Blood Types | American Red Cross

The need is constant. The gratification is instant. Give Blood. ™

· Careers
· About Us
· Media Center
· Students
· Fun & Games


· Español
· Search

Site Search

American Red Cross

· Donating Blood
· Learn about Blood
· Hosting a Blood Drive
· Volunteer
· For Hospitals

Home > Learn About Blood > Blood Types
    Printable Version

** Blood Types **

Although all blood is made of the same basic elements, not all blood is
alike. In fact, there are eight different common blood types, which 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.

**The ABO Blood Group System**

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:

· *Group A *– has only the A antigen on red cells (and B antibody in the
· *Group B *– has only the B antigen on red cells (and A antibody in the
· *Group** AB *– has both A and B antigens on red cells (but neither A
nor B antibody in the plasma)
· *Group O *– has neither A nor B antigens on red cells (but both A and
B antibody are in the plasma)

There are very specific ways in which blood types must be matched for a
safe transfusion: 

Blood type chart
Group O O Blood Type diagram linking blood types O Blood Type


how is blood type determined

Blood type - Wikipedia, the free encyclopedia


** Blood type **

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Blood type (or blood group) is determined, in part, by the ABO blood group
antigens present on red blood cells.

A *blood type* (also called a *blood group*) is a classification of blood
based on the presence or absence of inherited antigenic substances on the
surface of red blood cells (RBCs). These antigens may be proteins,
carbohydrates, glycoproteins, or glycolipids, depending on the blood group
system. Some of these antigens are also present on the surface of other
types of cells of various tissues. Several of these red blood cell surface
antigens can stem from one allele (or very closely linked genes) and
collectively form a blood group system.^[1] Blood types are inherited and
represent contributions from both parents. A total of 32 human blood group
systems are now recognized by the International Society of Blood
Transfusion (ISBT).^[2] The two most important ones are ABO and the RhD
antigen; they determine someone's blood type (A, B, AB and O, with + and -
denoting RhD status).

Many pregnant women carry a fetus with a blood type different from their
own, and the mother can form antibodies against fetal RBCs. Sometimes these
maternal antibodies are IgG, a small immunoglobulin, which can cross the
placenta and cause hemolysis of fetal RBCs, which in turn can lead to
hemolytic disease of the newborn called erythroblastosis fetalis, an
illness of low fetal blood counts that ranges from mild to severe.
Sometimes this is lethal for the fetus; in these cases it is called hydrops


· 1 Blood group systems

· 1.1 ABO blood group system
· 1.2 Rh blood group system
· 1.3 ABO and


© 2005-2021