Science and Engineering in Derby and Derbyshire
Blood, blood, glorious blood. Nothing quite like it for, emptying a room at a party…
So blood. It’s one of those things we all have, and then spend most of our lives avoiding discussion of it; lest it accidentally leak out upon hearing its name, or something. Some of us, yours truly included, even go so far as over-dramatically passing out at the very mention of the stuff. Yeah, imagine how much fun I am to have on your first aid course. But it is essential stuff, carrying as it does all that tasty Oxygen to your organs and cells, and taking away the no longer wanted Carbon Dioxide. And while most of us are happy for folk like Stacey to be the people dealing with blood outside the body, it is a curious substance…
Our blood, assuming you are a human that is, is red. Varying from pillar box, if you happen to have been poisoned by Carbon Monoxide (not recommended), to a rather distinguished claret colour in the veins. If you’ve ever seen a blood pouch in hospital you might be forgiven for thinking it was some kind of intravenous chocolate pudding. The redness, as most people know, comes from the haemoglobin which carries the Oxygen around. As the Oxygens get dropped off around the body your blood gets darker. Unless of course you’ve been Cyanide poisoned, in which case it remains a rather fetching shade of scarlet as the Oxygen is unable to hop off. If you happen to be an octopus (and my congratulations on getting a computer to work under the sea) your blood is a rather attractive blue instead. This is because mollusc blood contains hemocyanin instead of haemoglobin. Where haemoglobin contains iron to collect those Oxygens up, hemocyanin uses copper instead.
There are many medical conditions relating to the state of your blood, as you might expect from something that takes such an important role in your body (though only accounts for 7% of its weight…so no “my blood is heavy” excuses post Christmas).
When I was a child, like many of us slightly gruesome sorts, I used to watch Casualty addictively (re-watching the plane crash episode around 50 times), but was for a long time bemused by characters getting all in a fuffle about patients who were “in shock”.
We use the word shock generally to indicate being a bit surprised or horrified, and consequently I spent a good few years of my childhood thinking people dropped dead from being startled. It is not of course that kind of shock that gets medics all a flutter but rather circulatory shock. This kind of shock, which can (and does with some regularity) kill, is caused by the blood failing to perfuse into the capillaries of organs. This often happens if you have had a severe blood loss, say through a car accident, when there isn’t enough blood to oxygenate all the parts of you that need it.
A longer term, but equally threatening blood disorder is haemophilia. Haemophilia is an umbrella for a range of different genetic issues, with the same core symptom of a failure of blood to coagulate or clot. The conditions have usually been passed down through several generations, with females generally carrying the genes, sometimes unknowingly. Though it isn’t impossible for a women to have haemophilia it is very rare and most of those showing signs of the condition are male. Sometimes the condition seemingly comes out of nowhere, Queen Victoria’s sons and grandsons were one of the most well known affected families, but seemingly prior to them there was no evidence of the condition elsewhere in the royal families. Though some have suggested there might be a hint of Victoria being illegitimate, the more likely, if less exciting, explanation is that she was unfortunate enough to have a genetic mutation that did make a significant difference to her offspring.
The condition can be relatively mild and only be evident if someone is involved in a serious trauma that causes blood loss, which in their case may be above average, to very severe resulting in the slightest of bumps being a considerable risk. Many of the boys in the Saxe-Coburg-Gotha family that were haemophiliacs did not make it to adulthood. Discounting the infamous Alexi in Russia, who was shot during the October Revolution-something hard to survive regardless of your clotting status-several of Queen Victoria’s grandsons and great grandsons died from accidents that they would likely have otherwise survived.
However, for those living today the outlook is generally more optimistic. Patients can receive infusions of the clotting factor that they lack through serum, which may come from humans, pigs or synthetic sources. Due to their bodies developing antibodies to the serums some patients will go through several different types during their life. Unfortunately until the advent of screening blood, these clotting factors themselves carried some risk. As many as ten thousand haemophiliacs in the USA during the 1970s and 1980s contracted HIV through unscreened factors, and HIV and AIDS related complications continue to be a significant killer of haemophilia patients. The unscreened blood products of the period caused problems also for thalassemia patients who often need to receive whole blood transfusions on a regular basis.
Since we all need it, blood can be subject to high demand. Even if you live in a relatively peaceful place with no wars or manic driving, you still might find that when you need blood it isn’t there. For those who are in particularly unusual blood groups this is especially a problem, but even if you are a very common A+ (there’s millions of us in the UK) you might find that the demand outstrips the level of donation.
