Final answer:
Lymph nodes are responsible for filtering out most microbes from the body's accumulated fluids and play a crucial role in activating immune responses.
Step-by-step explanation:
Most microbes are filtered out of the fluids that accumulate in the body tissues by the lymph nodes. Lymph nodes act as biological filters, where dendritic cells and macrophages internalize and kill many of the pathogens that pass through. Additionally, the lymph nodes are sites of adaptive immune responses, where T cells and B cells play a crucial role in providing immunity. Other organs such as the spleen, liver, and kidneys are also involved in filtering blood and bodily fluids, but specifically for the microorganisms in the lymph, it is the lymph nodes that primarily serve this function.