Immune System Even Cleverer Than We Thought

In any branch of science there are moments when conventional wisdom is overturned. One of those moments has just occurred in immunology as a result of research at Stanford University. Our previous understanding was too simplistic. Things are even more complicated than we thought.

For years now everyone has believed that lymphocytes can learn to recognise specific molecules but that each type of lymphocyte can only learn a single lesson. One kind of lymphocyte can learn to recognise measles virus, another can learn to spot whooping cough bacterium on sight and another can only be activated by a particular protein made by prawns. Once a lymphocyte has had its initial exposure it will produce memory lymphocytes (CD4 cells) that will hang around for the rest of your life, waiting patiently to deal with a second encounter. This is how adaptive immunity and, of course, vaccination works. 

But the one lymphocyte = one lesson theory has just been blown out of the water. It seems that lymphocytes can generalise their learning.

The human brain can generalise easily. Learner drivers are taught to negotiate road junctions. Once the basic skill is there, they will be able tackle all kinds of road junctions. No two junctions are identical but nevertheless the competent driver tackles them all confidently. The learning has been generalised.

Now it seems that memory lymphocytes have some ability to do the same kind of thing. They are even cleverer than we thought. They can recognise not only the microbe that first activated them, but some other types as well.

We knew the immune system was magnificently complicated and now we have to acknowledge the existence of a whole new level of complexity. This new knowledge may shine a light several aspects of how the immune system learns about its environment, such as how benign bacteria help the immune system to develop in childhood.
http://www.sciencedaily.com/releases/2013/02/130207131602.htm

Cancer and Inflammation Pathway Found

A few years ago there was a very simple view of the relationship between the immune system and cancer. Immune cells, such as natural killer cells, had the capacity to destroy cancer cells in the laboratory. So they must do so inside the body, surely? The development of cancer was blamed on a failure of the immune system's surveillance - a failure to spot microtumours and dispatch them before they could take root.

Complementary therapists seized on this idea, reasoning that if you could boost up the immune system with a beautiful thought, a massage or a potion then you could reduce your chances of getting cancer - or even help the immune system attack fully-developed tumours.

But now a far more complicated picture is emerging. It is not a simple case of cancer cells bad and immune cells good.  We now know, for instance, that immune cells can sometimes help the cancer cells instead of attacking them.

Some recently-published research has demonstrated a new connection between cancer and immune cells. It has long been suspected that prolonged inflammation, for example in the stomach lining, might cause cancer but exact molecular mechanisms are hard to pin down. A team in Ohio has now discovered a link between immune cells, inflammation and a form of blood cancer. They were able to demonstrate this using a combination of mice and human leukaemia cells.

Immune cells communicate with other cells by releasing a range of chemicals, collectively know as cytokines or interleukins.  One of these, known as Interleukin-15, is released during inflammation. Inflammation is useful as a short term measure but if it becomes long term, you have an excess of Interleukin-15 in circulation.

The team has demonstrated that an excess of Interleukin-15 can stimulate a type of immune cell known as a large granular lymphocyte (LGL) to become malignant giving rise to a rare form of leukaemia.

Not content with this breakthrough, they managed to "turn off the pathway" and reverse the process - curing the mice of their LGL leukaemia.

So here we have a double success - demonstration of a molecular pathway whereby an immune chemical associated with inflammation can cause a specific cancer - and reversing the process.  

So if a complementary therapist tells you that something will “boost your immune system” proceed with caution. The immune system is not a simple device. It’s a vast collection of cells and complex chemicals, interacting in ways that we are only beginning to understand in detail.

http://www.sciencedaily.com/releases/2012/11/121112135512.htm

Should 'Flu Vaccination be a Condition of Employment for Health Workers?

A recent editorial in the Canadian Medical Association Journal makes the case for mandatory flu vaccinations for health care workers.

There are a number of arguments for requiring health care workers to take up this vaccine.

Health workers in many settings tend to be exposed to flu sufferers during an epidemic and if they fall ill, services are likely to be impaired. Absence rates amongst NHS staff are high when compared to most other UK employment sectors, which puts a significant pressure on hard pressed hospital budgets.

Even more persuasive is the argument that health professionals are in contact with vulnerable patients and could infect them. Individuals sometimes argue that they do not need the flu vaccine because they "never get ill" or that, if they do get 'flu, they will stay at home. The Canadian article points out that flu can be infectious before symptoms appear. We also know that not all those infected with a virus exhibit obvious symptoms.

