In schistosome immunity, which stage tends to evade the host immune response?

• A. Worms
• B. Eggs
• C. Cercariae
• D. Miracidia

Answer: (A)

The main idea is that different life stages of schistosomes interact with host immunity in distinct ways, and the adult worms have evolved the most effective camouflage. The adult worms live for years in the host’s blood vessels and wear a surface called the tegument, which acts as a shield. This tegument is largely antigen-poor and actively takes up host proteins, helping the worm blend in with the host and avoid detection. In addition, they release molecules that modulate the host’s immune responses, dampening inflammation and antibody activity, which supports long-term survival.

Eggs, by comparison, are highly antigenic and provoke strong immune reactions, driving granuloma formation and pathology. The larval stages that travel through skin (cercariae) or develop in snails (miracidia) are more exposed to defenses and are not as well protected once inside the host. So the stage that tends to evade the host immune response best is the adult worm, thanks to its camouflaged surface and immune-modulating tactics.