For most individuals, blood type is a lifelong genetic characteristic that does not change. Your blood type is determined by specific markers on the surface of your red blood cells, primarily categorized by the ABO and Rh systems. These markers are inherited from your parents.
How Your Blood Type is Determined
Blood type is determined by the presence or absence of specific antigens on the surface of red blood cells. The most widely recognized system is the ABO blood group, which classifies blood into four types: A, B, AB, and O. These types are defined by the presence of A antigens, B antigens, both A and B antigens, or neither antigen, respectively.
Inheritance patterns dictate your ABO blood type. The ABO gene has three common alleles: A, B, and O. Alleles A and B are codominant, meaning if both are inherited, both A and B antigens will be expressed, resulting in AB blood type. The O allele is recessive, so an individual must inherit two O alleles to have O blood type.
Beyond the ABO system, the Rh factor is another important blood group classification. This factor refers to the presence (Rh-positive) or absence (Rh-negative) of the RhD protein on the surface of red blood cells. Similar to ABO, the Rh factor is inherited, with the Rh-positive trait being dominant. Therefore, if you inherit at least one Rh-positive allele, you will be Rh-positive.
Rare Instances of Apparent Blood Type Change
While blood type is stable, certain rare medical scenarios can lead to an apparent change. The most notable instance occurs following a bone marrow transplant. This procedure replaces a patient’s diseased bone marrow with healthy stem cells from a donor.
Since red blood cells are produced in the bone marrow, if the donor has a different blood type than the recipient, the recipient’s blood type will gradually shift to match the donor’s. This conversion can take weeks to months as the new bone marrow begins producing blood cells with the donor’s antigens. This change impacts future medical care, including transfusions.
Other rare and temporary changes can occur due to certain medical conditions. Some bacterial infections can cause a temporary alteration in antigen expression on red blood cells, a phenomenon sometimes called “acquired B.” This can happen in patients with conditions like sepsis or colon cancer, where bacterial enzymes modify existing antigens to resemble a different blood type. Such changes are temporary and resolve once the underlying condition is treated. Malignancies or autoimmune diseases can also lead to alterations in blood group antigen expression.
Scientific Efforts to Modify Blood Type
Scientific research explores methods to modify blood type to enhance the availability of universal donor blood for transfusions. These efforts focus on altering blood outside the human body rather than changing an individual’s inherent blood type. A key area of research involves using enzymes to convert A and B type red blood cells into O type blood.
Type O blood is considered a universal donor because it lacks A and B antigens, meaning it can be safely transfused to patients of any ABO blood type. Researchers have identified specific enzymes that can remove the sugar molecules that define A and B antigens from the surface of red blood cells. This process effectively transforms A or B type blood into O type.
Recent advancements include the discovery of more efficient enzyme systems capable of converting A and B blood types to O, working effectively in whole blood. While promising, this technology is still experimental and faces challenges before it can be widely implemented in clinical practice. The goal is to create a more efficient utilization of donated blood and reduce the risk of transfusion reactions.