Relapsing and remitting experimental autoimmune encephalomyelitis in B cell deficient mice

Turncoat antibodies unmasked in a model of autoimmune demyelination: from biology to therapy

Autoantibodies contribute to many autoimmune diseases, yet there is no approved therapy to neutralize them selectively. A popular mouse model, experimental autoimmune encephalomyelitis (EAE), could serve to develop such a therapy, provided we can better understand the nature and importance of the autoantibodies involved. Here we report the discovery of autoantibody-secreting extrafollicular plasmablasts in EAE induced with specific myelin oligodendrocyte glycoprotein (MOG) antigens. Single-cell RNA sequencing reveals that these cells produce non-affinity-matured IgG antibodies. These include pathogenic antibodies competing for shared binding space on MOG's extracellular domain. Interestingly, the synthetic anti-MOG antibody 8-18C5 can prevent the binding of pathogenic antibodies from either EAE mice or people with MOG antibody disease (MOGAD). Moreover, an 8-18C5 variant carrying the NNAS mutation, which inactivates its effector functions, can reduce EAE severity and promote functional recovery. In brief, this study provides not only a comprehensive characterization of the humoral response in EAE models, but also a proof of concept for a novel therapy to antagonize pathogenic anti-MOG antibodies.

Systems profiling reveals recurrently dysregulated cytokine signaling responses in ER+ breast cancer patients' blood

Cytokines operate in concert to maintain immune homeostasis and coordinate immune responses. In cases of ER+ breast cancer, peripheral immune cells exhibit altered responses to several cytokines, and these alterations are correlated strongly with patient outcomes. To develop a systems-level understanding of this dysregulation, we measured a panel of cytokine responses and receptor abundances in the peripheral blood of healthy controls and ER+ breast cancer patients across immune cell types. Using tensor factorization to model this multidimensional data, we found that breast cancer patients exhibited widespread alterations in response, including drastically reduced response to IL-10 and heightened basal levels of pSmad2/3 and pSTAT4. ER+ patients also featured upregulation of PD-L1, IL6Rα, and IL2Rα, among other receptors. Despite this, alterations in response to cytokines were not explained by changes in receptor abundances. Thus, tensor factorization helped to reveal a coordinated reprogramming of the immune system that was consistent across our cohort.

Systems profiling reveals recurrently dysregulated cytokine signaling responses in ER+ breast cancer patients' blood

Cytokines mediate cell-to-cell communication across the immune system and therefore are critical to immunosurveillance in cancer and other diseases. Several cytokines show dysregulated abundance or signaling responses in breast cancer, associated with the disease and differences in survival and progression. Cytokines operate in a coordinated manner to affect immune surveillance and regulate one another, necessitating a systems approach for a complete picture of this dysregulation. Here, we profiled cytokine signaling responses of peripheral immune cells from breast cancer patients as compared to healthy controls in a multidimensional manner across ligands, cell populations, and responsive pathways. We find alterations in cytokine responsiveness across pathways and cell types that are best defined by integrated signatures across dimensions. Alterations in the abundance of a cytokine's cognate receptor do not explain differences in responsiveness. Rather, alterations in baseline signaling and receptor abundance suggesting immune cell reprogramming are associated with altered responses. These integrated features suggest a global reprogramming of immune cell communication in breast cancer.

Regulatory B cells in infection, inflammation, and autoimmunity

Regulatory B (Breg) cells are characterized by differential expression of CD5 and CD1d in mouse and CD24 and CD38 in human immune systems. The Breg family also includes LAG-3⁺CD138^hi plasma cells, CD1d CD5 CD21 CD23 cells, Tim1, PD-L1, PD-L2, CD200- expressing B cells, and CD39^hiKi67⁺ cells originating from the transitional, marginal zone or germinal centre of the spleen. Breg cells produce IL10 and IL35 and to cause immunosuppression. These cells respond to TLR2, TLR4, and TLR9 agonists, CD40 ligands, IL12p35 and heat shock proteins. Emerging evidence suggests that TLR signalling component Myd88 impacts the modulation of Breg cell responses and the host's susceptibility to infection. Breg cells are found to reduce relapsing-remitting experimental autoimmune encephalomyelitis. However, the Breg-mediated mechanism used to control T cell-mediated immune responses is still unclear. Here, we review the existing literature to find gaps in the current knowledge and to build a pathway to further research.

Reduced peripheral blood regulatory B cell levels are not associated with the Expanded Disability Status Scale score in multiple sclerosis

Objective To investigate levels of regulatory B (Breg) cells, plasma cells, and memory B cells in the peripheral blood, and interleukin (IL)-10 in the serum of multiple sclerosis (MS) patients, and to determine the correlation between Breg cell levels and the Expanded Disability Status Scale (EDSS) score. Methods Levels of Breg cells, plasma cells, and memory B cells in the peripheral blood of 12 MS patients were measured using flow cytometry. IL-10 serum levels were measured by enzyme-linked immunosorbent assay. The correlation between Breg cell levels and MS EDSS score was measured using Pearson's correlation coefficient. Results Compared with healthy controls, MS patients had decreased levels of CD19+CD24hiCD38hi Breg cells in their peripheral blood and reduced serum levels of IL-10; however, the ratios of CD19+CD27hiCD38hi plasma cells and CD19+CD27+CD24hi memory B cells to total B cells did not differ significantly between healthy controls and MS patients. CD19+CD24hiCD38hi Breg cell levels in the peripheral blood of MS patients were not significantly correlated with MS EDSS score. Conclusion Peripheral blood CD19+CD24hiCD38hi Breg cell levels and serum IL-10 levels were reduced in MS patients compared with controls, but Breg cell levels were not correlated with MS EDSS score.

