Answer to Question 1
ANS: B
AIDS is an acquired dysfunction of the immune system caused by a retrovirus (HIV) that infects and destroys CD4+ lymphocytes (T-helper cells). HIV infection begins when a virion binds to CD4, not a B cell. Infection requires a host cell receptor. The cell remains dormant but does not die.
Answer to Question 2
ANS: B
The clinical hallmark of immunodeficiency is a propensity to unusual or recurrent severe infec-tions. The type of infection usually reflects the immune system defect. Neither anemia, autoanti-body production, nor hypersensitivity is a manifestation of immunodeficiency.