Blood Types
Your blood is
typed, or classified, according to the presence or
absence of certain markers () found on red blood cells and
in the plasma that allow your body to recognize blood as its own. If another
blood type is introduced, your
recognizes it as foreign and attacks it,
resulting in a
transfusion reaction.
ABO blood type system
The ABO system consists of
A, B, AB, and O blood types. People with type A have
in the blood against type B. People with
type B have antibodies in the blood against type A. People with AB have no
anti-A or anti-B antibodies. People with type O have both anti-A and anti-B
antibodies. People with type AB blood are called universal recipients, because
they can receive any of the ABO types. People with type O blood are called
universal donors, because their blood can be given to people with any of the
ABO types. Mismatches with the ABO and Rh blood types are responsible for the
most serious, sometimes life-threatening, transfusion reactions.
Rh system
The Rh system classifies blood as
Rh-positive or Rh-negative, based on the presence or absence of Rh antibodies
in the blood. People with Rh-positive blood can receive Rh-negative blood, but
people with Rh-negative blood will have a transfusion reaction if they receive
Rh-positive blood. Transfusion reactions caused by mismatched Rh blood types
can be serious.
Minor blood types
There are over 100 other blood
subtypes. Most have little or no effect on blood transfusions, but a few of
them may be the main causes of mild transfusion reactions. Mild transfusion
reactions are frightening, but they are rarely life-threatening when treated
quickly.