Macrophage migration inhibition factor (MIF): reducing the variables.

Abstract While the phenomenon of macrophage migration inhibition is a useful indicator of lymphokine release, it may be caused by other substances, it is subject to considerable variability, and it may be masked by the concomitant presence of substances stimulating migration. We have investigated certain aspects of the lymphokine macrophage interaction in order to circumvent these problems. Cells from the murine macrophage cell line RAW 264-7 migrated with less variability than fresh guinea pig peritoneal macrophages and were more sensitive target cells for human macrophage migration inhibition factor (MIF). Assays were performed with serum-free and endotoxin-free medium and in all cases in the presence and absence of l -fucose. This added specificity to the assay in that biological MIF activity was invariably blocked by l -fucose whereas migration inhibition produced by antigen complexed antibody, endotoxin, and periodate was not affected by l -fucose. It was also possible to demonstrate MIF activity in mixtures of MIF and migration stimulation factor by using l -fucose. We suggest that MIF activity is determined with less variability by using a macrophage cell line as indicator cells and performing the assays in the presence and absence of l -fucose.