Have you ever been told by the doctor that your immune system was low when you once fell ill. I believe you wondered how that could happen.
We will try and understand that today. All around us there are invisible forms of life which we call germs. They are in the air, in the soil, in the water we drink and the food we eat.
Many of them are harmless or even beneficial to us, but others may cause diseases.
The human body has many natural weapons to fight off the attack of the harmful germs. For instance, the digestive juices and the blood itself kill off many kinds of germs.
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But certain ones enter the body and start infection. Then the anti-germ soldiers in the body spring into action. These are the white blood cells in the blood. They can pass right through the thin walls of the blood vessels and can wander all over the body. The white blood cells gather at the point of attack and destroy the germs by feeding on them.
But disease isn’t always caused by a direct attack of germs. Germs throw off a chemical substance called “toxin” which acts as poison in the body.
Once again, the body has a built -in defense. The toxin causes certain cells in the body to go to work to produce a substance that destroys the toxin. This is called an “antitoxin.” If the antitoxin is produced quickly enough and in enough quantity, the germ poison is neutralised. The body gets well.
This antitoxin is always a very special one that works only against the toxin for which it was produced. It remains in the blood for some time after the toxin has disappeared.
Now suppose the same germ attacks the body and produces new toxin. Instead of becomeing sick, we show no symptoms of the disease at all! The reason is that our body already has resistance to the disease; it has the antitoxin all ready.
We call this condition “acquired” immunity. It is “acquired” because our resistance came after the original attack of the germs.
Now let us suppose there is an attack of germs on the body, spreading toxins through our system, and yet we don’t get that specific disease. This means our blood had enough antitoxin in it to begin with to prevent the specific poison from doing any harm. We call this a “natural immunity”. It is a quality of our blood that we inherited.
If we introduce a little toxin in our blood so it can produce antitoxin to prevent disease, we call it artificial immunity. This is exactly what happens when we are vaccinated against measles, rubella and other diseases etc.