Tuesday, April 03, 2007

End to blood typing problems?

A life-saving method of converting blood from one group to another has been pioneered by scientists. The breakthrough could potentially mean the end of blood-donor shortages and boost supplies of sought-after group O negative blood. O negative blood is known as “universal” because it can be given to anyone in a blood transfusion. Giving patients the wrong type of blood can cause severe immune system reactions and can be fatal.

Writing in the journal Nature Biotechnology, an international team of researchers described how they converted blood from group A, B or AB to group O. The process uses bacterial enzymes found in fungi, which can be used as biological “scissors” to cut sugar molecules from the surface of red blood cells.

People inherit blood type through their parents’ genes, and the system of categorising groups as A, B, AB or O dates back to 1900. Those in groups A and B have blood containing one of two different sugar molecules that can trigger an immune response. People in group O, the most common group, have neither of these “antigens”, while those in group AB have both.

Patients produce antibodies against the antigens they lack. For this reason, AB individuals, who lack neither, can receive blood safely from any group. But group A patients cannot be given a transfusion of group B blood, and vice versa. Group O patients react badly against A, B or AB blood. However, their own blood, having neither of the sugar antigens, is suitable for people from all the ABO groups. Group O donors are therefore always in demand, and O blood is often in short supply.

A further antigen that can trigger an immune response, a protein called RhD, exists in blood labelled “rhesus positive”. Truly “universal” group O blood is rhesus negative, meaning that it is also missing this antigen, but at the moment this type makes up only 4 per cent of stocks for the National Blood Service (NBS).

The scientists, led by Henrik Clausen, from the University of Copenhagen, screened 2,500 types of fungi and bacteria looking for useful proteins. They found two bacteria, Elizabethingia meningosepticum and Bacterioides fragilis, that yielded enzymes capable of removing A and B antigens from red blood cells. In tests, the antigens were found to vanish from 200ml samples of A, B and AB blood after an hour’s exposure to the appropriate enzyme. The researchers wrote: “Clinical translation of this approach may allow improvement of the blood supply and enhancement of patient safety in transfusion medicine.” Group O blood created using the new method will have to be tested on human beings before it can be used in hospitals.

To create supplies of group O negative blood, rhesus negative A, B and AB blood would have to be selected. No way has yet been found to turn rhesus-positive blood into rhesus-negative. The present system of blood transfusions is wasteful, with 10 per cent of donations in the UK never reaching patients. It is also expensive, with each unit costing more than 120 pounds to extract, screen and store. The NBS, which serves England and North Wales, holds 40,000 units of blood in stock — enough to last about 5½ days. A unit is a single blood donation, or two thirds of a pint. Red blood cells can be stored for only 35 days, and stocks must be replenished continuously by donors.


A feelgood germ

FORGET the spring-cleaning. A study has found evidence that bacteria common in soil and dirt could improve people’s spirits. According to the research, the action of Mycobacterium vaccae (M vaccae) on the brain is similar to that of some commonly used antidepressants. The bacterium, which is related to the microbe that causes tuberculosis, appears to work by stimulating the body’s immune system. This, in turn, prompts certain cells in the brain to produce more serotonin, a hormone associated with feelings of wellbeing.

“These studies help us to understand how the body communicates with the brain and why a healthy immune system is important for maintaining mental health,” said Dr Chris Lowry, a neuroscientist at Bristol University who carried out the research. “They also leave us wondering if we shouldn’t all spend more time playing in the dirt.”

The finding follows separate research by other scientists into the impact of bringing children up in “overhygienic” conditions. They found evidence that exposure to a wide range of common microbes in early life helped to promote healthy development of the immune system. Without such exposure, the immune system seems more likely to mistake the body’s own cells as invaders and launch attacks on them. This could be one of the mechanisms underlying the surge in conditions such as asthma and eczema.

