The kinetics of apoptotic fragmentation of the chromosomal DNA was determin
ed in the influenza virus-infected MDCK, HeLa and KB cells, respectively. C
omparison of these kinetics with the kinetics of virus multiplication revea
led that the multiplication of influenza virus was observed only when apopt
osis was induced after the production of progeny virus in the infected cell
s. The extent of apoptotic response was reversely correlated with the permi
ssiveness of the cells.