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

Anyone who may have been exposed to measles should immediately consult a medical professional if they are pregnant, an infant, unimmunized, or have a weakened immune system, according to the department.

From Los Angeles Times • Jun. 14, 2026

Rather than requiring an exact match to fentanyl's structure, the immune system generated antibodies that recognized a broader molecular signature shared by many fentanyl-related compounds.

From Science Daily • Jun. 13, 2026

The disease, which affects around 50,000 in the UK, sees the immune system attack the body.

From BBC • Jun. 11, 2026

Scientists have identified a previously unknown mechanism that may be helping cancers evade the immune system.

From Science Daily • Jun. 9, 2026

He and many other scientists believed that cancer was caused by either a virus or an immune system deficiency, so Southam decided to use HeLa to test those theories.

From "The Immortal Life of Henrietta Lacks" by Rebecca Skloot