So if you have O- blood you can only receive O- blood right?
Btw: Do any of you donate blood regularly?
There are two distinct aspects here
1. Rhesus factor
2. ABO blood groups
1.
Rhesus factor:
Individuals either have the Rhesus factor (Rh+) or do not have it (RH-); the +/- denoted the presence or absence of the rhesus antogen on the surface of the red blood cells. The only way to develop antibodies to the rhesus antigen is through the transfer from the placenta.
It is rare and I am also O-. No idea what makes it special. I know that when I got pregnant and they found out I was O- I had to get a special injection in my thigh.
Something about if my blood crossed into the baby would kill off the babies blood.
If the mother is Rh negative, and has never been exposed to the Rh factor, she will have no antibodies to the Rh factor in her blood. BUT, if she is pregnant and the father of her baby is Rh positive, the child may be Rh positive. The mothers blood will be exposed through the placenta and will produce antibodies to the baby's blood, putting the fetus's blood at danger of attack by the mothers antibodies. This can cause what is known as
hemolytic disease of the newborn, where the baby's red blood cells are broken down. If not checked, this can cause death of the fetus.
2.
ABO group
The ABO group is explained by this chart.
The A and B are immunoglobulins of the IgM type. A person can have one antigen(A or B), both (AB) or none (O).
A person with type A blood has antibodies to type B antigen; when this person receives type B blood, there is an immune reaaction between the B type antigen from the donor and b antibodies in the recipient. This causes agglutination (clumping together) of red blood cells and can be fatal.
Similarly, type B individals have antibodies to A antigen; AB individuals have no antibodies and type O individuals have antibodies to both A and B antigens.
Hence type AB can theoretically receive blood from A, B, AB or O and are called
universal recipients.
Type O individuals have antibodies to both A and B and cannot receive blood from anyone except type O. However as they lack A and B antigens they can give blood to anyone and are called
universal donors.
Generally, the A and B antibodies do not cross the placenta so blood incompatibility due to ABO is rare (in rare cases, IgG type antibodies are made which can cross the placenta, so we cannot completely rule it out).
You have to take into account both the Rh factor and the ABO blood group for blood donation.