- The O blood group is one of the four major types in the ABO blood group system, which classifies human blood based on the presence or absence of specific antigens on the surface of red blood cells (RBCs).
- Individuals with blood group O lack both A and B antigens on their red blood cells and produce both anti-A and anti-B antibodies in their plasma. This immunological profile makes the O blood group unique in transfusion medicine and genetics.
- There are two subtypes of the O blood group based on the Rhesus (Rh) factor:
- O positive (O⁺): Has no A or B antigens but does have the Rh antigen.
- O negative (O⁻): Lacks A, B, and Rh antigens entirely.
- From a transfusion standpoint, O negative blood is considered the universal donor type for red blood cell transfusions because it carries none of the ABO or Rh antigens that could provoke an immune response in the recipient. This makes O⁻ blood especially critical in emergencies when the patient’s blood type is unknown. However, individuals with O blood type can only receive blood from other O donors because their plasma contains antibodies that will react against A and B antigens.
- Genetically, the O blood type results from inheriting two O alleles (genotype OO) from one’s parents. The ABO gene, located on chromosome 9, has three major alleles: A, B, and O. The O allele is recessive, which means an individual must inherit one O allele from each parent to express the O blood group. If an individual inherits an A or B allele along with an O allele, the dominant A or B trait will determine their blood type.
- Globally, the O blood group is the most common, especially in regions such as Central and South America, parts of Africa, and among Indigenous populations. Its high prevalence contributes to its essential role in blood donation systems, particularly for trauma care and surgeries.
- In terms of health, some studies suggest that individuals with type O blood may have a lower risk of cardiovascular disease and certain types of cancer compared to non-O blood types. Conversely, some research has linked O blood with a slightly increased risk of bleeding disorders due to lower levels of certain clotting factors, like von Willebrand factor.
