What role do lymph nodes play in the body?

Lymph nodes are integral components of the immune system, primarily functioning as sites where immune responses can be initiated. They contain a high concentration of white blood cells, notably lymphocytes, which are critical in the body's defense against pathogens such as bacteria, viruses, and other foreign invaders. When infections or other immune challenges arise, lymph nodes swell as they activate these white blood cells to target and eliminate threats. This essential role helps to monitor and respond to potential health issues throughout the body, thereby facilitating the overall immune response and maintaining the body's defense mechanisms.

The other options do not accurately represent the function of lymph nodes. Red blood cell production occurs mainly in the bone marrow, while nutrient storage is typically associated with organs like the liver. Filtering waste from the bloodstream is primarily conducted by the kidneys. Therefore, the correct understanding of lymph nodes emphasizes their specialized role in immune defense.