192 transfusion cells — the plasma rule runs backwards from the red cell rule
O can give red cells to all eight blood types, but its plasma only to O. AB is exactly the reverse. The same person is the universal donor for one component and useless for the other — because the antigens sit on the red cells and the antibodies float in the plasma. All 192 cells (three components × eight donors × eight recipients) are worked out from antigens and antibodies alone.
Red cells
The recipient's antibodies must not attack the antigens on the donated red cells.
Plasma
The donated plasma's antibodies must not attack the recipient's antigens — the direction is reversed.
Whole blood
Red cells and plasma go in together, so both conditions have to hold.
Where the rule flips
The antigens sit on the red cells; the antibodies float in the plasma. So when you move red cells, the recipient’s antibodies are the problem; when you move plasma, the donor’s antibodies are. The whole condition reverses, and so does the table — fold the red cell chart along its diagonal and you get the plasma chart.
Rh only matters for red cells
ABO antibodies are there from birth; anti-D is not. It only appears after an Rh− person has received Rh+ red cells. That is why the first such transfusion can pass uneventfully and the next one is the dangerous one — the same mechanism that matters in pregnancy. Plasma carries almost no red cells, so Rh is not checked for it.
This chart does not decide a real transfusion
Beyond ABO and RhD there are hundreds of other red cell antigens, and someone who has been transfused repeatedly may carry antibodies to some of them. A real transfusion is therefore decided by a crossmatch — the lab mixing those two people’s blood directly. This chart explains why the rules have the shape they do.
How to read it
- The name of a blood type is its antigen list — A has the A antigen, AB has both, O has none.
- Antibodies attack what you do not have — O carries both anti-A and anti-B.
- To move red cells, check whether the recipient’s antibodies attack the donated antigens.
- To move plasma, check the reverse: whether the donated antibodies attack the recipient’s antigens.
- Rh is checked only for red cells — there is no natural anti-D; it appears after exposure.
- Whole blood stacks both conditions, so only same-ABO pairs survive.
Common questions
Q. If O is the universal donor, why not for plasma?
Because the antigens sit on the red cells and the antibodies float in the plasma. O red cells carry no antigens, so nothing attacks them — but O plasma carries both anti-A and anti-B, which attack anyone who is not O. The universal plasma donor is AB.
Q. Why does whole blood need the same blood type?
Whole blood carries red cells and plasma together, so both conditions must hold — and stacking them leaves only pairs with identical antigens. It is not a separate rule; it falls out of the arithmetic.
Q. I am Rh−. Can I take Rh+ in an emergency?
Not red cells: you would start making anti-D, which then matters for the next transfusion or in pregnancy. Plasma is different — it carries almost no red cells, so Rh is not checked.
Q. Can I transfuse by this chart?
No. Beyond ABO and RhD there are hundreds of red cell antigens, so a real transfusion is decided by a crossmatch in which the lab mixes the two people’s blood directly.