During World War II American medic Charles Drew developed the “Plasma for Britain” programme, which established test tube analysis techniques still used on blood today, and sent 15,000 blood bags over the pond in a mere five months. The programme also developed battlefield friendly reconstituted blood, which front-line medics could reanimate much like dried milk. Achieving considerable prominence for a black doctor at the time Dr Drew sadly, and somewhat ironically, died from circulatory shock after a car accident.
Getting real blood, though, requires a lot of jolly nice folk willing to give up an armful, and an awful lot of tea and biscuits. Thus much work has been done on developing substitutes for blood. Many of these are still in their very early stages but it is hoped that they would be a solution in war zones, in places where high incidences of HIV make blood transfusions unsafe and as a backup for general blood donations. Three main types are currently being explored.
The first, and the most experimental group are called PFCs and the hope is that they will be able to transport Oxygen in the same way that blood does. However, though the PFC can be formed into emulsions (imagine a mixed up egg) with salts and vitamins they can’t mix with blood. Which is clearly something of a drawback. The next, and equally experimental type, comes from the University of Sheffield and is essentially made of what the researchers term plastic. Finally the most advanced type, and in final stage clinical trials in some parts of the world and already in use in others, is haemoglobin mixed substitutes. These make use of the haemoglobin from blood to transport the Oxygen, as in real blood, but this is a very complicated process and in Europe and the USA the risks of heart attack are currently too high for approval.
What’s your type?
As mentioned before one of the aspects that complicates blood donation, or rather blood receiving, is group or type. If I asked you what blood group you are you’d probably answer A, B, AB or O. If you are a native Britisher, of any ethnicity but particularly caucasian, you are most likely to be an O or an A. Whereas if you are from Saudi Arabia you have a pretty good chance of being O. These letters pertain to what kind of antibodies you have in your blood plasma and what kind of antigens are in the blood cells. A group folk have Anti-B in their plasma, B group have Anti-A and O have both. The ABs have neither. Then in the blood cells, the A folk have A antigens, the B have B, AB have both and the Os have none. The antibodies in the recipient blood and the antigens in the donor blood have to match up, you cannot give give B-antigen blood to someone with blood that contains Anti-B antibodies for example.
It is common these days to express blood type as a + or -, and this refers to the Rhesus Factor of the blood. Unlike the ABO system, which is relatively straightforward, the Rh system is where it begins to get more complicated. The Rhesus system primarily refers to the D antigen, and the plus or minus indicates whether you have it or not. So a B+ has B-antigen and D-antigen, whereas O- has neither. However, the D antigen isn’t the only one in the Rhesus group and for high levels of compatibility in transfusions there are also antigens C, c, E and e to consider. The Rh blood type is something that midwives get very interested in because of the very Victorian sounding Hemolytic disease of the newborn [HDN]. This immune disorder happens when the blood antibodies in the mother are incompatible with those in the foetus For women who are type O this can be problematic as they produce both anti-A and anti-B. Also associated with HDN is the Anti-U antibody, which is classified by the MNS blood group system. However, most people, the world over, have U antigens and so this causes a problem less often than the RhD.
More specific is the P antigen typing system which classifies blood by whether or not it contains the P antigen, which is a receptor for Parvovirus B19. Which is responsible for the delightfully named ‘slapped cheek’, the scourge of primary school classrooms the world over. However, more seriously it can cause miscarriage if a pregnant woman is exposed to it in the early weeks of pregnancy.
Whilst the brilliantly named Lutheran system does not, disappointingly, classify blood as to its opinion on sixteenth century religious schisms, but rather on the presence of the Lu antigen. Equally disappointing is that Lewis also has nothing to do with grizzled television detectives, but another antigen located on the same chromosome as Luther, chromosome 19.
The presence, or not, of the Duffy antigen is one of the components in natural protection against malaria, as it acts as a receptor to Plasmodium parasites. The absence of Duffy has been found to be more common in those of African descent, than those of European descent. The lack of this antigen has also been related to HIV not progressing into AIDS. However, lack of Duffy isn’t all good news, especially if you are a man. Absence of the Duffy antigen seems to have a role in the progression of prostate tumours, which may explain why men of African descent are not only more at risk of developing this type of cancer, but much more likely to die from it than other men.
More important in blood transfusions is the Kell-Cellano system which, named after the first two patients, classifies blood types as to the presence of antigens which attract several immune system diseases. A mutation on the XK protein, the Kell protein on the X chromosome, can cause Mcleod syndrome. In addition to causing some rather funky shaped blood cells it also, eventually, results in peripheral nerve failures, possible heart attacks, shakes and dementia.
However, for most people blood is an excellent and efficient transport system. It helps keep your organs supplied with oxygen, usually doesn’t leak out (and when it does it mostly stops pretty quickly) and contributes to your heart making that reassuring dum-dum-dum noise for as long as possible.