T- and B-cell responses to myelin oligodendrocyte glycoprotein in experimental autoimmune encephalomyelitis and multiple sclerosis

IFN-beta gene deletion leads to augmented and chronic demyelinating experimental autoimmune encephalomyelitis

Since the basic mechanisms behind the beneficial effects of IFN-beta in multiple sclerosis (MS) patients are still obscure, here we have investigated the effects of IFN-beta gene disruption on the commonly used animal model for MS, experimental autoimmune encephalomyelitis (EAE). We show that IFN-beta knockout (KO) mice are more susceptible to EAE than their wild-type (wt) littermates; they develop more severe and chronic neurological symptoms with more extensive CNS inflammation and demyelination. However, there was no discrepancy observed between wt and KO mice regarding the capacity of T cells to proliferate or produce IFN-gamma in response to recall Ag. Consequently, we addressed the effect of IFN-beta on encephalitogenic T cell development and the disease initiation phase by passive transfer of autoreactive T cells from KO or wt littermates to both groups of mice. Interestingly, IFN-beta KO mice acquired a higher incidence and augmented EAE regardless of the source of T cells. This shows that the anti-inflammatory effect of endogenous IFN-beta is predominantly exerted on the effector phase of the disease. Histopathological investigations of CNS in the effector phase revealed an extensive microglia activation and TNF-alpha production in IFN-beta KO mice; this was virtually absent in wt littermates. This coincided with an increase in effector functions of T cells in IFN-beta KO mice, as measured by IFN-gamma and IL-4 production. We suggest that lack of endogenous IFN-beta in CNS leads to augmented microglia activation, resulting in a sustained inflammation, cytokine production, and tissue damage with consequent chronic neurological deficits.

Anti-myelin oligodendrocyte glycoprotein B-cell responses in multiple sclerosis

Humoral auto-immunity to the myelin oligodendrocyte glycoprotein (MOG) is likely involved in the pathogenesis of multiple sclerosis (MS). In 44 MS patients and 30 controls, Ig-producing B cells were identified by their isotype and as MOG-specific spot-forming cells (SFC). Peripheral anti-MOG antibodies were assayed in ELISA as well as anti-butyrophilin antibodies to investigate for molecular mimicry. MS patients had significantly higher levels of IgA- and MOG-SFC than controls, as well as significantly higher antibody responses to MOG and butyrophilin. These data provide added support for the implication of anti-MOG humoral immunity in the pathophysiology of MS, and suggest a balance of systemic (anti-self) and mucosal (environment-modulated) immune reactions in an attempt at regulating the pathogenic specific immune response.

Generation of antibodies specific for beta-amyloid by vaccination of patients with Alzheimer disease

To characterize antibodies produced in humans in response to Abeta42 vaccination, we carried out immunohistochemical examinations of the brains of both transgenic mice and human patients with beta-amyloid pathology. We collected sera from patients with Alzheimer disease who received a primary injection of pre-aggregated Abeta42 followed by one booster injection in a placebo-controlled study. Antibodies in immune sera recognized beta-amyloid plaques, diffuse Abeta deposits and vascular beta-amyloid in brain blood vessels. The antibodies did not cross-react with native full-length beta-amyloid precursor protein or its physiological derivatives, including soluble Abeta42. These findings indicate that vaccination of AD patients with Abeta42 induces antibodies that have a high degree of selectivity for the pathogenic target structures. Whether vaccination to produce antibodies against beta-amyloid will halt the cognitive decline in AD will depend upon clinical assessments over time.

B cells regulate autoimmunity by provision of IL-10

To assess the importance of B cell control of T cell differentiation, we analyzed the course of the T helper type 1 (T(H)1)-driven disease experimental autoimmune encephalomyelitis in mice with an altered B cell compartment. We found that recovery was dependent on the presence of autoantigen-reactive B cells. B cells from recovered mice produced interleukin 10 (IL-10) in response to autoantigen. With a bone marrow chimeric system, we generated mice in which IL-10 deficiency was restricted to B cells but not T cells. In the absence of IL-10 production by B cells, the pro-inflammatory type 1 immune response persisted and mice did not recover. These data show that B cell-derived IL-10 plays a key role in controlling autoimmunity.

Myelin oligodendrocyte gene polymorphisms and childhood multiple sclerosis

Myelin oligodendrocyte glycoprotein (MOG) is a quantitatively minor glycoprotein of the CNS localized preferentially on the outermost myelin lamellae and the oligodendrocyte plasma membrane. In several animal models, MOG displays highly immunogenic properties by inducing a severe multiple sclerosis-like disease, characterized by inflammatory demyelinating lesions. Immunologic findings implicate MOG as a target autoantigen in multiple sclerosis. We have performed a molecular study on the MOG gene by sequencing the promotor and the entire coding region, as well as the exon-intron boundaries, in 75 children with multiple sclerosis. A total of five unknown polymorphic sites in the promotor region not affecting any of the putative cis-acting transcriptional regulation motifs as well as nine additional base changes in four different exons each with similar distribution in patients and controls (n = 100) were detected. Exon 2 coding for the Ig-like domain revealed two rare heterozygous missense mutations, possibly altering favorable conformational epitopes (P43H; R66P). P43 is part of the encephalitogenic epitope MOG(35-55). A putative C1q binding site in the C"-D loop of the Ig superfamily motif encompasses R66. In conclusion, the polymorphisms observed do not provide evidence to support a significant role for MOG in multiple sclerosis susceptibility.

Pathogenesis of multiple sclerosis: an update on immunology

Multiple sclerosis is characterized by demyelination and chronic inflammation of the central nervous system. Extensive studies in the animal model experimental autoimmune encephalomyelitis have suggested that multiple sclerosis is an autoimmune disorder mediated by myelin-specific CD4 T cells secreting T helper type 1 cytokines and tumor necrosis factor alpha. This concept has been widely used to develop new experimental therapies. However, recent findings in both experimental autoimmune encephalomyelitis and multiple sclerosis question a simple CD4 T helper type 1 T cell paradigm and provide evidence for the role of various immune cells in the pathogenesis of experimental autoimmune encephalomyelitis and multiple sclerosis. In this paper we review recent progress and discuss the implications for new therapeutic strategies.