Definitions - Topic 10 Diseases and immunity - CAIE Biology IGCSE

Active immunity

Resistance in an organism that has developed through the production of specific antibodies in response to a pathogen.

Antibodies

Proteins produced by white blood cells (lymphocytes) in response to a specific antigen, triggering an immune response.

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.

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.

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.

White blood cells

Cells of the immune system that protect the body from invading pathogens.