Biological and biochemical characterization of macrophage activating factor (MAF) in murine lymphocytes: role of mannopyranosyl residue of the MAF molecule in macrophage activation.

Activation of macrophages with macrophage activating factor (MAF) was evaluated by measuring the intracellular killing activity of murine macrophages against Salmonella typhimurium. Concanavalin A (Con A)-induced MAF-rich fraction was obtained by a Sephadex G-100 column, which contained molecules ranging from 25,000 to 67,000 daltons. The intracellular killing ability of mouse peritoneal macrophages against S. typhimurium was found to be increased by 0.1 M D-mannose as well as by Con A-induced MAF-rich fraction. Both 0.1 M D-mannose and MAF exhibited a similar timing pattern for macrophage activation. The same concentration of D-glucose or L-rhamnose did not change bacterial uptake and intracellular killing by macrophages. Moreover, when MAF-rich fraction was applied to a Con A-Sepharose column, a fraction that was adsorbed on Con A and eluted with 0.1 M alpha-methyl D-mannoside exhibited MAF activity. These results suggest the possibility that mannopyranosyl residues in the MAF molecules play an important role as a ligand in macrophage activation.