In vitro interaction of scrapie agent and mouse peritoneal macrophages.

Scrapie brain homogenate was mixed with mouse peritoneal macrophages in vitro. After 2 h of incubation at 37 degrees, a portion of the scrapie infectivity was associated with macrophages. In contrast, very little infectivity was associated with kidney cells that had been exposed to scrapie brain homogenate. After incubation of the scrapie brain homogenate-macrophage mixture at 4 degrees rather than 37 degrees, a reduced quantity of infectivity was associated with the macrophages. These result show that in vitro incubation, the scrapie agent was associated with macrophages, and the data suggest that phagocytic activity was involved.