This has raised the question of whether mouse cells could transmit viruses to human patients.
We were looking at mouse cells that had been infected with a monkey virus.
Human embryonic cells are expected to behave in the same general way as mouse cells, although few studies of them have been done.
Since mouse embryonic cells already can, he said, it is theoretically possible.
To confirm that the mouse cells were cleared of prions, the researchers stopped treatment to see what would happen.
In fact, no one has been able to do this even with mouse cells.
He put the gene into mouse cells of a type that require certain immune system hormones to survive.
One mouse cell lived and it was making thrombopoietin.
These arise when, for example, the hybrids are made in part from mouse cells and raised inside mice.
Cultures of mouse cells are used in the tests.