It was no more than 20 years ago that biologists believed that cell adhesion molecules were simply the glue of life, the stuff that served to hold cells and ligaments and everything together. Since then, however, understanding of these molecules has gone through a paradigm shift. It is now known that they play roles in just about every aspect of human biology--from the embryo, where they are crucial for tissue and organ development, to the adult, where they act as traffic signals to direct the actions of immune-system cells in wound-healing, inflammation, cancer, and even AIDS.
Today the study of cell adhesion molecules has been transformed from a backwater of biology into one of the hottest fields around. "There are probably more immunologists working on adhesive molecules," says Harvard Medical School biologist Timothy A. Springer, "than there are on T cell receptors." Springer should know. His laboratory is responsible for...