ICAM1+ neutrophils promote chronic inflammation via ASPRV1 in B cell-dependent autoimmune encephalomyelitis

Neutrophils contribute to demyelinating autoimmune diseases, yet their phenotype and functions have been elusive to date. Here, we demonstrate that ICAM1 surface expression distinguishes extra- from intravascular neutrophils in the mouse CNS during experimental autoimmune encephalomyelitis (EAE). Transcriptomic analysis of these 2 subpopulations indicated that neutrophils, once extravasated, acquire macrophage-like properties, including the potential for immunostimulation and MHC class II-mediated antigen presentation. In corroboration, super-resolution (3D stimulated emission-depletion [STED]) microscopy revealed neutrophils forming synapses with T and B cells in situ. Further, neutrophils specifically express the aspartic retroviral-like protease ASPRV1, which increases in the CNS during EAE and severe cases of multiple sclerosis. Without ASPRV1, mice immunized with a new B cell-dependent myelin antigen (but not with the traditional myelin oligodendrocyte glycoprotein peptide) develop a chronic phase of EAE that is less severe and even completely fades in many individuals. Therefore, ICAM1+ macrophage-like neutrophils can play both shared and nonredundant roles in autoimmune demyelination, among them perpetuating inflammation via ASPRV1.

Both Notch1 and its ligands in B cells promote antibody production

Notch1 signaling regulates B and T lymphocyte development and also in vitro promotes antibody secretion upon B cell activation. However, it is still unclear about the role of Notch1 in antibody production upon in vitro and in vivo mixture lymphocytes activation. We first showed that Notch1 expressed in LPS-activated CD19^hi B cells and CD19^cre mediated Notch1 knock-down in LPS-activated B cells. Furthermore, we demonstrated that Notch1 knock-down in B cells reduced antibody production in LPS-stimulated B cells but did not affect antibody production in LPS-stimulated splenocytes and in experimental allergic encephalomyelitis (EAE) mice. Importantly, Notch1 ligands Dll1 and Jag1 expressed in B cells and pre-coated Notch1 protein promotes Notch1-knocked down B cells to produce antibody in LPS-stimulated B cells suggesting that Notch1 in other cells may promote antibody production by binding its ligands Dll1 and Jag1 in B cells. Together, our results suggest that both Notch1 and its ligands in B cells play an important role in antibody production.

Mechanisms of Regulatory B cell Function in Autoimmune and Inflammatory Diseases beyond IL-10

In the past two decades it has become clear that in addition to antigen presentation and antibody production B cells play prominent roles in immune regulation. While B cell-derived IL-10 has garnered much attention, B cells also effectively regulate inflammation by a variety of IL-10-independent mechanisms. B cell regulation has been studied in both autoimmune and inflammatory diseases. While collectively called regulatory B cells (Breg), no definitive phenotype has emerged for B cells with regulatory potential. This has made their study challenging and thus unique B cell regulatory mechanisms have emerged in a disease-dependent manner. Thus to harness the therapeutic potential of Breg, further studies are needed to understand how they emerge and are induced to evoke their regulatory activities.

Identification of Liver Epithelial Cell-derived Ig Expression in μ chain-deficient mice

Growing evidence indicates that B cells are not the only source of immunoglobulin (Ig). To investigate this discovery further, we used μMT mice, which have a disruption of the first transmembrane exon of the μ heavy chain and do not express the membrane form of IgM. These mice lack mature B cells and thus serve as a good model to explore Ig expression by liver epithelial cells. We found that Ig heavy chains (μ, δ, γ and α) and light chains (κ and λ) were expressed in sorted liver epithelial cells of μMT mice. Surprisingly, each heavy chain class showed its respective variable region sequence characteristics in their variable region, instead of sharing the same VDJ usage, which suggests that class switching does not occur in liver epithelial cells. Moreover, the γ and α chains, but not the μ and δ chains, showed mutations in the variable region, thus indicating that different classes of Ig have different activities. Our findings support the concept that non-B cells, liver epithelial cells here, can produce different classes of Ig.

Two unresolved problems facing models of the Self-Nonself discrimination

Although the Associative (linked) Recognition of Antigen (ARA) model for a Self (S)-Nonself (NS) discrimination, now over 50 years old, is built on a solid conceptual and experimental base, two unsettled questions remain. In examining these questions, unanticipated aspects of the ARA Model itself had to be reconsidered. This essay spells out these problems and suggests possible solutions.

Role of glial 14-3-3 gamma protein in autoimmune demyelination

Background

The family of 14-3-3 proteins plays an important role in the regulation of cell survival and death. Here, we investigate the role of the 14-3-3 gamma (14-3-3 γ) subunit for glial responses in autoimmune demyelination.

