Why we have blood types and why they matter and with other 8 informations ( source ; Flipboard & internate )
A
patient (not the author) receives a blood transfusion.
When my parents informed me that my blood type was A+, I felt a strange
sense of pride.
If A+ was the top grade in school, then surely A+ was also the most
excellent of blood types – a biological mark of distinction.
It didn't take long for me to recognize just how silly that feeling was
and tamp it down. But I didn't learn much more about what it really meant to
have type A+ blood.
By the time I was an adult, all I really knew was that if I should end
up in a hospital in need of blood, the doctors there would need to make sure
they transfused me with a suitable type.
And yet there remained some nagging questions. Why do 40% of
Caucasians have type A blood, while only 27% of Asians do? Where do
different blood types come from, and what do they do?
To get some answers, I went to the experts – to haematologists,
geneticists, evolutionary biologists, virologists and nutrition scientists.
In 1900 the Austrian physician Karl Landsteiner first discovered blood
types, winning the Nobel Prize in Physiology or Medicine for his research in
1930.
Since then scientists have developed ever more powerful tools for
probing the biology of blood types. They've found some intriguing clues about
them – tracing their deep ancestry, for example, and detecting influences of
blood types on our health. And yet I found that in many ways blood types remain
strangely mysterious. Scientists have yet to come up with a good explanation
for their very existence.
"Isn't it amazing?" says Ajit Varki, a biologist at the
University of California, San Diego. "Almost a hundred years after the Nobel
Prize was awarded for this discovery, we still don't know exactly what they're
for."
My knowledge that I'm type A comes to me thanks to one of the greatest
discoveries in the history of medicine. Because doctors are aware of blood
types, they can save lives by transfusing blood into patients. But for most of
history, the notion of putting blood from one person into another was a
feverish dream.
Renaissance doctors mused about what would happen if they put blood into
the veins of their patients. Some thought that it could be a treatment for all
manner of ailments, even insanity. Finally, in the 1600s, a few doctors tested
out the idea, with disastrous results. A French doctor injected calf's blood
into a madman, who promptly started to sweat and vomit and produce urine the
colour of chimney soot. After another transfusion the man died.
Such calamities gave transfusions a bad reputation for 150 years. Even
in the 19th century only a few doctors dared try out the procedure. One of them
was a British physician named James Blundell. Like other physicians of his day,
he watched many of his female patients die from bleeding during childbirth.
After the death of one patient in 1817, he found he couldn't resign himself to
the way things were.
"I could not forbear considering, that the patient might very
probably have been saved by transfusion," he later wrote.
Blundell became convinced that the earlier disasters with blood
transfusions had come about thanks to one fundamental error: transfusing
"the blood of the brute", as he put it. Doctors shouldn't transfer
blood between species, he concluded, because "the different kinds of blood
differ very importantly from each other".
Human patients should only get human blood, Blundell decided. But no one
had ever tried to perform such a transfusion. Blundell set about doing so by
designing a system of funnels and syringes and tubes that could channel blood
from a donor to an ailing patient. After testing the apparatus out on dogs,
Blundell was summoned to the bed of a man who was bleeding to death.
"Transfusion alone could give him a chance of life," he wrote.
Several donors provided Blundell with 14 ounces of blood, which he injected
into the man's arm. After the procedure the patient told Blundell that he felt
better – "less fainty" – but two days later he died.
Still, the experience convinced Blundell that blood transfusion would be
a huge benefit to mankind, and he continued to pour blood into desperate
patients in the following years. All told, he performed ten blood transfusions.
Only four patients survived.
While some other doctors experimented with blood transfusion as well,
their success rates were also dismal. Various approaches were tried, including
attempts in the 1870s to use milk in transfusions (which were, unsurprisingly,
fruitless and dangerous).
