ABSTRACT
Cell adhesion molecules allow cells to communicate with each other and with their environment. Th e interactions between cell adhesion receptors and their ligands orchestrate the assembly of cells into tissues, organs and systems, and lead to the formation of multicellular organisms. Numerous diff erent adhesive events, which may be synergistic or antagonistic, are required for organizing a tissue or a cell behavior. It is the balance between these events that determines the structure of a tissue, or whether cells stay in tight association with other cells or migrate around the body. Th ere are four main families of cell adhesion receptors: the immunoglobulin superfamily, integrins, cadherins and selectins. Th e cadherins mediate strong cellcell adhesion and play a fundamental role in morphogenesis and development, while integrins are critical to cell-matrix interactions and cell migration through the extracellular matrix. Immunoglobulin superfamily members contribute to and modulate cell-cell interactions. Th ese three large families contribute to adhesive interactions between many cell types in diff erent tissues. Th e selectins have three family members and they perform a very specifi c role critical for leukocyte migration from the vasculature.
