Microglia in Fetal and Adult Human Brain Can Be Distinguished from Other Mononuclear Phagocytes through Their Lack of CD163 Expression

Abstract

From the introduction: Recently, a new 130- to 140-kD glycoprotein designated as CD163 (also known as M130, p155 or haemoglobin scavenger receptor) has been described to show expression restricted to the plasma membrane of human monocytes and monocyte-derived macrophages. Expression of this protein can be markedly up-regulated by anti-inflammatory agents, but is either not influenced or reduced by pro-inflammatory factors. CD163 can be detected on tissue sections by immunohistochemistry with the antibodies GHI/6, Ber-MAC-3, Ki-M8, RM3/1 and SM4. In a follow-up to our previous works, we investigated the expression of this marker in the human brain during fetal development and in the adult, using the monoclonal antibody Ber-MAC-3 (1:20 dilution, DakoCytomation Ltd., UK, DAKO ABC-HRP method). Here, we have shown that CD163 selectively identifies a population of mononuclear phagocytes termed 'perivascular cells' intimately associated with cerebral blood vessels in the normal adult human brain. In the human fetal brain, CD163 is expressed by mononuclear phagocytes in the choroid plexus and on cells in the meningeal layers and in the subpial granular layer. However, this marker is largely absent or undetectable on parenchymal microglia, including in certain neurodegenerative disorders (Alzheimer's disease, diffuse Lewy body disease, and multiple sclerosis; data not shown).