Respond thoughtfully and in your own words to the following discussion questions.

1. Injections of TC cells completely removed all Hepatitis B viruses from infected mice, but the injections killed only 5% of the infected liver cells. Explain how TC cells cured the mice.

2. A patient with AIDS has a low TH cell count. Why does this patient have trouble making antibodies? How does this patient make any antibodies?

3. Newborns (under 1 year) who contract dengue fever have a higher chance of dying from it if their mothers had dengue fever prior to pregnancy. Explain why.

4. A woman died from a Capnocytophaga bacterial infection introduced by a dog bite. Capnocytophaga kills only people who lack a spleen. What is the relationship between infection and the spleen?

5. In this case history, a 49 year-old man handled a parakeet with a respiratory illness on February 7. On March 9, he experienced intense pain in his legs, followed by severe chills and headaches. On March 16, he had chest pains, cough, and diarrhea, and his temperature was 40^°C. Appropriate antibiotics were administered on March 17, and his fever subsided within 12 hours. He continued taking antibiotics for 14 days. Identify each period in the pattern of disease that he experienced. Note: The disease is psittacosis. Can you find the etiology?

6.  Mycobacterium avium-intracellulare is prevalent in AIDS patients. In an effort to determine the source of this infection, hospital water systems were sampled. The water contained chlorine. What is the usual method of transmission for Mycobacterium? What is the probable source of infection in hospitals? How can such nosocomial infections be prevented?

7. Twenty-one percent of the patients in a large hospital acquired Clostridium difficile diarrhea and colitis during their hospital stay. Epidemiological studies provided the following information. What is the most likely mode of transmission of this bacterium in hospitals? How can transmission be prevented?