Host–Pathogen Interactions Practice Test

A 34-year-old pregnant woman develops fever, muscle aches, and diarrhea after consuming unpasteurized cheese. Blood cultures grow Listeria monocytogenes, a facultative intracellular bacterium. An effective immune response is mounted, and the patient recovers.

A 6-year-old boy is brought to the pediatrician for his third episode of bacterial pneumonia this year. He also has a history of recurrent giardiasis and sinus infections. Laboratory studies reveal undetectable levels of serum IgA, with normal levels of IgG and IgM. The diagnosis of selective IgA deficiency is made.