Defence against infection



  • very small cells
  • 1/100th the size of body cells
  • living cells that multiply rapidly
  • make us feel ill
    • by damaging cells
    • producing toxins and poisons


  • Not cells
  • Tiny, 1/100th the size of bacterium
  • replicate themselves by using the cells machienery to make copies
  • Cell damage makes you ill
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White Blood Cells and Antibodies

White Blood Cells

  • ingest pathogens and destroy them
    • engulfing and digesting
  • produce antibodies to destroy particular pathogens
    • the antibodies lock onto the antigen, and kill them
  • produce antitoxins that counteract the toxins released by pathogens.


  • Produced rapidly and carried all around the body
  • Only destroy specific antigens, not any others
  • Lock onto pathogens and destroy them


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Vaccinations protect from future infections

  • A small amount of dead or inactive pathogen is injected into the body
  • the white blood cells are stimulated to produce antibodies
  • if the pathogen comes into contact again, the white blood cells know how to fight it
    • a mass of antibodies are rapidly produced to kill the pathogen
    • Booster injections are given to inrease levels of antibodies


  • Help reduce existence of infection in the UK by controling them
  • Epidemics are prevented when a large percentage of the population in vaccinated 
    • this means that less people are being infected
    • and less people are passing it on


  • They don't always work- not always giving you immunity
  • bad reactions, such as swelling may occur (rare)
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Painkillers relieve symptoms of disease by blocking nerve impulses from the source, getting to the brain. However they don't stop or kill the illness.

Antibiotics kill bacteria or stop their growth. However bacteria can mutate, causing bacterium to become resistant to antibiotics. The bacteria strains that cannot be treated by antibiotics can develop into serious infection. e.g MRSA

The first antibiotic was penicillin' discovered by Alexander Flemming in 1928. He had left some bacteria in a Petri dish, however it had been killed naturally by Penicillian mouldSince the discovery of penicillin, many other antibiotics have been discovered and developed.

Ignaz Semmelweis saw that women were dying after childbirth in masses, during the 1840s, from a disease called puerperal fever. He preveted the spreading of bacteria from doctors by making them wash their hands before entering his ward. The death rate reduced greatly from the use of antiseptic solution.

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