Hematogenous origin of brain macrophages

Abstract
Del Rio-Hortega believed that phagocytic cells in the CNS arise from microglia; however, recent autoradiographic studies have suggested a hematogenous origin for brain macrophages. To clarify this issue, we studied a young man with acute lymphoblastic leukemia and a peripheral white blood cell count of 22/mm3 who had an embolic brain infarct 2 weeks before he died. Macrophages were scarce within the lesion, suggesting that the principal phagocytic cell is hematogenous.