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.

---

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

---

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.

---

Etymology

Origin of immune system

First recorded in 1960–65

Example Sentences

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

From Science Daily • Jun. 9, 2026

As co-directors of the Melanoma Institute Australia, over the past decade the pair's research on immunotherapy, which uses the body's immune system to attack cancer cells, has dramatically improved outcomes for advanced melanoma patients globally.

From BBC • Jun. 7, 2026

Summit’s drug, a so-called bispecific antibody, aims to evolve that strategy by activating the immune system while simultaneously starving the tumor.

From The Wall Street Journal • Jun. 6, 2026

A second study – involving around 200 people – will give a greater understanding of how well it is training the immune system.

From BBC • Jun. 4, 2026

Somehow, Phineas's immune system beat off their attack.

From "Phineas Gage" by John Fleischman