Abstract
The mechanism of antihamster macrophage serum (AHMS)-induced fusion of hamster macrophages was investigated using the serum alone or conjugated to ferritin or Sepharose beads. AHMS attaches to and is interiorized by hamster macrophages. When macrophages are brought into contact before AHMS bound to their surface is interiorized, fusion results. Macrophage fusion is probably the consequence of simultaneous endocytosis of particles or colloids. A similar mechanism may underlie the formation of macrophage giant cells in granulomata where closely packed macrophages attach to and interiorize the denatured materials produced in the chronically inflamed environment.