A critique of the methods used to assess leucocyte behaviour

Methods for assessing the adhesive and locomotory properties of leucocytes are reviewed critically and a suggestion made as to the best strategy for testing an unknown compound on leucocyte behaviour. In particular the distinction is made between reductionist assays, where a single property is being investigated, and realistic assays where an attempt is made to mimic the situation in vivo. The realistic assays are often difficult (or impossible) to interpret in behavioural terms, because more than one cell activity is involved, but such assays (e.g. simple Boyden chambers), used with caution, may be preferable for initial screening, If effects are obvious in an assay of this type then more complex reductionist assays, to determine the cause of the altered behaviour, can be tried. In discussing adhesion, data from a flow-chamber system is presented to show the very rapid changes in adhesiveness when cells encounter an immune complex-coated surface. A fully automated tracking system for obtaining speed and persistence parameters for neutrophils is described, and some of the problems involved in estimating these parameters are illustrated. Movement of neutrophils in collagen gels provides a more realistic model of the environment in which they must operate in vivo, and the effects of incorporating immune complexes into such gels are reported.