immune system

American  

noun

Anatomy.

1. a diffuse, complex network of interacting cells, cell products, and cell-forming tissues that protects the body from pathogens and other foreign substances, destroys infected and malignant cells, and removes cellular debris: the system includes the thymus, spleen, lymph nodes and lymph tissue, stem cells, white blood cells, antibodies, and lymphokines.

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immune system Scientific  

1. The body system in humans and other animals that protects the organism by distinguishing foreign tissue and neutralizing potentially pathogenic organisms or substances. The immune system includes organs such as the skin and mucous membranes, which provide an external barrier to infection, cells involved in the immune response, such as lymphocytes, and cell products such as lymphokines.

2. See also autoimmune disease immune response

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immune system Cultural  

1. The system in the body that works to ward off infection and disease. Central to this system are the white blood cells. Some white blood cells produce antibodies in response to specific antigens that may invade the body; others function as scavengers to fight infection by destroying bacteria and removing dead cells.

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Etymology

Origin of immune system

First recorded in 1960–65

Example Sentences

Actor Sam Neill says he is cancer-free after five years of living with lymphoma, thanks to a genetic therapy that modified his immune system.

From Barron's • Apr. 29, 2026

Sepsis, which can be life-threatening and is difficult to spot, is an emergency reaction to infection where the immune system overcompensates and damages tissues and organs.

From BBC • Apr. 26, 2026

Additional experiments in mice and human melanoma cell lines confirmed that this protein drives both blood vessel growth and immune system evasion.

From Science Daily • Apr. 21, 2026

Many pancreatic tumors also carry relatively few mutations overall, which makes them harder for the immune system to detect and attack.

From The Wall Street Journal • Apr. 21, 2026

Whether due to spirit intervention or a strong immune system, little Charley recovered, and Maria took him back home to western New York.

From "American Spirits" by Barb Rosenstock