A cytotoxin is any substance which has a toxic effect on cells. The term cyto is of Greek origin, and refers to 'a hollow container.' It is used as a preface when describing a biological cell. Some common examples of cytotoxins include chemical agents and certain snake venoms. Cytotoxins typically attack only a specific type of cell or organ, rather than an entire body.
Cells that have been affected by a cytotoxin can perish in several different ways. One is necrosis. In this form of cell death, the cells lose integrity in their membrane wall and collapse. Another type of possible cell death is apoptosis. This type of death is pre-programmed into the cell itself before the cytotoxin arrives. It is typically a beneficial property, as seen when cells in the fingers and toes of developing human babies undergo apoptosis, leading to the separation of digits.
When a cytotoxic apoptosis occurs, the pre-programmed death sequence of a cell is prematurely turned on. Once the sequence has begun, there is no way to reverse it. The genetic process make take minutes or days, but cell death is inevitable. Necrosis usually accompanies apoptosis in its later stages.
Cytotoxic agents can also kill clusters of cells simply by limiting their abilities to grow, divide, and reproduce. Although cytotoxins are often regarded as harmful substances, they are also used in medicine, particularly in the treatment of cancer. If the cancer cells in a neoplasm, or tumor, are targeted with a cytotoxin, they will die at a far faster rate than healthy cells, owing to their higher reproduction rate. A cytotoxin applied in the right dosage at the right time can cure a cancer with minimal harm to the patient. This form of cancer treatment is also known as chemotherapy, and it is because of healthy cell death, due to the administered cytotoxin, that such patients suffer hair loss and reduced immune system function.
Certain diseases also produce their own cytotoxins. Diphtheria and scarlet fever both generate toxins that worsen the effects of the illness. If left untreated, the cytotoxic process can progress to a stage in which a patient may not recover, even if the original disease is cured. An example of a common cytotoxin is the helicobacter pylori bacteria, which is found in the stomach and duodenum. This bacteria breaks down urease found in the stomach, which creates ammonia. This ammonia is toxic to the stomach's epithelial cells, and can lead to stomach ulcers and cancer.