Topic 5 - Defending ourselves against Infectious Diseases

Microorganisms that cause infectious diseases are called pathogens
- Bacteria and viruses may reproduce rapidly inside the body
- Bacteria may produce toxins (poisons) that make us feel ill
- Viruses live and reproduce inside cells, causing damage
White Blood Cells help to defend against pathogens by:
- Ingesting pathogens
- Producing antibodies
  - These destroy particular bacteria or viruses
- Producing antitioxins
  - These counteract the toxins released by the pathogens
Our body's immune system produces specific antibodies to kill a particular pathogen
- This leads to immunity from that pathogen
- In some cases, dead or inactive pathogens stimulate antibody production.
  - If a large proportion of the population is immune to a pathogen, the spread of the pathogen is very much reduced
People can be immunised against a disease by introducing small quantities of a dead or inactive forms of the pathogen into the body (vaccination
- Vaccines stimulate the white blood cells to produce antibodies that destroy the pathogen.
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