Adhesion : from the concept of affinity to thermodynamic models

This second lecture explores in greater depth the central theme of intercellular adhesion, which raises four major questions: the evolutionary origin of multicellularity, the emergence during embryonic development of the shape of tissues and organs, the chemical origin of intercellular molecular couplings, and the physical origin of cohesive forces within a tissue. The historical investigation of the concept of adhesion begins with the notions of affinity and specificity discussed by Johannes Holtfreter and Paul Weiss respectively. Experiments on cell dissociation, aggregation and sorting in sponges and then amphibians saw the transition from the qualitative notion of affinity to the quantitative, thermodynamic concept of adhesion. Steinberg's hypothesis of differential adhesion is discussed in detail, between the fundamental reservations expressed by A. Harris and the apparent experimental validation following the discovery of adhesion molecules.