Our immune system is a wonderful, and amazingly complicated system. It is there working twenty four hours a day, seven days a week – and simply put, without it we would be in a whole heap of trouble.

But why, when we get an infection, and our immune system is called in to action do we get a temperature?

When we have an infection you may have a temperature, and this is often referred to as “having a fever”.

When you have a temperature this is caused by something called pyrogens floating around in your bloodstream. The word “pyro” comes from the Greek word meaning fire. In the English language we define this word as meaning, fire, heat or high temperature. [*link]

Pyrogens can be produced either by our own body “endogenous” or by something external to our body, such as endotoxins produced by bacteria “exogenous”.

Pyrogens are produced by something called leukocytes, such as Interleukin-1 (IL-1). They are produced in response to stimulation by the exogenous pyrogens.

In your brain you have something called the hypothalamus and one of it’s responsibilities is to regulate your body temperature. Think of it as your own personalised thermometer.

When pyrogens make their way to the hypothalamus, they bind to receptors on the preoptic area and this in turn raises the limit your internal thermometer is allowed to reach – as a result – our body produces a fever.

One interesting fact is that some of the white blood cells of your immune system (monocytes, macrophages, neutrophils and eosinophils) do not produce the same type of pyrogens.

But why does our body want us to get a temperature in the first place? Well… certain bacteria and viruses can be very sensitive to temperature changes in the body.  Therefore, it is thought that by raising the temperature the immune system is either aiming to kill those foreign invaders, or at least slow them down, so as to give itself more time to mobilise other resources to fight the infection.

So next time you have a temperature, just remember, this is your bodies way of using some of the many tools on the tool belt of the immune system to help you get better again.

Image Credits: [credit – pijama61], [credit – TefiM].