IMMUNOCYTOCHEMICAL CHARACTERIZATION OF A NEW MARKER OF FIBROUS AND REACTIVE ASTROCYTES

A specific monoclonal antiserum (Mab 6.17) inducing a strong immunosta ining of the neuromuscular junction has been used to detect the possib le occurrence of the corresponding antigen throughout the intact or le sioned central nervous system of adult rats. In intact animals, 6.17-i mmunolabeling was essentially detected in astrocyte-like structures lo cated in white matter fasciculi of the brain, such as the optic tract, corpus callosum, fornix, and in the white matter of the spinal cord. The astroglial nature of such 6.17-immunolabeled profiles was verified by performing double or triple immunofluorescent labeling with Mab 6. 17 and with specific antisera against astrocytic markers, such as S100 protein, glial fibrillary acidic protein and vimentin. In the white m atter, all the structures reactive to Mab 6.17 were also reactive to a ntibodies against S100 protein, glial fibrillary acidic protein and vi mentin. On the other hand, astrocytes of the grey matter that were imm unoreactive to S100 and glial fibrillary acidic protein but negative t o vimentin, were devoid of 6.17-immunoreactivity. After lesions includ ing stab wound through the diencephalon or transection of the spinal c ord, a marked increase of 6.17-immunostaining was noted in the regions surrounding the lesions. In these regions, 6.17-immunolabeling was as sociated with S100-, GFAP- and vimentin-positive astrocytes constituti ng the glial scar. The ultrastructural localization of 6.17-immunoreac tivity indicated that, similar to glial fibrillary acidic protein and vimentin, the recognized antigen was mainly associated with gliofilame nts. These observations indicate that, in the central nervous system o f adult rats, Mab 6.17 recognizes a molecule associated with gliofilam ents, which is essentially associated to reactive astrocytes expressin g high levels of vimentin.