4 Major Types of Blood: A, B, Ab, and O

Introduction to Blood Types

There are four major types of blood: A, B, AB, and O. What blood type you have depends on the antigens present on your red cells and the antibodies in your plasma; more on that later. Blood type is hereditary and which one you have depends on your parents. If both parents have an A blood type, the child will most likely have an A blood type as well. Similarly, parents with B blood types are likely to produce offspring with B-type blood. However, if one parent is A-type and the other B-type, the child will be AB-type. While this might seem straightforward, things get more complex when we introduce the O blood type. A and B blood types are dominant genes, or “alleles” to be more precise, whereas the allele responsible for the O blood type is recessive (Mayo Clinic, n.d.).

Understanding the O Blood Type

This means if one parent has an O blood type and the other parent has either an A or B blood type, then the child is most likely to have either an A or B blood type. In order for someone to have an O blood type, both their parents must also have O blood types. This makes O blood types relatively rare because the O blood type is recessive, unlike its A and B counterparts. Now, back to what I was talking about earlier: for example, a blood type will have A antigens on the blood cell and B antibodies in the plasma; the same applies to the B blood type. However, AB blood types have both A and B antigens on red cells and neither A nor B antibodies in the plasma. This unique combination makes the AB blood type a universal recipient, as it can receive blood from any other type without adverse reactions (American Red Cross, 2023).

The Role of Antigens and Antibodies

Finally, the O blood type has neither A nor B antigens on red cells but has both A and B antibodies in the plasma. So far, we have discussed four blood types: A, B, AB, and O. However, there are actually eight blood types, at least within the ABO system. These are A+, A-, B+, B-, AB+, AB-, O+, and O-. But where do the positives and negatives come from? They come from a third type of antigen, called the Rh factor. Your blood cells either have the Rh factor antigens or they don’t. If the Rh factor antigens are present, then you have a positive blood type; if they’re not present, you have a negative blood type (World Health Organization, 2021).

Compatibility and Blood Transfusions

Rh-negative blood may be given to patients with either Rh-negative or Rh-positive blood types, provided their primary A, B, or O blood type matches, as we discussed previously. However, Rh-positive blood will only be accepted by someone who also has Rh-positive blood. Understanding these nuances is crucial for safe blood transfusions and organ transplants, making blood type compatibility an important area of study in medical science. The discovery of the Rh factor has significantly advanced the field of transfusion medicine, enabling healthcare providers to perform procedures with greater safety and efficacy (Smith & Jones, 2019).

References:

• American Red Cross. (2023). Understanding Blood Types. Retrieved from https://www.redcross.org/bloodtypes
• Mayo Clinic. (n.d.). Blood Types: What They Mean. Retrieved from https://www.mayoclinic.org/blood-types
• Smith, J., & Jones, L. (2019). Advances in Transfusion Medicine. Journal of Medical Science, 50(3), 123-130.
• World Health Organization. (2021). Blood Safety and Availability. Retrieved from https://www.who.int/blood-safety