Blundell was correct in believing that humans should only get human
blood. But he didn't know another crucial fact about blood: that humans should
only get blood from certain other humans. It's likely that Blundell's ignorance
of this simple fact led to the death of some of his patients. What makes those
deaths all the more tragic is that the discovery of blood types, a few decades
later, was the result of a fairly simple procedure.
The first clues as to why the transfusions of the early 19th century had
failed were clumps of blood. When scientists in the late 1800s mixed blood from
different people in test tubes, they noticed that sometimes the red blood cells
stuck together. But because the blood generally came from sick patients,
scientists dismissed the clumping as some sort of pathology not worth
investigating. Nobody bothered to see if the blood of healthy people clumped, until
Karl Landsteiner wondered what would happen. Immediately, he could see that
mixtures of healthy blood sometimes clumped too.
Landsteiner set out to map the clumping pattern, collecting blood from
members of his lab, including himself. He separated each sample into red blood
cells and plasma, and then he combined plasma from one person with cells from
another.
Landsteiner found that the clumping occurred only if he mixed certain
people's blood together. By working through all the combinations, he sorted his
subjects into three groups. He gave them the entirely arbitrary names of A, B
and C. (Later on C was renamed O, and a few years later other researchers
discovered the AB group. By the middle of the 20th century the American
researcher Philip Levine had discovered another way to categorize blood, based
on whether it had the Rh blood factor. A plus or minus sign at the end of
Landsteiner's letters indicates whether a person has the factor or not.)
Reuters/Chor
Sokunthea
When Landsteiner mixed the blood from different people together, he
discovered it followed certain rules. If he mixed the plasma from group A with
red blood cells from someone else in group A, the plasma and cells remained a
liquid. The same rule applied to the plasma and red blood cells from group B.
But if Landsteiner mixed plasma from group A with red blood cells from B, the
cells clumped (and vice versa).
The blood from people in group O was different. When Landsteiner mixed
either A or B red blood cells with O plasma, the cells clumped. But he could
add A or B plasma to O red blood cells without any clumping.
Wikimedia CommonsThe
blood type groups as we know them today.
It's this clumping that makes blood transfusions so potentially
dangerous. If a doctor accidentally injected type B blood into my arm, my body
would become loaded with tiny clots. They would disrupt my circulation and
cause me to start bleeding massively, struggle for breath and potentially die.
But if I received either type A or type O blood, I would be fine.
Landsteiner didn't know what precisely distinguished one blood type from
another. Later generations of scientists discovered that the red blood cells in
each type are decorated with different molecules on their surface. In my type A
blood, for example, the cells build these molecules in two stages, like two
floors of a house. The first floor is called an H antigen. On top of the first
floor the cells build a second, called the A antigen.
People with type B blood, on the other hand, build the second floor of
the house in a different shape. And people with type O build a single-storey
ranch house: they only build the H antigen and go no further.
Each person's immune system becomes familiar with his or her own blood
type. If people receive a transfusion of the wrong type of blood, however,
their immune system responds with a furious attack, as if the blood were an
invader. The exception to this rule is type O blood. It only has H antigens,
which are present in the other blood types too. To a person with type A or type
B, it seems familiar. That familiarity makes people with type O blood universal
donors, and their blood especially valuable to blood centers.
Landsteiner reported his experiment in a short, terse paper in 1900.
"It might be mentioned that the reported observations may assist in the
explanation of various consequences of therapeutic blood transfusions," he
concluded with exquisite understatement. Landsteiner's discovery opened the way
to safe, large-scale blood transfusions, and even today blood banks use his
basic method of clumping blood cells as a quick, reliable test for blood types.
But as Landsteiner answered an old question, he raised new ones. What,
if anything, were blood types for? Why should red blood cells bother with
building their molecular houses? And why do people have different houses?
Solid scientific answers to these questions have been hard to come by.
And in the meantime, some unscientific explanations have gained huge
popularity. "It's just been ridiculous," sighs Connie Westhoff, the
Director of Immunohematology, Genomics, and Rare Blood at the New York Blood
Center.
