11.   Blocking it from performing its task might kill cancer cells, but it could also harm healthy cells, causing serious side effects.

12.   A key advantage of angiogenesis-blocking drugs is their much lower toxicity than conventional cancer drugs that attack tumor cells but also unavoidably kill normal cells.

13.   A lamp, no bigger than a household toaster, has been used to kill cancer cells successfully.

14.   A second defense system, consisting of blood cells programmed to kill other cells infected by the virus, may be needed.

15.   According to one theory, prions clump together and block molecular traffic, killing the cells and leaving spaces where once there were nerves.

16.   After HIV infection, it can drop drastically as HIV kills the cells.

17.   But it is meant to trigger the body to produce a certain kind of immune cell that kills cells infected with HIV, the virus that causes AIDS.

18.   But the underlying disease that killed those cells also seems to kill any that are transplanted to replace them.

19.   By all accounts, the AIDS virus infects and kills T cells.

20.   By focusing on those processes, drug companies began working on drugs aimed to kill cancer cells without harming normal cells.