Methods

Expression of 14-3-3 γ in glial cell culture was investigated by reverse transcription polymerase chain reaction (RT-PCR) and immunocytochemistry. 14-3-3 γ knockout mice were subjected to murine myelin oligodendrocyte-induced experimental autoimmune encephalomyelitis (MOG-EAE), an animal model mimicking inflammatory features and neurodegenerative aspects of multiple sclerosis (MS).

Results

Expression studies in cell culture confined expression of 14-3-3 γ to both, oligodendrocytes (OL) and astrocytes. RT-PCR analysis revealed an increased expression of 14-3-3 γ mRNA in the spinal cord during the late chronic phase of MOG-EAE. At that stage, EAE was more severe in 14-3-3 γ knockout mice as compared to age- and gender-matched controls. Histopathological analyses on day 56 post immunization (p.i.) revealed significantly enhanced myelin damage as well as OL injury and secondary, an increase in axonal injury and gliosis in 14-3-3 γ −/− mice. At the same time, deficiency in 14-3-3 γ protein did not influence the immune response. Further histological studies revealed an increased susceptibility towards apoptosis in 14-3-3 γ-deficient OL in the inflamed spinal cord.

Conclusion

These data argue for a pivotal role of 14-3-3 γ-mediated signalling pathways for OL protection in neuroinflammation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-015-0381-x) contains supplementary material, which is available to authorized users.

IFN-γ ameliorates autoimmune encephalomyelitis by limiting myelin lipid peroxidation

Evidence has suggested both a pathogenic and a protective role for the proinflammatory cytokine IFN-γ in experimental autoimmune encephalomyelitis (EAE). However, the mechanisms underlying the protective role of IFN-γ in EAE have not been fully resolved, particularly in the context of CNS antigen-presenting cells (APCs). In this study we examined the role of IFN-γ in myelin antigen uptake by CNS APCs during EAE. We found that myelin antigen colocalization with APCs was decreased substantially and that EAE was significantly more severe and showed a chronic-progressive course in IFN-γ knockout (IFN-γ-/-) or IFN-γ receptor knockout (IFN-γR-/-) mice as compared with WT animals. IFN-γ was a critical regulator of phagocytic/activating receptors on CNS APCs. Importantly, "free" myelin debris and lipid peroxidation activity at CNS lesions was increased in mice lacking IFN-γ signaling. Treatment with N-acetyl-l-cysteine, a potent antioxidant, abolished lipid peroxidation activity and ameliorated EAE in IFN-γ-signaling-deficient mice. Taken together the data suggest a protective role for IFN-γ in EAE by regulating the removal of myelin debris by CNS APCs and thereby limiting the substrate available for the generation of neurotoxic lipid peroxidation products.

Thoughts engendered by Bretscher's Two-step, Two-signal model for a peripheral self-non-self discrimination and the origin of primer effector T helpers

There are three questions under re-examination here that have been inspired by Bretscher's 'Two-step, Two-signal' model. First, what is the nature of the steps required in order for antigen-responsive cells to become effectors? Second, how does the immune system get started? Third and the most troublesome, what is the mechanism that relates the delivery of the two signals? To answer the first question, Bretscher proposes a pathway that I will place in another context by comparing it with what had been envisaged under the Associative Recognition of Antigen (ARA) model. The second question, how does the immune system gets started, is crucial to our understanding of the self-non-self discrimination. This problem boils down to, what is the origin of the first effector T helper (eTh) cells required to activate all antigen-responsive cells including the T helpers themselves (the primer problem)? To deal with this question, I proposed an antigen-independent pathway to primer eTh. Bretscher presents us with an antigen-dependent pathway to primer eTh. As competing models are precious in clarifying thinking and in guiding experimentation, I felt it important to reanalyse the two models and look for ways to decide between them. The third question deals with the requirement for and the mechanism of associative (linked) recognition of antigen (ARA). The concept of ARA is so compelling at both the experimental and theoretical levels that to save it, a new perspective will be introduced.

Immune surveillance of the central nervous system in multiple sclerosis--relevance for therapy and experimental models

Treatment of central nervous system (CNS) autoimmune disorders frequently involves the reduction, or depletion of immune-competent cells. Alternatively, immune cells are being sequestered away from the target organ by interfering with their movement from secondary lymphoid organs, or their migration into tissues. These therapeutic strategies have been successful in multiple sclerosis (MS), the most prevalent autoimmune inflammatory disorder of the CNS. However, many of the agents that are currently approved or in clinical development also have severe potential adverse effects that stem from the very mechanisms that mediate their beneficial effects by interfering with CNS immune surveillance. This review will outline the main cellular components of the innate and adaptive immune system that participate in host defense and maintain immune surveillance of the CNS. Their pathogenic role in MS and its animal model experimental autoimmune encephalomyelitis (EAE) is also discussed. Furthermore, an experimental model is introduced that may assist in evaluating the effect of therapeutic interventions on leukocyte homeostasis and function within the CNS. This model or similar models may become a useful tool in the repertoire of pre-clinical tests of pharmacological agents to better explore their potential for adverse events.

