Transfer of multiple sclerosis into severe combined immunodeficiency mice by mononuclear cells from cerebrospinal fluid of the patients

Toward curing neurological autoimmune disorders: Biomarkers, immunological mechanisms, and therapeutic targets

Autoimmune neurology is a rapidly expanding field driven by the discovery of neuroglial autoantibodies and encompassing a myriad of conditions affecting every level of the nervous system. Traditionally, autoantibodies targeting intracellular antigens are considered markers of T cell-mediated cytotoxicity, while those targeting extracellular antigens are viewed as pathogenic drivers of disease. However, recent advances highlight complex interactions between these immune mechanisms, suggesting a continuum of immunopathogenesis. The breakdown of immune tolerance, central to these conditions, is affected by modifiable and non-modifiable risk factors such as genetic predisposition, infections, and malignancy. While significant therapeutic advancements have revolutionized treatment of certain diseases, such as neuromyelitis optica, our understanding of many others, particularly T cell-mediated conditions, remains limited, with fewer treatment options available. Future research should focus on improving effector function modeling and deepening our understanding of the factors influencing immune tolerance, with the goal of providing novel treatment options and improving patient care.

Spontaneous human CD8 T cell and autoimmune encephalomyelitis-induced CD4/CD8 T cell lesions in the brain and spinal cord of HLA-DRB1*15-positive multiple sclerosis humanized immune system mice

Autoimmune diseases of the central nervous system (CNS) such as multiple sclerosis (MS) are only partially represented in current experimental models and the development of humanized immune mice is crucial for better understanding of immunopathogenesis and testing of therapeutics. We describe a humanized mouse model with several key features of MS. Severely immunodeficient B2m-NOG mice were transplanted with peripheral blood mononuclear cells (PBMCs) from HLA-DRB1-typed MS and healthy (HI) donors and showed rapid engraftment by human T and B lymphocytes. Mice receiving cells from MS patients with recent/ongoing Epstein-Barr virus reactivation showed high B cell engraftment capacity. Both HLA-DRB1*15 (DR15) MS and DR15 HI mice, not HLA-DRB1*13 MS mice, developed human T cell infiltration of CNS borders and parenchyma. DR15 MS mice uniquely developed inflammatory lesions in brain and spinal cord gray matter, with spontaneous, hCD8 T cell lesions, and mixed hCD8/hCD4 T cell lesions in EAE immunized mice, with variation in localization and severity between different patient donors. Main limitations of this model for further development are poor monocyte engraftment and lack of demyelination, lymph node organization, and IgG responses. These results show that PBMC humanized mice represent promising research tools for investigating MS immunopathology in a patient-specific approach.

Progressive multiple sclerosis cerebrospinal fluid induces inflammatory demyelination, axonal loss, and astrogliosis in mice

Multiple sclerosis (MS) is an autoimmune disease characterized by inflammatory demyelination and neurodegeneration throughout the CNS, which lead over time to a condition of irreversible functional decline known as progressive MS. Currently, there are no satisfactory treatments for this condition because the mechanisms that underlie disease progression are not well understood. This is partly due to the lack of a specific animal model that represents progressive MS. We investigated the effects of intracerebroventricular injections of cerebrospinal fluid (CSF) derived from untreated primary progressive (PPMS), secondary progressive (SPMS), and relapsing/remitting (RRMS) MS patients into mice. We found discrete inflammatory demyelinating lesions containing macrophages, B cell and T cell infiltrates in the brains of animals injected with CSF from patients with progressive MS. These lesions were rarely found in animals injected with RRMS-CSF and never in those treated with control-CSF. Animals that developed brain lesions also presented extensive inflammation in their spinal cord. However, discrete spinal cord lesions were rare and only seen in animals injected with PPMS-CSF. Axonal loss and astrogliosis were seen within the lesions following the initial demyelination. In addition, Th17 cell activity was enhanced in the CNS and in lymph nodes of progressive MS-CSF injected animals compared to controls. Furthermore, CSF derived from MS patients who were clinically stable following therapy had greatly diminished capacity to induce CNS lesions in mice. Finally, we provided evidence suggesting that differential expression of pro-inflammatory cytokines present in the progressive MS CSF might be involved in the observed mouse pathology. Our data suggests that the agent(s) responsible for the demyelination and neurodegeneration characteristic of progressive MS is present in patient CSF and is amenable to further characterization in experimental models of the disease.

