LOCALIZATION OF THE CD15 CARBOHYDRATE IN THE VERTEBRATE RETINA

The distribution of the carbohydrate epitope CD15, a putative cell adh esion molecule, was studied in adult vertebrate retinas by light-micro scopic immunohistochemistry. Except for Old World primates, in which n o immunoreactivity was detectable, all other species expressed the epi tope on retinal interneurones. Subpopulations of stratified amacrine c ells were found in all species with the exception of bats and marmoset monkeys, and bipolar cells were immunoreactive in frogs and all amnio tic animals. Ganglion cells were labelled in urodelian, in all sauromo rphian, as well as in some mammalian species. In some species, the dis tribution of immunoreactive neurones was correlated to areas of retina l specialization such as the visual streak in frogs and the dorsotempo ral field in birds. In these parts of the retina with enhanced visual acuity, more CD15 glycosylated bipolar cells were found than in other parts. Among mammals, labelled bipolar cells were found exclusively in species with cone-dominated retinas. This comparative study shows tha t CD15 expression is consistently membrane associated in morphological ly defined subsets of amacrine, bipolar, and ganglion cells throughout the vertebrate phylum. Its distribution pattern was found to depend m ore on the visual behavior of a given species (cone-dominated or rod-d ominated retina) than on phylogenetic proximity between species.