Which antibody is associated with resistance to re-infection of schistosomes?

• A. IgA
• B. IgG
• C. IgM
• D. IgE

Answer: (D)

IgE antibodies are linked to resistance to re-infection with schistosomes because they activate eosinophils to kill the parasite through antibody-dependent cellular cytotoxicity. When IgE coats the surface of schistosome stages, eosinophils—via their Fcε receptors—bind and release cytotoxic granules like major basic protein that damage or destroy the parasite. This eosinophil-driven attack is a key mechanism of protective immunity against helminths and is why individuals with schistosome exposure develop partial resistance upon later exposures. Other antibody classes have different roles—IgA is mainly mucosal, IgM is an early, broad response, and IgG can contribute but does not mediate the same effective eosinophil- and surface-targeted killing against schistosomes as IgE does.