The experimental autoimmune encephalomyelitis (EAE) model of MS: utility for understanding disease pathophysiology and treatment

While no single model can exactly recapitulate all aspects of multiple sclerosis (MS), animal models are essential in understanding the induction and pathogenesis of the disease and to develop therapeutic strategies that limit disease progression and eventually lead to effective treatments for the human disease. Several different models of MS exist, but by far the best understood and most commonly used is the rodent model of experimental autoimmune encephalomyelitis (EAE). This model is typically induced by either active immunization with myelin-derived proteins or peptides in adjuvant or by passive transfer of activated myelin-specific CD4+ T lymphocytes. Mouse models are most frequently used because of the inbred genotype of laboratory mice, their rapid breeding capacity, the ease of genetic manipulation, and availability of transgenic and knockout mice to facilitate mechanistic studies. Although not all therapeutic strategies for MS have been developed in EAE, all of the current US Food and Drug Administration (FDA)-approved immunomodulatory drugs are effective to some degree in treating EAE, a strong indicator that EAE is an extremely useful model to study potential treatments for MS. Several therapies, such as glatiramer acetate (GA: Copaxone), and natalizumab (Tysabri), were tested first in the mouse model of EAE and then went on to clinical trials. Here we discuss the usefulness of the EAE model in understanding basic disease pathophysiology and developing treatments for MS as well as the potential drawbacks of this model.

Pathogenic and regulatory roles for B cells in experimental autoimmune encephalomyelitis

A dual role of B cells in experimental autoimmune encephalomyelitis (EAE), the animal model of the human autoimmune disease multiple sclerosis (MS), has been established. In the first role, B cells contribute to the pathogenesis of EAE through the production of anti-myelin antibodies that contribute to demyelination. On the contrary, B cells have also been shown to have protective functions in that they play an essential role in the spontaneous recovery from EAE. In this review, we summarize studies conducted in a number of species demonstrating the conditions under which B cells are pathogenic in EAE. We also discuss the phenotype and anti-inflammatory mechanisms of regulatory B cells.

The lymphoid chemokine, CXCL13, is dispensable for the initial recruitment of B cells to the acutely inflamed central nervous system

Cases of progressive multifocal leukoencephalopathy can occur in patients treated with the B cell depleting anti-CD20 antibody, rituximab, highlighting the importance of B cell surveillance of the central nervous system (CNS). The lymphoid chemokine, CXCL13, is critical for B cell recruitment and functional organization of peripheral lymphoid tissues, and CXCL13 levels are often elevated in the inflamed CNS. To more directly investigate the role of CXCL13 in CNS B cell migration, its role in animal models of infectious and inflammatory demyelinating disease was examined. During acute alphavirus encephalitis where viral clearance depends on the local actions of anti-viral antibodies, CXCL13 levels and B cell numbers increased in brain tissue over time. Surprisingly, however, CXCL13-deficient animals showed normal CNS B cell recruitment, unaltered CNS virus replication and clearance, and intact peripheral anti-viral antibody responses. During experimental autoimmune encephalomyelitis (EAE), CNS levels of CXCL13 increased as symptoms emerged and equivalent numbers of B cells were identified among the CNS infiltrates of CXCL13-deficient mice compared to control animals. However, CXCL13-deficient mice did not sustain pathogenic anti-myelin T cell responses, consistent with their known propensity to develop more self-limited EAE. These data show that CXCL13 is dispensable for CNS B cell recruitment in both models. The disease course is unaffected by CXCL13 in a CNS infection paradigm that depends on a pathogen-specific B cell response, while it is heightened and prolonged by CXCL13 when myelin-specific CD4+ T cells drive CNS pathology. Thus, CXCL13 could be a therapeutic target in certain neuroinflammatory diseases, but not by blocking B cell recruitment to the CNS.

Recent insights into the mechanism of action of glatiramer acetate

Glatiramer acetate (GA, Copaxone®, co-polymer 1) is an immunomodulatory therapy approved in 1996 by the United States Food and Drug Administration for treatment of relapsing-remitting multiple sclerosis. GA has a good safety profile, moderate efficacy, and a unique mode of action. Recent evidence in an animal model of MS, experimental autoimmune encephalomyelitis (EAE), suggests that GA effects on NK cells and B cells may contribute to therapeutic efficacy. We review the mechanism of action of GA, with particular focus on recent data suggesting a role for regulatory B cells.

A case for regulatory B cells in controlling the severity of autoimmune-mediated inflammation in experimental autoimmune encephalomyelitis and multiple sclerosis

Multiple sclerosis (MS) is considered to be a T cell-mediated autoimmune disease that results in the presence of inflammatory lesions/plaques associated with mononuclear cell infiltrates, demyelination and axonal damage within the central nervous system (CNS). To date, FDA approved therapies in MS are thought to largely function by modulation of the immune response. Since autoimmune responses require many arms of the immune system, the direct cellular mechanisms of action of MS therapeutics are not definitively known. The mouse model of MS, experimental autoimmune encephalomyelitis (EAE), has been instrumental in deciphering the mechanism of action of MS drugs. In addition, EAE has been widely used to study the contribution of individual components of the immune system in CNS autoimmunity. In this regard, the role of B cells in EAE has been studied in mice deficient in B cells due to genetic ablation and following depletion with a B cell-targeted monoclonal antibody (mAb) (anti-CD20). Both strategies have indicated that B cells regulate the extent of EAE clinical disease and in their absence disease is exacerbated. Thus a new population of "regulatory B cells" has emerged. One reoccurring component of regulatory B cell function is the production of IL-10, a pleiotropic cytokine with potent anti-inflammatory properties. B cell depletion has also indicated that B cells, in particular antibody production, play a pathogenic role in EAE. B cell depletion in MS using a mAb to CD20 (rituximab) has shown promising results. In this review, we will discuss the current thinking on the role of B cells in MS drawing from knowledge gained in EAE studies and clinical trials using therapeutics that target B cells.

