An introduction to the immune system
The immune system is the body’s defence mechanism – the army with which the body protects itself against disease-causing organisms such as viruses, bacteria or fungi, which are known as pathogens. The troops that make up this army are various types of white blood cells, which are produced in the bone marrow.
When working well, the immune system is constantly vigilant in order to protect us from infection, infestation and general invasion by bugs of all descriptions.
How does it work?
An invading pathogen has many obstacles to surmount in order to infect the body. Firstly, the pathogen must penetrate the external barrier of the skin, or survive the stomach acid if entering via the digestive tract. The nasal passages might seem a good potential entry route, but they secrete mucus that traps and then flushes away pathogenic matter. Saliva and tears both contain antibacterial enzymes, to neutralise pathogens that attempt to enter via the mouth or eyes.
Pathogens that make it past the salivary enzymes and stomach acid still have to contend with gastrointestinal mucus, which can trap and expel them. Additionally, the gut contains more than 70% of the body’s supply of immune cells, which seek out and destroy pathogens that have made it past the mouth and stomach. Any pathogenic matter that gets into the bloodstream from the digestive tract will have to travel through the liver, where more immune cells are on hand to deal with them.
If a pathogen gets past all these defences and manages to infect tissue cells, an immune response is triggered.
- The damaged cells call for help (by releasing chemicals such as TNF-α, that attract immune cells).
- Immune cells come along and identify the pathogen as bad/ unfriendly to the body and call up more troops that attack and hopefully kill the pathogen. Symptoms of this attack are a raised temperature, feeling tired and a little achy, slightly swollen lymph glands, and possibly a runny nose.
- The immune system can also make an antibody for that pathogen. An antibody is a bit like a customised pair of handcuffs, which attach to the baddie and make it easier for the alerted troops to spot and kill it. The antibody remains in the system, ready to use if that particular bug turns up again.
If your immune system is working well
- You don’t fall prey to every bug around
- You throw off infections quite easily
- You aren’t constantly itching or sneezing
- You generally feel well
If you have a fully functional immune system, then when you are exposed to a bug, you should kick it out quickly and symptoms such as a raised temperature will not last for long.
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What if it isn’t up to scratch?
Weak immune function makes it harder to withstand infection by viruses, bacteria or fungi. You will be more susceptible to contracting colds, flu and cold sores. The immune system will take longer to detect and conquer the bug, so symptoms such as raised temperature, swollen glands, sore throat, coughs, catarrh, etc., will be present more frequently.
Why might you have weak immune function?
- Eating a bad diet
- Eating lots of fatty foods
- Drinking excessive amounts of alcohol
- Being stressed and unhappy
- Not getting enough sleep