the 20 residues at the NH2 terminus of the full peptide. The usefulness of this unique experimental system in analyzing the role of immunodominance in peptide immunogenicity and immunopathogenicity is underscored.

Indomethacin augments in vitro proliferative responses of Lewis rat lymphocytes to myelin basic protein. Implications for experimental autoimmune encephalomyelitis

Indomethacin (IM), a specific inhibitor of prostaglandin (PG) synthesis, and PGE2 were studied in terms of their ability to modulate in vitro immune responses associated with experimental autoimmune encephalomyelitis (EAE) in Lewis rats. Lymphoid cells from either the spleens or the draining lymph nodes of myelin basic protein (MBP)-sensitized rats exhibited in vitro immune responses which were enhanced in the presence of IM. Specifically, IM enhanced (i) guinea pig MBP (GPMBP)- and rat MBP (RMBP)-stimulated lymphocyte proliferation, (ii) background proliferation, and (iii) interleukin 2 (IL-2)-stimulated proliferation. Conversely, PGE2 inhibited both GPMBP- and IL-2-stimulated proliferation of MBP-sensitized lymphocytes. Together, these results indicate that PGs secreted by cultured lymphoid cells can directly mitigate MBP- or IL-2-stimulated lymphocyte proliferation. Furthermore, the observation that IM and PGE2 modulate in vitro responses of MBP-specific lymphocytes may provide insight into how the in vivo administration of IM potentiates the severity of EAE (H. Ovadia and P.Y. Paterson, Clin. Exp. Immunol. 49, 386, 1982) and how PGs may be involved in the spontaneous remission of EAE in rats.

Lewis rat lymphoid dendritic cells can efficiently present homologous myelin basic protein to encephalitogenic lymphocytes

Lymphocytes isolated from Lewis rats immunised with protein antigen in adjuvant were stimulated to proliferate in vitro by splenic dendritic cells (DC) which had been pulsed with purified homologous myelin basic protein (MBP). By contrast, in parallel experiments, lymphocytes did not respond to ovalbumin unless the protein was first processed by macrophages by a chloroquine-sensitive mechanism. DC, pulsed with rat MBP at concentrations as low as 6 micrograms/ml, activated lymphocytes for transfer of severe experimental autoimmune encephalomyelitis (EAE). MBP dissociating from myelin membranes in physiological medium, as well as MBP purified from highly acidic extracts of myelin, was effective for pulsing DC; preincubating myelin with macrophages led to a reduction rather than an enhancement in the severity of the EAE transferred. It is concluded that macrophage-mediated antigen processing is not required for immunogenic presentation of the determinants of MBP which cause EAE in Lewis rats. Furthermore, MBP-pulsed DC may prove useful in experiments requiring activation of encephalitogenic T cells.

Resistance to experimental autoimmune encephalomyelitis induced by neonatal tolerization to myelin basic protein: clonal elimination vs. regulation of autoaggressive lymphocytes

The target autoantigen of experimental autoimmune encephalomyelitis (EAE), myelin basic protein (MBP), appears late in ontogeny. In the rat MBP is expressed first on days 2-3 post partum, at a development stage, when self tolerance to most other autoantigens has already developed. To shed light on the cellular mechanisms that lead to immunological self tolerance to MBP, we treated neonatal rats with high doses of MBP before ontogenetic appearance of this autoantigen. We found that high doses are required to confer MBP-specific tolerance lasting until the adult life. Neonatally tolerized, adult rats are completely resistant to induction of EAE by injection of MBP in complete Freund's adjuvant (CFA). Upon MBP CFA challenge, these animals develop a limited humoral response to MBP, but are completely unreactive to MBP on the T cell level. The function of antigen-presenting cells is unchanged by neonatal tolerization, and there is no evidence for the induction of suppressive mechanisms. Transfers of large numbers of tolerized lymphocytes to normal hosts fails to interfere with EAE inducibility. Moreover, neonatally tolerized lymphocytes do not reduce MBP reactivity of primed lymph node cells or T line cells in vitro. Finally, neonatally tolerized rats are susceptible to EAE transferred by activated primed lymphocytes or by in vitro-activated MBP-specific T line cells. The apparent deletion of MBP-specific T lymphocytes in neonatally tolerized rats is in striking contrast to the physiological self tolerance to MBP, which is characterized by the presence of MBP-specific clones in the normal immune repertoire.

Differences in the repertoire of the Lewis rat T cell response to self and non-self myelin basic proteins

We have examined the fine specificity of a panel of cloned T cell hybridomas generated from Lewis rats immunized with guinea pig (GP) or Lewis rat myelin basic protein (MBP) to determine the autoimmune T cell repertoire that develops in experimental allergic encephalomyelitis (EAE). This analysis has demonstrated that GP MBP, which was approximately 10-fold more potent for EAE induction than the autologous rat MBP, produced a population in which almost one-fourth of the members responded to GP-unique determinants and displayed no crossreactivity on the self antigen. The remaining majority of GP MBP-induced clones were specific for the 68-88 encephalitogenic determinant and could be subdivided into three groups based on their varying responses to the 68-88 peptide and rat and rabbit MBPs. Surprisingly, one of these groups showed equal reactivity to GP and rat MBPs. In contrast, the clonotype composition of the T cell population induced by rat MBP was quite different. One-half of these clones comprised a single group responding to the 68-88 determinant, reacting equally with GP and rat MBP. All of these responded to the same range of antigen concentrations as their GP-induced counterparts. The remaining half of that population contained a collection of clones that was nearly as encephalitogenic as the 68-88 population after propagation as a short-term T cell line. These clones were specific for at least three distinct antigenic determinants, all displaying extensive cross-species reactivity, and required as little or less rat MBP for maximal stimulation as did the 68-88-reactive clones. We therefore conclude that the T cell repertoire for MBP does include clones with reactivity to both 68-88 and non-68-88 determinants of GP and rat MBPs, and that both MBPs appear to be equally capable of stimulating these clones in vitro. However, the differences in the clonotype composition of the populations induced by immunization with these two antigens suggest that rat and GP MBPs are subject to different immunoregulatory constraints in the animal and may account for the difference in the encephalitogenic potential of these two antigens.

