CD15-containing glycoconjugates in the central nervous system

CD15-containing glycoconjugates have a common trisaccharide residue, 3-fucosyl-N-acetyllactosamine, which can be recognized by a panel of monoclonal antibodies. Immunohistochemical studies revealed a widespread distribution of CD15 in several epithelial non-neural tissues as well as in the CNS. In the mature mammalian brain CD15-containing glycolipids and glycoproteins are constantly present in astrocytes, whereas oligodendrocytes and particular subpopulations of neurons are variably immunostained. CD15 immunoreactive astrocytes are spatially distributed in some brain regions, which points to specialized functions of astroglial subpopulations. The expression of CD15 follows a timely ordered pattern during the development of glial cells and neurons of certain brain areas, such as the human and rat cerebellum and the mouse visual system. During morphogenesis, CD15 may exert either growth-promoting or growth-repulsive activities to guide cell migration. In CNS lesions altered expression patterns of CD15 may occur. For example, in human gliomas the staining intensity for CD15 inversely correlates with the grade of malignancy. In degenerative brain diseases reactive astrocytes may reveal an increased labelling intensity on their cell surface as well as an abnormal cytosolic accumulation of the epitope. The functional significance of CD15 in the CNS is not exactly known yet. The carbohydrate could be involved in cellular adhesion and/or as receptor molecule in signal transduction pathways, as has recently been demonstrated for leukocyte-platelet or leukocyte-endothelial cell interactions.