GSLII positivity is not confined to oligodendrocytes in adult mammalian CNS

The in vivo binding pattern of the lectin Griffonia simplicifolia II (GSLII ) was evaluated in sections of adult cat optic nerve following reports that it is a marker for oligodendrocytes in adult rodent CNS and that it may al so be an oligodendroglial lineage marker. Following as closely as possible the immunocytochemical methodology employed in these reports, staining for GSLII was incorporated into sets of consecutive one micron thick sections c omprising known cell-type specific reference markers backed up by electron microscopy. With this correlative protocol both lectin positive and lectin negative cells could be reliably identified. The material examined included normal control tissue and tissue containing previously studied demyelinati ng lesions of various ages in which oligodendrocyte progenitors and precurs ors have been characterized. GSLII was found to stain not only mature oligo dendrocytes in adult cat optic nerve but also activated microglia, macropha ges, polymorphonuclear leucocytes and other haematogenous cells. Lectin pos itivity was not found in oligodendroglial precursors, endothelial cells, as trocytes or ramified microglia. This study emphasises that care needs to be taken before assigning lineage marker status to individual lectins or anti bodies.