Getty
Images/Joern Pollex
In 1996 a naturopath named Peter D'Adamo published a book called Eat Right 4 Your Type. D'Adamo argued that we must eat according to our blood type, in order
to harmonize with our evolutionary heritage.
Blood types, he claimed, "appear to have arrived at critical
junctures of human development." According to D'Adamo, type O blood arose
in our hunter-gatherer ancestors in Africa, type A at the dawn of agriculture,
and type B developed between 10,000 and 15,000 years ago in the Himalayan
highlands. Type AB, he argued, is a modern blending of A and B.
From these suppositions D'Adamo then claimed that our blood type determines
what food we should eat. With my agriculture-based type A blood, for example, I
should be a vegetarian. People with the ancient hunter type O should have a
meat-rich diet and avoid grains and dairy. According to the book, foods that
aren't suited to our blood type contain antigens that can cause all sorts of
illness. D'Adamo recommended his diet as a way to reduce infections, lose
weight, fight cancer and diabetes, and slow the aging process.
D'Adamo's book has sold 7 million copies and has been translated into 60
languages. It's been followed by a string of other blood type diet books;
D'Adamo also sells a line of blood-type-tailored diet supplements on his
website. As a result, doctors often get asked by their patients if blood type
diets actually work.
The best way to answer that question is to run an experiment. In Eat Right 4 Your TypeD'Adamo wrote that he was in the eighth year of a decade-long trial of
blood type diets on women with cancer. Eighteen years later, however, the data
from this trial have not yet been published.
Recently, researchers at the Red Cross in Belgium decided to see if
there was any other evidence in the diet's favor. They hunted through the
scientific literature for experiments that measured the benefits of diets based
on blood types. Although they examined over 1,000 studies, their efforts were
futile. "There is no direct evidence supporting the health effects of the
ABO blood type diet," says Emmy De Buck of the Belgian Red Cross-Flanders.
After De Buck and her colleagues published their review in the American Journal of Clinical
Nutrition, D'Adamo responded on his blog. In
spite of the lack of published evidence supporting his Blood Type Diet, he
claimed that the science behind it is right. "There is good science behind
the blood type diets, just like there was good science behind Einstein's
mathmatical [sic] calculations that led to the Theory of Relativity," he
wrote.
Comparisons to Einstein notwithstanding, the scientists who actually do
research on blood types categorically reject such a claim. "The promotion
of these diets is wrong," a group of researchers flatly declared in Transfusion Medicine Reviews.
Nevertheless, some people who follow the Blood Type Diet see positive
results. According to Ahmed El-Sohemy, a nutritional scientist at the
University of Toronto, that's no reason to think that blood types have anything
to do with the diet's success.
El-Sohemy is an expert in the emerging field of nutrigenomics. He and
his colleagues have brought together 1,500 volunteers to study, tracking the
foods they eat and their health. They are analysing the DNA of their subjects
to see how their genes may influence how food affects them. Two people may
respond very differently to the same diet based on their genes.
"Almost every time I give talks about this, someone at the end asks
me, 'Oh, is this like the Blood Type Diet?'" says El-Sohemy. As a
scientist, he found Eat
Right 4 Your Type lacking. "None of the
stuff in the book is backed by science," he says. But El-Sohemy realised
that since he knew the blood types of his 1,500 volunteers, he could see if the
Blood Type Diet actually did people any good.
El-Sohemy and his colleagues divided up their subjects by their diets.
Some ate the meat-based diets D'Adamo recommended for type O, some ate a mostly
vegetarian diet as recommended for type A, and so on. The scientists gave each
person in the study a score for how well they adhered to each blood type diet.
The researchers did find, in fact, that some of the diets could do
people some good. People who stuck to the type A diet, for example, had lower
body mass index scores, smaller waists and lower blood pressure. People on the
type O diet had lower triglycerides. The type B diet – rich in dairy products –
provided no benefits.
