IGCSE Biology Diseases and Immunity

Pathogen

A microorganism that can cause diseases

Transmission

Passing a pathogen to an uninfected person

Transmissible diseases

A disease in which the pathogen can be passed from one host to another

Vector

An organism that carries a pathogen from one host to another

Immune system

The body's internal defence system

Immune

Able to fight off a particular pathogen before it causes any symptoms in the body

Phagocytes

White blood cells that surround, engulf and digest pathogens

Lymphocytes

White blood cells that produce and release antibodies

Memory cells

Cells produced by active lymphocytes that remain in the body and are able to respond quickly to a pathogen

Antigens

Chemicals on the surfaces of pathogens which are recognised as foreign by the body

Antibodies

Chemicals secreted by lymphocytes which attach to antigens and help to destroy them

Antibiotic

A drug that kills bacteria in the human body without killing human cells

Penicillin

An antibiotic which destroys bacteria by damaging their cell walls

Auto-immune disease

A disease caused by a person's own immune system attacking parts of their body

Vaccination

Introduction to the body of dead or weakened pathogens to make a person immune to an infectious disease

Active immunity

Defence against a pathogen by antibody production

Passive immunity

Short term defence against a pathogen by antibodies acquired from another individual