Age, pregnancy, injury, surgery and acute illness can all suppress the immune system. So imagine your vulnerable relative, entering a health care setting, minus a flu infection this winter. Would you want them cared for by an unvaccinated doctor or nurse?

There is a very strong argument that those who work in health and care settings should be required to have this vaccination.

Employers in the UK have traditionally been wary of imposing health-related rules on their employees. Smoking bans at work, for instance, were slow to take hold. Some would argue that imposing the requirement for vaccination would be discriminatory or an infringement of human rights.

A requirement on health workers would not be discriminatory if applied to all. It does not fall under any section of anti-discrimination law. As far as human rights are concerned, exemptions could be allowed in certain circumstances - if, for instance, someone had a religious objection to vaccination or was advised against it for medical reasons.

Otherwise there would seem to be nothing wrong in saying: It is a requirement of employment that all our staff are up to date with their vaccinations, including annual flu vaccine.

Make it part of the contract of employment when people join, so that new employees are clear that it is a requirement. Use peer pressure to encourage existing staff to comply. To prioritise employee rights over the safety of patients, would seem to be perverse logic.

http://bit.ly/VyUxzX

A Bitter End for Bacteria

The body protects itself in many ways. Some involve the immune system but other mechanisms act at the boundaries of the body, dealing with microbes before they enter. The eyes protect themselves with blinking and antiseptic “tears” for instance. Mucus in the nose traps and washes away microbes and other particles. Saliva is slightly acidic, making the mouth inhospitable to germs. There are many more examples. A recent experiment has identified a previously unknown method that operates in the upper airways. It has is a rather unexpected link to the sense of taste.

I have been aware for a few years now, that some people experience bitter tastes much more readily than I do. While I am happily chomping through a mild-tasting portion of broccoli, the person on the other side of the table is screwing up his face in disgust, and forcing it down. Apparently there is a gene that makes some people much more sensitive to the taste of bitter compounds than others. This might have a slight evolutionary advantage because bitterness can be associated with poisonous vegetation and fungi. So ancestors with this gene might have been less likely to die young from accidental poisoning. But it seems that it might bring an additional advantage when it comes to a bacterium that can cause pneumonia (Pseudomonas aeruginosa).

This airborne bacterium can stimulate bitterness receptors not on the tongue, but in the upper airways. In a laboratory experiment, tissue taken from human sinuses not only sensed the bitter taste of the bacteria but also produced nitric oxide to kill them. The author suggested to New Scientist recently that people with a greater ability to detect bitterness might as a consequence, have a better defence against this particular bug.

Those of us who are not so sensitive to bitterness can console ourselves that it is easier for us to eat our greens and so gain some health benefits from that source.

http://bit.ly/Swoe1h

Hygiene Hypothesis out and "Old Friends" are in

For some years now, increased rates of childhood asthma and eczema have been observed and the finger of suspicion has pointed to a lack of microbes in overly-clean homes. This idea is known as the hygiene hypothesis.

A recent report from the International Scientific Forum on Home Hygiene has concluded that this hypothesis is not correct.

It seems that microbes - or rather a lack of them - may well be implicated in the increase of allergies but it is not a reduced quantity of bacteria, viruses and intestinal worms that seems to be the problem.

We all have a vast population of "friendly" microbes that live on our skin and in our body cavities - nose, mouth, gut and so on. The bacteria alone are said to outnumber our body cells by ten to one. Without exposure to this vast array of microscopic life, we cannot be healthy. We know this, in part, because mice brought up in a sterile environment reliably fail to develop normal, healthy immune systems.

These "friendly" microbes stimulate the immune system in many interesting ways. They train it in infancy and help to keep it finely tuned throughout life.

There is a further range of microscopic life that lives in our homes – on surfaces, on dust flakes and so on. Living alongside these familiar life forms is normal and healthy. Of course there are also occasional pathogens that can cause illness. But every day babies and toddlers get away with licking floors and other household surfaces without picking up diseases.

The report concludes that the hygiene hypothesis should be replaced by the "Old Friends" hypothesis. This states that allergies are on the increase because the mix of microbes on and around us bodies has changed. It is no longer the same rich brew that co-habited with our ancestors and is no longer quite what the developing immune system needs.  Our immune systems evolved alongside these old friends, developing  complex and subtle symbiotic partnership.

