CELL BEHAVIOUR AND MOLECULAR MECHANISMS OF CELL‐CELL ADHESION

Summary 1. At the behavioural level, cell adhesion is generally non‐specific. The search for molecular mechanisms of adhesion should be conducted on this basis. 2. Cells in general, be they from slime moulds or vertebrate epithelia, possess multiple molecular adhesive mechanisms. In epithelial cells this is shown by the number of their different ultrastructurally recognizable intercellular junctions. Elucidation of the structure and composition of such intercellular junctions will make a valuable contribution to the understanding of cell adhesion. 3. The measurement of cell adhesion is fraught with difficulties. Commonly used assays by aggregation cannot give a true representation of the normal adhesive interactions of cells in tissues, and the results they yield must be interpreted with caution. This is because it takes dissociated tissue cells up to 24 h to develop their full adhesiveness after making initial contact. 4. Cell‐cell adhesion probably depends largely upon the interaction of complementary molecules on adjacent cell surfaces. Glycoproteins seem the most likely candidates but, as yet, there is no compelling evidence in any individual case and mechanisms of cell adhesion still remain obscure.