Humanized mice for the development and testing of human vaccines

Mouse models of human disease form a link between genetics and biology. However, mice and humans differ in many aspects of immune system biology. These differences might explain, in part, why many successful preclinical immunotherapy studies in mice turn out to be unsuccessful when used in clinical trials in humans. Pioneering studies in the late 1980s demonstrated the reconstitution of human lympho-hematopoietic cells in immunodeficient mice. Since this time, immunodeficient mice are being tested as hosts for human hematopoietic organs or cells in an effort to create an in vivo model of the complete human immune system. Such Humouse models could permit us to generate and test novel human vaccines.

Is multiple sclerosis an autoimmune disease?

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) with varied clinical presentations and heterogeneous histopathological features. The underlying immunological abnormalities in MS lead to various neurological and autoimmune manifestations. There is strong evidence that MS is, at least in part, an immune-mediated disease. There is less evidence that MS is a classical autoimmune disease, even though many authors state this in the description of the disease. We show the evidence that both supports and refutes the autoimmune hypothesis. In addition, we present an alternate hypothesis based on virus infection to explain the pathogenesis of MS.

Neuronal damage in autoimmune neuroinflammation mediated by the death ligand TRAIL

Here, we provide evidence for a detrimental role of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in neural death in T cell-induced experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). Clinical severity and neuronal apoptosis in brainstem motor areas were substantially reduced upon brain-specific blockade of TRAIL after induction of EAE through adoptive transfer of encephalitogenic T cells. Furthermore, TRAIL-deficient myelin-specific lymphocytes showed reduced encephalitogenicity when transferred to wild-type mice. Conversely, intracerebral delivery of TRAIL to animals with EAE increased clinical deficits, while naive mice were not susceptible to TRAIL. Using organotypic slice cultures as a model for living brain tissue, we found that neurons were susceptible to TRAIL-mediated injury induced by encephalitogenic T cells. Thus, in addition to its known immunoregulatory effects, the death ligand TRAIL contributes to neural damage in the inflamed brain.

Critical Roles of CXC Chemokine Ligand 16/Scavenger Receptor that Binds Phosphatidylserine and Oxidized Lipoprotein in the Pathogenesis of Both Acute and Adoptive Transfer Experimental Autoimmune Encephalomyelitis

The scavenger receptor that binds phosphatidylserine and oxidized lipoprotein (SR-PSOX)/CXCL16 is a chemokine expressed on macrophages and dendritic cells, while its receptor expresses on T and NK T cells. We investigated the role of SR-PSOX/CXCL16 on acute and adoptive experimental autoimmune encephalomyelitis (EAE), which is Th1-polarized T cell-mediated autoimmune disease of the CNS. Administration of mAb against SR-PSOX/CXCL16 around the primary immunization decreased disease incidence of acute EAE with associated reduced infiltration of mononuclear cells into the CNS. Its administration was also shown to inhibit elevation of serum IFN-gamma level at primary immune response, as well as subsequent generation of Ag-specific T cells. In adoptive transfer EAE, treatment of recipient mice with anti-SR-PSOX/CXCL16 mAb also induced not only decreased clinical disease incidence, but also diminished traffic of mononuclear cells into the CNS. In addition, histopathological analyses showed that clinical development of EAE correlates well with expression of SR-PSOX/CXCL16 in the CNS. All the results show that SR-PSOX/CXCL16 plays important roles in EAE by supporting generation of Ag-specific T cells, as well as recruitment of inflammatory mononuclear cells into the CNS.

B cells in multiple sclerosis

The most common laboratory abnormality in multiple sclerosis (MS) is an increased amount of cerebrospinal fluid IgG and the presence of oligoclonal bands. Despite studies of the humoral response that suggest the involvement of an infectious agent or autoantigen in disease, the major targets of the oligoclonal response are still unknown. Identification of these targets will reveal valuable insights into the cause and pathogenesis of MS and is likely to lead to effective treatment.

