Identification of IgE-positive cells and mast cells in frozen sections of multiple sclerosis brains.

There is evidence that nervous system mast cells may be involved in the pathogenesis of experimental demyelinating diseases, and that their involvement may be mediated by IgE. In order to examine the possible relevance of these observations to human demyelinating diseases, we have histologically and immunocytochemically examined multiple sclerosis (MS) and control brains for the presence of mast cells and IgE. Using a highly specific antiserum, we found IgE-positive cells in MS brains, but not in controls. IgE-positive cells could be detected in all regions of MS lesions, but were far more frequent in areas of active infiltration. Immunopositive staining was only observed when sections were pretreated with a methanolic peroxide solution, suggesting that the IgE was cytoplasmic. Positive cells typically exhibited plasma cell morphology. Mast cells were identified using chloroacetate esterase (CAE) staining, and we were able to confirm previous reports of an increased association of mast cells with MS lesions. Mast cells were seen in 7/14 MS brains compared with 1/8 controls. They were most commonly observed in demyelinated areas, but were also seen in association with infiltrate. Mast cells and IgE-positive cells were also observed in areas of perivascular infiltration in other inflammatory central nervous system diseases (subacute sclerosing panencephalitis, herpes encephalitis). Mast cells may represent a route for infiltrating cells to enter the brain in inflammatory disorders.