An ultrastructural study of inter-specific cell fusion induced by inactivated Sendai virus.

An electron-microscopic examination was made of the process of cell fusion induced by Sendai virus inactivated by ultraviolet light. Ehrlich ascites cells, HeLa cells, rabbit macrophages, rat lymphocytes and nucleated hen erythrocytes were chosen for study because it had previously been shown that these cells could be fused together, with varying degrees of facility, to form artificial heterokaryons. Cells which had large numbers of microvilli on their surfaces fused together more readily than those which had not, but the presence of microvilli was not essential for fusion to occur. Fusion appeared in all cases to be initiated by the formation of small cytoplasmic bridges between the cells; but virus particles, although present elsewhere on the surface of the cells, were not detected at or near the cytoplasmic bridges. HeLa-hen erythrocyte heterokaryons were formed by the fusion of HeLa cells with red cell ghosts.