Granulocyte macrophage colony-stimulating factor: a new putative therapeutic target in multiple sclerosis

Nogo-receptor 1 deficiency has no influence on immune cell repertoire or function during experimental autoimmune encephalomyelitis

The potential role of Nogo-66 Receptor 1 (NgR1) on immune cell phenotypes and their activation during neuroinflammatory diseases such as multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), is unclear. To further understand the function of this receptor on haematopoietically-derived cells, phenotypic and functional analyses were performed using NgR1-deficient (ngr1-/-) animals. Flow cytometry-based phenotypic analyses performed on blood, spleen, thymus, lymph nodes, bone marrow and central nervous-system (CNS)-infiltrating blood cells revealed no immunological defects in naïve ngr1-/- animals versus wild-type littermate (WTLM) controls. EAE was induced by either recombinant myelin oligodendrocyte glycoprotein (rMOG), a model in which B cells are considered to contribute pathogenically, or by MOG_35–55 peptide, a B cell-independent model. We have demonstrated that in ngr1-/- mice injected with MOG_35–55, a significant reduction in the severity of EAE correlated with reduced axonal damage present in the spinal cord when compared to their WTLM controls. However, despite a reduction in axonal damage observed in the CNS of ngr1-/- mice at the chronic stage of disease, no clinical differences could be attributed to a specific genotype when rMOG was used as the encephalitogen. Following MOG_35–55-induction of EAE, we could not derive any major changes to the immune cell populations analyzed between ngr1-/- and WTLM mice. Collectively, these data demonstrate that NgR1 has little if any effects on the repertoire of immune cells, their activation and trafficking to the CNS.

T-bet or not T-bet: taking the last bow on the autoimmunity stage

The search for the encephalitogenic factor driving pathogenic T cells in autoimmune diseases such as rheumatoid arthritis, multiple sclerosis (MS), and psoriasis has proven to be a long and difficult mission, which is not yet completed. In this issue of the European Journal of Immunology, the importance of the transcription factor T-bet, previously shown to be essential for the induction of autoimmune disease in mice, is challenged. Two independent groups, O'Connor et al. [Eur. J. Immunol. 2013. 43:2818-2823] report] and Grifka-Walk et al. [Eur. J. Immunol. 2013. 43:2824-2831], report that T-bet is not mandatory for T cells to cause experimental autoimmune encephalomyelitis (EAE), which serves as a paradigmatic T-cell-mediated autoimmune disease. Both groups found that T-bet KO mice were fully susceptible to develop EAE, both after immunization with self-antigen and after adoptive transfer of IL-23-polarized autoaggressive T cells. T-bet deficiency mediated the loss of IFN-γ expression but retained or even enhanced GM-CSF and IL-17 production by central nervous system (CNS)-infiltrating T cells. These findings indicate that we have lost the last transcriptional regulator previously held to be required for the generation of autoimmune pathogenic T cells.

GM-CSF as a therapeutic target in inflammatory diseases

GM-CSF is a well-known haemopoietic growth factor that is used in the clinic to correct neutropaenia, usually as a result of chemotherapy. GM-CSF also has many pro-inflammatory functions and recent data implicates GM-CSF as a key factor in Th17 driven autoimmune inflammatory conditions. In this review we summarize the findings that have led to the development of GM-CSF antagonists for the treatment of autoimmune diseases like rheumatoid arthritis (RA) and discuss some results of recent clinical trials of these agents.

CD28-inducible transcription factor DEC1 is required for efficient autoreactive CD4+ T cell response

The transcription factor DEC1 is induced by CD28 ligation and is required for optimal CD4⁺ T cell responses and the development of EAE.

During the initial hours after activation, CD4⁺ T cells experience profound changes in gene expression. Co-stimulation via the CD28 receptor is required for efficient activation of naive T cells. However, the transcriptional consequences of CD28 co-stimulation are not completely understood. We performed expression microarray analysis to elucidate the effects of CD28 signals on the transcriptome of activated T cells. We show that the transcription factor DEC1 is highly induced in a CD28-dependent manner upon T cell activation, is involved in essential CD4⁺ effector T cell functions, and participates in the transcriptional regulation of several T cell activation pathways, including a large group of CD28-regulated genes. Antigen-specific, DEC1-deficient CD4⁺ T cells have cell-intrinsic defects in survival and proliferation. Furthermore, we found that DEC1 is required for the development of experimental autoimmune encephalomyelitis because of its critical role in the production of the proinflammatory cytokines GM-CSF, IFN-γ, and IL-2. Thus, we identify DEC1 as a critical transcriptional mediator in the activation of naive CD4⁺ T cells that is required for the development of a T cell–mediated autoimmune disease.

GM-CSF alters dendritic cells in autoimmune diseases

Autoimmune diseases arise from an inappropriate immune response against self components, including macromolecules, cells, tissues, organs etc. They are often triggered or accompanied by inflammation, during which the levels of granulocyte macrophage colony-stimulating factor (GM-CSF) are elevated. GM-CSF is an inflammatory cytokine that has profound impact on the differentiation of immune system cells of myeloid lineage, especially dendritic cells (DCs) that play critical roles in immune initiation and tolerance, and is involved in the pathogenesis of autoimmune diseases. Although GM-CSF was discovered decades ago, recent studies with some new findings have shed an interesting light on the old hematopoietic growth factor. In the inflammatory autoimmune diseases, GM-CSF redirects the normal developmental pathway of DCs, conditions their antigen presentation capacities and endows them with unique cytokine signatures to affect autoimmune responses. Here we review the latest advances in the field, with the aim of demonstrating the effects of GM-CSF on DCs and their influences on autoimmune diseases. The summarized knowledge will help to design DC-based strategies for the treatment of autoimmune diseases.

