A 14-16 yr old 10 swollen lymph nodes. 5-1.5 CM and 1 big one 2.5 all very soft and moveable. Docs say they fine. Go down with antibiotics then big?

Monitoring Centers. Lymphatic system absorbs/carries things too big to go into the arteries/veins like bacteria eaten by white cells/digested food. Lymph nodes "taste" the lymph everywhere for bad stuff 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. They shrink when all is well.
Biopsy. My rule of thumb for a persisting enlarged lymph node greater than 1 CM diameter, particularly if it remains nontender, is to have it biopsied. This is especially true if there is no present signs or symptoms of infectious process. However i might try a course of antibiotics such as Dicloxacillin before doing this.