T-cell vaccination for autoimmune diseases: immunologic lessons and clinical experience in multiple sclerosis

Autoreactive T-cells are regulated under the normal conditions and play an important role in autoimmune pathologies when they are dysregulated as a result of genetic, environmental and other unknown factors associated with various autoimmune diseases. The immune regulation of autoreactive T-cells may be regained by activating the regulatory network, such as the idiotype anti-idiotypic network. Immunization with inactivated autoreactive T-cells (T-cell vaccination) can be used as a powerful means of activating the idiotype anti-idiotypic network to deplete specific subsets of autoreactive T-cells potentially involved in autoimmune conditions. It induces regulatory immune responses that closely resemble the in vivo situation, where the immune system is challenged by clonal activation and expansion of given T-cell populations in various autoimmune diseases. Recent clinical trials in multiple sclerosis have begun to reveal the role of T-cell vaccination in the understanding of in vivo regulation of autoreactive T-cells and in the development of effective therapeutic strategies for multiple sclerosis and other autoimmune conditions. In this article, we will review the recent advances in T-cell vaccination in relationship to the regulatory mechanism induced by T-cell vaccination and the potential of T-cell vaccination as a treatment for T-cell-mediated autoimmune diseases. Current issues and thoughts related to the preparation of T-cell vaccine, the relevant sources of autoimmune T-cells and epitope spreading are also discussed.

Induction of cardiomyopathy in severe combined immunodeficiency mice by transfer of lymphocytes from patients with idiopathic dilated cardiomyopathy

Growing evidence suggests that autoimmune mechanisms play an important role in the pathogenesis of idiopathic dilated cardiomyopathy (DCM). The aim of the study was to evaluate the effects of transfer of lymphocytes from patients with DCM into severe combined immunodeficiency (SCID) mice on the heart structure and function. Thirty CB-17 SCID (6-8 weeks old) mice were used and divided into 3 groups (n = 10). Mice were injected intraperitoneally with up to 25 x 10(6) peripheral blood lymphocytes (PBL) from either patients with DCM which contain human autoantibodies against cardiac beta1-adrenergic receptors and M2-muscarinic receptors (DCM group) or PBL from healthy controls (control-H group). Ten mice did not receive any injections and were used as baseline controls (control-N group). Echocardiography and morphological studies were performed seventy five days after the transfer. Results showed that in DCM group, left ventricle dimensions (LVD) in diastole were increased (4.2 +/- 0.1mm) as compared to both control-H group (3.8 +/- 0.1mm) and control-N group (3.6 +/- 0.1 mm) (p < 0.01). Further, there was a trend for increased LVD in systole. Fractional shortening was not different between groups. Histological evaluation revealed accumulation of human lymphocytes in the capillaries and scarce infiltration of the lymphocytes in the hearts from DCM group. Diffuse fibrosis was significant increased in DCM mice as compared to mice receiving PBL from normal subjects (2.2 +/- 0.3% vs. 0.8 +/- 0.1%, p < 0.01). In conclusion, transfer of the PBL from the patients with DCM was able to induce early stage of heart dilatation in SCID mice. These data provide for the first time the direct evidence supporting that the autoimmune mechanism is important in the pathogenesis of human DCM.

The effect of apoptosis inhibitors on experimental autoimmune encephalomyelitis: apoptosis as a regulatory factor

The effect of apoptosis inhibitors on experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis, was investigated by intraperitoneal or intracisternal administration of apoptosis inhibitors Ac-YVAD-cmk and zVAD-fmk. After onset of the disease, these agents had no suppressive effect on EAE and resulted in impaired recovery or earlier relapse. Histological examination revealed that administration of zVAD-fmk suppressed the apoptotic death of inflammatory cells in the central nervous system (CNS) of mice with EAE. The results indicated that the apoptotic elimination of infiltrated cells in the CNS might be one of the recovery mechanisms in EAE.

Multiple sclerosis--in need of a critical reappraisal

Multiple sclerosis (MS) is a disease that currently defies clinical and scientific definitions. Despite intensive clinical and basic research, very little is known about its possible cause(s) or pathogenesis, and the course and prognosis of MS practically remain unchanged. The aim of the present article is to outline some of the reasons for the constant failure to improve the therapy of MS. It also attempts to offer several guidelines which may enable a fresh and different approach to this devastating condition.

