A Monoclonal Antibody Defining a Carbohydrate Epitope Restricted to Glial Cells

To follow cell lineage segregation of glial cell precursors in the central and peripheral nervous systems (CNS and PNS), we made monoclonal antibodies against purified avian myelin glycoproteins and made detailed studies of antibodies reacting with cellular antigens expressed early in development. We describe here the cellular and molecular characterization of the 4B3 epitope, which is first expressed at day 2.5 in quail embryos and appears strictly specific to glial cell membranes in the PNS and CNS. We demonstrate that, not only oligodendrocytes and astrocytes but also myelinating and non-myelinating Schwann cells, satellite cells of sensory and autonomic ganglia and enteric glial cells are 4B3-positive. This epitope was identified as an N-linked carbohydrate determinant shared by several unrelated molecules, one of them already described as the SMP glycoprotein.