Which is a classic example of a type IV (delayed, cell-mediated) hypersensitivity reaction?

The tuberculin (PPD) response is a T-cell-mediated delayed (type IV) reaction peaking at 48-72 hours; contact dermatitis is another example.Other options: Anaphylaxis is type I (IgE); hemolytic transfusion reaction is type II (cytotoxic); serum sickness is type III (immune complex).Key exam takeaway: Type IV = delayed, T-cell-mediated (PPD test, contact dermatitis, TB granulomas).