Macrophage populations associated with multiple sclerosis plaques

The macrophage population within and outside plaques from eight cases of multiple sclerosis (MS) (two clinically acute, four chronic progressive and two chronic non-progressive) has been examined in fresh frozen sections with a panel of monoclonal antibodies of macrophage, monocyte and MHC class II specificity. The majority of cells in active, hypercellular plaques, and at active borders, reacted with macrophage- and class II MHC-specific antibodies, and such cells extended beyond the border between demyelinated and myelinated parenchyma. In inactive plaques such cells that reacted with macrophage-specific antibodies were sparse and reacted only inconstantly with class II MHC-specific antibodies. Macrophage heterogeneity was evident in as much as one macrophage antibody, RFD7, reacted only with perivascular and not parenchymal macrophages in most plaques, but reacted with a variable proportion of parenchymal macrophages in active plaques. It is suggested that the RFD7 antibody may identify a sub-population of acute plaques, and that its use may clarify interpretation of findings related to other inflammatory cell populations by providing greater precision of classification of active plaques.