One of my hobbies when I was a kid, was reading OLD medical textbooks. This used to be called "haemolytic disease of the newborn" and was a common cause of neonatal jaundice. of course these days with this much better known and controlled, neonatal jaundice has a number of other known unrelated causes.
Blood groups - they are antigens on the surface of red blood cells. All living creatures with blood cells have blood groups. We discovered this the hard way at work, we were collecting blood from animals for a prac class where we had to provide our students with washed red blood cells. We SHOULD have collected the blood right into the centrifuge tubes, but one of our technicians was lazy (I've told you about my sociopath former colleague) and he just used a single beaker to collect all the blood. By about the third collection, the whole beaker agglutinated. We lost the lot. Idiot. We were using rabbits at the time. We ended up having to go to the vet school nearby and ask for some spare dog blood. This time I had to do it, the boss wouldn't let idiot near the place. The dogs were okay, regularly used to supply blood samples. But we needed a lot, and so I was there a long time while they brought out dog after dog. The blood went straight into heparinised centrifuge tubes - this also slowed us down a lot, but at least what we got was not mixed and therefore risked being wasted.
Back to blood groups - there are a lot of different kinds. They just happen to be there, they are part of our individual body defences against attack by anything foreign to our bodies. This can include foreign blood (say, you and your mate are fighting a saber tooth tiger and you both get cut, some of your blood and your mate's gets mixed. Your bodies use blood group antigens, among other things, to help identify what has to be destroyed).
The main blood group system we use is the ABO system. it is incompletely dominant - there are two antigens, A and B. O blood group is missing both A and B. AB is where both are present. You get the drift. What we OBSERVE is the phenotype, the blood group the tests pick up. But what determines it in our DNA is the genotype. Short of DNA testing, this can be inferred from medical history. For example, my father was blood group O. My mother was blood group A. This means that ALL us children are carrying only one A at most. Those with blood group A also carry a gene for O. I am blood group O, so I know I must be carrying both genes for O.
RH factor (named for the Rhesus monkeys they used in their early experiments) is a different and independent blood group. People's blood was identified according to whether it reacted to Rhesus blood or not - Rhesus positive or Rhesus negative. Probably it was one particular monkey, I suspect Rhesus monkeys, like other apes, mammals and animals with blood cells, have a range of different blood groups.
In my family, my grandmother had miscarriage after miscarriage. She had two daughters first. i don't know what problems, if any, she had with her second child. Both were healthy as far as I knew. They had a son, ten years later, "adopted" we were told on the quiet. He looked very much like his adoptive father, and just before she died my mother told one of my sisters that yes, he was the natural son and her half-brother. But surrogacy would have been misconstrued in those days.
The problem occurs because for someone who is Rh-, their blood will agglutinate with RH+ blood. Someone who is Rh+ can accept blood from someone who is Rh- but not the other way around. As most of the population is Rh+, this is not a problem except for those few who are Rh-.
When someone who is Rh- is dosed, accidentally or culpably, with Rh+ blood, they will then develop antibodies to the Rh+ factor. Their blood will now recognise Rh+ next time it is encountered. A second encounter will result in a stronger immune response against the 'invading' factor. Again, not generally a problem because when does this ever happen? It happens sometimes by accident in blood transfusions, and it happens during childbirth. Also in miscarriage. When the baby is being delivered, the placenta contains a double circulatory system, supposed to be in isolation. But it all breaks up and tears on delivery, and that is when mixing can occur, when a mother can be inocluated with a sample of her baby's blood. A second exposure - stronger reaction. If a reaction is going to occur, depending on the factors.
When they found an injection that could prevent the antibodies developing, it was a breakthrough. But the problem is - the injection still has to be delivered, within a narrow time window, after delivery and also after miscarriage, IF the mother is Rh- and HER BABY is Rh+. I suspect with my aunt, she may have also been Rh- and hence the pregnancy was not in danger. But I'm not sure - my grandmother lost about ten babies, I was told. The odds of all the ten being Rh+ if there is a 50:50 chance (dad carrying a gene for each) is remote. So I think my aunt must have just been very lucky. Although she never had children before she died, so we never knew her blood group. They were only just discovering the RH factor at the time she died (during WWII, in her early 20s).
My mother was RH+, but had to be heterozygous - she carried a gene for Rh+ and Rh-. So with Dad a "universal donor" (ie O-) then us kids had a 50:50 chance of being RH-. And so it is - I have a sister who is Rh- and had to have the injections after each pregnancy terminated (either in miscarriage or delivery). I'm thankfully Rh+. But our girls - we had them tested. Both positive. husband is blood group B so a family joke is "B positive - not just a blood group but a way of life!" husband is B-, by the way, so our girls had a 50:50 chance of being RH- too. One or two of our kids are blood group O, which means husband has to be carrying a hidden gene for O. And of our kids who are B: their kids have a 50:50 chance of inheriting either a B or an O from my child.
When the damage has been done and an Rh- person inoculated without preventive injections, nothing can really prevent problems. However, pregnancies can be monitored for problems and a lot more can be done during pregnancy to help it along and counter the hassles. I've heard of babies being given exchange blood transfusions while in utero, to save them from antibody attack.
The question now is - what is the genotype of the father? Does he carry a gene for each? Or does he carry two Rh+ genes? If the latter, then every baby will be Rh+ and there will be worse problems each time. The mother's heightened immune response is designed to kill the invader that is Rh+ and as soon as the mother's body detects this, the baby is in danger. But if she can fall pregnant with a Rh- baby, that pregnancy will not have these problems.
There are other blood group systems too, they keep finding more. Most don't cause problems, but can be used, used to be used, to identify people in criminal cases as well as other differential measures. Back in my uni days we were able to test ourselves for some of these other, lesser-known blood groups. I think for organ transplants they do deeper grouping for compatibility matching. I remember the world's second heart transplant patient, and the first to survive to leave hospital, was Philip Blaiberg (South Africa - a Christiaan Barnard patient). He was reported to have done so well because his door heart was such a brilliant match. Interesting for a country at the time deeply immersed in apartheid, Blaiberg was a white dentist and his donor was a black man who died of an aneurysm on a day at the beach. Apartheid was not an issue in medicine; only in politics. Philip Blaiberg wrote a book (I read the Readers Digest version) in which he described how it felt to be the first man in the world to hold his own heart in a jar, in his hands. The first transplant patient, Louis Washkansky, had not lived long enough or well enough after his surgery to be able to do this.
Sometimes I'm amazed at the information I find buried in my skull...
Marg