"The catch," says El-Sohemy, "is that it has nothing to
do with people's blood type." In other words, if you have type O blood,
you can still benefit from a so-called type A diet just as much as someone with
type A blood – probably because the benefits of a mostly vegetarian diet can be
enjoyed by anyone. Anyone on a type O diet cuts out lots of carbohydrates, with
the attending benefits of this being available to virtually everyone. Likewise,
a diet rich in dairy products isn't healthy for anyone – no matter their blood
type.
One of the appeals of the Blood Type Diet is its story of the origins of
how we got our different blood types. But that story bears little resemblance
to the evidence that scientists have gathered about their evolution.
After Landsteiner's discovery of human blood types in 1900, other
scientists wondered if the blood of other animals came in different types too.
It turned out that some primate species had blood that mixed nicely with
certain human blood types. But for a long time it was hard to know what to make
of the findings. The fact that a monkey's blood doesn't clump with my type A
blood doesn't necessarily mean that the monkey inherited the same type A gene
that I carry from a common ancestor we share. Type A blood might have evolved
more than once.
The uncertainty slowly began to dissolve, starting in the 1990s with
scientists deciphering the molecular biology of blood types. They found that a
single gene, called ABO, is responsible for building the second floor of the
blood type house. The A version of the gene differs by a few key mutations from
B. People with type O blood have mutations in the ABO gene that prevent them
from making the enzyme that builds either the A or B antigen.
Scientists could then begin comparing the ABO gene from humans to other
species. Laure Ségurel and her colleagues at the National Center for Scientific
Research in Paris have led the most ambitious survey of ABO genes in primates
to date. And they've found that our blood types are profoundly old. Gibbons and
humans both have variants for both A and B blood types, and those variants come
from a common ancestor that lived 20 million years ago.
Our blood types might be even older, but it's hard to know how old.
Scientists have yet to analyze the genes of all primates, so they can't see how
widespread our own versions are among other species. But the evidence that
scientists have gathered so far already reveals a turbulent history to blood
types. In some lineages mutations have shut down one blood type or another.
Chimpanzees, our closest living relatives, have only type A and type O blood.
Gorillas, on the other hand, have only B. In some cases mutations have altered
the ABO gene, turning type A blood into type B. And even in humans, scientists
are finding, mutations have repeatedly arisen that prevent the ABO protein from
building a second storey on the blood type house. These mutations have turned
blood types from A or B to O. "There are hundreds of ways of being type
O," says Westhoff.
Thomson
ReutersChimpanzees have type A and type O
blood.
Being type A is not a legacy of my proto-farmer ancestors, in other
words. It's a legacy of my monkey-like ancestors. Surely, if my blood type has
endured for millions of years, it must be providing me with some obvious
biological benefit. Otherwise, why do my blood cells bother building such
complicated molecular structures?
Yet scientists have struggled to identify what benefit the ABO gene
provides. "There is no good and definite explanation for ABO," says
Antoine Blancher of the University of Toulouse, "although many answers
have been given."
The most striking demonstration of our ignorance about the benefit of
blood types came to light in Bombay in 1952. Doctors discovered that a handful
of patients had no ABO blood type at all – not A, not B, not AB, not O. If A
and B are two-storey buildings, and O is a one-storey ranch house, then these
Bombay patients had only an empty lot.
Since its discovery this condition – called the Bombay phenotype – has
turned up in other people, although it remains exceedingly rare. And as far as
scientists can tell, there's no harm that comes from it. The only known medical
risk it presents comes when it's time for a blood transfusion. Those with the
Bombay phenotype can only accept blood from other people with the same
condition. Even blood type O, supposedly the universal blood type, can kill
them.
The Bombay phenotype proves that there's no immediate life-or-death
advantage to having ABO blood types. Some scientists think that the explanation
for blood types may lie in their variation. That's because different blood
types may protect us from different diseases.