The research by Lowry and a team of 12 scientists at Bristol and University College London (UCL) takes this “hygiene hypothesis” a step further by linking exposure to the microbes found in dirt with good mental, as well as physical, health. Interest in the project arose after human cancer patients being treated with M vaccae unexpectedly reported increases in their quality of life. This could have been caused by the microbe having indirectly activated the brain cells that produce serotonin.

The researchers injected some mice with the bacteria while others were made to inhale it. They then analysed the blood and brains of the infected mice to see what effect the microbes might have had on their immune systems and on serotonin levels. Details will be published in Neuroscience, an academic journal, this week.

The study is highly unlikely to lead to new therapies for depression in the near future but it does build on the growing body of research showing the importance of the human immune system in regulating even the subtlest aspects of health. There are a range of studies supporting the hygiene hypothesis and the idea that exposure to microbes is good for long-term health. In families with several children, the youngest often has the least allergies, most likely because it picks up the elder siblings’ infections so activating the child’s immune system.

Graham Rook, a professor of immunology at UCL who worked with Lowry, has already published research into the link between exposure to microbes and subsequent development of allergies. Rook and two of his co-researchers are also working with S R Pharma, a company looking into whether M vaccae could become the basis of treatments for conditions such as asthma. Rook believes that improved cleanliness may be a contributory factor in diseases such as asthma, eczema and hay fever, along with autoimmune diseases such as Type 1 diabetes and inflammatory bowel disorders such as Crohn’s disease. He said: “We’ve known for a couple of decades now that a whole group of chronic inflammatory disorders are becoming much commoner in the rich developed world.”

The body’s response to such inflammatory diseases is regulated by immune cells which, said Rook, need to encounter harmless bacteria early in life in order to work out how to respond effectively to real threats. Without these encounters, he said, the regulatory cells can malfunction, leading to health problems.

Mark Pepys, professor of medicine at UCL, said that there was “quite a lot of evidence” to support the hygiene hypothesis but said he would be cautious about extending the theory to mental wellbeing.



Just some problems with the "Obesity" war:

1). It tries to impose behavior change on everybody -- when most of those targeted are not obese and hence have no reason to change their behaviour. It is a form of punishing the innocent and the guilty alike. (It is also typical of Leftist thinking: Scorning the individual and capable of dealing with large groups only).

2). The longevity research all leads to the conclusion that it is people of MIDDLING weight who live longest -- not slim people. So the "epidemic" of obesity is in fact largely an "epidemic" of living longer.

3). It is total calorie intake that makes you fat -- not where you get your calories. Policies that attack only the source of the calories (e.g. "junk food") without addressing total calorie intake are hence pissing into the wind. People involuntarily deprived of their preferred calorie intake from one source are highly likely to seek and find their calories elsewhere.

4). So-called junk food is perfectly nutritious. A big Mac meal comprises meat, bread, salad and potatoes -- which is a mainstream Western diet. If that is bad then we are all in big trouble.

5). Food warriors demonize salt and fat. But we need a daily salt intake to counter salt-loss through perspiration and the research shows that people on salt-restricted diets die SOONER. And Eskimos eat huge amounts of fat with no apparent ill-effects. And the average home-cooked roast dinner has LOTS of fat. Will we ban roast dinners?

6). The foods restricted are often no more calorific than those permitted -- such as milk and fruit-juice drinks.

7). Tendency to weight is mostly genetic and is therefore not readily susceptible to voluntary behaviour change.

8). And when are we going to ban cheese? Cheese is a concentrated calorie bomb and has lots of that wicked animal fat in it too. Wouldn't we all be better off without it? And what about butter and margarine? They are just about pure fat. Surely they should be treated as contraband in kids' lunchboxes! [/sarcasm].

Trans fats:

For one summary of the weak science behind the "trans-fat" hysteria, see here. Trans fats have only a temporary effect on blood chemistry and the evidence of lasting harm from them is dubious. By taking extreme groups in trans fats intake, some weak association with coronary heart disease has at times been shown in some sub-populations but extreme group studies are inherently at risk of confounding with other factors and are intrinsically of little interest to the average person.