Which two classes of antibodies are commonly associated with allergic transfusion reactions?

• A. IgM and IgG
• B. IgD and IgE
• C. IgA and IgG
• D. IgG or IgE

Answer: (D)

Allergic transfusion reactions arise when donor plasma proteins are recognized as foreign by the recipient’s immune system, triggering an allergic response. The primary mediator is IgE, which binds to the allergen and causes mast cells to release histamine, leading to itching, hives, and sometimes airway symptoms. IgG can also play a role in these reactions, contributing through immune complex formation or other pathways that amplify the response. Because both IgG and IgE can drive allergic-type responses to transfused plasma, they are the antibody classes commonly associated with these reactions. In contrast, IgM is more linked to acute hemolytic reactions against red cell antigens, and IgA-related anaphylaxis is a special case seen mainly in IgA-deficient individuals, not the typical allergic transfusion reaction.