A patient undergoes a tuberculin skin test (PPD). A positive result, characterized by induration and erythema 48-72 hours after injection, indicates which type of hypersensitivity reaction?

✓ Correct Answer: Option D

The PPD test is a classic example of a Type IV, or delayed-type, hypersensitivity reaction. It involves T-cell activation and macrophage recruitment, leading to a visible reaction hours to days after antigen exposure.