Brain-specific hyaluronate-binding protein: an immunohistological study with monoclonal antibodies of human and bovine central nervous system

Abstract

Hyaluronectin is a protein isolated from acid extracts of human brain by affinity chromatography on immobilized hyaluronate. With polyclonal antibodies, it was immunohistologically localized in the rat at the nodes of Ranvier of central and peripheral myelinated fibers and in mesenchymal tissues. Compared to adult rat, hyaluronectin-immunoreactive material was more abundant in embryonal rat brain and mesenchyma. We report a different localization in human and bovine tissues with monoclonal antibodies reacting with human hyaluronectin by NaDodSO4/PAGE and immunoblotting but not staining rat tissues by immunohistology. In human and calf the antigen reacting with hyaluronectin monoclonal antibodies was brain specific, while several peripheral tissues were stained by the polyclonal antibodies. In human and bovine central nervous system monoclonal antibodies stained white matter and tissues formed predominantly by glial fibers (e.g., subependymal glia). In white matter hyaluronectin-immunoreactive material formed a delicate mesh surrounding individual myelinated fibers, a pattern compatible with the distribution of fine astroglial processes in this location. Gray matter did not stain with monoclonal antibodies, the granular layer of the cerebellum excepted. The findings suggest that human hyaluronectin is heterogeneous and comprises at least two fractions. The main fraction is a brain-specific protein, probably produced by white matter astrocytes. Another fraction cross-reacting with rat is more abundant in embryonal tissues, including mesenchyma and brain.