The detection of a contractile apparatus in murine multinucleate giant cells.

Cinemicrographic investigations have shown multinucleate giant cells to be motile and contractile while immunofluorescent and biochemical studies have demonstrated the presence of actin-like proteins. These contractile proteins are concentrated in the centrospheric and perinuclear regions, while a more streaky distribution is present in the more peripheral parts of the polykaryon. This distribution corresponds with that of cytoplasmic filaments measuring 6-7 nm as seen by electron microscopy. The presence of similar proteins in macrophages, the precursor cells of multinucleate giant cells, indicates that these contractile proteins continue to be produced after macrophage fusion and that they are reorganised within the structural arrangements of the syncytium.