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.