Modeling the heterogeneity of multiple sclerosis in animals

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system (CNS) manifested with varying clinical course, pathology, and inflammatory patterns. There are multiple animal models that reflect different aspects of this heterogeneity. Collectively, these models reveal a balance between pathogenic and regulatory CD4(+) T cells, CD8(+) T cells, and B cells that influences the incidence, timing, and severity of CNS autoimmunity. In this review we discuss experimental autoimmune encephalomyelitis (EAE) models that have been used to study the pathogenic and regulatory roles of these immune cells; models that recapitulate different aspects of the disease seen in patients with MS, and questions remaining for future studies.

Human adipose-derived mesenchymal stem cells engineered to secrete IL-10 inhibit APC function and limit CNS autoimmunity

Interleukin (IL)-10 is an important immunoregulatory cytokine shown to impact inflammatory processes as manifested in patients with multiple sclerosis (MS) and in its animal model, experimental autoimmune encephalomyelitis (EAE). Several lines of evidence indicate that the effectiveness of IL-10-based therapies may be dependent on the timing and mode of delivery. In the present study we engineered the expression of IL-10 in human adipose-derived mesenchymal stem cells (Adi-IL-10-MSCs) and transplanted these cells early in the disease course to mice with EAE. Adi-IL-10-MSCs transplanted via the intraperitoneal route prevented or delayed the development of EAE. This protective effect was associated with several anti-inflammatory response mechanisms, including a reduction in peripheral T-cell proliferative responses, a decrease in pro-inflammatory cytokine secretion as well as a preferential inhibition of Th17-mediated neuroinflammation. In vitro analyses revealed that Adi-IL-10-MSCs inhibited the phenotypic maturation, cytokine production and antigen presenting capacity of bone marrow-derived myeloid dendritic cells, suggesting that the mechanism of action may involve an indirect effect on pathogenic T-cells via the modulation of antigen presenting cell function. Collectively, these results suggest that early intervention with gene modified Adi-MSCs may be beneficial for the treatment of autoimmune diseases such as MS.

Characterization of pathogenic human monoclonal autoantibodies against GM-CSF

The origin of pathogenic autoantibodies remains unknown. Idiopathic pulmonary alveolar proteinosis is caused by autoantibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF). We generated 19 monoclonal autoantibodies against GM-CSF from six patients with idiopathic pulmonary alveolar proteinosis. The autoantibodies used multiple V genes, excluding preferred V-gene use as an etiology, and targeted at least four nonoverlapping epitopes on GM-CSF, suggesting that GM-CSF is driving the autoantibodies and not a B-cell epitope on a pathogen cross-reacting with GM-CSF. The number of somatic mutations in the autoantibodies suggests that the memory B cells have been helped by T cells and re-entered germinal centers. All autoantibodies neutralized GM-CSF bioactivity, with general correlations to affinity and off-rate. The binding of certain autoantibodies was changed by point mutations in GM-CSF that reduced binding to the GM-CSF receptor. Those monoclonal autoantibodies that potently neutralize GM-CSF may be useful in treating inflammatory disease, such as rheumatoid arthritis and multiple sclerosis, cancer, and pain.

Adaptive immune responses in CNS autoimmune disease: mechanisms and therapeutic opportunities

The processes underlying autoimmune CNS inflammation are complex, but key roles for autoimmune lymphocytes seem inevitable, based on clinical investigations in multiple sclerosis (MS) and related diseases such as neuromyelitis optica, together with the known pathogenic activity of T cells in experimental autoimmune encephalomyelitis (EAE) models. Despite intense investigation, the details of etiopathology in these diseases have been elusive. Here we describe recent advances in the rodent models that begin to allow a map of pathogenic and protective immunity to be drawn. This map might illuminate previous successful and unsuccessful therapeutic strategies targeting particular pathways, whilst also providing better opportunities for the future, leading to tailored intervention based on understanding the quality of each individual's autoimmune response.

Role of Th17 cells in the pathogenesis of CNS inflammatory demyelination

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS). The etiology of MS is not well understood, but it is believed that myelin-specific CD4(+) T cells play a central role in initiating and orchestrating CNS inflammation. In this scenario, CD4(+) T cells, activated in the periphery, infiltrate the CNS, where, by secreting cytokines and chemokines, they start an inflammatory cascade. Given the central role of CD4(+) T cells in CNS autoimmunity, they have been studied extensively, principally by using experimental autoimmune encephalomyelitis (EAE), an animal model of MS. In the late 1980s, CD4(+) T cells, based on their cytokine production, were divided into two helper lineages, Th1 and Th2 cells. It was postulated that Th1 cells, which produce IFN-γ, mediate inflammation of the CNS in MS/EAE, while Th2 cells, which produce IL-4, have a beneficial effect in disease, because of their antagonistic effect on Th1 cells. The Th1/Th2 paradigm remained the prevailing view of MS/EAE pathogenesis until 2005, when a new lineage, Th17, was discovered. In a relatively short period of time it became apparent that Th17 cells, named after their hallmark cytokine, IL-17A, play a crucial role in many inflammatory diseases, including EAE, and likely in MS as well. The Th17 paradigm developed rapidly, initiating the debate of whether Th1 cells contribute to EAE/MS pathogenesis at all, or if they might even have a protective role due to their antagonistic effects on Th17 cells. Numerous findings support the view that Th17 cells play an essential role in autoimmune CNS inflammation, perhaps mainly in the initial phases of disease. Th1 cells likely contribute to pathogenesis, with their role possibly more pronounced later in disease. Hence, the current view on the role of Th cells in MS/EAE pathogenesis can be called the Th17/Th1 paradigm. It is certain that Th17 cells will continue to be the focus of intense investigation aimed at elucidating the pathogenesis of CNS autoimmunity.