Models of autoimmune demyelination in the central nervous system: on the way to translational medicine

Multiple sclerosis (MS) is the most common neurologic disease of young adults. In the recent years, our understanding on disease pathomechanisms has considerably improved and new therapies have emerged. Yet a cure for this devastating disorder is still a far cry away and human resources on ex vivo specimens are limited. More than 70 years after its first description, experimental autoimmune encephalomyelitis (EAE) remains an important tool to understand concepts of T cell mediated autoimmunity as well as the roles of the innate and the humoral immune systems. Some EAE models also well reflect mechanisms of tissue damage including demyelination, axonal injury and also cortical changes. A limitation of the classical EAE model is a neglect of CD8 T cell mediated immune mechanisms. Moreover, well characterized models for primary progressive MS or demyelination patterns involving primary oligodendrocyte dystrophy are still not available. Yet many current therapeutic concepts including glatiramer acetate or natalizumab stem from their successful first application in EAE models. New strategies include the widespread use of conditional knockout mice to understand the cell-type specific function of single genes, innovative approaches to establish models on the roles of B cells and CD8 T cells as well as on the relation of inflammation to primary degeneration. In summary, EAE models continue to play an important role in neuroimmunology thereby also stimulating research in other fields of the neurosciences and immunobiology.

Cooperation of B cells and T cells in the pathogenesis of multiple sclerosis

B cells and T cells are two major players in the pathogenesis of multiple sclerosis (MS) and cooperate at various check points. B cells, besides serving as a source for antibody-secreting plasma cells, are efficient antigen presenting cells for processing of intact myelin antigen and subsequent activation and pro-inflammatory differentiation of T cells. This notion is supported by the immediate clinical benefit of therapeutic B cell depletion in MS, presumably abrogating development of encephalitogenic T cells. However, different B cell subsets strongly vary in their respective effect on T cell differentiation which may relate to B cell phenotype, activation status, antigen specificity and the immunological environment where a B cell encounters a naïve T cell in. In this regard, some B cells also have anti-inflammatory properties producing regulatory cytokines and facilitating development and maintenance of other immunomodulatory immune cells, such as regulatory T cells. Reciprocally, differentiated T cells influence T cell polarizing B cell properties establishing a positive feedback loop of joint pro- or anti-inflammatory B and T cell developments. Further, under the control of activated T helper cells, antigen-primed B cells can switch immunoglobulin isotype, terminally commit to the plasma cell pathway or enter the germinal center reaction to memory B Cell development. Taken together, B cells and T cells thus closely support one another to participate in the pathogenesis of MS in an inflammatory but also in a regulatory manner.

A rationalized set of default postulates that permit a coherent description of the immune system amenable to computer modeling

This discussion delineates and rationalizes a set of postulates that permit a coherent understanding of immune function. Although analytical tools such as mathematics and computer modeling have become very popular, simulation and data mining in the absence of a conceptual framework cannot increase understanding. The goal of this essay is to provide the foundation for a discussion that has as its goal the formulation of an agreed upon set of default postulates. Such a set is required to guide the algorithms needed to analyze complex immune behavior.

Antibodies to myelin oligodendrocyte glycoprotein are not involved in the severity of chronic non-remitting experimental autoimmune encephalomyelitis

To elucidate the role of antibodies in development of chronic non-remitting experimental autoimmune encephalomyelitis (EAE) in C57BL/6 mice, which is a well-established Th1-mediated autoimmune disease, and the involvement of activation-induced cytidine deaminase (AID) in Th1-mediated function, we have investigated the myelin oligodendrocyte glycoprotein (MOG)-induced EAE in mice deficient of AID, which is absolutely required for class switching and somatic hypermutation. Following immunization with MOG, AID(-/-) had completely same levels of clinical and pathological severity of EAE when compared with AID(+/-) and AID(+/+), although AID(-/-) did not produce IgG and anti-MOG IgG. Similar levels of T cell proliferation and a modest increase of anti-MOG IgM synthesis were found in spleen cells of AID(-/-) stimulated with MOG. These results indicate that antibodies are not involved in development of EAE in C57BL/6 mice.

