Lymph nodes are found throughout the body and are part of the immune system. They help to filter and trap bacteria, viruses, and other pathogens that may be present in the lymph fluid. Swollen lymph nodes are a common symptom of infection or inflammation, and can be a signal of a more serious underlying condition such as cancer or an autoimmune disorder. If lymph nodes remain swollen for a prolonged period of time, it is important to seek medical attention to determine the cause and appropriate treatment.