Lassmann, Hans

Stimulation of remyelination in multiple sclerosis lesions may be one possible therapeutic approach. However, since the pathology and pathogenesis of multiple sclerosis may be heterogeneous, it is important to analyze in what patients and at what stages of the disease such a therapy can be reasonable and feasible. Spontaneous remyelination is pronounced in some MS patients. The extent of remyelination correlates well with the presence of oligodendrocytes in the lesions. Yet, the source and origin of the remyelinating cells is still unclear. These may be derived from either undifferentiated progenitor cells or, in part from mature oligodendrocytes, that have escaped destruction during lesional activity. Complete remyelination of plaques is possible, leading to the formation of 'shadow plaques'. No reliable data are available at present on the frequency of remyelination in different forms of MS. However, most studies agree that remyelination is especially prominent at the early stages of the disease, whereas it is sparse after several years of disease duration. In addition, very little remyelination is found in cases of primary progressive MS.

Abstract The susceptibility to multiple sclerosis (MS), a chronic neurological autoimmune disease that primarily targets CNS myelin, has long been associated with HLA class-II genes. Although several other HLA and non-HLA disease predisposing alleles have been identified, alleles of the HLA-DR15 haplotype (DRB1*1501, DRB5*0101, and DQB1*0602) remain the strongest susceptibility factor. Many studies have suggested that the HLA-DRB1*1501 allele determines MS-associated susceptibility. However, due to strong linkage disequilibrium within the HLA class II region, it has been difficult to unequivocally determine the relative roles of the DRB1*1501 and DQB1*0602 products. In this study we use HLA class-II transgenic mice to illuminate the relative contributions of the DRB1*1501 and DQB1*0602 alleles or their combination to susceptibility toward a new “humanized” MS-like disease induced by myelin-associated oligodendrocytic basic protein (MOBP). Although many immunological studies have focused overwhelmingly on the role of the HLA-DRB1*1501 product in MS, we show that HLA-DRB1*1501 transgenics are refractory to MOBP disease induction, whereas the HLA-DQB1*0602 transgenics are susceptible via T cells reactive against MOBP15–36 and MOBP55–77 encephalitogenic epitopes. Although both transgenics react against these epitopes, the MOBP15–36- and MOBP55–77-reactive T cells are of Th2-type in HLA-DRB1*1501 transgenics and are pathogenic Th1/Th17 cells in the HLA-DQB1*0602 transgenic mice. This new humanized model of MS further implicates autoimmunity against MOBP in MS pathogenesis, provides the first evidence of pathogenic HLA-DQ-associated anti-myelin autoimmunity, and is the first to offer a rationale for HLA-DQB1*0602 association with MS. These findings have important bearing on the candidacy of the DQB1*0602 allele as a genetic risk factor for MS.

Controversy exists regarding the pathogenic or predictive role of anti-myelin oligodendrocyte glycoprotein (MOG) antibodies in patients with multiple sclerosis (MS). Four immunopathological patterns (IP) have been recognized in early active MS lesions, suggesting heterogeneous pathogenic mechanisms. Whether MOG antibodies contribute to this pathological heterogeneity and potentially serve as biomarkers to identify specific pathological patterns is unknown. Here we report the frequencies of antibodies to human recombinant MOG (identified by Western blot and enzymelinked immunoabsorbent assay (ELISA)) in patients with pathologically proven demyelinating disease, and investigate whether antibody status is associated with clinical course, HLA-DR2 genotype, IP or treatment response to plasmapheresis. The biopsy cohort consisted of 72 patients: 12 pattern I, 43 pattern II and 17 pattern III. No association was found between MOG antibody status and conversion to clinically definite MS, DR-2 status, IP or response to plasmapheresis. There was poor agreement between Western blot and ELISA (kappa=0.07 for MOG IgM). Fluctuations in antibody seropositivity were seen for 3/4 patients tested serially by Western blot. This study does not support a pathologic pattern-specific role for MOG-antibodies. Variable MOG-antibody status on serial measurements, coupled with the lack of Western blot and ELISA correlations, raises concern regarding the use of MOG-antibody as an MS biomarker and underscores the need for methodological consensus.

The present review will focus on the current knowledge of the pathology of primary progressive multiple sclerosis lesions. Multiple sclerosis (MS) is an inflammatory demyelinating disease with a broad clinical variability. The main disease courses are relapsing-remitting, secondary progressive and primary progressive MS. Pathological studies examining the specific underlying pathology of a defined clinical subtype are rare. Here, we focus on the phatological characteristics of the MS lesions and summarize the current findings of the phatology of primary progressive MS with respect to inflammation, oligodendrocyte/myelin pathology, axon destruction and immunopathology of the lesions.