Disease and immunity

Active immunity - Resistance in an organism that has developed through the

production of specific antibodies in response to a pathogen. This may occur due to

infection by a pathogen or by vaccination. It provides long-lasting immunity as

memory cells are produced.

Antibodies - Proteins produced by white blood cells (lymphocytes) in response to a

specific antigen, triggering an immune response. Antibodies have binding sites

complementary to a particular antigen.

Antigen - A unique chemical present on the surface of a cell that induces an immune

response.

Autoimmune disease - A disease in which the immune system targets and destroys

its own healthy body cells.

Chemical barrier - A non-specific defence that destroys invading pathogens, e.g. mucus,

stomach acid.

Host - The organism from which a pathogen or parasite obtains nutrients and/or shelter.

Mechanical barrier - A non-specific defence that physically blocks the entry of a pathogen,

e.g. skin, nose hairs.

Memory cell - A type of white blood cell that remains in the blood and provides

immunological memory to a specific antigen on a pathogen.

Passive immunity - Resistance in an organism acquired via the transfer of antibodies

e.g. mother to infant by breastfeeding. It provides short-term immunity as no memory

cells are produced.

Pathogen - A disease-causing organism, e.g. virus, fungus, bacterium, protist.

Phagocytosis - The process by which white blood cells (phagocytes) engulf and destroy

pathogens.

Transmissible disease - A disease that is caused by a pathogen which can be spread

between hosts (either directly or indirectly).

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Type 1 diabetes - A type of diabetes in which the pancreas fails to produce enough insulin.

It is considered to be an autoimmune disease.

Vaccination - The deliberate exposure of an individual to a harmless pathogen in order to

provide active immunity.

Water treatment - Any process that improves water quality and ensures that it is not

contaminated by disease-causing bacteria (from untreated sewage for example).

White blood cells - Cells of the immune system that protect the body from invading

pathogens.

Addiction - Uncontrolled, compulsive behaviour associated with the inability to stop doing

something or using a substance that has harmful consequences.

Alcohol - A depressant drug which slows impulse transmission at synapses. It increases

reaction times and can result in a loss of self-control. Excessive alcohol consumption may

cause liver damage (cirrhosis).

Anabolic steroids - A class of performance enhancing drugs structurally similar to

testosterone. They are used illegally by athletes to promote muscle development.

Antibiotic - A chemical or compound produced by a living organism that kills or prevents the

growth of bacteria. Antibiotics have no effect on the cells of the host organism or viruses.

Antibiotic-resistant bacteria - Bacteria that mutate to become resistant to an antibiotic,

survive and reproduce very rapidly, passing on their antibiotic resistance.

Cancer - A non-communicable disease caused by changes in a cell which lead to

uncontrolled growth and division.

Carbon monoxide - A chemical found in cigarette smoke that lowers the ability of red blood

cells to carry oxygen. This results in an increased heart rate, raising the risk of

cardiovascular disease.

Chronic bronchitis - A respiratory disease caused by the deposition of tar in the airways.

This leads to inflammation and prevents the cilia from beating. Mucus containing dirt and

bacteria collects in the bronchi, resulting in infection.

Chronic obstructive pulmonary disease (COPD) - Refers to a group of lung conditions

which cause breathing difficulties, including chronic bronchitis and emphysema.

Cirrhosis - Scarring of the liver tissue resulting from the breakdown of alcohol into toxic

products in the liver.

Coronary heart disease - A disease caused by the build-up of fatty deposits inside the

coronary arteries, narrowing them and reducing blood flow to the heart tissue. High blood

pressure, a diet high in saturated fats, lack of exercise and smoking increase the risk of

coronary heart disease.

Drug - A substance that when introduced into the body, alters the body’s chemical reactions.

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Emphysema - A respiratory disease caused by the breakdown of the alveoli as a result of

chemicals present in tobacco smoke. This reduces the surface area available for gas

exchange, leading to shortness of breath, shallow breathing and difficulty exhaling.

Heroin - An illegal drug that acts as a depressant. It stimulates receptors at synapses in

the brain, causing dopamine release and a short-lived ‘high’.

Lung cancer - A respiratory disease often caused by chemical carcinogens present in

tobacco smoke. The development of tumours (which may block the airways) results in

symptoms such as shortness of breath, wheezing, a persistent cough and blood-stained

sputum.

MRSA - A type of bacteria commonly found in hospitals that is resistant to almost all

antibiotics.

Nicotine - An addictive chemical found in cigarette smoke that raises heart rate and blood

pressure, increasing the risk of cardiovascular disease.

Tar - A carcinogen present in tobacco smoke that becomes deposited in the airways causing

inflammation. It also stimulates the production of excess mucus which paralyses the cilia.

Testosterone - A male sex hormone released by the testes that is involved in the

development of the male secondary sexual characteristics. Testosterone supplements can

be used to increase bone and muscle mass in athletes.

Tobacco smoke - Cigarette smoke that damages the cilia resulting in a build-up of mucus.

Withdrawal symptoms - The physical effects that follow the discontinuation of an addictive

drug which the body is dependent on.