11. Type III secretion systems are used to inject “effector” proteins directly into a host cell. Salmonella uses a type III secretion system to help the pathogen to

A. survive the acid pH of the stomach
B. secrete LT (heat-labile toxin) and ST (heat-stable toxin) into the lumen of the intestine
C. survive within macrophages
D. activate T cells to proliferate and secrete cytokines

12. Which of these cytokines is also known under the name cachectin?

A. Interferon-gamma
B. Interleukin 2
C. Tumor necrosis factor (TNF)
D. None of the above

13. Which is not a major defense mechanism in the stomach?

A. Proteolytic enzymes
B. Low pH
C. Dense normal flora
D. All of these

14. The agent responsible for causing mad cow disease is thought to be a

A. fungus
B. protozoan
C. prion
D. virus

15. The “A” subunit of diphtheria toxin

A. binds host cell receptors found on heart cells
B. cause ADP ribosylation of a factor involved in protein synthesis
C. forms cAMP that leads to fluid accumulation
D. lysis macrophages with the release of cytokines