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

The pathogenesis of multiple sclerosis (MS) is believed to involve an autoimmune component directed against the myelin sheath. One potential target Ag for such autoimmune attack is the myelin-oligodendrocyte glycoprotein (MOG) because an anti-MOG mAb has profound influence on the course of experimental autoimmune encephalomyelitis, which to some extent represents an experimental model of MS. Using single cell assays, we have evaluated T and B cell reactivities to MOG in MS patients and controls. T cell reactivity was estimated by counting the number of cells that secreted IFN-gamma in response to MOG, whereas B cell reactivity was estimated by enumerating cells secreting antibodies that bound to MOG. MOG reactive T cells were detected in the peripheral blood of the majority of the 16 MS patients examined (mean 1/7299 mononuclear cells), but infrequently and at lower numbers in samples from neurologic controls. MOG-reactive T cells were more frequent among MS patients' cerebrospinal fluid (CSF) mononuclear cells (mean 1/450 cells). The T cell response to MOG was evidently MHC class II restricted, because Fab fragments of a rabbit polyclonal anti HLA-DR antibodies abrogated the Ag-induced increase in number of cells that secreted IFN-gamma, as analyzed on CSF and PBMC from three patients with MS. Anti-MOG IgG antibody-secreting cells were detected in blood in 8 of 16 MS patients (mean 1/25,641 cells), but they were also strongly accumulated in CSF, being detected in 8 of 10 MS patients examined (mean 1/265 cells), while rarely found in controls. The findings imply that MOG may represent a pathogenetically important target Ag in MS.