Is there a role for NK cells in the pathogenesis of multiple sclerosis? A case study

We report on a patient with multiple sclerosis (MS) in which we documented an elevated percentage of activated CD56+ natural killer (NK) cells in peripheral blood lymphocytes. NK cells from the patient lysed preferentially glioblastoma but not neuroblastoma cells. Killing of glial cells was not inhibited by a monoclonal antibody against a monomorphic determinant of MHC class I gene products. Lymphokine activated killer (LAK) cell function in the MS patient was comparable to that of controls. Analysis of cytokine production during resting or activated states demonstrated that this patient had a deficit in the ability to secrete T cell derived cytokines associated with increased production of TNFalpha, a product of NK cells. Taken together, these data indicate a possible involvement of NK cells in the pathogenesis of MS.

Repeated subcutaneous injection of staphylococcal enterotoxin B-stimulated lymphocytes retains epidermal thickness of psoriatic skin-graft onto severe combined immunodeficient mice

Several approaches have recently been carried out to attempt to establish a mouse transplantation model of psoriasis. To study the effects of superantigen-driven peripheral blood mononuclear cells (PBMCs) on the persistence of psoriasiform epidermis and cytokine gene expression of the grafted psoriatic skin, staphylococcal enterotoxin B (SEB)-stimulated PBMCs (SEB-PBMCs) from psoriatic patients were subcutaneously injected once or repeatedly under the grafted full-thickness involved psoriatic skin onto severe combined immunodeficient (SCID) mice. After 5 weeks, the persistence of a psoriasiform epidermis was most distinct in mice with repeated injection of SEB-PBMCs. E-selectin expression was observed on endothelial cells in the upper dermis in mice with repeated injection of both SEB-stimulated and unstimulated PBMCs, while mice with single injection of unstimulated or SEB-PBMCs did not show positive staining. Both interleukin-1 beta (IL-1 beta) and interferon-gamma (IFN-gamma) mRNA were detected after 5 weeks, only in mice with repeated injection of SEB-PBMCs. It is concluded that continuous supply of the activated PBMCs may help the persistence of psoriasiform architecture more clearly, and that this transplantation mouse model may serve as an in vivo model for the study of the pathogenesis and therapy of psoriasis.

Aminoguanidine, a selective inhibitor of the inducible nitric oxide synthase, has different effects on experimental allergic encephalomyelitis in the induction and progression phase

To elucidate the role of excessive nitric oxide (NO) via the inducible nitric oxide synthase (iNOS) in experimental allergic encephalomyelitis (EAE), the effect of a selective iNOS inhibitor, aminoguanidine, was investigated using mice with actively induced EAE. Administration of aminoguanidine by intraperitoneal or intracisternal injection from day 2 to day 12 after immunization produced a significant delay in the onset of EAE. On the other hand, administration of aminoguanidine by intraperitoneal or intracisternal injection for 10 days after the onset of EAE enhanced the clinical severity and mortality rate and hastened the onset of relapse significantly. The histological study at day 11 after the onset revealed that more inflammatory cells were present in the central nervous system of mice treated with aminoguanidine as compared with mice without aminoguanidine treatment. These results suggested that NO via iNOS was a pathogenetic factor in the induction phase of EAE, but had an inhibitory role in the progression phase of EAE. Although the effect of NO synthase inhibitors on EAE has been controversial, the present study suggested that the timing of administration might be an important consideration and might explain the previous contradictory reports.

Biochemical and functional characterization of xenoreactive natural antibodies in hu-PBL-SCID mice

An in vivo model system to understand the mechanism of xenograft rejection was established using human peripheral blood leukocyte-reconstituted SCID (hu-PBL-SCID) mice. Human xenoreactive natural antibodies (XNA), of IgM and IgG subtypes, capable of binding to pig aortic endothelial cells (PAEC) were detected in the sera of hu-PBL-SCID by ELISA and flowcytometric methods. Western blot analysis of PAEC lysates showed that IgM and IgG XNA from hu-PBL-SCID recognized xenoantigens with similar molecular mass as those recognized by XNA from normal human serum (NHS). This result demonstrated that hu-PBL-SCID contained XNA representing the same repertoire as that of the NHS. XNA from NHS and hu-PBL-SCID were also able to induce intracellular Ca2+ signals in cultured PAEC several fold above the basal level. This result revealed their functional similarity and demonstrated for the first time that XNA in the absence of C can activate PAEC, which may lead to the pathology of xenograft rejection. In vivo, PAEC transplanted under the kidney capsule of hu-PBL-SCID mice showed deposition of human IgM and mouse C. In summary, the present study demonstrates that hu-PBL-SCID can serve as a useful model to characterize innate immunity against xenograft.

