In developed countries, an enormous change has occurred within the human body over the past century—the loss of parasitic worms. Due to improvements in sanitation, roundworms that have inhabited human intestines (such as the hookworm above) and challenged our immune system for millions of years are no longer a threat. Does the end of this long-term relationship come at a cost? Pattern-recognition receptors have been identified that recognize worm products. Explain how these receptors are used to activate the adaptive immune response most appropriate for worm infection.