B cells limit epitope spreading and reduce severity of EAE induced with PLP peptide in BALB/c mice

The role of B cells and antibody in experimental autoimmune encephalomyelitis (EAE) appears to differ based on the identity and state (protein vs. encephalitogenic peptide) of the inducing antigen and the strain of mouse utilized. The involvement of B cells in the induction of EAE by peptides of proteolipid protein (PLP) in BALB/c mice was investigated. Wild-type and B cell-deficient (B cell-/-) mice on the BALB/c background were immunized with overlapping PLP peptides, and the disease course was followed. Although incidence and onset of PLP(180-199)-induced EAE was similar in WT and B cell-/- mice, the clinical course was more severe in B cell-/- mice. During acute disease, proliferation and interferon-gamma production by lymphoid cells from both strains were similar and were elicited predominantly in response to the immunizing antigen. However, during chronic disease lymphoid cells isolated from B cell-/- mice proliferated to a greater extent and produced more interferon-gamma in response to the overlapping peptide PLP185-206 and to the smaller internal peptide PLP185-199 than did WT mice. These data suggest that B cells regulate PLP-induced EAE in BALB/c mice through control of epitope spreading.

The role of B cells in multiple sclerosis: rationale for B-cell-targeted therapies

Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system with no clear etiology. Until recently, most studies have emphasized the role of T cells in the pathogenesis of multiple sclerosis. Data suggesting that B cells play a role in the pathogenesis of multiple sclerosis have been accumulating for the past five decades, demonstrating that the cerebrospinal fluid and central nervous system tissues of multiple sclerosis patients contain B cells, plasma cells, antibodies, and immunoglobulins. Data suggest that B cells are involved in antigen capture and presentation to T cells, cytokine production, antibody secretion, demyelination, tissue damage, and remyelination in multiple sclerosis. These advances in the understanding of B-cell and antibody roles in the pathophysiology of multiple sclerosis provide a strong rationale for B-cell-targeted therapies.

A biological context for the self-nonself discrimination and the regulation of effector class by the immune system

An effective immune response to an antigen requires two sets of decisions: Decision 1, the sorting of the repertoire, and Decision 2, the regulation of effector class. The repertoire, because it is somatically generated, large, and random, must be sorted by a somatic mechanism that subtracts those specificities (anti-self) that, if expressed, would debilitate the host, leaving a residue (anti-nonself) that, if not expressed, would result in the death of the host by infection. The self-nonself discrimination is the metaphor used to describe Decision 1, the sorting of the repertoire. In order to be functional, the sorted repertoire must be coupled to a set of biodestructive and ridding effector functions, such that the response to each antigen is treated in a coherent and independent manner. Although a reasonably complete framework for Decision 1 exists, Decision 2 lacks conceptualization. The questions that must be considered to arrive at a proper framework are posed. It should be emphasized that manipulation at the level of Decision 2 is where clinical applications are likely to be found.

Expansion of CD4+CD25+ regulatory T cells by intravenous immunoglobulin: a critical factor in controlling experimental autoimmune encephalomyelitis

The clinical use of intravenous immunoglobulin (IVIg) based on its immunomodulatory and anti-inflammatory potential remains an ongoing challenge. Fcγ receptor-mediated effects of IVIg, although well elucidated in certain pathologies, cannot entirely account for its proven benefit in several autoimmune disorders mediated by autoreactive T cells. In this study, we show that prophylactic infusion of IVIg prevents the development of experimental autoimmune encephalomyelitis (EAE), an accepted animal model for multiple sclerosis (MS). The protection was associated with peripheral increase in CD4+CD25+Foxp3+ regulatory T cell (Treg) numbers and function. The protection was Treg-mediated because IVIg failed to protect against EAE in mice that were depleted of the Treg population. Rather than inducing de novo generation from conventional T cells, IVIg had a direct effect on proliferation of natural Treg. In conclusion, our results highlight a novel mechanism of action of IVIg and provide a rationale to test the use of IVIg as an immunomodulatory tool to enhance Treg in early onset MS and other autoimmune and inflammatory conditions.

Autoantibody-mediated demyelination depends on complement activation but not activatory Fc-receptors

The precise mechanisms leading to CNS inflammation and myelin destruction in both multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE) remain the subject of intense debate. In both MS and EAE, autoantibodies (autoAbs) are thought to be involved in tissue destruction through recruiting Fc receptor (FcR)-bearing cells or direct cytotoxic effects through the activation of the complement pathway. Whereas intrathecal immunoglobulin (Ig) production and Ig deposition in inflammatory lesions is a hallmark of MS, mice deficient in B cells and Igs develop severe EAE. Paradoxically, mice of the same genetic background but deficient in FcRgamma are EAE-resistant. We found that the functional expression of FcRgamma on systemic accessory cells, but not CNS-resident cells, appears to be vital for the development of CNS inflammation, independent of antigen-presenting cell function or Ab involvement. On the other hand, we found that the injection of antimyelin oligodendrocyte glycoprotein-Abs drastically worsens disease severity, inflammation, and demyelination. Using FcRgamma(-/-) and C1q(-/-) mice, we could definitively establish that the demyelinating capacity of such autoAb in vivo relies entirely on complement activation and is FcR-independent.

