A10-year-old boy has a bacterial pneumonia. The etiologic agent had M type-1 protein and grew on blood agar. The patient’s immune system appeared incapable of controlling the infection. A decrease in which of the following is most directly related to the immunological failure?
(A) antibody activity
(B) cytotoxic T-cell function
© IL-4 and IL-10 levels
(D) mast cell degranulation
(E) platelet aggregation
Explanation
(A) A deficiency in immunoglobulin production or activity is directly related to susceptibility to common extracellular microbes such as streptococci. Cytokines such as the interleukins, IL-4 and IL-10 (choice C), the function of T cells (choice B) or mast cells (choice D), and nonantibody factors (choice E) are not directly involved in increased susceptibility to bacterial infections.