ABO Blood Group

SWBIC Educational Resources  >> Activities & Materials  >> ABO Blood Group

Human red blood cells contain protein molecules in their cell membranes. These particular proteins are called “antigens” and determine the blood type of an individual. There are three kinds of antigens that may be used on human red blood cells: an antigen named “A”, an antigen named “B”, and an antigen named “Rh”.

All of the red blood cells in a single individual contain the same antigens. A person whose red blood cells have the “A antigen” has the blood type A. People whose red blood cells have the “B antigen” have the blood type B. Some people have red blood cells that contain both “A and B antigens” so they have the blood type AB. Other people have red blood cells with “neither A nor B antigens” so they have the blood type O.

The other antigen, Rh, is present in some people and absent in others. The “Rh factor” may be found along with the A and/or B antigens. People with the Rh antigens are distinguished with a “+” in their blood type, and those without the Rh antigen have a “-” in their blood type.

Blood Type Antigen Present


antigen A and the Rh antigen


antigen A


antigen B and the Rh antigen


antigen B


antigen A, antigen B and the Rh antigen


antigen A and antigen B


Rh antigen


no antigen present on the red blood cells

ACTIVITY to practice “Typing Blood”: On the attached sheet, identify and label the red blood cells according to the type t hey represent.

The type of antigens on the red blood cells is only part of the story. The other part of the story is about “antibodies”. Antibodies are “Y-shaped” proteins produced by the individual’s immune system to protect against foreign antigens. Whatever antigens are not produced by an individual are recognized as foreign and are sought out and bound by antibodies.

For example, people with Blood Type A+ carry the A antigen and the Rh antigen, and produce antibodies against the B antigen. Those with Blood Type B- carry the B antigen, and produce antibodies against the A antigen and the Rh antigen.

People who have the blood type AB- produce antibodies against ___________________.

Those with blood type O+ produce antibodies against ____________________________.

What antibodies does someone with the B+ Blood Type produce? ________________.

ACTIVITY to practice production of antibodies against foreign red blood cell antigens: On the attached “ANTIBODY” sheet,(1) identify each of the antibodies in terms of the antigen it binds, and (2) identify the blood type(s) of the people who produce each of the specific antibodies.

So, why is this antigen-antibody stuff important to anyone? It is primarily important for a person receiving a blood transfusion (and the people who love them). The binding of antibodies to antigen causes at least two serious problems. First, the tails on the “Y-shaped” antibodies become tangled up causing “clumps” of red blood cells with the antibodies, the red blood cells can no longer pick up or deliver oxygen, and they could block blood vessels. The second problem caused by antibody-antigen binding is that the cells that are bound are marked for destruction and will be killed shortly after being bound.

Developed for SWBIC by Arlene Antilla, Ph.D, Northern New Mexico Community College