ABO Incompatibility


Multimedia

Definition

ABO incompatibility is an immune system reaction that occurs when blood from two different and incompatible blood types are mixed together.

See also: Transfusion reaction - hemolytic


Causes, incidence, and risk factors

A, B, and O are the three major blood types. The types are based on small substances (molecules) on the surface of the blood cells. In people who have different blood types, these molecules act as immune system triggers (antigens).

Each person has a combination of two of these surface molecules. Type O lacks any molecule. The different blood types are:

  • Type A (AA or AO molecules)
  • Type B (BB or BO molecules)
  • Type AB (one A and one B molecule)
  • Type O

People who have one blood type form proteins (antibodies) that cause their immune system to react against other blood types. Being exposed to another type of blood can cause a reaction. This is important when a patient needs to receive blood (transfusion) or have an organ transplant. The blood types must be matched to avoid an ABO incompatibility reaction.

For example:

  • A patient with type A blood will react against type B or type AB blood
  • A patient with type B blood will react against type A or type AB blood
  • A patient with type O blood will react against type A, type B, or type AB blood
  • A patient with type AB blood will NOT react against type A, type B, or type AB blood

Because type O does not have any surface molecules, type O blood does not cause an immune response based on ABO incompatibility. This is why type O blood cells can be given to patients of any blood type. People with type O blood are called "universal donors." However, people with type O can only receive type O blood.

Since antibodies are in the liquid part of blood (plasma), both blood and plasma transfusions must be matched to avoid an immune reaction.


References

Goodnough L. Transfusion medicine. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 183.

Wu YY, Mantha S, Snyder EL. Transfusion reactions. In: Hoffman R, Benz E Jr, Shattil S, et al, eds. Hematology: Basic Principles and Practice. 5th ed. Philadelphia, Pa: Churchill Livingstone; 2008:chap 153.


Request An Appointment

Review Date: 8/24/2011
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 2004 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

adam.com
Last Updated 2/14/2012
Find a Doctor

e.g., "allergy," "diabetes"

US News Best Hospital AwardANCC Magnet Association AwardBest Doctors 2011-2012 AwardConsumer Choice #1 Award 2011-2102US News Best Medical Schools 2011 Award

Disclaimer: The information on this website is for general informational purposes only and SHOULD NOT be relied upon as a substitute for sound professional medical advice, evaluation or care from your physician or other qualified health care provider.