Different concentrations of mactinin in the upper and lower compartments of chemotactic chambers define the 'checkerboard' analysis of mactinin as a chemotactic or chemokinetic factor. Results (means ± SEM) are the average number of migrated cells per oil field (counting three fields) from three filters. Significant results, compared with controls with no mactinin below the membrane and either an equivalent amount of mactinin or no mactinin above the membrane by Student's t-test, are indicated by asterisks (P < 0.05). This represents one of two experiments with similar results. Neither 10 nM intact α-actinin nor 0.1 nM GST had significant activity. NT, not tested.