Which of the following is indicative of a parasitic infection?

• A. Increased IgA Levels
• B. Increased IgE Levels
• C. Increased IgG Levels
• D. Increased IgM Levels

Answer: (B)

Elevated IgE levels point to a parasitic infection because the immune response to helminths and similar parasites is dominated by a Th2-type reaction. This response promotes switching of B cells to produce IgE, driven by IL-4, while IL-5 activates eosinophils. IgE binds to parasites via FcεRI on eosinophils and mast cells, and when parasite antigens cross-link these bound IgE molecules, eosinophils release cytotoxic granules that help kill or damage the parasite. This IgE-eosinophil axis is a hallmark of parasitic infections, more so than the other immunoglobulins. IgM typically rises first in many infections but isn’t parasite-specific; IgG can increase with many infections and may reflect past exposure; IgA is important for mucosal defense but doesn’t specifically indicate parasites.