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Several findings indicate that infectious events play a role in the pathogenesis of multiple sclerosis (MS). At the same time, T-cell autoimmunity to myelin antigens is widely believed to be crucial to the development of MS lesions. Several mechanisms have been put forward to explain the presumed link between microbial infections and myelin-directed autoimmunity. These include molecular mimicry, bystander activation including epitope spreading and superantigenic activation of T cells. Evidence that either one of these mechanisms actually occurs in MS patients, however, is still weak. Also, none of the above mechanisms explain why MS is unique to humans. We propose an alternative link between microbial infection and myelin autoimmunity, which we refer to as 'mistaken self'. In this mechanism, peripheral microbial infections of lymphoid cells prime the human T-cell repertoire not only to microbial antigens but also to the stress protein alpha B-crystallin that is expressed de novo in infected lymphoid cells. Subsequently, stress-induced accumulation of this self antigen in oligodendocytes/myelin can provoke pro-inflammatory responses as the recruited memory T-cell repertoire then mistakes the self protein for a microbial antigen. In this paper we review the currently available evidence that 'mistaken self' centering on alpha B-crystallin represents a powerful source of anti-myelin autoimmunity in a way that is unique to humans. Copyright (C) 2000 Elsevier Science B.V. Chemicals/CAS: CrystallinsChemicals/CAS: Crystallins

Human T-cell responses to the stress protein alpha B-crystallin in multiple sclerosis (MS)-affected brain samples are dominant when compared to other myelin antigens. The establishment of the apparent autoimmune repertoire against this antigen has been suggested to involve cross-priming during viral infection. Yet, another possibility would be that determinant spreading during ocular inflammation could generate a response to alpha B-crystallin, since it is also a major component of the eye. In this study, we compared serum IgG, IgA and IgM repertoires against a range of eye lens-derived ocular antigens using sera from healthy control subjects and MS patients with or without uveitis. This comparison revealed that among ocular antigens, alpha B-crystallin is the dominant target antigen for serum autoantibodies in both MS patients and healthy controls. Uveitis generally did not affect the antibody reactivity profile. These data provide further support for the notion that a normal adult human immune system is selectively reactive to alpha B-crystallin and they indicate that this responsiveness is unlikely to result from determinant spreading following ocular inflammation. © 2006 Edward Arnold (Publishers) Ltd. Chemicals / CAS: immunoglobulin G, 97794-27-9; immunoglobulin M, 9007-85-6; alpha-Crystallin B Chain; Autoantibodies; Autoantigens; Eye Proteins

We present the first comparative analysis of serum immunoglobulinG reactivity profiles against the full spectrum of human myelin-associated proteins in multiple sclerosis patients and healthy control subjects. In both groups, serum antibodies display a consistent and prominent reaction to αB-crystallin (CRYAB) versus other myelin proteins. As an apparently major target for the adaptive immune system in humans, CRYAB selectively accumulates in oligodendrocytes, but not in astrocytes, or axons in so-called preactive multiple sclerosis lesions. These are clusters of activated HLA-DR-expressing microglia in myelinated normal-appearing white matter with no obvious leukocyte infiltration. They are found in most multiple sclerosis patients at all stages of disease. In these lesion areas, CRYAB in oligodendrocytes may come directly in contact with activated HLA-DR microglia. We demonstrate that CRYAB activates innate responses bymicroglia by stimulating the secretion of leukocyte-recruiting factors, including tumor necrosis factor, interleukin 17, CCL5, and CCL1, and immune-regulatory cytokines such as interleukin 10, transforming growth factor-β, and interleukin 13. Together, these data suggest that CRYAB accumulation in preactive lesions may be part of a reversible reparative local response that involves both oligodendrocytes and microglia. At the same time, however, accumulated CRYAB may represent a major target for adaptive immune responses that could contribute to progression of preactive lesions to a stage of demyelination. © 2010 by the American Association of Neuropathologists, Inc.

Alpha B-crystallin (αB) is a small heat shock protein that is strongly up-regulated in multiple sclerosis (MS) brain tissue, and can induce strong T cell responses. Assessing a potential encephalitogenic function for αB protein in MS and experimental autoimmune encephalomyelitis (EAE) has been challenging due to its ubiquitous expression that likely maintains central and peripheral tolerance to this protein in mice. To address this issue, we obtained αB-knockout (αB-KO) mice in H-2b background that lack immune tolerance to αB protein, and thus are capable of developing αB-specific T cells that could be tested for encephalitogenic activity after transfer into αB-expressing wild type (WT) mice. We found that T cell lines from spleens of αB protein-immunized αB-KO mice proliferated strongly to αB protein itself, and the majority of T cells were CD4+ and capable of secreting pro-inflammatory Th1 cytokines upon restimulation. However, transfer of such αB-reactive T cells back into WT recipients was not sufficient to induce EAE, compared to the transfer of mouse MOG-35-55 peptide-reactive T cells from the same donors that induced severe EAE in recipients. Moreover, αB-specific T cells failed to augment severity of actively induced EAE in WT mice that were expressing high levels of αB message in the CNS at the time of transfer. These results suggest that αB-specific T cells are immunocompetent but not encephalitogenic in 129SvEv mice, and that immune tolerance may not be the main factor that limits the encephalitogenic potential of αB. © 2006 Elsevier B.V. All rights reserved. Chemicals / CAS: crystallin, 11046-99-4; encephalitogenic protein, 29705-91-7; alpha-Crystallin B Chain; Glycoproteins; myelin oligodendrocyte glycoprotein (35-55); Peptide Fragments