Facts About Blood and Blood Types

How Blood Type Is Determined And Why You Need To Know

Blood types are determined by the presence or absence of certain antigens – substances that can trigger an immune response if they are foreign to the body.  Since some antigens can trigger a patient's immune system to attack the transfused blood, safe blood transfusions depend on careful blood typing and cross-matching. Do you know what blood type is safe for you if you need a transfusion?

There are four major blood groups determined by the presence or absence of two antigens – A and B – on the surface of red blood cells. In addition to the A and B antigens, there is a protein called the Rh factor, which can be either present (+) or absent (–), creating the 8 most common blood types (A+, A-,  B+, B-,  O+, O-,  AB+, AB-).

Group A has only the A antigen on red cells (and B antibody in the plasma)

Group B has only the B antigen on red cells (and A antibody in the plasma)

Group AB has both A and B antigens on red cells (but neither A nor B antibody in the plasma)

Group O has both A and B antigens on red cells (but neither A nor B antibody in the plasma)

Each year 4.5 million lives are saved by blood transfusions.

There are very specific ways in which blood types must be matched for a safe transfusion. The right blood transfusion can mean the difference between life and death. 

Rh-negative blood is given to Rh-negative patients, and Rh-positive or Rh-negative blood may be given to Rh-positive patients. The rules for plasma are the reverse. 

• The universal red cell donor has Type O negative blood.
• The universal plasma donor has Type AB blood.

Sources:
1. https://www.redcrossblood.org/donate-blood/blood-types.html
2. https://sites.google.com/site/padraigmcdowelln9738142/evidence-for