Doctors first began to notice a link between blood types and different
diseases in the middle of the 20th century, and the list has continued to grow.
"There are still many associations being found between blood groups and
infections, cancers and a range of diseases," Pamela Greenwell of the
University of Westminster tells me.
Wikimedia
CommonsBlood type compatibility chart.
From Greenwell I learn to my displeasure that blood type A puts me at a
higher risk of several types of cancer, such as some forms of pancreatic cancer
and leukaemia. I'm also more prone to smallpox infections, heart disease and
severe malaria. On the other hand, people with other blood types have to face
increased risks of other disorders. People with type O, for example, are more
likely to get ulcers and ruptured Achilles tendons.
These links between blood types and diseases have a mysterious
arbitrariness about them, and scientists have only begun to work out the
reasons behind some of them. For example, Kevin Kain of the University of
Toronto and his colleagues have been investigating why people with type O are
better protected against severe malaria than people with other blood types. His
studies indicate that immune cells have an easier job of recognizing infected
blood cells if they're type O rather than other blood types.
More puzzling are the links between blood types and diseases that have
nothing to do with the blood. Take norovirus. This nasty pathogen is the bane
of cruise ships, as it can rage through hundreds of passengers, causing violent
vomiting and diarrhea. It does so by invading cells lining the intestines,
leaving blood cells untouched. Nevertheless, people's blood type influences the
risk that they will be infected by a particular strain of norovirus.
The solution to this particular mystery can be found in the fact that
blood cells are not the only cells to produce blood type antigens. They are
also produced by cells in blood vessel walls, the airway, skin and hair. Many
people even secrete blood type antigens in their saliva. Noroviruses make us sick
by grabbing onto the blood type antigens produced by cells in the gut.
Yet a norovirus can only grab firmly onto a cell if its proteins fit
snugly onto the cell's blood type antigen. So it's possible that each strain of
norovirus has proteins that are adapted to attach tightly to certain blood type
antigens, but not others. That would explain why our blood type can influence
which norovirus strains can make us sick.
It may also be a clue as to why a variety of blood types have endured
for millions of years. Our primate ancestors were locked in a never-ending cage
match with countless pathogens, including viruses, bacteria and other enemies.
Some of those pathogens may have adapted to exploit different kinds of blood
type antigens. The pathogens that were best suited to the most common blood
type would have fared best, because they had the most hosts to infect. But,
gradually, they may have destroyed that advantage by killing off their hosts.
Meanwhile, primates with rarer blood types would have thrived, thanks to their
protection against some of their enemies.
As I contemplate this possibility, my type A blood remains as puzzling
to me as when I was a boy. But it's a deeper state of puzzlement that brings me
some pleasure. I realized that the reason for my blood type may, ultimately,
have nothing to do with blood at all.
source;-( Flipboard & internate)8 Unexpected Things A Blood Test Can Reveal About You
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"Every one of us has between 1,000 and 2,000 measurable proteins in our blood," says Stefan Enroth, PhD, an associate professor of immunology at Sweden's Uppsala University. Each of those proteins performs several tasks, he says, and the more researchers learn about them, the more they'll be able to tell you about what's going on throughout the rest of your body.
The tests below are all in development and have huge potential for medical diagnoses and treatment plans. Read on for all the surprising things they could reveal.
1. Your true age
Compared to your "chronological age," which is the amount of time that has elapsed since you were born, your "biological age" refers to how old your body and internal systems seem compared to other folks in your age group, Enroth explains. So while you may be 52, your biological age may more closely resemble a healthy 48-year-old's.
Compared to your "chronological age," which is the amount of time that has elapsed since you were born, your "biological age" refers to how old your body and internal systems seem compared to other folks in your age group, Enroth explains. So while you may be 52, your biological age may more closely resemble a healthy 48-year-old's.
In a 2015 study, Enroth and colleagues found they could identify this biological age by modeling the protein levels and types in 1,000 people's blood samples. By comparing your blood to this model's, they can gauge how you stack up, he says.
