Plasma Compatibility Chart: Why AB Is the Universal Plasma Donor
For red cells, O-negative is the universal donor. For plasma, the rule inverts: AB plasma is compatible with everyone. This guide explains why. Updated April 2026.
Why Plasma Rules Are the Inverse of Red Cell Rules
Red cell compatibility is about antigens: you cannot receive antigens your immune system does not recognise. Plasma compatibility is about antibodies: you cannot receive antibodies that attack your own red cells.
Plasma carries antibodies (among many other proteins). O-type plasma carries both anti-A and anti-B antibodies. If you give O plasma to an A-type patient, the anti-A antibodies in the plasma would attack the patient's own A-type red cells.
AB plasma has no anti-A and no anti-B antibodies (because AB-type people carry both A and B antigens and produce neither antibody). AB plasma is therefore safe for any recipient - there are no antibodies present that could attack any standard ABO blood type's red cells. This is why AB plasma is universally compatible.
Plasma Compatibility Table
| Donor type | Antibodies in plasma | Can donate plasma to |
|---|---|---|
| A+ | Anti-B | A+, A- |
| A- | Anti-B | A+, A- |
| B+ | Anti-A | B+, B- |
| B- | Anti-A | B+, B- |
| O+ | Anti-A, Anti-B | Universal - all 8 types |
| O- | Anti-A, Anti-B | Universal - all 8 types |
| AB+ | Anti-B | Universal - all 8 types |
| AB- | Anti-B | Universal - all 8 types |
Note: Rh factor is not typically considered for plasma compatibility (plasma does not carry Rh antigens). The table above lists all +/- variants for completeness; the key compatibility factor for plasma is the ABO antibody content.
The ABO Plasma Compatibility Summary
Universal donor
No anti-A or anti-B. Safe for all 8 blood types.
A and O recipients
Contains anti-B. Cannot give to B or AB recipients.
B and O recipients
Contains anti-A. Cannot give to A or AB recipients.
O recipients only
Contains anti-A and anti-B. Most restricted plasma type.
What Is Plasma and How Is It Donated?
Plasma is the liquid component of blood - the straw-coloured fluid that carries red cells, white cells, and platelets through your body. Plasma makes up about 55% of blood by volume and consists primarily of water (about 92%), along with proteins including clotting factors, immunoglobulins (antibodies), albumin, and other molecules.
Plasma is used clinically to treat bleeding disorders, liver failure, severe burns, and infections. Plasma-derived products include clotting factor concentrates for haemophilia, IVIG (intravenous immunoglobulin) for immune disorders, and albumin for volume replacement.
Plasma donation (plasmapheresis) uses an apheresis machine to collect only the plasma from a donation, returning the red cells and platelets to the donor. Because the red cells are returned, donors recover quickly and can donate plasma every 28 days - more frequently than whole blood (every 56 days).
AB-type donors are the most valuable plasma donors. If you are AB-positive or AB-negative, blood banks specifically need your plasma. Contact your local blood bank or American Red Cross to schedule a plasma appointment.