Why are lymph nodes important to the immune system?

Lymph nodes play a crucial role in the immune system primarily because they filter harmful substances and serve as a residence for immune cells. Located throughout the body, lymph nodes act as checkpoints for lymph fluid, which collects waste products and pathogens from tissues. As lymph fluid passes through the lymph nodes, it is screened for foreign invaders such as bacteria, viruses, and other harmful agents.

Within the lymph nodes, various types of immune cells, including lymphocytes (such as T-cells and B-cells), are activated in response to these pathogens. When lymphocytes recognize a threat, they proliferate and initiate an immune response, effectively helping the body to fight infections. This filtration process and the activity of immune cells in lymph nodes are vital for maintaining a robust immune defense.

The other choices do not relate to the primary functions of lymph nodes. The production of red blood cells occurs mainly in the bone marrow, while hormone generation is handled by glands such as the thyroid and adrenal glands. Digestive functions are primarily managed by the gastrointestinal tract.