Expression of GM-CSF in T cells is increased in multiple sclerosis and is suppressed by IFN-β therapy (BA11P.136)

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS). Studies in animal models of MS have shown that granulocyte-macrophage colony-stimulating factor (GM-CSF) produced by T cells is necessary for development of autoimmune CNS inflammation. This suggests that GM-CSF may have a pathogenic role in MS as well. The objective of this study was to characterize GM-CSF production by T cells of MS patients, and to determine the effect of interferon-beta (IFN-β) therapy on its production. GM-CSF production by peripheral blood (PB) T cells and the effects of IFN-β were characterized in samples of untreated and IFN-β-treated MS patients vs. healthy subjects. GM-CSF production by T cells in MS brain lesions was analyzed by immunofluorescence. Untreated MS patients had significantly greater numbers of GM-CSF + CD4 + and CD8 + T cells in PB compared to healthy controls and IFN-β-treated MS patients. IFN-β strongly suppressed GM-CSF production by T cells in vitro . A number of CD4 + and CD8 + T cells in MS brain lesions expressed GM-CSF. Elevated GM-CSF production by PB T cells in MS is indicative of aberrant hyperactivity of the immune system. Given its essential role in animal models, abundant GM-CSF production at the sites of CNS inflammation suggests that GM-CSF contributes to MS pathogenesis. Our findings also reveal a potential mechanism of IFN-β therapy, namely suppression of GM-CSF production.