- The AB blood group is one of the four main blood types in the ABO blood group system, characterized by the presence of both A and B antigens on the surface of red blood cells and the absence of anti-A and anti-B antibodies in the plasma. This unique antigen-antibody profile gives individuals with AB blood a special status in transfusion medicine—they are considered universal recipients of red blood cells in the ABO system because they can safely receive blood from any ABO group (A, B, AB, or O), as their plasma contains no antibodies to attack A or B antigens.
- There are two main variants of the AB blood group based on the Rh (Rhesus) factor:
- AB positive (AB⁺): Has both A and B antigens and the Rh antigen; this is the true universal recipient for red cell transfusions.
- AB negative (AB⁻): Has A and B antigens but lacks the Rh antigen; can receive blood from A⁻, B⁻, AB⁻, and O⁻ donors.
- AB individuals, despite being universal recipients for red cells, are universal plasma donors, especially AB plasma, which contains no anti-A or anti-B antibodies and is therefore safe to give to recipients of any ABO type. This makes AB plasma especially valuable in emergency medicine and trauma care.
- From a genetic perspective, the AB blood type results from codominant inheritance of the A and B alleles from each parent. The ABO gene, located on chromosome 9, has three main alleles: A, B, and O. A person with an AB blood group inherits the A allele from one parent and the B allele from the other, resulting in the simultaneous expression of both antigens on the red blood cells.
- AB is the rarest blood type globally, accounting for less than 5% of the population in most regions. This rarity can pose challenges in blood banking, especially for AB-negative individuals who require matched Rh-negative blood for transfusion.
- In addition to transfusion relevance, the AB blood group has been studied in relation to disease susceptibility and immune system behavior. Some studies suggest that individuals with AB blood may have a slightly increased risk of certain cardiovascular conditions or clotting disorders, although these associations are still being investigated and are influenced by many other factors, including genetics and lifestyle.