IL-17 plays an important role in the development of experimental autoimmune encephalomyelitis

IL-17 is a proinflammatory cytokine that activates T cells and other immune cells to produce a variety of cytokines, chemokines, and cell adhesion molecules. This cytokine is augmented in the sera and/or tissues of patients with contact dermatitis, asthma, and rheumatoid arthritis. We previously demonstrated that IL-17 is involved in the development of autoimmune arthritis and contact, delayed, and airway hypersensitivity in mice. As the expression of IL-17 is also augmented in multiple sclerosis, we examined the involvement of this cytokine in these diseases using IL-17(-/-) murine disease models. We found that the development of experimental autoimmune encephalomyelitis (EAE), the rodent model of multiple sclerosis, was significantly suppressed in IL-17(-/-) mice; these animals exhibited delayed onset, reduced maximum severity scores, ameliorated histological changes, and early recovery. T cell sensitization against myelin oligodendrocyte glycoprotein was reduced in IL-17(-/-) mice upon sensitization. The major producer of IL-17 upon treatment with myelin digodendrocyte glycopritein was CD4+ T cells rather than CD8+ T cells, and adoptive transfer of IL-17(-/-) CD4+ T cells inefficiently induced EAE in recipient mice. Notably, IL-17-producing T cells were increased in IFN-gamma(-/-) cells, while IFN-gamma-producing cells were increased in IL-17(-/-) cells, suggesting that IL-17 and IFN-gamma mutually regulate IFN-gamma and IL-17 production. These observations indicate that IL-17 rather than IFN-gamma plays a crucial role in the development of EAE.

TCR vaccination in aluminum adjuvant protects against autoimmune encephalomyelitis

Experimental Allergic Encephalomyelitis (EAE) is a neuroinflammatory, autoimmune disorder in which myelin-reactive Th1 T cells with a restricted TCRVbeta repertoire play a pathogenic role. Here, I show that an engineered single-chain TCR containing dominant TCRValpha/Vbeta encephalitogenic elements, when administered in aluminum adjuvant, generates a marked anti-TCR humoral response that correlated with protection against the development of EAE in Vbeta8-expressing B10.PL but not in Vbeta8-deficient SJL mice. sc-TCR/Al vaccination was highly efficient in preventing murine EAE in a TCR-specific manner through a mechanism involving anti-TCR B cells and/or antibodies. Collectively, these data have important implications for designing preventive or therapeutic strategies combining TCR vaccination with the use of aluminum adjuvant in the treatment of multiple sclerosis and other human autoimmune inflammatory diseases.

A deficiency in Drak2 results in a T cell hypersensitivity and an unexpected resistance to autoimmunity

DRAK2 is a member of the death-associated protein (DAP)-like family of serine/threonine kinases. Members of this family induce apoptosis in various cell types. DRAK2, in particular, is specifically expressed in T cells and B cells, and it is differentially regulated during T cell development. To determine whether DRAK2 regulates lymphocyte apoptosis, we produced Drak2(-/-) mice. Contrary to our expectations, Drak2(-/-) T cells did not demonstrate any defects in apoptosis or negative selection; however, T cells from Drak2(-/-) mice exhibited enhanced sensitivity to T cell receptor-mediated stimulation with a reduced requirement for costimulation. These results provide evidence that DRAK2 raises the threshold for T cell activation by negatively regulating signals through the TCR. In contrast to other models of T cell hypersensitivity, Drak2(-/-) mice were remarkably resistant to experimental autoimmune encephalomyelitis (EAE). These results expose a new pathway regulating T cell activation and highlight the intricacies of induced autoimmune disease.

Dendritic cells under investigation in autoimmune disease

Autoimmune disorders play an increasing role in public health, especially in light of the fact of the growing aged population, which primarily develop such diseases. A clear understanding of the mechanisms leading to the development of autoimmune responses and finally to autoimmune disease does not exist. Autoimmunity is characterized by the presence of autoantibodies and/or autoreactive T cells and the corresponding organ manifestation. Following the discovery of autoreactive T cells found in the periphery of mice and humans, the old immunological concept that autoreactive T cells are completely deleted in the thymus during evolution has been revised in recent years. Although antigen-presenting cells and particularly dendritic cells are known to play an important role in the regulation of immune responses and the activation of T cells, recent evidence suggests that the role of dendritic cells in the development of autoimmunity has been underestimated previously. This article aims to give a general overview on the basic immunological principles involved and gives a short review of the current literature on the functional relevance of dendritic cells in various human and murine autoimmune disorders.

Epicutaneous Immunization with Autoantigenic Peptides Induces T Suppressor Cells that Prevent Experimental Allergic Encephalomyelitis

Information on how suppressor/regulatory T cells can be generated directly in vivo and prevent autoimmunity remains fragmentary. We show here that epicutaneous immunization (ECi) with the immunodominant peptide of myelin basic protein (MBP), Ac1-11, protects mice that are transgenic for an Ac1-11-specific T cell receptor against both the induced and spontaneous forms of experimental allergic encephalomyelitis (EAE). This protection was antigen specific and antigen dose dependent, and was mediated by CD4(+)/CD25(-) T cells whose suppressive activity required cell-cell contact and could transfer protection to naive recipients. These ECi-induced suppressor T cells controlled naive MBP-specific CD4 T cells by inhibiting both their activation and their capacity to secrete IFN-gamma. There was no CD4 T cell infiltration in the brain of protected mice. Finally, ECi with autoantigenic peptides protected two nontransgenic models from relapsing-remitting EAE in an antigen-specific and antigen dose-dependent manner.