Immune deficiency in SCID mice

Since the discovery of SCID mice in 1983, numerous studies utilizing these mice were carried out. These investigations can be classified into two major groups. First, the analysis of the immune defect has revealed defective V(D)J recombination and defective DNA double-strand break repair, and has lead to the identification of the candidate gene for SCID mice. Second, the use of SCID mice to explore ways to introduce a murine or xenogeneic immune system into SCID mice by taking advantage of the immune deficiency of the mice has provided an animal model to examine the in vivo function of transferred human or murine immune cells. In this review, we summarize the recent advances made in these two areas of SCID mouse research.

T cell subsets in multiple sclerosis: a serial study

The relevance of abnormalities in the distribution of peripheral blood T lymphocyte subsets to the clinical manifestations of multiple sclerosis is not firmly established. A clinical and immunological follow-up of relapsing-remitting multiple sclerosis patients was performed in order to study the relationship of immune changes with the clinical course of the disease. Twenty patients were monitored monthly during a mean time of nine months for peripheral blood lymphocyte subsets (CD3, CD4, CD8, CD19), including the immunoregulatory subsets CD4CD29 (helper-inducer), and CD4CD25) by flow cytometry. A total of 14 untreated relapses was included. The most significant observations were a decrease in T suppressor-inducer CD4+ CD45RA+ subset during clinical relapses (P = 0.028) that was also detectable one month before (P = 0.020) and the lack of changes in CD4+ CD29+ and CD8+ T cells. In addition, variations in the percentage of CD4+ CD25+ activated T helper cells were not associated with clinical exacerbations. These results indicate the existence of a temporal association of immune changes in peripheral blood, but not activation, with the clinical manifestations of multiple sclerosis.

Immunization with anti-neutrophil cytoplasmic antibody (ANCA) induces the production of mouse ANCA and perivascular lymphocyte infiltration

Wegener's granulomatosis (WG) is a granulomatous necrotizing vasculitis associated with the presence of ANCA, predominantly directed against proteinase 3 (PR3). The titres of ANCA correlate with disease activity and titre increases may precede disease exacerbations. Previously, we have shown that it is possible to induce autoimmune disease (systemic lupus erythematosus (SLE) and anti-phospholipid syndrome) in naive mice following active immunization with human autoantibodies, namely anti-DNA and anti-cardiolipin, respectively. The mice developed first anti-autoantibodies and, after about 4 months anti-anti-autoantibodies (Ab3), simulating auto-antibodies (Ab1) in their binding activities, and their presence was associated with the development of disease manifestations, characteristic of the human disease. So far, there is no good animal model for WG. In the current study we have immunized mice with human ANCA with the aim of inducing experimental WG. In two separate studies 30 mice were immunized in their footpads with autoantigen-purified IgG fraction (ANCA) from the sera of two patients with untreated WG, emulsified in Freund's complete adjuvant, followed 3 weeks later by ANCA injection in PBS. In the first experiment mice immunized with ANCA developed sterile microabscesses in the lungs after 8 months, and died after 8-15 months. In the second experiment, mice immunized with ANCA developed after 4 months mouse ANCA, with specificity both to PR3 and to myeloperoxidase, as well as anti-endothelial autoantibodies (AECA), as shown by radioimmunoprecipitation. Pathologically, the immunized mice developed proteinuria but not haematuria, and histological sections of the lungs demonstrated mononuclear perivascular infiltration, while diffuse granular deposition of immunoglobulins was noted in the kidneys. Our results point to a pathogenic role of ANCA in WG, and confirm the importance of the idiotypic network in the etiopathogenesis of autoimmune conditions.

Transfer of rheumatoid arthritis into severe combined immunodeficient mice. The pathogenetic implications of T cell populations oligoclonally expanding in the rheumatoid joints

