Phagocytosis of myelin by microglia in vitro

AbstractPrevious experiments from this laboratory have shown that peritoneal macrophages in culture will phagocytize myelin. Myelin preopsonized with myelin antibodies is phagocytized to a much greater extent than untreated myelin, indicating that macrophages ingest myelin by an Fc receptor. The present work was undertaken to determine the characteristics of myelin phagocytosis by microglia, the resident macrophages of the central nervous system. Microglia isolated from 4–5 day primary cultures of newborn rat brains were shown to bind and phagocytize myelin labeled in the lipids by 14C‐acetate. Both binding and phagocytosis as shown by the appearance of 14C‐cholesterol ester were greatly increased if labeled myelin was preopsonized with antiserum to myelin basic protein or galactocerebroside. Both preopsonized and untreated myelin were phagocytized more actively by microglia than by peritoneal macrophages under the same culture conditions. Microglia cultured in the presence of GM‐CSF showed slightly increased cholesterol ester production from opsonized myelin, but the effect of GM‐CSF was significantly greater than myelin pretreated with control serum (34% increase) or untreated my