Novel B cell population producing functional IgG in the absence of membrane IgM expression

Surface expression of IgM is a characteristic feature of the development of most B cells. Only pre-B cells bearing functional IgM heavy chains mu chains) are selected for clonal expansion and differentiation. Cells lacking mu chains are normally eliminated. muMT mice carrying a deletion of the first exon coding for the transmembrane domain of the immunoglobulin mu chain gene were described as mice deficient for mature B cells, plasma cells and immunoglobulins in serum. In this study, we describe in muMT/BALB/c mice the presence of a novel B cell population, producing IgG, IgA and IgE in the absence of IgM membrane expression. Moreover, this small population of B cells is able to recognize antigens and to differentiate into plasma cells. These "non-conventional" mu(- / -) B cells produce functional immunoglobulins after immunization, undergo germinal center reactions, and maintain B cell memory. Our findings support the concept, that a small percentage of mu -non-expressing pre-B cells can escape elimination, switch to downstream immunoglobulin heavy chains and respond to antigens. It remains an open question how the reactivity of these B cells is regulated and in which extent such B cells play a role in physiological and pathological processes such as autoantibody production and autoimmunity.

The immunosuppressive agent 15-deoxyspergualin functions by inhibiting cell cycle progression and cytokine production following naive T cell activation

Immunosuppressive agents are commonly used in the prevention of graft rejection following transplantation and in the treatment of autoimmunity. In this study, we examined the immunosuppressive mechanism of the drug 15-deoxyspergualin (DSG), which has shown efficacy in the enhancement of graft survival and in the treatment of autoimmunity. Using a murine model of chronic relapsing and remitting experimental autoimmune encephalomyelitis, we were able to demonstrate that DSG both delayed and reduced the severity of experimental autoimmune encephalomyelitis. Subsequent in vitro studies to examine the mechanism of immune suppression showed that DSG was not able to inhibit early activation of naive CD4 T cells, but DSG did effectively inhibit the growth of naive CD4 T cells after activation. An analysis of cell proliferation and cell cycle showed that DSG treatment led to a block in cell cycle progression 2-3 days following Ag stimulation. In addition, DSG treatment inhibited the production of IFN-gamma by Th1 effector T cells. These studies suggest that CD4 T cells are a predominant target for DSG and the immunosuppressive effects of the drug may result from reduced CD4 T cell expansion and decreased polarization into IFN-gamma-secreting Th1 effector T cells in the induction of certain autoimmune disorders.

Increased severity of experimental allergic encephalomyelitis in lyn-/- mice in the absence of elevated proinflammatory cytokine response in the central nervous system

lyn, a member of the src kinase family, is an important signaling molecule in B cells. lyn(-/-) mice display hyperactive B-1 cells and IgM hyperglobulinemia. The role of lyn on T cell function and development of Th1-mediated inflammatory disease is not known. Therefore, we examined the effect of disruption of the lyn gene on the development of experimental allergic encephalomyelitis (EAE), a well-established Th1-mediated autoimmune disease. Following immunization with myelin oligodendrocyte protein (MOG) p35-55, lyn(-/-) mice had higher clinical and pathological severity scores of EAE when compared with wild type (WT). The increase in the severity of EAE in lyn(-/-) mice was not associated with a commensurate increase in the production of proinflammatory cytokines in the CNS. lyn(-/-) mice with EAE showed elevation in serum anti-IgM MOG Ab levels over that seen in WT mice, along with a modest increase in the mRNA levels of complement C5 and its receptor, C5aR, in the spinal cord. Transfer of serum from MOG-immunized lyn(-/-) mice worsened EAE in WT mice, suggesting a pathogenic role for anti-MOG IgM Abs in EAE. These observations underscore the potential role of lyn in regulation of Th1-mediated disease and the role of autoantibodies and complement in the development of EAE.

Role of B cells as antigen-presenting cells in vivo revisited: antigen-specific B cells are essential for T cell expansion in lymph nodes and for systemic T cell responses to low antigen concentrations

Studies in B cell-deficient mice generated by continuous injection of anti-mu antibodies (muSM) showed that T cell priming in lymph nodes was dependent on antigen presentation by B cells. This concept has recently become controversial since a wide range, from complete deficiency to near normal T cell responses, was reported in studies carried out with B cell-deficient mice generated by gene disruption (muMT). In this study we show that in the absence of B cells, T cell responses are greatly reduced in all the available muMT mouse strains although responses in muMT of the C57BL/6 background (which were used for most studies with muMT) were much more variable and could reach up to 42% of control. In contrast, T cell responses in muMT --> F(1) bone marrow chimeras which have the same phenotype as muMT were totally impaired, suggesting a principle difference between mice developing without B cells (muMT mice) and muSM which are made B cell deficient only after birth. Normal T cell priming was completely restored by reconstitution of muMT and muMT --> F(1) mice with syngeneic B cells. Interestingly, only B cell populations containing antigen-specific B cells were capable of reconstituting T cell responses. Monoclonal B cells taken from Ig transgenic mice could not reconstitute responses to an irrelevant antigen. We also found that B cells were also required for systemic T cell priming when antigen concentrations were limiting but were not required for priming (for T cell help) when mice were immunized with a high antigen dose.