Lymphocytes with cytotoxic activity induce rapid microtubule axonal destabilization independently and before signs of neuronal death

MS (multiple sclerosis) is the most prevalent autoimmune disease of the CNS (central nervous system) historically characterized as an inflammatory and demyelinating disease. More recently, extensive neuronal pathology has lead to its classification as a neurodegenerative disease as well. While the immune system initiates the autoimmune response it remains unclear how it orchestrates neuronal damage. In our previous studies, using in vitro cultured embryonic neurons, we demonstrated that MBP (myelin basic protein)-specific encephalitogenic CD4 T-cells induce early neuronal damage. In an extension of those studies, here we show that polarized CD4 Th1 and Th17 cells as wells as CD8 T-cells and NK (natural killer) cells induce microtubule destabilization within neurites in a contact-independent manner. Owing to the cytotoxic potential of these immune cells, we isolated the luminal components of lytic granules and determined that they were sufficient to drive microtubule destabilization. Since lytic granules contain cytolytic proteins, we determined that the induction of microtubule destabilization occurred prior to signs of apoptosis. Furthermore, we determined that microtubule destabilization was largely restricted to axons, sparing dendrites. This study demonstrated that lymphocytes with cytolytic activity have the capacity to directly drive MAD (microtubule axonal destabilization) in a bystander manner that is independent of neuronal death.

The kinase PKCα selectively upregulates interleukin-17A during Th17 cell immune responses

Transforming growth-factor β (TGFβ) has been implicated in T helper 17 (Th17) cell biology and in triggering expression of interleukin-17A (IL-17A), which is a key Th17 cell cytokine. Deregulated TGFβ receptor (TGFβR) signaling has been implicated in Th17-cell-mediated autoimmune pathogenesis. Nevertheless, the full molecular mechanisms involved in the activation of the TGFβR pathway in driving IL-17A expression remain unknown. Here, we identified protein kinase C α (PKCα) as a signaling intermediate specific to the Th17 cell subset in the activation of TGFβRI. We have shown that PKCα physically interacts and functionally cooperates with TGFβRI to promote robust SMAD2-3 activation. Furthermore, PKCα-deficient (Prkca^−/−) cells demonstrated a defect in SMAD-dependent IL-2 suppression, as well as decreased STAT3 DNA binding within the Il17a promoter. Consistently, Prkca^−/− cells failed to mount appropriate IL-17A, but not IL-17F, responses in vitro and were resistant to induction of Th17-cell-dependent experimental autoimmune encephalomyelitis in vivo.

Cytokine control of inflammation and repair in the pathology of multiple sclerosis

Cytokines are secreted signaling proteins that play an essential role in propagating and regulating immune responses during experimental autoimmune encephalomyelitis (EAE), the mouse model of the neurodegenerative, autoimmune disease multiple sclerosis (MS). EAE pathology is driven by a myelin-specific T cell response that is activated in the periphery and mediates the destruction of myelin upon T cell infiltration into the central nervous system (CNS). Cytokines provide cell signals both in the immune and CNS compartment, but interestingly, some have detrimental effects in the immune compartment while having beneficial effects in the CNS compartment. The complex nature of these signals will be reviewed.

GM-CSF promotes inflammatory dendritic cell formation but does not contribute to disease progression in experimental autoimmune myocarditis

BACKGROUND

Granulocyte macrophage-colony stimulating factor (GM-CSF) is critically required for the induction of experimental autoimmune myocarditis (EAM), a model of post-inflammatory dilated cardiomyopathy. Its specific role in the progression of myocarditis into end stage heart failure is not known.

METHODS AND RESULTS

BALB/c mice were immunized with myosin peptide and complete Freund's adjuvant at days 0 and 7. Heart-infiltrating inflammatory CD133(+) progenitors were isolated from inflamed hearts at the peak of inflammation (day 21). In the presence of GM-CSF, inflammatory CD133(+) progenitors up-regulated integrin, alpha X (CD11c), class II major histocompatibility complex, CD80 and CD86 co-stimulatory molecules reflecting an inflammatory dendritic cell (DC) phenotype. Inflammatory DCs stimulated antigen-specific CD4(+) T cell proliferation and induced myocarditis after myosin peptide loading and adoptive transfer in healthy mice. Moreover, GM-CSF treatment of mice after the peak of disease, between days 21 and 29 of EAM, transiently increased accumulation of inflammatory DCs in the myocardium. Importantly, bone marrow-derived CD11b(+) monocytes, rather than inflammatory CD133(+) progenitors represent the dominant cellular source of heart-infiltrating inflammatory DCs in EAM. In contrast, GM-CSF treatment neither affected numbers of heart-infiltrating CD45(+) and CD3(+) T cells nor the development of post-inflammatory fibrosis.

CONCLUSIONS

GM-CSF treatment promotes formation of inflammatory DCs in EAM. In contrast to the active roles of GM-CSF and DCs in EAM induction, GM-CSF-induced inflammatory DCs neither prevent resolution of active inflammation, nor contribute to post-inflammatory cardiac remodelling. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Cardiac Pathways of Differentiation, Metabolism and Contraction.

Mechanisms regulating regional localization of inflammation during CNS autoimmunity

Multiple sclerosis (MS) is a disease of the central nervous system (CNS) characterized by inflammatory, demyelinating lesions localized in the brain and spinal cord. Experimental autoimmune encephalomyelitis (EAE) is an animal model of MS that is induced by activating myelin-specific T cells and exhibits immune cell infiltrates in the CNS similar to those seen in MS. Both MS and EAE exhibit disease heterogeneity, reflecting variations in clinical course and localization of lesions within the CNS. Collectively, the differences seen in MS and EAE suggest that the brain and spinal cord function as unique microenvironments that respond differently to infiltrating immune cells. This review addresses the roles of the cytokines interferon-γ and interleukin-17 in determining the localization of inflammation to the brain or spinal cord in EAE.

