What is an Antigen?
The human immune system will attack any foreign substance entering the body by generating antibodies which will attack and destroy them. Hence, these substances which trigger antibody creation are called antigens.
Now there are various useful sugars and proteins on the surface of our red blood cells, which our immune system might otherwise mistake to be foreign bodies and generate antibodies to kill them. However, our immune system is trained to ignore these self antigens (the antigens which are generated inside our body).
The human blood group classification is based on these antigens on our Red Blood Cells (RBC), and there are around 32 Human Blood Group classifications based on the various antigen groups.
What is ABO Blood Group Classification?
ABO is a classification of human blood group based on the presence or absence of A or B antigens.
So if your blood has only A antigens, then your blood group is A, if it has only B antigens, then your blood group is B, if it has both of these, then your blood group is AB, and if it has neither, then your blood group is O. Simple, isn’t it?
Now the reason for taking into account this group for blood transfusion is that, if you have A antigen (A Blood Group), then the human immune system will not attack A antigens if the donor’s blood contains A. However if a person with B or AB blood group is given to a person whose blood group is A, then the recipient’s body will attack the B antigens in the received blood as it has not been trained to ignore B antigens. Similarly if A or AB or B blood is given to a person whose blood group is O, then it will attack both A and B antigens. So mismatching blood transfusion can be fatal. And it is for this reason that AB is Universal Recipient as the person’s blood will reject neither A or B antigens, while the O group is Universal Donor as it has no A or B antigens which can be rejected by the recipient’s body.
So what about blood groups like B+ve and O-ve which we keep hearing about?
The Rh Blood Group Classification
The second most important classification of human blood group is based on Rh antigens. While the ABO classification is based on the two antigens A and B, the Rh group has 50 antigens! However, the main Rh classification is based on one single antigen of special importance, called the D antigen. So, if your blood has the Rh D antigen, then your blood group is Rh positive, else it is Rh negative. The reason for the importance of this antigen is that a mismatch in the D antigen can prove fatal during blood transfusion, just like it does in AB antigen mismatch.
So A+ve means a blood group which has A antigen and Rh D antigen. O-ve means a blood group which has neither A nor B antigens, nor Rh D antigen. AB-ve means a blood group which has both A and B antigens, but has no Rh D antigen.
Which is why in case of an emergency when there is no time to match for any other antigen reactions, O-ve is the safest blood transfusion that can be done without any prior tests because of the absence of A, B and Rh antigens in it.
Mother’s blood group proving fatal to the newborn
There is a possibility that a mother whose blood group is Rh negative, carries a child whose blood group is Rh positive, and if mother’s blood comes in contact with the fetus blood, then the mother’s immune system upon finding an antigen foreign to its body, Rh D antigen, will produce antibodies against the Rh parties in the fetus blood which can prove fatal to the fetus.
So, if the father is Rh positive and mother is Rh negative, then extra care should be taken during pregnancy. If the mother’s immune system has prior knowledge of Rh D antigen, either due to some previous blood transfusion of Rh +ve blood group, or if this is not the first pregnancy and the earlier pregnancies carried a Rh positive child, then chances are that the mother’s immune system is already aware of Rh D antigen and has antibodies against it ready, which can be of an immediate concern for the fetus health. Tests are done during early stages of pregnancy, and if the mother is Rh -ve and the child is Rh +ve, then an injection which prevents the mother’s immune system from generating antibodies against Rh D antigen is given during pregnancy. This will ensure that the fetus remains unaffected by the fact that the mother’s blood is Rh negative and ensures a safe delivery of the child.
Does Rh-ve indicate alien blood or Reptilian Blood or Blood of the Gods?
Recently came across this theory which suggests that those with Rh negative blood group might be the descendants of ancient alien astronauts. But before that one more fact. Around 85% of humans are Rh positive, which means they have Rh D antigen in their blood, only around 15% are Rh negative which means they do not have Rh D antigen in their blood. This is also the reason why blood groups like O-ve are very rare.
Back to the alien blood group theory which states that
If all mankind evolved from the same ancestor their blood would be compatible. Where did the Rh negatives come from? If they are not the descendants of prehistoric man, could they be the descendants of the ancient astronauts?
This makes one believe as if Rh negative indicates the “presence of something rare in one’s blood”. But as we learn earlier, Rh negative indicates the “absence of the Rh D antigen” which otherwise is quite abundant in most (85%) humans. So what could be the contribution of alien blood here? Obviously, there is nothing alien here, because there is no alien genes present here, its actually the “absence” of our own genes which produce the Rh D antigen in most humans.
