What role do lymph nodes play in the immune response?

Lymph nodes play a critical role in the immune response by acting as structures where immune cells can gather and interact. When pathogens such as bacteria and viruses enter the body, they can be transported through the lymphatic system to the lymph nodes. Within these lymph nodes, immune cells, primarily lymphocytes, can detect and respond to the presence of these pathogens.

The lymph nodes contain specialized cells that can trap and process antigens—substances that provoke an immune response—presenting them to T cells and B cells. This interaction leads to an activated immune response, which involves the proliferation of these immune cells and the production of antibodies to help neutralize the pathogens.

This vital role of the lymph nodes in capturing infectious agents underlines their importance in the body's defense mechanisms, making the choice of trapping bacteria and viruses the correct answer. The other options do not accurately reflect lymph node functions; oxygen transport is primarily a function of blood and its associated cells, hormone production is related to glands in the endocrine system, and nutrient filtering is associated with organs such as the liver and kidneys.