Expression of alpha 2-glycoprotein by glial precursor cells: an immunocytochemical study with glial cultures

Studies on the presence of the brain-specific alpha 2-glycoprotein in cultures of newborn rat brain cells revealed that a population of glial precursor cells expressed this antigen at an early stage of development. This cell population consisted of small, phase-dark cells that proliferated in culture and occupied the surface of a layer of flat epithelial-like astrocytes. The latter cell type did not react with the antibodies. The number of alpha 2-glycoprotein positive cells gradually decreased from a high concentration of 88% of the total overlying cells at 6 days of culture to 44% at 23 days. The morphological heterogeneity of the overlying cells was noticeable after 10 days in culture as clusters of cells with elaborate processes started to develop. alpha 2-Glycoprotein was found to be concentrated in these structures. A glioma cell line (C-6 glia) which represents a unique in vitro model for the glial progenitor cells, was also found to express this glycoprotein antigen.