11.   They discovered that the immune defenses in the two groups were quite distinct.

12.   Was there something different about their immune defenses?

13.   With the animal dead, its immune defenses are paralyzed and, from the bacterial perspective, it is just a harmless bag of nutrients.

14.   Perhaps giving the xenotransplant patient some bone marrow taken from the same pig that provides the organ will make the immune defenses tolerate the new tissue.

15.   And somehow it primed their immune defenses to ward off real SIV.

16.   However, some of the Australians now appear to show weakening immune defenses.

17.   Maybe there is not enough time between infections to build immune defenses, the researchers said.

18.   The drug, called cidofovir or Vistide, is used to treat eye infections caused by cytomegalovirus, which can afflict people with HIV-weakened immune defenses.

19.   These are diseases caused by usually innocuous germs that are dangerous because of the lack of strong immune defenses.

20.   Two companies said they have produced litters of cloned miniature pigs that lack one copy of a gene that makes pig parts incompatible with human immune defenses.