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Amoeboid microglial cells(AMC)in the developing brain are active macrophages.The macrophagic nature of these cells has been demonstrated by many methods,such as the localization of various hydrolytic enzymes and the presence of comple-ment type 3 surface receptors in them.More importantly is the direct visualizationof these cells engaged in the phagocytosis of degenerating cells at the ultrastruc-tural level.Further evidence of them being active macrophages is the avid inter-nalization of tracers administered by the intravenous or intraperitoneal routes indeveloping rats.The potential involvement of AMC in immune functions is sup-ported by the induced expression of major histocompatibility complex class I andII antigens on them when challenged by lipopolysaccharide or interferon-γ.Im-munosuppressive drugs,such as glucocorticoids and immune function-enhanc-ing drugs like melatonin,affect the expression of surface receptors and antigensand the release of cytokines by AMC.Recent studies in our laboratory haveshown the expression of insulin-like growth factors,endothelins,2',3'-cyclic nucle-otide 3'-phosphodiesterase,and N-methyl-D-asparate receptors.This along withthe release of chemokines,such as stromal derived factor-la and monocytechemoattractant protein-1,suggests multiple functional roles of AMC in earlybrain development.
Amoeboid microglial cells (AMC) in the developing brain are active macrophages. The macrophagic nature of these cells has been demonstrated by many methods, such as the localization of various hydrolytic enzymes and the presence of comple- ment type 3 surface receptors in them. More importantly is the direct visualization of these cells engaged in the phagocytosis of degenerating cells at the ultrastruc-tural level. Further evidence of them being active macrophages is the avid inter-nalization of tracers administered by the intravenous or intraperitoneal routes indeveloping rats. potential involvement of AMC in immune functions is sup-ported by the induced expression of major histocompatibility complex class I and II antigens on them when challenged by lipopolysaccharide or interferon-gamma. Im-munosuppressive drugs, such as glucocorticoids and immune function-enhanc-ing drugs like melatonin, affect the expression of surface receptors and antigens and the release of cytokines by AMC.Recent studies in our laboratory have show that the expression of insulin-like growth factors, endothelins, 2 ', 3'-cyclic nucleotide-3'-phosphodiesterase, and N-methyl-D-asparate receptors.This along with the release of chemokines, such as stromal derived factor-la and monocytechemoattractant protein-1, suggesting multiple functional roles of AMC in earlybrain development.