What does cytotoxin mean?
A cytotoxin is any substance that is poisonous to living cells, causing their injury or death. The word belongs mainly to medicine and biology, where it describes agents that damage cellular tissue — whether they come from bacteria, plants, animals such as snakes and scorpions, or from the body's own immune defences. Natural killer cells and cytotoxic T lymphocytes, for example, release cytotoxins like perforin and granzymes to destroy virus-infected or malignant cells, while many chemotherapy drugs act as cytotoxins against rapidly dividing tumour cells. Because of this dual character — harmful when produced by pathogens, therapeutic when harnessed by medicine — the term carries a strongly scientific register rather than an everyday one, appearing most often in research papers, clinical discussions, and pharmaceutical writing alongside its adjective 'cytotoxic' and noun 'cytotoxicity'. Understanding 'cytotoxin' offers a window into how modern medicine turns cellular poisons into weapons against disease.
nounA substance that is poisonous to cells, capable of killing or damaging living cells; especially one produced by or used against tumour cells or by certain immune cells.
- Any substance that is toxic to cells, killing or damaging them (used in immunology, oncology, and general biology).
- Specifically, a toxin produced by T cells or natural killer cells (e.g. perforin, granzymes) to destroy target cells.
"The chemotherapy drug works by releasing a cytotoxin that destroys rapidly dividing cancer cells."
"The scorpion's venom contains a powerful cytotoxin that ruptures the membranes of its victims' cells."
"Cytotoxic T lymphocytes release granzymes — cytotoxins that trigger apoptosis in infected cells."
Standard English plural; commonly used when discussing multiple such substances.
"The venom contains several distinct cytotoxins."
Your own immune system manufactures cytotoxins on demand — natural killer cells deploy them to punch holes in infected or cancerous cells.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of cytotoxin
The word combines two classical roots: 'cyto-', from Greek 'kytos' meaning a hollow vessel or cell, and '-toxin', from Greek 'toxikon' meaning poison for arrows, which entered modern scientific Latin via 'toxicum'. The compound form arose in late 19th-century biomedical science as researchers began classifying substances by their effects on cells, part of the broader wave of Greek-derived terminology in cytology and immunology. It shares those roots with related terms such as cytokine, cytoplasm, and toxic.
Related word forms
How cytotoxin is actually used
A technical term used chiefly in medical, biological, and pharmacological contexts; rarely encountered in everyday speech. Often appears in adjectival form as 'cytotoxic', as in 'cytotoxic drugs'.
Easily confused with cytotoxin
An endotoxin is specifically a toxin released when certain bacteria are destroyed and are part of the bacterial cell wall, whereas a cytotoxin is any substance toxic to cells.
The cytoskeleton is the structural protein framework inside a cell, not a poison; the shared 'cyto-' prefix simply refers to cells.