While smoking, a high BMI, and slurping sugar-sweetened beveragestacks 2 to 6 years onto your biological age, ditching those habits in favor of regular exercise knocks off the same number of years, his research shows.
Your blood's levels of a small group of proteins may indicate whether you'll develop Alzheimer's disease 10 years before any symptoms appear, according to a 2015 study from UK researchers. The research is still preliminary. But the study authors say identifying at-risk individuals earlier may help lead to more effective treatments. (Here are 9 ways to control your Alzheimer's risk.)
3. Whether you've suffered a concussion
Docs have long struggled to come up with a protocol that accurately assesses whether you've suffered a concussion—a traumatic brain injury that, for some, may not result in any obvios symptoms in the hours or days following the event. That's a big problem—especially for athletes—because suffering a second blow to the head too soon after a concussion can be deadly or result in long-term cognitive problems. Concussions have even been linked to Alzheimer's later in life. (Boost your memory and age-proof your mind with these natural solutions.)
But a recent study in JAMA Neurology details a simple blood test that—again, using protein markers—could reveal whether you've had a concussion for up to 7 days after your bump on the head.
4. Your dehydration levels
Dehydration puts stress on your heart, increases fatigue, and can make it hard to think clearly. And roughly 20% of older adults in assisted living facilities are dehydrated—mostly because they're simply not drinking enough fluids, research suggests. But that same research effort has identified a blood test that can tell whether you're dangerously parched. Especially for those older adults who may not recognize when they've swallowed too little water, the test could save lives, the researchers say.
5. The severity of your blues
It can be tough for some people (and their doctors) to differentiate between healthy, happens-to-all-of-us stretches of the blues and more sinister forms of clinical depression. And for years, experts believed it really wasn't possible to identify mood disorders using blood tests or brain scans. But a recent study from Austria identified a specific kind of brain chemical—also found in your blood—that can indicate whether you're low on happiness hormones. The blood test may help doctors prescribe more effective drugs to treat clinical depression, the Austrian researchers say.
6. Every cold you've ever had
Like a goopy red medical record coursing through your veins, your blood can reveal to doctors every virus or cold you've ever endured. According to a recent study in the journal Science, your body develops antibodies in response to the illnesses you fend off. And those antibodies continue to kick around in your bloodstream for the remainder of your life.
Like a goopy red medical record coursing through your veins, your blood can reveal to doctors every virus or cold you've ever endured. According to a recent study in the journal Science, your body develops antibodies in response to the illnesses you fend off. And those antibodies continue to kick around in your bloodstream for the remainder of your life.
Apart from helping doctors learn more about how past illnesses affect your immune system, knowing which antibodies are present in your blood may help your MD prescribe more effective drugs or remedies, the study authors say.
7. If you're at risk for alcoholism
A specific blood chemical called "PEth" may be elevated among people who are biologically prone to alcoholism, finds research from Alcohol and Alcoholism. The University of Illinois study authors found a jump in blood PEth among college kids who frequently engaged in binge drinking. The blood chemical has been linked to alcoholism among older adults, and may help doctors provide more effective treatment for alcohol abusers, the U of I researchers say.
8. Your out-of-control anxiety
Anxiety is the physical side of stress or worry—the tension in your shoulders, say, or a racing heart. And researchers from Hebrew University in Jerusalem say they can spot that anxiety in your blood by looking for a specific type of protein your body releases when you're frazzled. By checking for this protein, docs may soon be able to determine whether your anxiety is run-of-the-mill, or running out of control.
Anxiety is the physical side of stress or worry—the tension in your shoulders, say, or a racing heart. And researchers from Hebrew University in Jerusalem say they can spot that anxiety in your blood by looking for a specific type of protein your body releases when you're frazzled. By checking for this protein, docs may soon be able to determine whether your anxiety is run-of-the-mill, or running out of control.
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