Assays of leukocyte locomotion and chemotaxis

This review discusses the range of methods which are currently available for measuring locomotion and chemotaxis of leukocytes in vitro, their history, and some definitions of terms. Assays of the net migration of large cell populations, such as the filter assay are the most popular and are useful for identifying chemoattractant molecules, but give no direct information about how these molecules influence the speed and direction of cell movement (chemokinesis and chemotaxis). Visual assays including measures of orientation in gradients and time-lapse filming give detailed information about cell paths and direct evidence for chemotaxis and chemokinesis. The polarization assay is a useful visual screening assay. Assays which simulate the situation in living tissues are becoming more popular and include migration through collagen or fibrin gels or through monolayers of vascular endothelium. Locomotion is a complex process, no single assay gives full information and the use of more than one assay is recommended.