The entire theory seems to have been built upon an incorrect understanding of blood groups, antigens and antibody response. Because Rh D is not the ONLY antigen either, in Rh group itself we have around 50 such antigens, and human blood group classification itself has around 32 types based on different groups of antigens.
The theory then states
All animals and other living creatures known to man can breed with any other of their species. Relative size and color makes no difference. Why does infant’s haemolytic disease occur in humans if all humans are the same species?
This seems to suggest that other animals are free from such instances of mother’s immune system attacking the child’s blood. Well, it is not. We have seen newborns die because of this attack even in horses and mules! It appears in all those species where the mother has a negative antigen blood group, and the fetus has a positive antigen blood group, and mother’s blood comes in contact with fetal blood.
For that matter, it is not only restricted to Rh D antigen either. After all, it is also very much possible that mother whose blood group is O, gives birth to a child whose blood group is B, and if the mother’s blood comes in contact with fetal blood, then there will be antibodies against B produced by the mother’s blood! Its only that in this case it is not life threatening, while in the case of Rh D it can be life threatening to the baby.
All combinations where mother is negative antigen, and child is positive antigen can cause scenarios where mother’s immune system produces antibodies against the child’s positive antigen. It is only that while some of them cause no harm, some cause mild issues, and the ones like Rh D can be severe.
So there is nothing alien here, and this is a common evolutionary compromise across the human species.
The extraterrestrial origin theory also asks a question
Why would a mother’s body reject her own offspring?
In evolution, the immune system has been trained only to accept its own antigens, anything foreign will be attacked by the immune system, and Rh D is not an exception, nor is the only case of its kind. The Rh D in the child came from the father who has to be Rh positive, and there is no way for the mother’s immune system to treat the father’s Rh D antigen as its own, isn’t it? And so, it will attack it.
The theory also asks
Why does it so violently reject the Rh factor?
As we saw earlier, the immune system treats ALL unknown antigens as foreign and attacks them. Rh D looks violent only because, attack on Rh D can cause serious complications in the baby. Not because, mother’s immune system reacts violently ONLY to the Rh D antigen. The response is the same for ANY antigen not found in the mother’s own body.
Evolution of the Rh D negative blood group
Most humans have Rh D antigen, and are hence Rh positive. Very few do not have it and hence are Rh negative. So what caused this mutation where some humans stopped having this antigen in their blood? What purpose did this serve?
It is interesting to note that Rh -ve or the absence of Rh D producing genes is common in the European population, even though it is rare in rest of the world. This suggests that there might be an evolutionary advantage in this European population over NOT having Rh D antigen, than having it. Some recent studies have indicated that Rh negative people are resistant to some parasites like Toxoplasma, or to their effects on the body. So it might as well have served an advantage in this geography NOT to have the Rh D antigen, rather than have it. And hence, such humans evolved to be Rh negative.
And one can find many such instances across human evolution. For example humans who come from an ancestry which started domesticating cattle, and consuming dairy products have digestive systems which generate an enzyme called lactase which helps in digesting milk by digesting the sugar lactose in the milk. However a significant population of humans are also lactose intolerant, which means they cannot digest milk products which contain lactose, because their body does not produce lactase. If these lactose intolerant people drink milk, then they will have symptoms like bloating, sometimes even vomiting. Does this mean lactose intolerant population are from an alien ancestry?
Some evolutionary gene modifications might prove fatal when exposed, but are nevertheless are useful while they remain dormant and hence are continued to be carried. For instance, Sickle Cell anemia is a fatal disease where RBCs sickle up causing life threatening complications. However, those humans who are only carriers of the gene causing Sickle Cell Anemia, but who don’t have the disease are resistant to Malaria! So in such cases such evolution is useful to the body in areas affected by Malaria even though it may cause problems in those kids where the gene becomes active.
So to summarize:
- Rh negative does not indicate the presence of anything special or alien, it is the absence of Rh D antigen which is pretty common in humans otherwise.
- Rh D is just another normal antigen and there are lot many antigens similar to Rh D.
- Rh negative is NOT the only antigen which can cause problems to the baby.
- Mother’s body does not selectively react violently ONLY to the Rh D antigen.
- Cases where mother’s blood group causes problems to the child are not restricted to humans alone.
- There is nothing alien or out of this planet about Rh D negativity