What does cytokine mean?
A cytokine is a small protein that acts as a chemical messenger within the body, allowing one cell to influence the behaviour of another. Released chiefly by cells of the immune system, cytokines coordinate responses to infection and injury: some promote inflammation to help fight pathogens, while others calm the reaction once the threat has passed. Familiar examples include interleukins, interferons, and tumour necrosis factor. The term is technical, appearing mainly in immunology, medical research, and science journalism rather than casual conversation. Cytokines have gained wider public attention because of their role in severe illness — an overproduction known as a 'cytokine storm' can cause dangerous inflammation, notably in some serious infections. Many modern medicines, from arthritis treatments to cancer therapies, work by boosting, mimicking, or blocking particular cytokines, making this word central to contemporary biomedical science.
nounA cytokine is any of a class of small proteins secreted by cells of the immune system and other cell types that act as signalling molecules, regulating immune responses, inflammation, and communication between cells.
- Any of various small signalling proteins released by cells (especially immune cells) that regulate immunity, inflammation, and intercellular communication.
"Interleukin-6 is a cytokine that rises sharply during infection and helps orchestrate the body's inflammatory response."
"Doctors measured levels of the pro-inflammatory cytokine TNF-alpha to assess how active the patient's rheumatoid arthritis was."
"New biologic drugs work by blocking specific cytokines before they can fuel chronic inflammation."
Regular plural; commonly used when referring to classes or panels of these molecules, e.g. in laboratory reports listing multiple measured cytokines.
"Blood tests revealed elevated levels of several inflammatory cytokines."
In severe COVID-19 cases, the immune system's own chemical messengers — cytokines — can turn traitor, triggering the infamous 'cytokine storm' that does more damage than the virus itself.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of cytokine
The word cytokine was coined in the 20th century from two Greek-derived elements: cyto-, from Greek kytos meaning 'hollow vessel' or 'cell', and -kin(e), related to kinetic movement or activity, reflecting its role as a cell-moving or cell-activating messenger. It emerged as immunologists recognised that lymphocytes and other immune cells secreted soluble factors mediating communication between cells. Related terms sharing the cyto- prefix include cytology, cytoplasm, and cytokinesis.
Related word forms
How cytokine is actually used
Cytokine is a technical term used chiefly in immunology, medicine, and biomedical science. It carries no everyday informal register; in popular writing it most often appears in connection with inflammation or 'cytokine storms'. It is almost always used as a countable noun.
Easily confused with cytokine
Both are signalling molecules, but hormones travel mainly through the bloodstream to distant organs, whereas cytokines typically act locally over short distances between neighbouring cells.