Monoclonal autoantibody SCH94.03, which promotes central nervous system remyelination, recognizes an antigen on the surface of oligodendrocytes

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Abstract
A monoclonal antibody SCH94.03, made in syngeneic mice by injection of spinal cord homogenate, promotes central nervous system remyelination when injected into SJL/J mice chronically infected with Theiler's virus. To elucidate the mechanism of antibody-mediated remyelination, SCH94.03 was investigated by immunocytochemistry, flow cytometry, immunoelectron microscopy, Western blotting, and immuno-thin layer chromatography. All cell types investigated in vitro showed strong cytoplasmic staining with a pattern resembling a cytoskeletal protein. In contrast, among the primary cultured cells studied, only oligodendrocytes showed strong surface reactivity. Other cell types, including astrocytes, microglia, Schwann cells, myoblasts, and T and B lymphocytes, were negative. Mouse and rat oligodendrocytes which showed strong surface reactivity exhibited a well-differentiated morphology, and ∼50% expressed myelin basic protein. Since oligodendrocyte progenitors were negative for surface staining, the expression of the antigens recognized by this monoclonal antibody appears to be developmentally regulated, i.e., transiently expressed on younger, terminally differentiating oligodendrocytes. Among the cell lines studied, only two rat oligodendrocyte lineage cell lines showed surface reactivity with SCH 94.03. Western blotting of secondary isolated oligodendrocytes lysates revealed reactivity with multiple protein bands of 27, 32, 50, 100, and 106 kDa, whereas there was no reactivity to lipid antigens by immuno-thin layer chromatography. These results raise the possibility that SCH94.03 recognizes a novel oligodendrocyte-specific surface antigen, and may act directly on oligodendrocytes to promote remyelination.