Evaluation of various filter membranes for Boyden-type leukocyte migration studies.

Various types and makes of membranes were assessed for suitability in Boyden-type chemotaxis studies. Pooled exudate neutrophils and macrophages from the rat were used as indicator cells. Sartorius filters were found to be superior to other cellulose ester filters both in efficiency and consistency of cell migration. Variations between and within Sartorius filter lots were small and filter inconsistency could be ruled out as a factor in day-to day variation in efficiency of cell migration. In our hands, Millipore membranes were unsatisfactory for chemotaxis studies. With the exception of the shortened incubation times, polycarbonate filters did not offer significant advantages over Sartorius filters when the vigorously responding rat exudate cells were tested. The orientation of the cellulose ester filters in the chemotaxis chambers was found to be a critical factor when the lowermost level counting method was used. The observed polarity could not readily be washed out by acid, alkali or ethanol treatment nor by boiling the filters in distilled water and remains unexplained.