Which antibody class is linked to resistance to reinfection with schistosomes?

• A. IgA
• B. IgG
• C. IgM
• D. IgE

Answer: (D)

IgE-mediated immune responses are central to resistance to reinfection with schistosomes because this antibody class effectively calls in eosinophils and other effector cells to attack the parasite. When schistosome antigens are recognized, IgE binds to them and engages Fc receptors on eosinophils and mast cells. This triggers antibody-dependent cell-mediated cytotoxicity and release of toxic mediators that damage or kill the larvae and worms, reducing the establishment of new infections. Other antibody classes don’t coordinate this eosinophil-driven attack as efficiently in this context. IgA mainly protects mucosal surfaces and isn’t the primary defender against circulating schistosomes; IgM is an early, short-lived response that doesn’t provide the durable, memory-based protection associated with IgE; and while IgG can help in some infections, the well-established protective mechanism against schistosome reinfection is driven by IgE in concert with eosinophils.