Distinct immunomodulatory and migratory mechanisms underpin the therapeutic potential of human mesenchymal stem cells in autoimmune demyelination

Mesenchymal stem cells (MSCs) are efficacious in a variety of intractable diseases. While bone marrow (BM)-derived MSCs (BM-MSCs) have been widely investigated, MSCs from other tissue sources have also been shown to be effective in several autoimmune and inflammatory disorders. In the present study, we simultaneously assessed the therapeutic efficacy of human BM-MSCs, as well as MSCs isolated from adipose tissue (Ad-MSCs) and umbilical cord Wharton's jelly (UC-MSCs), in experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis (MS). Prior to in vivo experiments, we characterized the phenotype and function of all three MSC types. We show that BM-MSCs were more efficient at suppressing the in vitro proliferation of mitogen or antigen-stimulated T-cell responses compared to Ad-MSCs and UC-MSCs. Notably BM-MSCs induced the differential expression of cytokines from normal and stimulated T-cells. Paradoxically, intravenous transplantation of BM-MSCs into C57Bl/6 mice with chronic progressive EAE had a negligible effect on the disease course, even when multiple MSC injections were administered over a number of time points. In contrast, Ad-MSCs had the most significant impact on clinical and pathological disease outcomes in chronic progressive and relapsing-remitting EAE models. In vivo tracking studies revealed that Ad-MSCs were able to migrate to the central nervous system (CNS), a property that most likely correlated with their broader expression of homing molecules, while BM-MSCs were not detected in this anatomic region. Collectively, this comparative investigation demonstrates that transplanted Ad-MSCs play a significant role in tissue repair processes by virtue of their ability to suppress inflammation coupled with their enhanced ability to home to the injured CNS. Given the access and relatively ease for harvesting adipose tissue, these data further implicate Ad-MSCs as a cell therapeutic that may be used to treat MS patients.

Induction and molecular signature of pathogenic TH17 cells

Interleukin 17 (IL-17)-producing helper T cells (T(H)17 cells) are often present at the sites of tissue inflammation in autoimmune diseases, which has led to the conclusion that T(H)17 cells are main drivers of autoimmune tissue injury. However, not all T(H)17 cells are pathogenic; in fact, T(H)17 cells generated with transforming growth factor-β1 (TGF-β1) and IL-6 produce IL-17 but do not readily induce autoimmune disease without further exposure to IL-23. Here we found that the production of TGF-β3 by developing T(H)17 cells was dependent on IL-23, which together with IL-6 induced very pathogenic T(H)17 cells. Moreover, TGF-β3-induced T(H)17 cells were functionally and molecularly distinct from TGF-β1-induced T(H)17 cells and had a molecular signature that defined pathogenic effector T(H)17 cells in autoimmune disease.

Cytokine-neuroantigen fusion proteins as a new class of tolerogenic, therapeutic vaccines for treatment of inflammatory demyelinating disease in rodent models of multiple sclerosis

Myelin-specific induction of tolerance represents a promising means to modify the course of autoimmune inflammatory demyelinating diseases such as multiple sclerosis (MS). Our laboratory has focused on a novel preclinical strategy for the induction of tolerance to the major encephalitogenic epitopes of myelin that cause experimental autoimmune encephalomyelitis (EAE) in rats and mice. This novel approach is based on the use of cytokine-NAg (neuroantigen) fusion proteins comprised of the native cytokine fused either with or without a linker to a NAg domain. Several single-chain cytokine-NAg fusion proteins were tested including GMCSF-NAg, IFNbeta-NAg, NAgIL16, and IL2-NAg. These cytokine-NAg vaccines were tolerogenic, therapeutic vaccines that had tolerogenic activity when given as pre-treatments before encephalitogenic immunization and also were effective as therapeutic interventions during the effector phase of EAE. The rank order of inhibitory activity was as follows: GMCSF-NAg, IFNbeta-NAg > NAgIL16 > IL2-NAg > MCSF-NAg, IL4-NAg, IL-13-NAg, IL1RA-NAg, and NAg. Several cytokine-NAg fusion proteins exhibited antigen-targeting activity. High affinity binding of the cytokine domain to specific cytokine receptors on particular subsets of APC resulted in the concentrated uptake of the NAg domain by those APC which in turn facilitated the enhanced processing and presentation of the NAg domain on cell surface MHC class II glycoproteins. For most cytokine-NAg vaccines, the covalent linkage of the cytokine domain and NAg domain was required for inhibition of EAE, thereby indicating that antigenic targeting of the NAg domain to APC was also required in vivo for tolerogenic activity. Overall, these studies introduced a new concept of cytokine-NAg fusion proteins as a means to induce tolerance and to inhibit the effector phase of autoimmune disease. The approach has broad application for suppressive vaccination as a therapy for autoimmune diseases such as MS.

Cutting edge: suppression of GM-CSF expression in murine and human T cells by IL-27

GM-CSF is a potent proinflammatory cytokine that plays a pathogenic role in the CNS inflammatory disease experimental autoimmune encephalomyelitis. As IL-27 alleviates experimental autoimmune encephalomyelitis, we hypothesized that IL-27 suppresses GM-CSF expression by T cells. We found that IL-27 suppressed GM-CSF expression in CD4+ and CD8+ T cells in splenocyte and purified T cell cultures. IL-27 suppressed GM-CSF in Th1, but not Th17, cells. IL-27 also suppressed GM-CSF expression by human T cells in nonpolarized and Th1- but not Th17-polarized PBMC cultures. In vivo, IL-27p28 deficiency resulted in increased GM-CSF expression by CNS-infiltrating T cells during Toxoplasma gondii infection. Although in vitro suppression of GM-CSF by IL-27 was independent of IL-2 suppression, IL-10 upregulation, or SOCS3 signaling, we observed that IL-27-driven suppression of GM-CSF was STAT1 dependent. Our findings demonstrate that IL-27 is a robust negative regulator of GM-CSF expression in T cells, which likely inhibits T cell pathogenicity in CNS inflammation.

