B1: 1.5 - Defence mechanisms

There are many ways that pathogens can be spread from one person to another.
1. Droplet infection - when you cough, sneeze or talk you expel tiny droplets full of pathogens from your breathing system.
2. Direct contact - some diseases are spread by contact of the skin.
3. Contaminated food and drink - eating raw or undercooked food, or drinking water containing sewage can spread disease.
4. Through a break in your skin - pathogens can enter your body through cuts, scratches and needle punctures.
The main ways of preventing microbes getting into your body are your skin, your blood and your mucus.
If pathogens get inside the body they will meet your second line of defence - the white blood cells.
1. Some white blood cells ingest pathogens which destroy them so they can't make you ill.
2. Some white blood cells produce special chemicals called antibodies. They target particular bacteria or viruses, you need a antibody for for each pathogen so once they are made once, the pathogen is remembered and that antibody can be made very quickly again.
3. Some white blood cells produce antitoxins, they counteract the toxins released by pathogens.

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