Your greatest friend in the battle against SARS-CoV2, the virus that causes Covid-19, is your own immune system. Its job is to keep you safe from nasty germs that might infect you and most of the time it does a great job. This is why 80pc of people will fight this virus with minor symptoms

But sometimes your immune system isn't up to the job. This can be because you become infected with a massive dose of a virus, which runs amok and makes you feel awful. Or perhaps you are over 65 and, like most things in your body, your immune system is less able. Or you might be taking drugs that suppress your immune system if you have an inflammatory disease. Or if your heart or lungs are weak, the virus can really harm you. So the question is, is there anything you can do to boost your immune system? The answer is a resounding yes.

Look after your immune system

To know how to take care of your immune system, first you need to understand the weapons your immune system has, which are actually very impressive. When you come into contact with a germ you've never met before you've got various barriers to try to stop it getting into your body. As well as skin, you have mucus - snot is a really important barrier as it traps germs and has special biochemicals that can kill them, in this case mainly bacteria. Your body is also actually covered in bacteria, inside and out (bet you didn't know that), and many of these are beneficial. They out-compete the bad guys and even make chemicals to poison them. This stops the invader from eating the resident bacterias' lunch.

The germs can sometimes win, however. They have cunning tricks up their sleeves to breach the defences. A virus like SARS-CoV2 burrows inside the cells that line your lungs. That's where they multiply. However, pretty soon the rapid response unit of your immune system will arrive. Special white blood cells can attack the invader. So-called macrophages (which means 'big eater') eat the germs up and destroy them. They also call the alarm to bring out another white blood cell called a T lymphocyte. These are like the garda superintendents, controlling everything and even killing off the virally-infected cell themselves to stop the virus spreading. It's the T lymphocytes that remember, so that when you get reinfected they are good to go. T lymphocytes are an important aspect of why vaccines work. They also control another important white blood cell, the B lymphocyte. This is the cell that makes antibodies. These are very specific proteins that are great at stopping a virus like SARS-CoV2 in its tracks and B lymphocytes also remember.

We remain optimistic that there will be a vaccine soon. Vaccines are weakened forms of a germ or part of it, which causes a weak immune response. But the cells of the immune system are now trained. And when the intruder comes they kill it. It's a bit like the sheriff has put up wanted posters around town and when the bad guy turns up he's recognised and killed quickly and you won't even know you've been infected. This is why it's so important to get a vaccine for Covid-19.

What can you do?

The trick is to keep all these cells of your immune system fit and healthy. This begins with what you eat. A varied diet with lots of high-fibre foods really boosts your immune system - immune cells love healthy food and hate fatty foods, so a healthy diet is essential.

Also, if you don't over-eat and have good gaps between meals, this really mobilises the immune system increasing the numbers of immune cells by as much as three-fold, so lay off that second piece of pie and have gaps of at least four hours between meals. Don't over-do this, though, as being malnourished has a hugely negative effect, as can be seen in developing countries where it's a huge cause of death from diseases like TB.

Do probiotic drinks work?

The evidence for taking probiotic supplements is mixed. It's much more effective to change your diet to a healthier one.

And what about vitamins?

Vitamin D has become a hot topic in immunology. It is used by our immune cells, and is something that people in Ireland can get quite low on in the winter. So it's good to take in more of it. Taking extra vitamin C, however, is probably a waste of time for the well-fed Irish. Eating your five-a-day of fruits and vegetables is the best way to maintain necessary levels. It's water soluble so you will just pass any excess into your urine.