Limiting multiple sclerosis related axonopathy by blocking Nogo receptor and CRMP-2 phosphorylation

Multiple sclerosis involves demyelination and axonal degeneration of the central nervous system. The molecular mechanisms of axonal degeneration are relatively unexplored in both multiple sclerosis and its mouse model, experimental autoimmune encephalomyelitis. We previously reported that targeting the axonal growth inhibitor, Nogo-A, may protect against neurodegeneration in experimental autoimmune encephalomyelitis; however, the mechanism by which this occurs is unclear. We now show that the collapsin response mediator protein 2 (CRMP-2), an important tubulin-associated protein that regulates axonal growth, is phosphorylated and hence inhibited during the progression of experimental autoimmune encephalomyelitis in degenerating axons. The phosphorylated form of CRMP-2 (pThr555CRMP-2) is localized to spinal cord neurons and axons in chronic-active multiple sclerosis lesions. Specifically, pThr555CRMP-2 is implicated to be Nogo-66 receptor 1 (NgR1)-dependent, since myelin oligodendrocyte glycoprotein (MOG)(35-55)-induced NgR1 knock-out (ngr1(-)(/)(-)) mice display a reduced experimental autoimmune encephalomyelitis disease progression, without a deregulation of ngr1(-)(/)(-) MOG(35-55)-reactive lymphocytes and monocytes. The limitation of axonal degeneration/loss in experimental autoimmune encephalomyelitis-induced ngr1(-)(/)(-) mice is associated with lower levels of pThr555CRMP-2 in the spinal cord and optic nerve during experimental autoimmune encephalomyelitis. Furthermore, transduction of retinal ganglion cells with an adeno-associated viral vector encoding a site-specific mutant T555ACRMP-2 construct, limits optic nerve axonal degeneration occurring at peak stage of experimental autoimmune encephalomyelitis. Therapeutic administration of the anti-Nogo(623-640) antibody during the course of experimental autoimmune encephalomyelitis, associated with an improved clinical outcome, is demonstrated to abrogate the protein levels of pThr555CRMP-2 in the spinal cord and improve pathological outcome. We conclude that phosphorylation of CRMP-2 may be downstream of NgR1 activation and play a role in axonal degeneration in experimental autoimmune encephalomyelitis and multiple sclerosis. Blockade of Nogo-A/NgR1 interaction may serve as a viable therapeutic target in multiple sclerosis.

Comparative study on the therapeutic potential of neurally differentiated stem cells in a mouse model of multiple sclerosis

BACKGROUND

Transplantation of neural stem cells (NSCs) is a promising novel approach to the treatment of neuroinflammatory diseases such as multiple sclerosis (MS). NSCs can be derived from primary central nervous system (CNS) tissue or obtained by neural differentiation of embryonic stem (ES) cells, the latter having the advantage of readily providing an unlimited number of cells for therapeutic purposes. Using a mouse model of MS, we evaluated the therapeutic potential of NSCs derived from ES cells by two different neural differentiation protocols that utilized adherent culture conditions and compared their effect to primary NSCs derived from the subventricular zone (SVZ).

METHODOLOGY/PRINCIPAL FINDINGS

The proliferation and secretion of pro-inflammatory cytokines by antigen-stimulated splenocytes was reduced in the presence of SVZ-NSCs, while ES cell-derived NSCs exerted differential immunosuppressive effects. Surprisingly, intravenously injected NSCs displayed no significant therapeutic impact on clinical and pathological disease outcomes in mice with experimental autoimmune encephalomyelitis (EAE) induced by recombinant myelin oligodendrocyte glycoprotein, independent of the cell source. Studies tracking the biodistribution of transplanted ES cell-derived NSCs revealed that these cells were unable to traffic to the CNS or peripheral lymphoid tissues, consistent with the lack of cell surface homing molecules. Attenuation of peripheral immune responses could only be achieved through multiple high doses of NSCs administered intraperitoneally, which led to some neuroprotective effects within the CNS.

CONCLUSION/SIGNIFICANCE

Systemic transplantation of these NSCs does not have a major influence on the clinical course of rMOG-induced EAE. Improving the efficiency at which NSCs home to inflammatory sites may enhance their therapeutic potential in this model of CNS autoimmunity.

Adjuvant immunotherapy of experimental autoimmune encephalomyelitis: immature myeloid cells expressing CXCL10 and CXCL16 attract CXCR3+CXCR6+ and myelin-specific T cells to the draining lymph nodes rather than the central nervous system

