Requirement for Α-l-fucose on the Macrophage Membrane Receptor for Mif

alpha-L-fucose abolishes the activity of guinea pig migration inhibitory factor (MIF) on the macrophages. Other sugars such as alpha-D-glucose, beta-D-galactose, alpha-L-rhamnose, methyl-alpha-D-mannoside, and N-acetyl-beta-D-glucosamine had no effect. Theabolition of MIF activity by alpha-L-fucose was reversible. When macrophages were incubated with alpha-L-fucosidase, a glycosidase which splits terminal alpha-L-fucose from oligosaccharides, the macrophages no longer responded to MIF. On the other hand, MIF incubated with alpha-L-fucosidase was still active. These experiments strongly suggest that alpha-L-fucose comprises an essential part of a macrophage membrane receptor for MIF.