Immune promotion of central nervous system remyelination

Future directions for spinal cord injury research: recent developments and model systems contributions

The authors look forward and discuss future directions in spinal cord injury (SCI) from a perspective of biomedical, psychosocial and technologic research. This discussion is based both on recent developments from various fields of knowledge and, more specifically, on SCI Model Systems' research contributions to medical rehabilitation. Biomedical research, as described here, includes (1) the process of moving from the "bench to bedside" and harnessing knowledge from basic science to produce new clinical treatment options for SCI during the life span; (2) the rapid proliferation of clinical trials aimed at neurologic recovery; (3) the growth of new technologies to restore and improve function; and (4) the challenges of developing relevant outcome measures to evaluate efficacy and effectiveness of interventions. Recent progress in psychosocial research has contributed significantly to understanding of the many factors associated with disability during the life course, the importance of quality of life issues, and the value of activity, participation, and the environment in promoting successful rehabilitation outcomes following SCI. Technology and bioengineering advances are discussed in relation to access to high-quality technology; restoration and replacement of movement; and technology to enhance rehabilitation outcomes.

CD28 costimulatory blockade exacerbates disease severity and accelerates epitope spreading in a virus-induced autoimmune disease

Theiler's murine encephalomyelitis virus (TMEV) is a natural mouse pathogen which causes a lifelong persistent infection of the central nervous system (CNS) accompanied by T-cell-mediated myelin destruction leading to chronic, progressive hind limb paralysis. TMEV-induced demyelinating disease (TMEV-IDD) is considered to be a highly relevant animal model for the human autoimmune disease multiple sclerosis (MS), which is thought to be initiated as a secondary consequence of a virus infection. Although TMEV-IDD is initiated by virus-specific CD4(+) T cells targeting CNS-persistent virus, CD4(+) T-cell responses against self myelin protein epitopes activated via epitope spreading contribute to chronic disease pathogenesis. We thus examined the ability of antibodies directed against B7 costimulatory molecules to regulate this chronic virus-induced immunopathologic process. Contrary to previous studies showing that blockade of B7-CD28 costimulatory interactions inhibit the initiation of experimental autoimmune encephalomyelitis, treatment of SJL mice at the time of TMEV infection with murine CTLA-4 immunoglobulin or a combination of anti-B7-1 and anti-B7-2 antibodies significantly enhanced clinical disease severity. Costimulatory blockade inhibited early TMEV-specific T-cell and antibody responses critical in clearing peripheral virus infection. The inhibition of virus-specific immune responses led to significantly increased CNS viral titers resulting in increased damage to myelin-producing oligodendrocytes. Following clearance of the costimulatory antagonists, epitope spreading to myelin epitopes was accelerated as a result of the increased availability of myelin epitopes leading to a more severe chronic disease course. Our results raise concern about the potential use of B7-CD28 costimulatory blockade to treat human autoimmune diseases potentially associated with acute or persistent virus infections.

Oligodendroglial response to the immune cytokine interferon gamma

In the human demyelinating disorder multiple sclerosis, and its animal model experimental allergic encephalomyelitis, there is a breakdown of the blood-brain barrier and an infiltration of immune cells into the CNS. Infiltrating T lymphocytes and macrophages are believed to be key mediators of the disease process. Considerable circumstantial and experimental evidence has suggested that the pleiotropic cytokine interferon gamma (IFN-gamma), which is exclusively expressed by T cells and natural killer cells, is a deleterious component of the immune response in these disorders. When experimentally introduced into the CNS IFN-gamma promotes many of the pathological changes that occur in immune-mediated demyelinating disorders. In vitro, this cytokine elicits a number of effects on oligodendrocytes, including cell death. The harmful actions of IFN-gamma on CNS myelin are likely mediated through direct effects on the myelinating cells, as well as through the activation of macrophages and microglia. In this review we summarize relevant studies concerning the action of IFN-gamma in demyelinating disorders and discuss possible mechanisms for the observed effects.

The controversy surrounding the pathogenesis of the multiple sclerosis lesion

The main issues in multiple sclerosis research revolve around four fundamental questions. (1) What initiates the disease-that is, autoimmune T cells, a virus, or a toxin? (2) Is the inflammatory response primary to the development of demyelination, or is it a secondary response to injury? (3) Is the oligodendrocyte, the myelin-producing cell, the primary target? (4) How can myelin repair be promoted? This review focuses on the controversies revolving around these important questions. Although many investigators believe that T-cell receptors on CD4+ cells interact with myelin antigens to initiate an inflammatory cascade that leads to myelin destruction, others maintain that a viral agent may have a direct or indirect role in the pathogenesis of multiple sclerosis. The concept that the immune system contributes to the tissue destruction in multiple sclerosis is generally accepted; however, the debate about cause versus consequence of the pathologic process remains unresolved, as does the identification of the initial event or focus of the damage. Electron microscopic studies have disclosed evidence of remyelination (albeit often incomplete) in lesions of multiple sclerosis. Enhanced understanding of the factors limiting remyelination could help formulate strategies to promote repair. By innovative experimental design and application of available molecular techniques, the answers to these questions may provide insights on how to prevent or treat multiple sclerosis.

Distinct patterns of multiple sclerosis pathology indicates heterogeneity on pathogenesis

Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system. The hallmark of its pathology is the demyelinated plaque with reactive glial scar formation. However, a detailed analysis of the patterns of demyelination, oligodendroglia cell pathology and the reaction of other tissue components suggests that the pathogenesis of myelin destruction in this disease may be heterogeneous. In this review we present a new classification scheme of lesional activity on the basis of the molecular composition of myelin degradation products in macrophages. When these criteria are used, different patterns of demyelination can be distinguished, including demyelination with relative preservation of oligodendrocytes, myelin destruction with concomitant and complete destruction of oligodendrocytes or primary destruction or disturbance of myelinating cells with secondary demyelination. Furthermore, in some cases a primary selective demyelination may be followed by a secondary oligodendrocyte loss in the established lesions. Finally, some extraordinarily severe conditions may result in destructive lesions with loss of myelin, oligodendrocytes, axons and astrocytes. This heterogeneity of plaque pathology is discussed in the context of recent experimental models of inflammatory demyelination, which show that different immunological pathways may lead to the formation of demyelinated plaques that reveal the diverse structural aspects described above. Our data indicate, that the demyelinated plaques of multiple sclerosis may reflect a common pathological end point of a variety of different immunological mechanisms of myelin destruction in this disease.