Hypersensitivity — Immunology Aspect

A 35-year-old man with a history of severe drug allergy (penicillin-induced anaphylaxis) requires urgent treatment for a serious infection. Skin testing confirms IgE-mediated hypersensitivity to penicillin. He must receive a β-lactam antibiotic. Which drug is the safest choice given his allergy history?

A 28-year-old woman presents with acute onset dyspnea, urticaria, and angioedema 15 minutes after receiving intravenous penicillin. She has a history of severe reactions to cephalosporins. Which investigation is most appropriate to confirm the diagnosis of IgE-mediated hypersensitivity?

A 35-year-old man with a history of atopy presents with recurrent episodes of allergic rhinitis triggered by dust mite exposure. Which of the following is the most common cell type responsible for the chronic inflammatory phase of this Type I hypersensitivity reaction?

Which of the following cytokines is the primary mediator of the delayed-type hypersensitivity (Type IV) response?

A 42-year-old man with a history of penicillin allergy presents to the clinic with a 7-day history of fever, joint pain (knees and ankles), and a pruritic maculopapular rash on his trunk and limbs. He was started on amoxicillin 5 days ago for a respiratory tract infection. On examination, he has lymphadenopathy and hepatosplenomegaly. Serum complement levels (C3, C4) are low. Which type of hypersensitivity reaction best explains his clinical presentation?