Utilization of purified human monocytes in the agarose droplet assay for measuring migration inhibitory factors.

Human monocytes, highly purified by counter-current elutriation, are excellent indicator cells for evaluation of human migration inhibitory factors (MIFs). We have adapted the agarose droplet MIF assay initially developed for guinea pig peritoneal exudate cells to utilize human monocytes. The experimental variables have been evaluated and standardized to make this assay a quantitative and sensitive method for measuring MIF activity. The assay can be performed serum-free in RPMI 1640 medium without protein or hormone additives, thereby increasing the sensitivity and eliminating potential masking of MIF effects by serum components. Cryopreserved monocytes also performed well in this assay, migrating approximately the same distance per unit time and showing migration inhibition in response to inhibitory factors. This assay provides a powerful tool in evaluating MIF-like activities of various lymphokines and factors, and could be used to monitor the activity of fractions produced during the physicochemical separation of MIFs from lymphokine-containing supernatants.