CFA is a strong adjuvant capable of stimulating cellular immune responses. Paradoxically, adjuvant immunotherapy by prior exposure to CFA or live mycobacteria suppresses the severity of experimental autoimmune encephalomyelitis (EAE) and spontaneous diabetes in rodents. In this study, we investigated immune responses during adjuvant immunotherapy of EAE. Induction of EAE in CFA-pretreated mice resulted in a rapid influx into the draining lymph nodes (dLNs) of large numbers of CD11b(+)Gr-1(+) myeloid cells, consisting of immature cells with ring-shaped nuclei, macrophages, and neutrophils. Concurrently, a population of mycobacteria-specific IFN-γ-producing T cells appeared in the dLNs. Immature myeloid cells in dLNs expressed the chemokines CXCL10 and CXCL16 in an IFN-γ-dependent manner. Subsequently, CD4(+) T cells coexpressing the cognate chemokine receptors CXCR3 and CXCR6 and myelin oligodendrocyte glycoprotein (MOG)-specific CD4(+) T cells accumulated within the chemokine-expressing dLNs, rather than within the CNS. Migration of CD4(+) T cells toward dLN cells was abolished by depleting the CD11b(+) cells and was also mediated by the CD11b(+) cells alone. In addition to altering the distribution of MOG-specific T cells, adjuvant treatment suppressed development of MOG-specific IL-17. Thus, adjuvant immunotherapy of EAE requires IFN-γ, which suppresses development of the Th17 response, and diverts autoreactive T cells away from the CNS toward immature myeloid cells expressing CXCL10 and CXCL16 in the lymph nodes.

Identification of a second mimicry epitope from Acanthamoeba castellanii that induces CNS autoimmunity by generating cross-reactive T cells for MBP 89-101 in SJL mice

We had previously reported that Acanthamoeba castellanii (ACA) contains a mimicry epitope for proteolipid protein 139-151 capable of inducing central nervous system (CNS) autoimmunity in SJL/J mice. We now present evidence that ACA also contains a mimicry epitope for myelin basic protein (MBP) 89-101, a derivative from amoebic nicotinamide adenine dinucleotide dehydrogenase subunit 2 (NAD). The epitope, NAD 108-120, contains a discontinuous stretch of six amino acids in the core region (VVFFKNIILIGFL) sharing 46% identity with MBP 89-101 (VHFFKNIVTPRTP; identical residues are underlined). SJL mice immunized with NAD 108-120 develop encephalomyelitis similar to the disease induced by the cognate peptide. We demonstrate that NAD 108-120 induces T cells that cross-react with MBP 89-101; the antigen-sensitized T cells, which produce predominantly T helper (T(h)) 1 and T(h)17 cytokines, transfer disease in naive SJL recipients reminiscent of the disease induced with MBP 89-101. This is the first report to demonstrate that a solitary microbe can induce CNS autoimmunity by generating cross-reactive T cells for multiple myelin antigens.

Regulation of systemic and local myeloid cell subpopulations by bone marrow cell-derived granulocyte-macrophage colony-stimulating factor in experimental inflammatory arthritis

OBJECTIVE

Even though there are clinical trials assessing granulocyte-macrophage colony-stimulating factor (GM-CSF) blockade in rheumatoid arthritis (RA), questions remain as to how GM-CSF acts as a proinflammatory cytokine. The aims of this study on the regulation of arthritis progression by GM-CSF were to determine the source of the GM-CSF, whether there are systemic effects, the changes in synovial tissue leukocyte populations, and the arthritis model dependence on GM-CSF.

METHODS

Bone marrow chimeras were used to determine the source of GM-CSF required for the development of collagen-induced arthritis (CIA). The K/BxN serum-transfer model of arthritis was tested in GM-CSF(-/-) mice and using anti-GM-CSF monoclonal antibodies. Cell populations from arthritic mice were assessed by differential staining and flow cytometry.

RESULTS

In the CIA model, GM-CSF produced by bone marrow-derived cells was required for arthritis development. GM-CSF blockade, while ameliorating the development of CIA, was found to have systemic effects, limiting the increase in circulating Ly-6C(high) monocytes and neutrophils. GM-CSF blockade led to fewer synovial macrophages (both Ly-6C(high) and Ly-6C(low)), neutrophils, and lymphocytes. In the absence of GM-CSF, K/BxN serum-transfer arthritis initially developed normally; however, the numbers of Ly-6C(high) monocytes and synovial macrophages (both Ly-6C(high) and Ly-6C(low)) were again reduced, along with the peak disease severity and maintenance.

CONCLUSION

GM-CSF is a key player in two arthritis models, participating in interactions between hemopoietic cells, both locally and systemically, to control myeloid cell numbers as well as presumably to "activate" them. These results could be useful for the analysis of current clinical trials targeting GM-CSF in patients with RA.

Batf3-dependent CD11b(low/-) peripheral dendritic cells are GM-CSF-independent and are not required for Th cell priming after subcutaneous immunization

Dendritic cells (DCs) subsets differ in precursor cell of origin, functional properties, requirements for growth factors, and dependence on transcription factors. Lymphoid-tissue resident CD8α(+) conventional DCs (cDCs) and CD11b(low/-)CD103(+) non-lymphoid DCs are developmentally related, each being dependent on FMS-like tyrosine kinase 3 ligand (Flt3L), and requiring the transcription factors Batf3, Irf8, and Id2 for development. It was recently suggested that granulocyte/macrophage colony stimulating factor (GM-CSF) was required for the development of dermal CD11b(low/-)Langerin(+)CD103(+) DCs, and that this dermal DC subset was required for priming autoreactive T cells in experimental autoimmune encephalitis (EAE). Here, we compared development of peripheral tissue DCs and susceptibility to EAE in GM-CSF receptor deficient (Csf2rb(-/-)) and Batf3(-/-) mice. We find that Batf3-dependent dermal CD11b(low/-)Langerin(+) DCs do develop in Csf2rb(-/-) mice, but that they express reduced, but not absent, levels of CD103. Further, Batf3(-/-) mice lacking all peripheral CD11b(low/-) DCs show robust Th cell priming after subcutaneous immunization and are susceptible to EAE. Our results suggest that defective T effector priming and resistance to EAE exhibited by Csf2rb(-/-) mice does not result from the absence of dermal CD11b(low/-)Langerin(+)CD103(+) DCs.

