The interconnected network of cells, tissues, organs, and biological processes that protects the body from infectious agents, abnormal cells, and other potentially harmful substances.
The immune system includes components such as white blood cells, antibodies, lymphatic tissues, bone marrow, the thymus, lymph nodes, and the spleen. It uses both innate and adaptive immune defenses.
The immune system must distinguish harmful or abnormal targets from the body’s own healthy tissues. When immune activity is inadequate, excessive, or misdirected, disease can result.
QUICK FACT
The immune system does not only fight infections; it also helps identify and remove damaged or abnormal cells.
COMMONLY CONFUSED WITH
Immune response: the specific coordinated reaction produced by the immune system; the immune system is the broader network that produces those responses.
SEE ALSO
