The shelves of health food shops are always instructive places, for the pills and potions that sit there mirror our feelings as well as our health concerns. Today, it's clear that many see a hostile, dangerous world out there. Our bodies are perceived as under attack from all quarters: chemicals, pollution, electromagnetic radiation, processed food, the pace of modern life and stress. The only shield between "out there" and total health breakdown is the immune system. Thus it is that every second bottle promises it will "boost" or "strengthen" this mysterious and complex internal bastion.
The immune system has become an all-pervading metaphor for our age. It represents everything we vulnerable, frail humans feel about our place in a world that seems out of control. Our last defence.
The concept of immunity is relatively modern. The term was coined in 1882 by Russian zoologist Elie Metchnikoff who, having poked a starfish with a thorn, observed, unsurprisingly, a robust defensive inflammatory action which he called immunity. But the term "immune system" is less than 30 years old. It's one of those bits of science terminology which has been assimilated into the fabric of everyday popular culture, while also being subjected to retro-fitting.
For instance, if our immune systems can be suppressed and impaired, surely it's logical to believe that the system is inherently fragile and cannot deal with multiple onslaught - for instance, from several vaccines in one shot. Commonsense, perhaps?
Yet consider the toddler's graze in the garden. Several hundred invaders swarm into the body at once. There is no orderly queueing system. No deli-counter ticketing. "Unknown soil bacterium No 327, wait your turn, don't you know we can only cope with one at a time here." Even newborns are not spared. Greet the world in a hospital and your immune system will instantly meet thousands of things it's never encountered before. Arrive at Malaga airport with your bucket and spade, or just take a bus trip, and it's a whole new world of foreign antigens. It's what our bodies do. Encounter loads of stuff, all at the same time. Yet this stellar accomplishment of the cellular team effort within us is now frequently denied.
If you get a cold, something is considered to be amiss. Your immune system must be impaired, by stress, processed food or partying. And while of course there is evidence that poor nutrition, stress and lack of sleep affect our ability to fight infection, being ill is part of how our system works, not evidence of weakness within.
Drop a cold virus direct into the noses of volunteers with healthy immune systems, and 95% of them will come down with a cold. "Getting better quickly is a better indicator of immune health," says Dr Dennis Alexander, head of molecular immunology at the Babraham institute, Cambridge, who also points out the blindingly obvious, that you need to be infected with something to develop protection against it. "T cells [major players in developing immunity] don't mount a proper antiviral defence for 10-14 days after infection with something new." In other words, a healthy system works on the premise that stuff will get through the first-line defences.
Another current take on the immune system is that if you are healthy and normal and look after yourself, you will only have a mild version of what's going around. "In truth, there's no such thing as a normal immune system," says Angus Dalgleish, professor of oncology at St George's Hospital, London, who works on cancer vaccines. He says the immune system is naturally very variable. It has to be because therein lies the key to protection of our species from annihilation. For instance, there are some people, perhaps 1 in 20,000, whose bodies are capable of almost total HIV lockout. While they resist HIV, they might also have a personal and very specific immunological Achilles heel in their genome, such as "access all areas" entry to the measles virus. Measles for these people will mean serious damage or death, rather than a few spots.
The rise of allergies is also claimed to be evidence of the immune system performing under par. "But far from our systems being beaten down, it's exactly the reverse," says Graham Rook, professor of medical microbiology at London's Royal Free hospital. "We're also seeing a rise in the level of auto-immune diseases [where the body attacks itself] and inflammatory bowel disease, where there's a greater level of immune activity." It's not a duff immune system causing this but one that hasn't been exposed to the bugs it evolved with in grubbier times and which helped train its responses. We are inappropriately regulated, not knackered by modern life.
Each age has its defining illness. Ours is weakness of the immune system, manifesting itself in ill health of all sorts. We feel the need to get away to a simpler, less stressful life of organic food and fresh air to restore our defences. The Victorians had neurasthenia, a lack of nervous energy brought on by the stresses of modern society and yes, you needed to get away to a simpler less stressful life etc etc to restore nervous energy.
Neurasthenia appeared when electrophysiology was the science story of the moment. No surprise the need for immune boosting didn't make an appearance until HIV became the big medical story. Where next? Just keep an eye on the health food shelves.
