Cytochemical markers for mononuclear phagocytes as demonstrated in reactive microglia and globoid cells

Several cytochemical characteristics of mononuclear phagocytes which are used as identifying markers were studied in reactive microglia from traumatically damaged brain tissue of guinea pigs and humans as well as in globoid cells from a child with familial globoid cell leukodystrophy (Krabbes' disease). The following cytochemical methods were used: acid phosphatase, lysozyme, peroxidase, alpha-naphthyl acetate esterase, alpha-naphthyl butyrate esterase, adenosine triphosphatase, and the periodic acid-Schiff reaction (PAS reaction). Distinct activity of almost all enzymes and the PAS reaction were demonstrable in reactive microglia and globoid cells. Peroxidase however could not be demonstrated in globoid cells. The similarity of the cytochemical characteristics for mononuclear phagocytes, reactive microglia, and globoid cells tends to indicate a common identity for these cell types. The lack of peroxidase in globoid cells may be due to a final maturation and differentiation after the monocyte stage.