Molecular Sciences Bldg 21, James Cook University,
Townsville, 4811, Queensland, Australia
Telephone: 61-7-4781 6265 Fax: 61-7-4781 6078
I've just recovered from URTI, an upper respiratory tract infection. The chances are that you have too. Half of Australia seems to be coughing and spluttering, and lying prone during the last two weeks. That's why I sounded a bit like Kamahl on steroids in the last couple of programs.
But the point is, how did we recover without thinking about it, yet again? As the great radio doctor, Earle Hackett used to say, 'We always recover from an illness, apart from the last one.'
Well it's an impressive process, and that's what Dr Alan Baxter in Townsville, Northern Queensland, is here to talk about today. Your immune system, how it works best, and how it goes wrong.
The immune system is as complex and has as many different parts as a Boeing 747. One of the key features of our immune system is its ability to remember infections that we have been exposed to before. For example, the childhood viral infections, measles, mumps and chicken pox, very rarely recur because of our improved immunity to them.
This is the principle by which vaccination works. The deliberate exposure to killed or weakened microbes provides immunity against a much stronger organism of the same type.
The immune system's memory is a consequence of the activities of two types of white blood cell, the T cells and the B cells. Although they are called blood cells, they spend much of their time in the lymphoid organs, the lymph nodes and the spleen. The lymph nodes are the glands a doctor feels for in your neck, under your arms, and in your groin, when you have the flu. They filter the tissue fluid, or 'lymph', on its return to the heart, and capture microbes: viruses, bacteria, fungi and parasites, or microbial fragments, for the T cells and the B cells to examine.
T and B cells circulate in the blood, but leave it to enter the lymph nodes when they pass through the specialised blood vessels the nodes contain. If a node has not trapped microbial fragments to which the T and B cells can respond, the cells make their way back through the lymph ducts to the large blood vessels at the base of the neck, and re-enter the bloodstream.
If the node has trapped microbial fragments to which the B cells can respond, they become activated, start to proliferate and produce antibodies which are the proteins that circulate in the blood and tissue fluids and neutralise foreign cells, such as bacteria, by binding to their surfaces.
Similarly, if the node has trapped microbe fragments to which the T cells can respond, they also become activated and start to proliferate.
The T cells do not make antibody. They either produce cell hormones that support the activities of the B cells, or else mature into 'killer' cells that can eliminate virus infected cells. As the specific B and T cells keep multiplying, their numbers become larger and larger, forming a formidable army of responding cells which only starts to shrink again once the invading microbes have been eliminated.
The end result is that the infection is routed, and the only signs that it was ever there are the slight increases in the numbers of specific T and B cells, and the presence of anti-microbial antibody circulating in the blood.
It is the residual anti-microbial antibody and the increase in the resting numbers of specific T and B cells that accounts for the immune system's memory following infection. The immune system's ability to expand the numbers of anti-microbial T and B cells up to 100,000 times and then shrink them back down to near-resting level, is equivalent of flying a Boeing-747 from London to Sydney, and then landing on a 200-metre runway.
Sometimes it doesn't all work according to plan.
Three sorts of things can go wrong with the immune system. Firstly, its response can be too violent for the nature of the foreign matter it is attacking. Allergies are typical of this problem, and result in asthma, eczema and hay fever. Secondly, the immune system can inappropriately target the body's own tissues. This results in auto-immune diseases such as childhood diabetes, multiple sclerosis and systemic lupus.
The third thing that can go wrong with the immune system is that its responses can be too weak, or too slow to overcome the infecting organism.
Many people are unhappy with the service provided by their immune system and wish to manipulate its performance. A Google search on the phrase, 'Boost your immune system' results in over 1,280,000 hits. Among the recommended immune boosters are air and water.
Now I can pretty much assure you that without air or water, your immune system is in a pretty bad shape. Not to mention the rest of you.
The nutritional remedies, suggested by sites on the internet, cover just about every imaginable food. And the folksy and alternative remedies cover a huge range of products, often extracted from either unconventional parts of common foods, such as pumpkin seeds, rhubarb root and wheat grass, or else obtained by killing protected species. And among the most disturbing remedies are colostrum, urine and faeces.
There are a couple of serious points I want to make here. Firstly, if the answer to a question is actually known, there are relatively few solutions offered. For example, if you break a long bone in your arm, your doctor will suggest you have it put in plaster, or fixed with a surgical pin. If you develop bacterial pneumonia, your doctor will administer antibiotic treatment, usually intravenously. It is because the people suggesting immune boosters don't know what they're talking about that they are talking so much.
Secondly, when we compare the performance of the immune system, with its expansion in cell numbers of 100,000 times and contracting down to the very precise levels, as equivalent to flying a Boeing-747 14,000 kilometres, and then landing it on a short runway in Sydney, do you really want to boost its performance?
Do you really want to have, just as your 747 is touching down on a 200-metre runway, some idiot hit full throttle on four Rolls Royce turbofan jet engines providing nearly 1000 kiloNewtons of thrust?
