What do lymph nodes primarily contain to help fight infection?

Lymph nodes primarily contain lymphocytes, which are a type of white blood cell essential for the immune response. These cells, including T cells and B cells, play critical roles in identifying and responding to pathogens such as bacteria and viruses. When an infection occurs, lymphocytes proliferate within the lymph nodes, coordinating the body's immune response, including the production of antibodies by B cells to neutralize the pathogens.

While neutrophils are also important in the immune response, they primarily act in the early stages of infection and are found in the bloodstream and tissues rather than being concentrated in lymph nodes. Red blood cells are not involved in the immune defense; their main function is to transport oxygen. Antibodies are produced by activated B lymphocytes but are not found in significant amounts in lymph nodes themselves; rather, they circulate throughout the body after being released into the bloodstream. Thus, lymphocytes are fundamental components of lymph nodes that are vital for fighting infections.