Building on the video, the immune system has a variety of cells used throughout the body for communication. They are part of the Cytokine family and they travel in the blood stream and the lymph system. These are the things that make us feel awful when we have a cold. Cytokines make us feel awful in various ways and this blog will explore how and why – and give the simplest thing to do when suffering from a cold1
There are various types of cytokines. In this case we are involved with three: interferons, interleukins and cachectins. Interferons activate those white blood cells which fight viruses and cancer. Interleukins are central to the T Cell cascade as talked about in the video. The interleukin of particular interest here, for simplicity, is called Interleukin-1, shortened to IL-1.2 It is IL-1 that carries the alarm message from the macrophage, where it is made, to the T-Cells. IL-1 also does other things to us.
IL-1 has receptors in the brain where it influences temperature regulation. Our body is set to a temperature of 98.6° and IL-1 shifts this set point upwards causing us to run a fever. It also makes the body release Corticotropin-releasing factor, mercifully shortened to CRF. Now the fascinating thing about CRF is that it triggers the same stress response as we would get if we stumbled upon an angry Cobra whilst out doing a bit of weeding in the garden (I am writing this in the UK, so such an event would be a huge shock). Immediately we would take an enormous leap backwards and probably run screaming up the garden, busily releasing CRF as we go. To enable our little legs to carry us away, CRF blocks energy storage, specifically fats and sugars, instead releasing them as energy into the muscles. It reduces our appetite, sex drive and reproductive processes. And so it is during an infection; neither food nor sex are appealing when we just want the winceyette nightie and a hot water bottle. IL-1 also makes us sleepy.
The reason why we ache when we’ve got a cold is because IL-1 lowers the pain threshold of the nerves, so our joints ache, old injuries play us up and our head aches.
The macrophages also release the 3rd cytokine, a cachectin. The receptors for this are in the body fat. Cachectins will kill some types of tumour, hence the more recent name, TNF or Tumour Necrosis Factor. Cachectins also stimulate a fever and suppress appetite.
Now it takes an enormous amount of energy to fight a virulent pathogen. The immune system is ramped up, producing immune cells and antibodies and heat is generated by the fever during which we shiver and shake. So it makes sense that the body will do all it can to make us rest -aches and pains mean we don’t want to go running about, we feel sleepy and cold since we are running a fever. Most pathogens thrive best in temperatures below 98.6°, so by increasing our core temperature, we make life much more difficult for the pathogens to multiply. Unless the fever is dangerously high, it is better to run the fever and let it get on with frying the pathogens than to suppress it which will only lengthen the cold3.
So if a cold is caught, the best thing to do is listen to the body: go to bed and try not to take fever suppressants like aspirin or ibuprofen. Drink plenty of water and read an easy book. Sleep a lot. Let the body get on with healing itself. And the same goes for the children. If sore throats are involved, wrap a soft scarf around the neck.
The next blog will deal with supplements that we can take to stop getting a cold in the first place. And should we still be unlucky enough to catch one, the cold will be gone in 2 -3 days.
- This blog is based on the book ‘The Trouble with Testosterone’ by Robert Sapolsky with particular reference to the chapter ‘Why you feel crummy when you are sick’. [↩]
- there are other interleukins, but collectively they all do the above [↩]
- Kluger MJ Is Fever Beneficial? The Yale Journal of Biology and Medicine 59 (1986) 89-95 [↩]