VISUALIZATION OF A CELL-SURFACE GLYCOPROTEIN, THE RETINA COGNIN, ON EMBRYONIC-CELLS BY IMMUNO-LATEX LABELING AND SCANNING ELECTRON-MICROSCOPY

Antiserum prepared against the retina cell-aggregating glycoprotein (referred to as the retina cognin) was used for immunolabeling the antigen on the surface of chick embryo cells and its detection by scanning electron microscopy (SEM). The cognin was isolated from membranes of neural retina cells of 10-day chick embryos and was highly purified prior to its use as antigen in rabbits. Cells dissociated from embryonic neural retina and from other neural and nonneural tissues (of 10-day chick embryos) were surveyed in vitro for the presence on their surface of binding sites specific for antibodies to retina cognin. Cells were treated with the antiserum (or with control nonimmune serum), and then labeled with latex-GAR (polystyrene latex microbeads coated with goat anti-rabbit immunoglobulins) to visualize the binding sites for detection by SEM. Retina cells freshly dissociated with trypsin showed no labeling because of disruption of the antigen sites by the protease; however, if the cells were first incubated at 37°C to allow recovery of their surface and of their capacity for morphogenetic cell reaggregation, then virtually all the cells labeled with the cognin antiserum-latex GAR. Similarly tested cells from several nonneural tissues showed no labeling with this antiserum, which indicates that the retina cognin is not present on their surface. However, neural tissues (particularly optic tectum) were found to contain a proportion of cells which labeled with the retina cognin antiserum after recovery from dissociation; it remains to be determined whether the labeling of these cells is due to the presence of retina cognin, or of other surface molecules which share partial antigenic similarity with this cognin. © 1979.