Why do we have lymph nodes?

Part of immunity: Lymph nodes are an essential part of our immune system. They not only generate precursor cells to what is termed "fixed tissue immune" processes, but they aid in formation of antibodies, they help fight any foreign materials in our body and they may be helpful in fighting certain tumors. We have a very complex and effective system to help combat disease and they are a big part.

Monitoring Centers: The lymphatic system absorbs and carries things too big to go into the arteries and veins like bacteria eaten by white cells and digested food. The lymph nodes "taste" the lymph to see if anything bad is there like bacteria, viruses, cancers, etc. When it detects a problem, it alerts the immune system and your body reacts. They enlarge in response to the inflammation they create when they react.