Purification of a monocytosis-producing activity from Listeria monocytogenes.

The monocytosis-producing activity (MPA) from Listeria monocytogenes is shown to be associated with the cell envelope. Both MPA and immunosuppressive activity were readily extracted with aqueous solvents and separated as two independent activities by gel filtration and ion-exchange chromatography. As little as 10 microng of the resulting MPA-containing fraction caused a ninefold elevation in the level of circulating monocytes. The molecular weight of the fraction was approximately 22,000, and it contained phosphorus and carbohydrate.