The molecular and cellular biology of the chemokines

Chemokines are the largest mammalian cytokine family so far identified. They have distinct molecular structures and are unique among the cytokines in their chemotactic properties and ability to inhibit bone marrow progenitor‐cell growth. A wealth of in vitro and in vivo data show that chemokines act as directional forces in immune and inflammatory responses, working with integrins to target subsets of effector cells to specific tissue sites. The selective action of individual chemokines on leucocyte subsets makes them ideal molecules to sort, as well as direct, leucocyte traffic. In addition to their in vitro and in vivo actions on haemopoietic precursors, chemokines can also modulate angiogenesis and some may activate leucocytes. There is still much to learn about the chemokines and their intracellular pathways, and more ligands and receptors will undoubtedly be discovered. However, chemokines are aleady known to be central to the co‐ordination of leucocyte responses and represent important therapeutic targets in a number of diseases.