A 25-year-old man is exposed to Ascaris but does not develop clinical signs of infection. Which of the following mechanisms is likely to be responsible for his resistance to infection?

Ans. (d)Local inflammatory responses such as that induced by IgE can inhibit attachment of roundworms to the intestinal wall. Ascaris is a large worm and is not damaged by antibodies directed at it or by complement, CTLs or phagocytes.