To investigate the pathogenicity of T cells infiltrating in the rheumatoid joints, mononuclear cells (MNC), predominantly T cells, isolated from either synovial fluid or synovial tissues of the patients with RA were transferred into severe combined immunodeficient (SCID) mice by intraarticular injections. According to our observations in this experimental system, patients with RA could be classified into at least two groups. In one group of patients, the infiltrating MNC induced synovial hyperplasia in the recipient SCID mice (the positive group). Whereas, in the other group no synovial hyperplasia was observed (the negative group). The induction of synovial hyperplasia observed in the positive group was prevented by an anti-human CD3 antibody (OKT3), indicating T cell mediation. Analysis of T cell receptor (TCR) V beta usage by reverse transcriptase polymerase chain reaction in the infiltrating MNC transferred into SCID mice revealed a marked skew towards the preferential use of certain V beta genes, which was not seen in the peripheral blood MNC, in only the positive group. The patterns of TCR/V beta skew were not uniform among the patients. The analysis of the PCR-amplified genes of such skewed TCR/ V beta by single strand conformational polymorphism showed distinct bands, indicating that the T cell populations expanding in rheumatoid joints of the positive group were oligoclonal. Furthermore, the enrichment of the T cell populations expressing such skewed TCR/V beta by in vitro stimulation of peripheral blood MNC of the patients with the relevant superantigen enabled the induction of synovial hyperplasia in the SCID mice. These results suggest that the pathogenic T cells could be activated locally in rheumatoid joints by certain antigens in some, but not in all patients with RA.

A human monoclonal antibody to a human self-antigen, CD2 derived from human peripheral blood lymphocytes engrafted in SCID mice

To establish human hybridoma lines, production of human immunoglobulin (Ig) and behavior of the implanted human peripheral blood lymphocytes (PBL) were characterized in severe combined immunodeficiency (SCID) mice. Human PBL from healthy donors were injected into the peritoneal cavity of SCID mice, and they were immunized with self-antigen, CD2. CD45+ cells (human PBL) migrated to lymphoid tissues in the mice as early as 4 days, accounting for more than half the lymph node cells and thymocytes. The number of cells releasing human IgG specific to the antigen increased 3.5 weeks after immunization without the usual constraint that production of the IgG, an autoantibody, is prohibited by immunological tolerance in humans. Therefore, we established several human hybridomas secreting human IgG to CD2, since splenocytes and lymph node cells from the implanted SCID mice at 3.5 weeks were fused with a human B lymphoblastoid cell line. A human anti-CD2 monoclonal antibody (MAb) was confirmed to bind to natural CD2 on human T cells by flow cytometric analysis. The epitope for the MAb was identical with a portion that the ligand LFA-3 binded, so that the MAb might reduce the inflammatory reaction caused by preventing activation of human T cells. Here, we report that the human immune system could be reconstituted in SCID mice to develop human hybridomas producing human MAb to a human self-antigen.

Multiple sclerosis: immune mechanism and update on current therapies

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS) afflicting approximately 250,000 individuals in the United States. This inflammatory disease has variable clinical manifestations, ranging from a relapsing-remitting course to a chronic progressive disease. Approximately one third of MS patients have chronic progressive disease often leading to severe impairment of mobility, paralysis, poor vision, and disturbances of bladder and bowel function. Although the etiology and pathogenesis remain unknown, accumulating evidence supports the hypothesis that exposure to an as-yet-unidentified infectious agent(s) triggers an aberrant immune response against self nervous tissue in genetically susceptible individuals. The tenfold higher concordance rate for MS in monozygotic twins compared to dizygotic twins, the increased incidence of MS in women compared to men (2:1), and the familial and racial occurrence of MS provide strong evidence that genetic factors influence susceptibility to MS. The major predisposing genes in MS are the human leukocyte antigen (HLA) class II molecules, DR15 and DQw6, molecularly defined as HLA-DRB1, 1501-DQA1 0102-DQB1 0602. In certain ethnic groups, MS susceptibility is more strongly associated with other DR molecules. Environmental factors are also believed to play a role, as suggested by the unique worldwide prevalence, migration effects, and epidemiological studies. Increased serum and cerebrospinal fluid antibody titers to numerous viruses have been reported; however, there have been no confirmed studies detecting viral RNA or antigen in MS brain tissue. At the present time, no known treatment can significantly alter the progression of MS. Based on the postulate that MS is an autoimmune disease associated with abnormalities in immunoregulation, a number of different immunosuppressive and immunomodulating agents have been tested as therapeutic modalities. In this article, we review the circumstantial evidence suggesting that immune system abnormalities are associated with the disease process, and provide an update on current therapies used in MS.

