Serological determinants of fluorescent granular perithelial cells along small cerebral blood vessels in rodent

As reported previously, the perivascular cells laden with fluorescent granules (FGP cell) are situated in Virchow-Robin space and show marked uptake capacity for intraventricularly administered substances. The phagocytic FGP cells are derived developmentally from leptomeningeal cells and are recognizable in various kinds of animals, including humans. In the present paper, the FGP cells of rodents are studied by immunological techniques. It is clearly demonstrated that rat FGP cells express the antigenic determinant for Ia antibody at about 7 days after birth, and also that mouse FGP cells show a positive reaction against mouse Fc and splenic macrophage antibodies at about the same developmental stage. The specific determinants of FGP cells appear concurrently with the initiation of horseradish peroxidase uptake. On the other hand, Ia antigen is also shown in subarachnoid macrophages, but not in immature FGP cells, endothelium and pericyte. Based on these findings, it seems reasonable to consider that the FGP cells are indigenous cerebral macrophages and significant for the local immune response in a cerebral tissue. Further, in this paper, to prevent confusion of the FGP cell with the other perivascular cells, the authors propose designating the FGP cell as Mato cell.