My grandmother grew up in the country, playing on the dung heaps in the yard, in a home that teemed with rural bacteria. When she had ear infections, the treatment was to pour her own urine into her ear. As her young immune system dealt with this environment, it learned to deal with a mix of bacteria that had probably changed little through the millennia.

My grandchildren, growing up in an urban environment, have encountered a different range of microbes. If you could analyse their microbe population it would not be smaller, but would certainly be different to that of their great, great grandmother. There will be an absence of some of the "old friends" that evolved alongside their ancestors for millennia.

It is not just an absence of dung heaps that has caused this change. It has become normal for children to have several courses of antibiotics for chest or ear infections. This will have affected their blend of gut bacteria. Hygienic caesarian birth probably has an effect and so might bottle-feeding from a sterilised teat instead of a mother's microbe-rich breast. Factors like this are probably far more significant than how often their parents clean the bathroom.

You may say this is not a revolutionary change of hypothesis, so does it matter? Should we worry about hygiene, and if so where and when?

Well yes, food and kitchen hygiene are important if we want to avoid food poisoning. Hand washing can reduce the number of “tummy bugs” and colds we contract. If someone in the family has a compromised immune system, then extra vigilance is needed. And if someone in the family is already asthmatic, then reducing house dust exposure might be helpful.

But we still have a lot to learn about friendly bacteria and intestinal parasites. We don’t know the identity of these old friends and whether it would be helpful to hold a reunion or not. It is a branch of science that is relatively new and is only just starting to yield interesting information. It will be a while before it comes up with any practical suggestions.

So if you were worried about your house being too clean, then you can indulge in a bit of anxiety-free cleaning. And if you were worried about a degree of household squalor, then worry no more. The friendly bacteria will carry on doing what they do, and cleaning, or not cleaning will probably have no effect whatsoever. 

To read more, here is a link to Science Daily

http://www.sciencedaily.com/releases/2012/10/121003082734.htm

A New Role for Vitamin D ?

Everyone seems convinced that vitamin C has wonderful preventative and curative powers for viral illnesses like colds and 'flu despite the fact that there is very little evidence to support the belief. Evidence is starting to build though, that vitamin D might be much more significant in the maintenance of health.

There are two main ways to top up your vitamin D supplies. One is to expose you skin to sunlight and the other is to eat animal fats - in particular oily fish.  

It has been long been recognised as the substance that prevents rickets - a deficiency disease in babies and young children in which bones are inadequately calcified. The leg bones bend under the child's weight, the skull can be as thin as a ping-pong ball and the whole skeleton is deformed.

We now know that there are receptors for vitamin D on the surface of cells all over the body, including immune cells and not just in bone cells. Receptors are like mail boxes - you don't have them, unless you are expecting some mail. There is particular research interest in the way this vitamin interacts with tuberculosis (TB).

TB is a bacterial disease that has evolved a unique relationship the immune system. Many people infected with the TB bacterium remain healthy. The immune system often manages to contain pockets of infection as harmless nodules so that the disease is “latent”. As long as the immune system can successfully maintain this state of siege the TB cannot spread and inflict further damage. It is well know that those with an HIV-damaged immune system are susceptible.

Before the advent of antibiotics, TB was very difficult to treat but sunshine therapy was one of the methods that seemed to be helpful in pushing the disease back into latency. There is a complex interplay between immune cells and TB bacteria and there is a strong suspicion that one of the things that helps the immune system to maintain its ability to contain the disease is to have an adequate supply of vitamin D in the body. Research recently published seems to show that giving patients supplements of vitamin D (alongside their antibiotics) significantly speeds recovery.

There are other clinical trials taking place into the links between vitamin D and a range of diseases. This is one of the most interesting lines of current research, in terms of things individuals might be able to do to support the function of their own immune systems.

A variety of TB that is resistant to all available drug treatments is no longer a spectre but a reality. Several cases have been identified in India. Once this starts spreading across the globe, and spread it inevitably will, TB will become an incurable killer as it was in the 19^th and early 20^th centuries. Anything we can discover that will help people resist this disease will be important to individual and public health.

Queen Mary, University of London. "High doses of vitamin D help tuberculosis patients recover more quickly." ScienceDaily, 3 Sep. 2012. Web. 24 Sep. 2012. http://www.sciencedaily.com/releases/2012/09/120903154008.htm