Transfer of Sjögren's syndrome-like autoimmune lesions into SCID mice and prevention of lesions by anti-CD4 and anti-T cell receptor antibody treatment

We describe the successful transfer of murine Sjögren's syndrome-like autoimmune lesions from MRL/lpr mice (H-2k) to severe combined immunodeficiency (SCID) mice (H-2d) and prevention of lesions by anti-CD4 and -T cell receptor V beta 8 antibody treatment. Mononuclear cells (1 x 10(6)) isolated from the inflamed submandibular salivary gland tissues of MRL/lpr mice were transferred intraperitoneally into SCID mice. Autoimmune lesions resembling those seen in Sjögren's syndrome developed in the salivary and lacrimal glands of SCID mice 8 weeks after the injection, whereas other organs did not show any lesion. This pathology resembles Sjögren's syndrome in humans involving both the salivary and lacrimal glands. Immunohistochemically, a major proportion of these infiltrating cells in transferred SCID mice were CD4+ and V beta 8+. When the spleen cells from MRL/lpr mice were injected, severe inflammatory lesions, probably resulting from a graft-versus host reaction, were observed in multiple organs of SCID mice. The disease could not be induced by intraperitoneal administration of the sera from MRL/lpr mice, or of the spleen cells from C3H/He (H-2k) and BALB/c (H-2d) mice. We detected autoantibody production specific for the salivary gland tissue in sera from transferred SCID mice. Moreover, we found that the lesions were prevented by administration of the isolated cells treated in vitro with anti-CD4 and anti-V beta 8 monoclonal antibodies. These results suggest that CD4- and V beta 8-bearing T cells are involved in recognizing an autopeptide and triggering autoimmunity in the salivary and lacrimal glands, and therapies designed with anti-CD4 and anti-V beta 8 antibodies may prove effective in treating the murine autoimmune disease.

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.

Pathogenesis of Sjögren's syndrome-like autoimmune lesions in MRL/lpr mice

Sjögren's syndrome in humans is a chronic inflammatory disease with a presumed autoimmune etiology of the exocrine organs, involving in particular the salivary and lacrimal glands. The pathogenesis of this syndrome remains unclear, but the majority of infiltrating cells in the salivary glands are CD4+ T cells both in humans and rodents. Since many cytokines are involved in the development of T cell-mediated autoimmunity, local cytokine gene expression was analyzed in vivo using an animal model for Sjögren's syndrome in MRL/lpr mice. Overexpression of interleukin-1 (IL-1)beta and tumour necrosis factor (TNF) was detected before the onset of inflammatory lesions in the salivary gland, and the upregulation of IL-6 mRNA was also found in accordance with autoimmune sialadenitis in MRL/lpr mice. The inflammatory cytokines such as IL-1 beta, TNF, and IL-6 have proved to play important roles as regulatory proteins inducing autoimmune phenomena. In addition, the expression of T cell antigen receptor beta (TCR) beta transcripts in the salivary gland tissues was analyzed. Transcript for V beta 8 was predominantly detected in the T cells infiltrating sialadenitis from the onset of the disease, suggesting that CD4+ T cells bearing TCR V beta 8 play an essential role in recognizing unknown autopeptide in the autoimmune sialadenitis of MRL/lpr mice. Furthermore, Sjögren's syndrome-like autoimmune lesions were successfully transferred into severe combined immunodeficiency (SCID) mice, and these lesions were prevented by administration of anti-CD4, and anti-V beta 8 monoclonal antibodies. This article will review recent observations of these pathogenetic analyses of autoimmune sialadenitis as it occurs in MRL/lpr mice.

CD4+ T cells from collagen-induced arthritic mice are essential to transfer arthritis into severe combined immunodeficient mice

The role of T lymphocytes in the adoptive transfer of collagen-induced arthritis (CIA) in DBA/1J mice to severe combined immunodeficient (SCID) mice was investigated. Spleen cells from non-immunized, type I collagen (CI) or type II collagen (CII)-immunized DBA/1J mice were injected into SCID mice which lack functional T and B cells. Specific antigenic stimulation of arthritogenic cells was required since only lymphocytes from arthritic CIA mice plus simultaneous administration of CII transferred arthritis to 11 of 12 SCID mice with a marked increase in CII antibody titre. However, CI-immunized or non-immunized DBA/1J mice cells did not induce arthritis in SCID mice. SCID recipients of pre-arthritic CIA lymphocytes presented increase in CII antibody, but showed no clinical signs of arthritis, suggesting that antibodies to CII alone can not induce CIA. Depletion of CD4+ T cells inhibited the transfer of arthritis to SCID mice, with a decrease in CII antibody titre in chimaeras. In contrast, depletion of CD8+ T cells enhanced the onset of arthritis in SCID mice. The results imply that CD4+ T cells are required for the induction of CIA. In addition, CD8+ T cells might have a suppressive role in the etiology of this disease. It is probable that memory CD4+ T cells stimulate production of antibodies to CII and subsequent arthritis. This study clarifies the role of T lymphocytes in the transfer of CIA to SCID mice.