A sequence pattern common to T cell epitopes

An analysis of the known cytotoxic and helper T cell epitopes has revealed similarity within their primary sequences. These similar motifs, characteristic of the known determinants, have been incorporated into predictive templates that have been used successfully to define eight helper and three cytotoxic epitopes in four different proteins. When the defined epitopes are segregated by restriction element, allele specific subpatterns emerge centering around the general pattern. The presence of similarities argues that the binding of peptide antigens to class I and class II is similar in nature. In addition, these motifs can be used to predict accurately areas within proteins capable of being recognized by individual MHC class I and class II molecules.

Response of rat encephalitogenic T lymphocyte lines to synthetic peptides of myelin basic protein

T lymphocyte lines and clones selected from Lewis rats immunized with guinea pig basic protein (GP-BP) proliferate and acquire the ability to transfer experimental autoimmune encephalomyelitis (EAE) after activation by the 68-88 peptide of GP-BP in concert with autologous I-A major histocompatibility antigens. In order to evaluate the amino acid sequence required for activation, encephalitogenic T lymphocytes were stimulated with synthetic peptides representing the 69-89, 69-84, 72-84, and 75-84 sequence of GP-BP. The three longest peptides, but not the 75-84 peptide, induced encephalitogenic lines and clones to proliferate and to transfer clinical EAE; none of the peptides, however, could activate T cell lines of a different epitope specificity. The 69-89 sequence was the most efficient of the synthetic peptides, inducing optimal stimulation comparable to GP-BP at 10 micrograms/ml. The 69-84 and 72-84 sequences induced comparable levels of stimulation at 250 micrograms/ml, but the 75-84 sequence was not active at any concentration. These results show that the 11 amino acids representing the 72-84 sequence of GP-BP are sufficient to trigger encephalitogenic T cell activity, and suggest that the 85-89 sequence may stabilize the conformation of the encephalitogenic epitope. The close association observed between proliferation and EAE transfer activities, induced in highly purified T cell populations using synthetic peptides, suggests that these two functional properties of T cells result from a common activation pathway involving a single T cell receptor specificity.

T-cell epitope of the autoantigen myelin basic protein that induces encephalomyelitis

Chronic relapsing paralysis and demyelination within the central nervous system (CNS), features associated with the human disease multiple sclerosis (MS), develop in mice after injection of murine T-cell clones specific for the autoantigen myelin basic protein (MBP). We examined the fine specificity of three independently derived encephalitogenic T-cell clones using synthetic polypeptides derived from portions of the N-terminal sequence of MBP. These clones appear functionally identical; they all respond to an epitope in the N-terminal nine amino acid residues in association with the same class II (I-A) molecules of the major histocompatibility complex (MHC). Both the N-terminal acetyl moiety and the first residue (Ala) are necessary for recognition. Only N-terminal MBP peptides recognized by these clones were found to cause encephalomyelitis (EAE) in vivo. These results show that the N-terminal MBP-specific T lymphocytes that mediate autoimmune encephalomyelitis are a small population with a limited repertoire; they all recognise the same combination of MHC and target.

Heteroclitic antibodies in Fischer 344 rats to a synthetic encephalitogenic myelin basic protein peptide

Fischer 344 rats, immunized with the synthetic encephalitogenic myelin basic protein peptide YS49 (YGSLPQKAQRPQDENG), produced heteroclitic antibodies that reacted much more extensively and with a much higher affinity with the cross-reacting encephalitogenic guinea pig sequence S49S (GSLPQKSQRSQDENG) than they did with the immunogenic YS49. On the other hand, antisera against S49S reacted in a normal manner with homologous S49S and cross-reacted only poorly with YS49. The phenomenon of heteroclisis in Fischer 344 rats correlated with the greater encephalitogenic potency of the cross-reacting entity. Kibler et al. (J. Exp. Med., 146 (1977) 1323-1331), by comparing the encephalitogenic guinea pig sequence to a less potent analog, had also previously observed what now would be termed a heteroclitic phenomenon at the T cell level in Lewis rats. In their hands, however, as well as in ours Lewis rat antisera against the encephalitogenic peptide region were much too complex to be analyzed with respect to heteroclisis. It was shown in the present experiments that by utilizing the Fischer 344 system one may also readily obtain heteroclisis at the B cell level against encephalitogenic peptides. Neither YS49 nor S49S as immunogen produced detectable antibody in Brown Norway (BN) rats with exception of two immunized with YS49. In those two cases heteroclitic antibodies were obtained that had a very low significant (greater than 3 SD above baseline) antigen binding capacity for S49S and no detectable reactivity for the homologous YS49 ligand.

Monoclonal and polyclonal antibodies to myelin basic protein determinants

A detailed immunochemical examination of monoclonal and polyclonal antibody responses to myelin basic protein (MBP) and its peptides has revealed the existence of as many as 27 antigenic determinants, many of them conformational. Topological mapping of the potential antigenic determinants onto a model of MBP secondary structure places these determinants within 11 separate regions of the molecule, including those portions that have been found to be encephalitogenic. MBP and its peptides, therefore, fall under the umbrella of the Multideterminant-Regulatory Model of Benjamin et al. (1984). However, in the case of MBP, multideterminant immunogenicity appears to represent mainly an escape from tight regulation through the avenue of conformational change.