Question 233

Question:

A 3-year-old boy has a history of repeated pyogenic infections. He had normal antibody responses following childhood immunizations and normal recovery from chickenpox and measles. Decreased numbers or functional defects in which of the following cells best explains the cause of his infections?

Correct Answer: D.  Neutrophils

The question stem provides 3 useful hints which all point to Neutrophils (D) as the answer.
First, the boy’s infections are of pyogenic origin, indicating bacterial infection that results in pus formation. Pus consists primarily of expended neutrophils. Since there is a defect in the pyogenic response (resulting in repeated infection), there is most likely a defect in the action of Neutrophils.
Second, his normal antibody response to immunizations can help you rule out B Lymphocytes (A) or Macrophages (C, the most common antigen presenting cell type) as the answers.
Third, a normal recovery from chickenpox and measles (both viruses) requires intact function of T lymphocytes (E) and Eosinophils (B, because they contain abundant RNAses).
The other answers do not play a direct role in the body’s response to pyogenic infections.