Enhanced expression of a protein antigen (J1-31 antigen, 30 kilodaltons) by reactive astrocytes in lacerated spinal cord.

A mouse monoclonal antibody (MAb J1-31, isotype IgG 2b) was raised against an autopsy sample of cerebral white matter from a multiple sclerosis (MS) patient. MAb J1-31 recognizes a protein (J1-31 antigen) in human brain which has a molecular weight of approximately 30,000 daltons (30 kD) as determined by immunoprecipitation followed by SDS-gel electrophoresis (reducing conditions) and autoradiography (Singh et al.: Biosci Rep 6:73-79, 1986). By immunofluorescence microscopy, MAb J1-31 stains glial fibrillary acidic protein (GFAP)-positive cells, namely astrocytes, of both human and rat. Yet J1-31 antigen is distinct from GFAP (Predy et al.: Biosci Rep 7:491-502, 1987). In this paper we report that greatly enhanced staining for J1-31 antigen is exhibited by reactive astrocytes which arise following CNS injury. (Laceration-type surgical lesion of the rat spinal cord served as the experimental model). Enhanced expression of J1-31 antigen reveals some new aspect of the astrocyte response to injury, involving transformation to the reactive state. Consequently, MAb J1-31 may be a useful marker for studies on reactive astrocytes.