T(H)17 cytokines in autoimmune neuro-inflammation

It has been firmly established that IL-23 polarized T(H)17 cells are potent effectors in the pathogenesis of experimental autoimmune encephalitomyelitis (EAE). However, the relative importance of these cells in comparison to other encephalitogenic T(H) subsets, and the mechanisms that they employ to effect inflammatory demyelination, are topics of continuing investigation. Interestingly, deletion of individual 'T(H)17 cytokines', such as IL-17A, IL-17F, IL-22 and IL-21, does not phenocopy the complete EAE-resistance of IL-23-deficient mice. The instability of T(H)17 cells in vivo introduces an additional layer of complexity to their role in the context of relapsing or chronic disease. Recent data indicate that IL-23 drives the production of myeloid activating factors, such as GM-CSF, by myelin-reactive T cells and facilitates their accumulation in the CNS. This review discusses the above issues in relation to the use of T(H)17 cells and related factors as potential therapeutic targets and biomarkers in CNS autoimmune diseases such as multiple sclerosis (MS).

T(H)17 cytokines in autoimmune neuro-inflammation

It has been firmly established that IL-23 polarized T(H)17 cells are potent effectors in the pathogenesis of experimental autoimmune encephalitomyelitis (EAE). However, the relative importance of these cells in comparison to other encephalitogenic T(H) subsets, and the mechanisms that they employ to effect inflammatory demyelination, are topics of continuing investigation. Interestingly, deletion of individual 'T(H)17 cytokines', such as IL-17A, IL-17F, IL-22 and IL-21, does not phenocopy the complete EAE-resistance of IL-23-deficient mice. The instability of T(H)17 cells in vivo introduces an additional layer of complexity to their role in the context of relapsing or chronic disease. Recent data indicate that IL-23 drives the production of myeloid activating factors, such as GM-CSF, by myelin-reactive T cells and facilitates their accumulation in the CNS. This review discusses the above issues in relation to the use of T(H)17 cells and related factors as potential therapeutic targets and biomarkers in CNS autoimmune diseases such as multiple sclerosis (MS).

Protection against Nippostrongylus brasiliensis infection in mice is independent of GM-CSF

Granulocyte macrophage-colony stimulating factor (GM-CSF) is a cytokine with the capacity to promote inflammation in a wide variety of infectious and inflammatory diseases. These conditions include allergic airway inflammation, which is driven by T-helper 2 (Th2) cells. Because of the importance of Th2 cells in parasite infections, we have investigated the role of GM-CSF in mice infected with the nematode Nippostrongylus brasiliensis. The effect of primary and secondary infection was investigated in mice lacking functional genes for GM-CSF (CSF2 genes) (ΔGM-CSF mice), and in mice lacking the cytokine receptor common β chain (Δβ mice), the latter being unable to signal in response to GM-CSF and interleukin (IL)-5. ΔGM-CSF mice showed no significant defect in parasite immunity, measured by larval numbers in the lungs, worm numbers in the intestine or egg numbers in the faeces, in either primary or secondary infection. By contrast, the Δβ mice showed increased parasite burden, with higher numbers of lung larvae after secondary infection and higher numbers of intestinal worms and faecal eggs after both primary and secondary infection. Unexpectedly, there were increased numbers of circulating eosinophils in the ΔGM-CSF mice, associated with significantly reduced larval numbers in the lungs. These results indicate that GM-CSF is redundant in protection against N. brasiliensis infection, and that the increased susceptibility of Δβ mice to infection is likely to be attributed to the lack of IL-5 signalling in these mice. The results suggest that clinical use of agents that neutralise GM-CSF may not be associated with increased risk of parasite infection.

Augmented expression of glia maturation factor in Alzheimer's disease

We have previously demonstrated that glia maturation factor (GMF), a brain-specific protein, isolated, sequenced, and cloned in our laboratory, is a prominent mediator of inflammation in the CNS leading to the death of neurons. In the present study, we demonstrate, for the first time, a significant upregulation of the GMF protein in various regions of Alzheimer's disease (AD) brains compared with age-matched non-demented (ND) control brains. We analyzed AD and ND brain samples by quantitative enzyme-linked immunosorbent assay (ELISA) using a combination of highly specific monoclonal and polyclonal anti-GMF antibodies developed and characterized in our laboratory. For the comparison between ND controls and AD cases, we examined brain tissue from 12 ad cases (ages ranging from 78-92 years) and eight age-matched ND controls (ages ranging from 76-88 years). We observed a significant increase in GMF concentration in entorhinal cortex, parietal cortex, frontal cortex, occipital cortex, perirhinal cortex, and temporal cortex of AD patients. Our results clearly demonstrate that the GMF protein levels are significantly higher in all AD-affected brain regions than in ND controls. The immunohistochemistry analysis revealed co-localization of GMF with amyloid plaques (AP) and neurofibrillary tangles (NFTs) in AD brains. Our results imply that under conditions of neurodegeneration the expression of GMF is significantly upregulated.

Macrophage diversity in cardiac inflammation: a review

Cardiac inflammatory disease represents a significant public health burden, and interesting questions of immunopathologic science and clinical inquiry. Novel insights into the diverse programming and functions within the macrophage lineages in recent years have yielded a view of these cells as dynamic effectors and regulators of immunity, host defense, and inflammatory disease. In this review, we examine and discuss recent investigations into the complex participation of mononuclear phagocytic cells in the pathology of animal models of myocarditis.

