Leucocyte chemotaxis: physiological considerations and abnormalities.

Expression of the inflammatory process is dependent on mobilisation of leucocytes, which require leucocyte chemotaxis. Recent technological advances have enabled extensive in vitro biological characterisation of the chemotatic stimuli (factors) and the cellular events of migration. The chemotatic stimuli include products of complement activation, fibrinolytic and kinin generating systems, collagen products as well as products of bacterial growth and products released from virus-infected tissues. Chemotatic factors are also released as a result of lymphocyte activation and phagocytosis by neutrophils. Other neutrophils products released during phagocytosis activate the complement system. A complex mechanism for limiting production or activity of chemotactic factors has been identified. These antichemotatic agents include serum and cell-derived chemotactic factor inactivators as well as specific inhibitors of leucocyte migration and complement inactivators released from neutrophils during the phagocytic process. The mechanism by which cells respond to chemotatic factors is poorly understood by cell adherence to the substratum, cell deformability, random migration, and directed migration are required. These processes are complex and require modifications of the leucocyte surface, calcium and magnesium, activation of esterases, function of contractile elements and assembly of a cytoskeleton, which is probably modulated by cyclic nucleotide metabolism.