The simple fact is that most people who think their immune system needs boosting, fall into one or more of three groups. They may be children who have not yet built up an immunological memory of most of the common viral infections in our community. Remember, up to 20 colds per year is normal for a young child in childcare or prep school.
Second, they may be parents of children who are therefore exposed to these walking, talking, snotting, 37-degree microbial incubators.
Finally, they may be pen suckers or nose pickers, who for reasons best known to themselves spend much of the day deliberately introducing other people's microbes directly into their own body cavities.
But what can we do to protect our immune system, to let it operate effectively? I have three pieces of advice.
Firstly, don't get AIDS. HIV is a virus that invades the CD4 T cells, ruining them, and setting them up as targets to be killed by CD8 T cells. Without your CD4 T cells you're in serious trouble and your immune system is helpless. Literally.
Secondly, avoid by-passing the body's defences. Probably the most important one here is the skin. While the skin has evolved to cope very well with scratches and abrasions, it is completely by-passed by needles. Some people who catch HIV in Australia these days had someone inject it directly through their skin. Same with the nasty causes of viral hepatitis. So what about acupuncture? Isn't that good for your immune system? Doesn't it boost your immunity? I have no idea if it has any positive effects, but I can tell you this: unless those needles are sterile, it can have a hell of a bad effect.
Well then, what about vaccines? Exactly the same rules apply. If the vaccine, needles and syringes used are not sterile, terrible consequences can occur. In 1928 in Bundaberg, a local doctor injected a class of schoolchildren with the same vial of vaccine that had been used before and stored at room temperature on a shelf. The vial had become contaminated with skin bacteria, which has grown within the vial to large numbers, before being injected into the children. Eighteen became dreadfully ill. Twelve died. The moral of the story is, don't let your doctor inject something into you unless you see it come out of its sterile package.
My third piece of advice for protecting your immune system is limit the use of medications that suppress immunity. The strongest of these are the drugs used to treat transplant rejection, autoimmunity, and allergies.
One example of these is the class of drugs known as corticosteroids. Your doctor should only prescribe these if your immune system is causing serious trouble. It is his or her job, and yours, to balance the risk of infection against the benefits they provide.
Many Chinese herbal remedies contain corticosteroids, sometimes listed as dried adrenal gland, but usually obtained from a pharmaceutical company. These remedies can be very effective at treating inflammatory conditions. But usually at a risk that your doctor is not prepared to take.
A large number of other drugs readily available from your pharmacist, also have inhibitory effects on your immune system. Anti-inflammatory drugs like aspirin, Brufen and Voltaren inhibit the ability of the immune system to direct the white blood cells to areas of local damage and infection. This is, after all, what inflammation is. Perhaps if you have a headache, paracetamol might be a better alternative.
You have all heard how good antioxidants are for you: fish oil, Omega-3 fatty acids, evening primrose oil, and a host of others, all inhibit the production and/or activities of oxygen radicals. This results in less damage of DNA, reducing the risk of cancer. They may also have a host of other benefits, particularly for the vascular system. But your immune system was using those oxygen radicals. They are one of our tools for killing bacteria. The message is, moderation.
I'd like to finish with a comment about stress. Stress is in the eye of the beholder. I have a friend who likes skydiving, and unless he can go every few weeks, he gets very twitchy and rather unpleasant to be with. Now I, on the other hand, would find what he loves doing, particularly stressful. Stress, however it is interpreted by the stressee, has very well characterised effects on the immune system. It results in the natural secretion of corticosteroids, the same corticosteroids that are used to suppress transplant rejection, autoimmunity and allergies. Corticosteroids not only inhibit inflammation, but suppress the activities of the white blood cells and shut down their production. In fact, in order to avoid the whole 'eye of the beholder' thing, scientists sometimes define stress as something that causes the natural secretion of corticosteroids.
Stress is probably evolved to help us escape danger. You don't really want a bunch of inflammation making it painful to run away from that lion. Stress in the short term, giving a talk on the radio for example, probably does no harm. It is long term stress that can cause serious problems.
So Tai Chi, yoga, exercise, rest, meditation, fun and laughter and even the occasional beverage, do help your immune system, because they reduce chronic stress, reduce production of corticosteroids, helping to not boost your immune system, but let it fly.
I'll drink to that. Another good excuse to uncork a good vintage. Dr Alan Baxter de-stresses in Northern Queensland at the Comparative Genomics Centre, James Cook University. He's also Professor of Biochemistry there. Next week we go retro with Bill Hall in Adelaide.
I'm Robyn Williams.
'Let Your Immune System Fly' is © Alan G Baxter 2008
Autoimmunity Research Group, Centenary Institute of Cancer Medicine and Cell Biology, Key words: Autoimmune diabetes, Type 1 diabetes mellitus, childhood diabetes, lupus, systemic lupus erythematosus, hemolytic anaemia, hemolytic anemia, Coombs' test, antinuclear antibodies, renal failure, glomerulonephritis, gastritis, type A gastritis, pernicious anemia, immunology, popular science, biology.