A 3-year-old boy experiences recurrent sinusitis and an episode of severe pneumonia. As part of his evaluation, Candida extract is injected intradermally. Forty-eight hours later, he returns to the clinic with a firm nodule measuring 16 mm in diameter where the extract was injected. Which of the following cell types is most likely responsible for the reaction observed in this patient?

Question

A 3-year-old boy experiences recurrent sinusitis and an episode of severe pneumonia.  As part of his evaluation, Candida extract is injected intradermally.  Forty-eight hours later, he returns to the clinic with a firm nodule measuring 16 mm in diameter where the extract was injected.  Which of the following cell types is most likely responsible for the reaction observed in this patient?

Quizplus · Accepted Answer

Eductional Objective: Type IV (delayed) hypersensitivity reactions (eg, Candida extract skin test, contact dermatitis) are characterized by erythema and induration that develops 24-48 hours after repeat exposure to an antigen. T lymphocytes mediate the inflammation in these reactions through cytokine release, CD8⁺ cytotoxicity, and macrophage recruitment.

A 3-Year-Old Boy Experiences Recurrent Sinusitis and an Episode of Severe