21.  Ironically, the drug works by briefly blocking a gene that is a natural defense against cancer.

22.  Ironically, the drug, pifithrin, works by briefly blocking a gene that is a natural defense against cancer.

23.  Many people suffer only headaches before their bodies natural defenses beat the fungal infection, but Ellis said early diagnosis and treatment are still critical.

24.  The mountains and rivers were natural defenses against invading Japanese troops.

25.  Interferon is a natural protein that strengthens the natural defenses of a cell against an aggressor.

26.  Once inside the body the harmless mutant HIV might stimulate a more robust natural defense against AIDS.