Peptide specificity of anti-myelin basic protein antibodies in patients with acute optic neuritis and the HLA system

Multiple sclerosis (MS) may be an autoimmune disease, partially caused by autoreactivity to myelin basic protein (MBP) and other central nervous system proteins. Acute optic neuritis (ON) is a frequent first symptom of MS. The role of the HLA system in anti-MBP antibody production in ON was investigated employing a restriction fragment length polymorphism system for genomic HLA-DQ and -DR typing and an immunospot assay for the detection of individual cells secreting antibodies to three different synthetic MBP peptides. Thirty-two out of 40 patients (80%) with ON had cells in cerebrospinal fluid secreting anti-MBP peptide antibodies while this occurred in 10/19 patients with other neurological diseases (53%; mainly in patients with inflammatory diseases in the central nervous system). This difference was statistically significant (P = 0.03). None of the three examined peptides were immunodominant in any patient group. It was found, however, that presence of HLA DR15, which is associated with MS, may be associated further with predominant production of antibodies to the MBP amino acids 63-88 in patients with ON (P = 0.002, corrected for multiple comparisons).

Autoimmunity versus allo- and xeno-reactivity in SCID mice

The ability of SCID mice to accept xenografts has been exploited to study the survival, function and potential of peripheral blood mononuclear cells (PBMC) from patients with autoimmune disorders to produce tissue injury in the mouse. Studies performed with PBMC obtained from patients with organ specific and multisystem autoimmune diseases indicate that human PBMC survive in SCID mice for several months, produce IgG and autoantibodies with the same specificities as are found in the donor. Tissue injury is not generally observed in the SCID mouse recipient. SCID mice have also been partially reconstituted with bone marrow from BB (diabetic) and MRL (lupus) mice. SCID mice injected with both spleen cells from mice with collagen induced arthritis together with native bovine collagen developed more severe arthritis than the donors. SCID mice have therefore proven to be a useful resource to study autoimmunity. In both xeno- and allografts of mature lymphocytes, graft versus host reactions occur. Further studies will be necessary to improve donor cell survival without aggravating graft versus host disease.

The severe combined immunodeficient (SCID) mouse as a model for the study of autoimmune diseases

There are no readily available in vivo models to study immune cells from humans with autoimmune diseases. SCID mice, which virtually lack both T and B lymphocytes and accept xenogeneic cells, have been used during the last 5 years to provide a milieu for lymphocytes isolated from individuals with various autoimmune diseases, or for lymphocytes from mice that have a systemic lupus erythematosus-like syndrome. Whilst human autoantibodies to organ antigens have been demonstrated in most SCID mice engrafted with human lymphocytes from the peripheral blood or the target organ, inflammation of the mouse target organ has not generally been observed. This review critically analyses experiments in this area reported so far. Some pitfalls of the SCID mouse model of human autoimmune diseases are mentioned, and future experiments to study mouse and human autoimmunity with this model are proposed.

Polyomavirus models of brain infection and the pathogenesis of multiple sclerosis

Multiple sclerosis (MS) is generally considered to be an autoimmune disorder with myelin as the target and with several unidentified viruses playing ancillary roles, possibly through molecular mimicry. Although this paradigm has led to important progress on potential mechanisms of myelin loss, neither a target antigen in myelin nor a triggering mechanism has yet been identified, leaving the etiology of MS still unknown. Animal models of viral demyelination and studies showing that JC virus (JCV), the polyomavirus which causes progressive multifocal leukoencephalopathy (PML), may be latent in some normal human brains suggest another possibility. A host immune response targeting proteins expressed at low levels from viral DNA latent in the central nervous system (CNS) might underlie a focal demyelinating disease such as MS. A shift from autoimmunity to a latent-virus model is not a trivial substitution of target antigens. This shift would expand the search for a definitive laboratory test for MS and could lead to improved therapeutic and preventive approaches.