RORγt drives production of the cytokine GM-CSF in helper T cells, which is essential for the effector phase of autoimmune neuroinflammation

Although the role of the T(H)1 and T(H)17 subsets of helper T cells as disease mediators in autoimmune neuroinflammation remains a subject of some debate, none of their signature cytokines are essential for disease development. Here we report that interleukin 23 (IL-23) and the transcription factor RORγt drove expression of the cytokine GM-CSF in helper T cells, whereas IL-12, interferon-γ (IFN-γ) and IL-27 acted as negative regulators. Autoreactive helper T cells specifically lacking GM-CSF failed to initiate neuroinflammation despite expression of IL-17A or IFN-γ, whereas GM-CSF secretion by Ifng(-/-)Il17a(-/-) helper T cells was sufficient to induce experimental autoimmune encephalomyelitis (EAE). During the disease effector phase, GM-CSF sustained neuroinflammation via myeloid cells that infiltrated the central nervous system. Thus, in contrast to all other known helper T cell-derived cytokines, GM-CSF serves a nonredundant function in the initiation of autoimmune inflammation regardless of helper T cell polarization.

The encephalitogenicity of T(H)17 cells is dependent on IL-1- and IL-23-induced production of the cytokine GM-CSF

Interleukin 17 (IL-17)-producing helper T cells (T(H)17 cells) require exposure to IL-23 to become encephalitogenic, but the mechanism by which IL-23 promotes their pathogenicity is not known. Here we found that IL-23 induced production of the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) in T(H)17 cells and that GM-CSF had an essential role in their encephalitogenicity. Our findings identify a chief mechanism that underlies the important role of IL-23 in autoimmune diseases. IL-23 induced a positive feedback loop whereby GM-CSF secreted by T(H)17 cells stimulated the production of IL-23 by antigen-presenting cells. Such cross-regulation of IL-23 and GM-CSF explains the similar pattern of resistance to autoimmunity when either of the two cytokines is absent and identifies T(H)17 cells as a crucial source of GM-CSF in autoimmune inflammation.

Cytokines and effector T cell subsets causing autoimmune CNS disease

Although experimental autoimmune encephalomyelitis (EAE) is limited in its potency to reproduce the entirety of clinical and histopathologic features of multiple sclerosis (MS), this model has been successfully used to prove that MS like autoimmunity in the CNS is orchestrated by autoantigen specific T cells. EAE was also very useful to refute the idea that IFN-γ producing T helper type 1 (Th1) cells were the sole players within the pathogenic T cell response. Rather, "new" T cell lineages such as IL-17 producing Th17 cells or IL-9 producing Th9 cells have been first discovered in the context of EAE. Here, we will summarize new concepts of early and late T cell plasticity and the cytokine network that shapes T helper cell responses and lesion development in CNS specific autoimmunity.

In vitro affinity maturation of HuCAL antibodies: complementarity determining region exchange and RapMAT technology

Monoclonal antibodies gain ever-increasing importance in the treatment of human diseases across a broad range of indications. Diverse technologies currently exist, which are used to generate recombinant therapeutic antibodies that are basically indistinguishable from naturally occurring human immunoglobulins. We describe how human combinatorial antibody libraries are used together with unique optimization techniques to produce such therapeutically relevant proteins, for instance in the areas of oncology and inflammation.

Fate mapping of IL-17-producing T cells in inflammatory responses

We describe a reporter mouse strain designed to fate-map cells that have activated IL-17A. Here we show that T_H17 cells show distinct plasticity in different inflammatory settings. Chronic inflammatory conditions in EAE caused a switch to alternative cytokines in T_H17 cells, whereas acute cutaneous infection with Candida albicans, did not result in deviation of T_H17 to alternative cytokine production, although IL-17A production was shut off in the course of the infection. During development of EAE, IFN-γ and other pro-inflammatory cytokines in the spinal cord were produced almost exclusively by ‘ex-T_H17’ cells whose conversion was driven by IL-23. Thus, this model allows relating the actual functional fate of effector T cells to T_H17 developmental origin irrespective of IL-17 expression.

EAE mediated by a non-IFN-γ/non-IL-17 pathway

Previous studies have shown that EAE can be elicited by the adoptive transfer of either IFN-γ-producing (Th1) or IL-17-producing (Th17) myelin-specific CD4(+) T-cell lines. Paradoxically, mice deficient in either IFN-γ or IL-17 remain susceptible to EAE following immunization with myelin antigens in CFA. These observations raise questions about the redundancy of IFN-γ and IL-17 in autoimmune demyelinating disease mediated by a diverse, polyclonal population of autoreactive T cells. In this study, we show that an atypical form of EAE, induced in C57BL/6 mice by the adoptive transfer of IFN-γ-deficient effector T cells, required IL-17 signaling for the development of brainstem infiltrates. In contrast, classical EAE, characterized by predominant spinal cord inflammation, occurred in the combined absence of IFN-γ and IL-17 signaling, but was dependent on GM-CSF and CXCR2. Our findings contribute to a growing body of data, indicating that individual cytokines vary in their importance across different models of CNS autoimmunity.

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.

MicroRNA-155 promotes autoimmune inflammation by enhancing inflammatory T cell development

Mammalian noncoding microRNAs (miRNAs) are a class of gene regulators that have been linked to immune system function. Here, we have investigated the role of miR-155 during an autoimmune inflammatory disease. Consistent with a positive role for miR-155 in mediating inflammatory responses, Mir155(-/-) mice were highly resistant to experimental autoimmune encephalomyelitis (EAE). miR-155 functions in the hematopoietic compartment to promote the development of inflammatory T cells including the T helper 17 (Th17) cell and Th1 cell subsets. Furthermore, the major contribution of miR-155 to EAE was CD4(+) T cell intrinsic, whereas miR-155 was also required for optimum dendritic cell production of cytokines that promoted Th17 cell formation. Our study shows that one aspect of miR-155 function is the promotion of T cell-dependent tissue inflammation, suggesting that miR-155 might be a promising therapeutic target for the treatment of autoimmune disorders.