cy·​to·​kine | \ ˈsī-tə-ˌkīn How to pronounce cytokine (audio) \
plural cytokines

Definition of cytokine

: any of a class of immunoregulatory proteins (such as interleukin or interferon) that are secreted by cells especially of the immune system Most cytokines are produced primarily in the presence of disease or immunization and contribute to immune responses, inflammation, and endothelial cell activation; others are involved in tissue repair.— Charles A. Dinarello et al. The proinflammatory cytokine interleukin-2 determines the magnitude and duration of the T-cell response immediately after antigen encounter and assists in the maturation of macrophages and the proliferation of B cells and natural killer cells …— Chiea C. Khor et al.

Examples of cytokine in a Sentence

Recent Examples on the Web Kelsey's immune system had reached this point, known to doctors as a cytokine storm. Mark Johnson,, "A Wisconsin mom gave birth in a COVID-19 coma before slipping to the brink of death," 18 Mar. 2021 The payload itself mustn’t cause such problems as the cytokine storm of immune overreaction. Elizabeth Cooney, STAT, "Novartis and the Gates Foundation aim to create a more practical gene therapy for sickle cell patients around the world," 17 Feb. 2021 In severe cases, the immune system churned out a flood of cytokine proteins. Jennifer Couzin-frankel, Science | AAAS, "‘Every minute counts.’ This immunologist rapidly reshaped her lab to tackle COVID-19," 27 Oct. 2020 Giving interferon later in the course of disease could encourage a destructive immune overreaction called a cytokine storm, in which the immune system does more damage than the virus. NBC News, "'Breakthrough finding' reveals why certain Covid-19 patients die," 13 Nov. 2020 Some of those who get really sick with COVID-19 develop dangerous, systemic inflammation, triggered by an overactive immune response called a cytokine storm. Tom Avril, Star Tribune, "Test shows markers that may predict worst COVID-19 cases," 31 Oct. 2020 Physicians say overreactive immune responses, called cytokine storms, have been responsible for many of the most severe cases of COVID-19 and quite a few deaths. Peter Fimrite,, "T cells, the body’s antiviral snipers, look promising for a coronavirus vaccine," 23 Aug. 2020 The overreactive immune response, called a cytokine storm, is also seen with herpes, Ebola, and other viruses, as well as cancer and auto-immune diseases. Robin Marantz Henig, National Geographic, "To end this pandemic, we must trust science," 13 Oct. 2020 Edy Kim, a critical care physician at Brigham and Women’s, explains that a striking feature of the COVID-19 pandemic is how many patients suffer complications from the cytokine storm. Monique Brouillette, Scientific American, "Trump’s COVID Case Could Be Entering a Crucial Stage," 9 Oct. 2020

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'cytokine.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of cytokine

1974, in the meaning defined above

History and Etymology for cytokine

cyt- + -kine (as in lymphokine)

Keep scrolling for more

Learn More about cytokine

Time Traveler for cytokine

Time Traveler

The first known use of cytokine was in 1974

See more words from the same year

Statistics for cytokine

Last Updated

24 Mar 2021

Cite this Entry

“Cytokine.” Dictionary, Merriam-Webster, Accessed 12 Apr. 2021.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon

Keep scrolling for more

More Definitions for cytokine


cy·​to·​kine | \ ˈsīt-ə-ˌkīn How to pronounce cytokine (audio) \

Medical Definition of cytokine

: any of a class of immunoregulatory proteins (as interleukin, tumor necrosis factor, and interferon) that are secreted by cells especially of the immune system

More from Merriam-Webster on cytokine Encyclopedia article about cytokine

Comments on cytokine

What made you want to look up cytokine? Please tell us where you read or heard it (including the quote, if possible).


Test Your Vocabulary

The Exceptions Quiz III

  • one green toy robot amidst many red toy robots
  • Which of these words does not mean "nonsense"?
Name That Thing

Test your visual vocabulary with our 10-question challenge!


Anagram puzzles meet word search.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!