Blood type AB is one of the rare blood types, characterized by both A and B antigens on red blood cells and the absence of antibodies in the plasma.
1. Factors that determine blood type
In a normal human body, red blood cells are produced in the bone marrow and are responsible for transporting oxygen throughout the body. There are about 1 billion red blood cells in 2-3 drops of blood. Among them, the number of red blood cells far exceeds that of platelets and white blood cells (for every 600 red blood cells, there are about 40 platelets and 1 white blood cell).
According to the spokesperson of the American Society of Hematology, red blood cells always have proteins attached to carbohydrates on their surface, which is a fundamental sign used to determine a person’s blood type. Typically, there are 8 basic blood types: A, B, AB, and O, with each type further classified into Rh+ and Rh-.
Blood type A is the type that has only A antigens on the surface of red blood cells, while blood type B has only B antigens. Blood type AB contains both A and B antigens, and blood type O has no antigens on the surface of red blood cells. These are the 4 basic blood types, which are essential for determining whether a patient can receive a safe blood transfusion.
In cases where a patient receives incompatible blood, it can cause a very dangerous reaction because the immune system will recognize foreign antigens on the surface of the blood cells, leading to hemolysis or other complications.
2. Why is blood type AB rare?
In fact, people with blood type AB are very rare and unique because they have both A and B antigens on the surface of red blood cells but do not have antibodies in the plasma.
All blood contains basic components including white blood cells, red blood cells, platelets, and plasma (a liquid component of blood that helps keep red blood cells, white blood cells, and platelets within the circulatory system). Red blood cells are produced in the bone marrow and perform the task of transporting oxygen to the body. Compared to platelets, red blood cells are more numerous and are responsible for oxygen transport, while platelets help with clotting and preventing excessive bleeding, and white blood cells are responsible for protecting the body from pathogens and diseases.
Stanford Medical School (USA) conducted a survey and calculated the distribution of blood types in the general population, with the following results:
O+: 37.4%, O-: 6.6%, A+: 35.7%, A-: 6.3%, B+: 8.5%, B-: 1.5%, AB+: 3.4%, AB-: 0.6%. However, these percentages are general and, in reality, there are slight differences based on ethnicity. People with blood type B are more common in Asia than among Caucasians, while blood type O is more prevalent in Spain.
People with blood type AB can inherit the A gene from their father and the B gene from their mother. Those who have this rare blood type have a significant advantage as they can receive any blood type, especially AB+. However, due to the presence of both antigens on the red blood cells of AB blood type, individuals with this blood type can only donate blood to others with the same AB blood type. In the case of AB blood with Rh-, they can only receive blood from someone with Rh- blood type, as receiving blood from someone with Rh+ may cause dangerous complications during the transfusion.
In reality, people with rare blood types who need an urgent blood transfusion due to blood loss from an accident or emergency surgery may not always have access to a reserve blood supply in the hospital. Therefore, if you have blood type AB, you should proactively take care of yourself and donate blood to a blood bank in case it's needed. If possible, consider joining a support group for individuals with rare blood types to help each other in emergencies.
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