Use of fluorochromes in the determination of chemotaxis and haptotaxis of granulocytes by micropore filter assays.

Most conventional assays for the in vitro measurement of polymorphonuclear leukocyte (PMN) migration are modifications of the Boyden chamber technique, which requires quantification of migrated cells on micropore filters. This quantification is accompanied by several disadvantages, comprising errors in direct cell counting, low sensitivity of turbidimetric methods, the loss of marker enzymes by activation of PMNs, or the use of radioactive isotopes. We set up an improved fluorometric method to measure chemotactic and haptotactic migration of PMNs using polycarbonate filter-bearing Transwell culture plate inserts. This improved fluorometric method allows the evaluation of effects of fluorescent-dye labeling on chemotaxis and haptotaxis - defined as cell migration due to cell surface- or matrix-bound gradients of chemoattractants - by collecting data in an automated system. Results were compared with data obtained from direct microscopic cell counting in Transwell experiments as well as in conventional 48-multiwell Boyden chamber assays. Calcein-AM and BCECF-AM proved to be fluorochromes with minimal effect on both types of PMN migration. We conclude that the fluorochromes are powerful tools for the analysis of PMN migration and allow modifications of chemotaxis/haptotaxis assays for automated quantification.