Novel astrocytic protein in multiple sclerosis plaques.

Monoclonal antibody J1-31 (MAb J1-31, isotype IgG 2b) was raised against crude homogenate of brain tissue from a multiple sclerosis (MS) patient (autopsy sample; Malhotra et al.: Microbios Letters 26:151-157, 1984). In human brain, MAb J1-31 recognizes an intracellular protein antigen (J1-31 antigen), which bands at approximately 30,000 daltons under reducing conditions for sodium dodecyl sulfate gel electrophoresis (Singh et al.: Bioscience Reports 6:73-79, 1986). By immunofluorescence microscopy, MAb J1-31 stains those cells that are also stained by antiserum to glial fibrillary acidic protein (GFAP), namely astrocytes, retinal Müller cells, and tanycytes in the ependyma (Predy et al.: Bioscience Reports 7:491-502, 1987). In addition, MAb J1-31 stains ciliated ependymal cells that do not express GFAP. Using a model system for gliosis (laceration-type injury of rat spinal cord), we were able to show that astrocytes responding to central nervous system injury exhibit greatly enhanced staining for J1-31 antigen (Predy et al.: Journal of Neuroscience Research 19:397-404, 1988; Predy and Malhotra: Brain Research Bulletin in press, 1989). In this article, we demonstrate that immunofluorescence staining owing to MAb J1-31 is greatly enhanced in MS plaques, as compared to adjacent "apparently normal" white matter. (This is consistent with previous results as MS plaques characteristically show an astroglial response [reactive gliosis] leading to the formation of a glial scar [McKhann: Annual Review of Neuroscience 5:219-239, 1982].) In addition, we present further evidence that J1-31 antigen is distinct from GFAP, although these two proteins may be associated spatially with one another.