Two distinct adhesion mechanisms in embryonic neural retina cells. II. An immunological analysis

Antibodies were raised against neural retina cells prepared by dissociation in EGTA alone (E cells, Ca²⁺-independent aggregation), in trypsin + Ca²⁺ (TC cells, Ca²⁺-dependent aggregation), or in trypsin + EGTA (TE cells, nonadhesive). Anti-E-cell Fab selectively inhibited Ca²⁺-independent aggregation, anti-TC-cell Fab selectively inhibited Ca²⁺-dependent aggregation, and anti-TE-cell Fab inhibited neither. Fab from a fourth preparation, also raised against E cells, inhibited both Ca²⁺-independent and Ca²⁺-dependent aggregation but was separated by immunoadsorption into two fractions, one specific for each mode of aggregation. In cells which utilize both modes simultaneously (LTC cells), each was inhibited exclusively by the appropriate Fab. The immunological data presented here demonstrate the existence in the same cells of two distinct and functionally independent adhesion mechanisms, each responsible for one of the two modes of aggregation. The differing adhesive properties of retinal cells prepared by different procedures are explained by the presence, absence, or degree of activity of these two mechanisms, qualities regulated by the concentrations of trypsin and Ca²⁺ used in the tissue dissociation.