Flow microfluorometry detects IgM autoantibody to oligodendrocytes in multiple sclerosis

Freshly isolated canine oligodendrocytes were reacted by indirect membrane immunofluorescence with 44 sera from patients with multiple sclerosis (MS). Using analysis by flow microfluorometry (FMF), we found significant IgM antibody binding to the surfaces of oligodendrocytes in the MS sera. The fluorescence intensity of cell surface reactions for MS sera (F.I. > 40 = 37.2±21.34%) was significantly different ( P < 0.001) to that for 53 sera from normal subjects (10.0±8.97%), 15 sera from patients with Murray Valley encephalitis (6.18±5.3%), 22 with brain tumours (6.28±5.3%), 25 with SLE (13.42±3.04%). Cell surface binding was and 7 miscellaneous neurological disorders (6.87±3.045). Cell surface binding was restricted to oligodendrocytes and was absorbed out by oligodendrocytes but not by liver cells or kidney cells. Oligodendrocytes were identified by conventional histology, phase-contrast optics, electron microscopy (EM) and by cell surface reactions with anti-galactocerebroside, a specific immunocytological marker for oligodendrocytes. A cell sort of the single 0° FMF scatter peak followed by EM examination confirmed that the reactive cells consisted exclusively of oligodendrocytes. Viability of oligodendrocytes before and after the staining reactions, was >80% as assessed by trypan blue and fluorescein diacetate exclusion. The possibility that immune reactions mediated by the surface-reactive antibody with readily accessible cell surface autoantigens in vivo may contribute to the loss of oligodendrocytes and demyelination in MS is raised.