Antibodies to myelin components are routinely detected in multiple sclerosis patients. However, their presence in some control subjects has made it difficult to determine their contribution to disease pathogenesis. Immunization of C57BL͞6 mice with either rat or human myelin oligodendrocyte glycoprotein (MOG) leads to experimental autoimmune encephalomyelitis (EAE) and comparable titers of anti-MOG antibodies as detected by ELISA. However, only immunization with human (but not rat) MOG results in a B cell-dependent EAE. In this study, we demonstrate that these pathogenic and nonpathogenic anti-MOG antibodies have a consistent array of differences in their recognition of antigenic determinants and biological effects. Specifically, substituting proline at position 42 with serine in human MOG (as in rat MOG) eliminates the B cell requirement for EAE. All MOG proteins analyzed induced high titers of anti-MOG (tested by ELISA), but only antisera from mice immunized with unmodified human MOG were encephalitogenic in primed B cell-deficient mice. Nonpathogenic IgGs bound recombinant mouse MOG and deglycosylated MOG in myelin (tested by Western blot), but only pathogenic IgGs bound glycosylated MOG. Only purified IgG to human MOG bound to live rodent oligodendrocytes in culture and, after cross-linking, induced repartitioning of MOG into lipid rafts, followed by dramatic changes in cell morphology. The data provide a strong link between in vivo and in vitro observations regarding demyelinating disease, further indicate a biochemical mechanism for anti-MOGinduced demyelination, and suggest in vitro tools for determining autoimmune antibody pathogenicity in multiple sclerosis patients. multiple sclerosis ͉ experimental autoimmune encephalomyelitis ͉ lipid rafts ͉ B cell-deficient mice ͉ encephalitogenicity M ultiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system (CNS) in which both T cells and antibodies against myelin antigens are routinely detected (1, 2). B cell responses in MS pathogenesis are implicated by the presence of Ig deposits and myelin debris in demyelinating lesions (3-8), and the observation that plasma exchange dramatically reduces clinical disease in a subset of patients (9). Of particular interest to the present study, antibodies to myelin oligodendrocyte glycoprotein (MOG) are detected in the sera and plaques of MS patients (10), and thus are possible predictors of disease progression (11). However, because some control subjects can also harbor anti-myelin antibodies (1, 2, 12), their contribution to MS pathogenesis has been controversial and difficult to identify in individual patients. Further complicating the issue, MS may be several diseases of differing etiologies (5), whereby anti-myelin antibodies may be pathogenic in some forms of MS but merely a reflection of tissue damage in others. Thus, an understanding of whether anti-myelin antibodies are in fact pathogenic, and if so, by what mechanisms they operate, could provide important information for novel diagnosti...

C57BL/6 mice immunized with the extracellular Ig-like domain of rat myelin oligodendrocyte glycoprotein (MOG) developed experimental autoimmune encephalomyelitis (EAE) resembling that induced by rodent MOG 35-55 in its B cell independence and predominantly mononuclear CNS infiltrate. In contrast, human MOG protein-induced EAE was B cell dependent with polymorphonuclear leukocytes. Human MOG differs from rat MOG at several residues, including a proline for serine substitution at position 42. Human MOG 35-55 was only weakly encephalitogenic, and a proline substitution in rat MOG at position 42 severely attenuated its encephalitogenicity. However, human MOG 35-55 was immunogenic, inducing proliferation and IFN-γ and IL-3 to human, but not rodent MOG 35-55. The B cell dependence of EAE induced by human MOG protein was not due to a requirement for Ag presentation by B cells, because spleen cells from B cell-deficient mice processed and presented human and rat MOG proteins to T cells. The different pathogenic mechanisms of human and rat MOG proteins might result from different Abs induced by these proteins. However, rat and human MOG proteins induced Abs to mouse MOG that were equivalent in titer and IgG subclass. These data demonstrate that EAE can be induced in C57BL/6 mice by two mechanisms, depending on the nature of the immunogen: an encephalitogenic T cell response to rat MOG or rodent MOG 35-55, or an encephalitogenic B cell response to epitopes on human MOG protein that most likely cross-react with mouse determinants.

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Background: It is widely acknowledged that oral administration of many antigens induces antigen–specific systemic tolerance. In this study we tested the hypothesis that oral administration of a low dose of dinitrochlorobenzene (DNCB) could induce local tolerance in the absence of systemic tolerance. We also hypothesized that the mucosal adjuvant cholera toxin (CT), which prevents the induction of local and systemic tolerance to coadministered antigens, would be unable to break an established tolerance to an orally administered antigen. Methods: Tolerance was induced in BALB/c mice by oral administration of either a high (5.0 mg) or a low (0.05 mg) oral dose of the contact–sensitizing agent DNCB. This pretreatment was followed by parenteral or oral administration of dinitrophenyl (DNP)–carrier protein conjugates. Results: As anticipated, the high DNCB dose induced systemic tolerance, as evidenced by depressed delayed type hypersensitivity responses to DNCB and reduced serum IgG anti–DNP responses. Oral pretreatment with the high dose of DNCB also induced local tolerance, as indicated by reduced fecal IgA and IgG anti–DNP responses. Conversely, oral pretreatment with the low dose of DNCB induced only local, not systemic tolerance. In addition, CT was incapable of breaking the preexisting tolerance induced by oral DNCB pretreatment. Conclusion: This study and others support the notion that the mucosal arm of the immune system is more sensitive to the induction of tolerance than the systemic arm, and that CT may not be an effective adjuvant for antigens to which the mucosal immune system has previously been exposed.