In vivo analysis of glial cell phenotypes during a viral demyelinating disease in mice

The in vivo distribution of the type 1 and type 2 astrocytes in the spinal cord somehow differs from that described in the rat optic nerve Miller et al., 1985) . GFAP+ only type 1 astrocytes were scattered in grey matter as well as in deep regions of the white matter. The white matter appeared to be divided in two zones with respect to the GFAP and 04 staining. A number of radially oriented 04 + GFAP+ astrocytes were detected in the peripheral regions of the white matter. By analogy with the optic nerve Miller et al., 1985) , we had expected that the radially oriented astrocytes forming the glial limiting membrane of the spinal cord would be type 1 astrocytes unreactive with the O4 antibody. Instead we found cell bodies, radial processes, and pial endfeet strongly 04 as well as GFAP positive. These peripheral astrocytes have also been stained with the monoclonal antibody A2B5 as well as with the antibody to the GD3 ganglioside (Hirano and Goldman, 1988) and therefore exhibit the type 2 astrocyte antigenic phenotype. However, the radial glia of the spinal cord differentiates well before myelination and in that regard must be distinguished from the type 2 astrocytes described in optic nerve (Miller et al., 1985; Liuzzi and Miller, 1987) . Except for these radially oriented astrocytes at the periphery of the white matter, the other 04+ GFAP+ cells of spinal cord fulfilled both the antigenic and positional criteria for type 2 astrocytes since they were located deeper in the white matter (Miller et al., 1985; Liuzzi and Miller, 1987) . These type 2 stellate astrocytes were more frequent in the ventral zone than the dorsal zone. Their processes were much thinner than those of the peripheral radial glia (Fig. 2 d and Fig. 4 f) .