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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.

Verified step by step guidance

1. Pattern-recognition receptors (PRRs) are a crucial part of the innate immune system. They identify pathogen-associated molecular patterns (PAMPs) present on parasitic worms.
2. When PRRs recognize worm products, they trigger an initial immune response, which includes the activation of innate immune cells such as macrophages and dendritic cells.
3. Dendritic cells, once activated, process and present antigens from the worms on their surface using major histocompatibility complex (MHC) molecules.
4. These antigen-presenting cells then migrate to lymph nodes, where they interact with T cells, specifically helper T cells (Th2), which are crucial for the adaptive immune response against parasitic worms.
5. The activated Th2 cells release cytokines that stimulate B cells to produce antibodies, particularly IgE, and recruit other immune cells like eosinophils and mast cells, which are effective in combating worm infections.

Key Concepts

Pattern-recognition receptors (PRRs)

Pattern-recognition receptors are proteins on or in cells that recognize specific molecular patterns associated with pathogens, such as parasitic worms. These receptors play a crucial role in the innate immune system by detecting foreign invaders and initiating an immune response. PRRs identify worm products, triggering signaling pathways that lead to the activation of immune cells and the production of cytokines, which help coordinate the body's defense mechanisms.

Adaptive immune response

The adaptive immune response is a specialized defense mechanism that targets specific pathogens with precision. Upon activation by signals from the innate immune system, such as those from PRRs, adaptive immunity involves the proliferation of lymphocytes—B cells and T cells—that recognize and remember specific antigens. This response is tailored to effectively combat worm infections by producing antibodies and activating immune cells that can directly attack or neutralize the parasites.

Immune system adaptation to parasitic worms

The human immune system has evolved to manage parasitic worm infections through a complex interplay between innate and adaptive responses. Historically, the presence of worms has shaped immune function, promoting tolerance and regulation to prevent excessive inflammation. The loss of these parasites in developed countries may impact immune regulation, potentially leading to increased susceptibility to autoimmune diseases, as the immune system may become overly reactive without the modulatory influence of worms.