Cortical demyelination can be modeled in specific rat models of autoimmune encephalomyelitis and is major histocompatibility complex (MHC) haplotype-related.

In recent years, a number of histopathologic studies revealed the presence of cortical demyelination in multiple sclerosis (MS). The underlying mechanisms responsible for cortical demyelination are unresolved. Recently, the presence of cortical lesions in autoimmune encephalomyelitis (EAE) induced in marmosets and Lewis rats has been demonstrated. So far, it is not known whether cortical demyelinated lesions are also present in other models of EAE. In this study, we analyzed a large spectrum of different rat strains actively immunized with myelin oligodendrocyte glycoprotein (MOG), a model strongly mimicking MS for cortical demyelination. By using sets of rat strains with the constant EAE-permissive LEW nonmajor histocompatability complex (MHC) genome, but different MHC haplotypes, we demonstrated that considerable cortical demyelination was only found in LEW.1AR1 (RT1) and LEW.1W (RT1) strains. These rat strains have the isotypes and alleles RT1.BD in the MHC II region and RT1.C in the nonclassic MHC I region in common. Because cortical demyelination was most prominent in LEW.1AR1 rats, an additional strong influence is promoted by the RT1.A MHC class I allele. Demyelination was accompanied by microglia infiltration and deposition of immunoglobulins on myelin sheaths. Our study shows that extensive cortical demyelination can be reproducibly induced in certain rat strains by active immunization with MOG. Furthermore, our findings suggest that cortical demyelination in EAE depends on particular combinations of MHC I and class II isotypes and alleles. The mechanisms for this influence and any similar effects in humans will be important to define.