[Mechanism of intercellular contacts and the change in cell membranes during differentiation].

The recent data concerning the molecular mechanism of cell-cell recognition are discussed. The specificity of recognition may be based on the interaction of the carbohydrate-containing molecule and the carbohydrate-binding protein. The carbohydrate-binding proteins are the cell surface lectins and glycosyltransferases. It is supposed that these proteins may recognize the fine structure of the suitable carbohydrate chains, and not only the terminal sugar residues. Cell differentiation and the arrangement of specific cell-cell contacts is accompanied by the accumulation of specific proteins and carbohydrate-containing molecules in the plasma membrane. It is the accumulation and interaction of these molecules that may cause the decrease in the mobility of different cell surface molecules, including Concanavalin A (ConA) receptors, in the plane of the membrane. Possibly this is why the differentiating cells lose their ability to agglutinate in the presence of ConA. Therefore it is suggested that cell agglutination by ConA is a test revealing the characteristic change in the cell membrane during differentiation, i.e. a decrease in the mobility of the cell surface molecules in the plane of the membrane.