A monoclonal antibody to astrocytes, subepithelial fibroblasts of small intestinal villi and interstitial cells of the myenteric plexus layer

A monoclonal antibody was developed, using cultured subepithelial fibroblasts of rat duodenal villi as the antigenic material, by in vitro immunization. Hybridomas were selected on cryosections of rat brain and small intestine using indirect immunofluorescence techniques. The monoclonal antibody, termed 8E1, was very useful to label GFAP-positive astrocytes in the adult rat brain, subepithelial fibroblasts of intestinal villi and Thuneberg's fibroblast-like interstitial cells associated with the myenteric plexus layer. These cells are known to be stellate in shape, forming a cellular network with extended cell processes that communicate via gap junctions. Immature astrocytes such as radial fibers were not immunolabeled with mAb-8E1. Immunoelectron microscopy revealed clustered gold labeling of 8E1 antigen on the intermediate filaments of cultured astrocytes and cultured subepithelial fibroblasts. This staining pattern was different from the continuous and linear gold labeling of GFAP and vimentin. MAb-8E1 did not immunoblot purified human brain GFAP nor bovine lens vimentin, and so was not neutralized by preabsorption with these molecules. Immunoblot analysis after SDS-PAGE showed that the antigen recognized by mAb-8E1 was a Mr 50K protein in the rat cerebra, and a Mr 56K protein in the cultured subepithelial fibroblasts. This study showed that astrocytes and some types of stellate cells share distinct antigenic properties in the components of their intermediate filaments.