Every person has a blood type. Blood types are classifications of the properties of a person's blood concerning how the blood reacts to new blood via a blood transfusion, and are often organized into a system of ABO blood types. Knowing the differences in blood types helps doctors prevent patients from having dangerous allergic reactions during blood transfusions.
ABO Blood Types:
Blood types are determined and named by the existence of two different antigens present on the surface of red blood cells; A antigens and B antigens. These antigens, which can be sugars or proteins, are essentialy markers attached to red blood cell membranes that let the body's immune system know which type of blood is natural to the body and which should be destroyed. For example, someone with A antigens would not be able to recieve B antigen blood, as the immune system would attack what it sees as "incompatible" blood. The immune system responds to blood types through the use of antibodies produced by the blood. These antibodies are made to counter antigens of the opposite type - ie: anti-A antibodies attack B antigens and anti-B antibodies attack A antigens. The main blood types are:
Type A: This type contains A antigens and produces anti-B antibodies.
Type B: This type contains B antigens and produces anti-A antibodies.
Type AB: This type contains both A and B antigens. As such, type AB blood will attack neither type A nor type B blood because it accepts both antigens as being natural to the body. This means AB blood is able to accept any type of blood during transfusions, making it a universal acceptor.
Type O: This type contains no antigens. This means that O blood will not react with antibodies produced by other blood types, making it a universally accepted blood type for transfusions, also called a universal donor.
Type A: This type contains A antigens and produces anti-B antibodies.
Type B: This type contains B antigens and produces anti-A antibodies.
Type AB: This type contains both A and B antigens. As such, type AB blood will attack neither type A nor type B blood because it accepts both antigens as being natural to the body. This means AB blood is able to accept any type of blood during transfusions, making it a universal acceptor.
Type O: This type contains no antigens. This means that O blood will not react with antibodies produced by other blood types, making it a universally accepted blood type for transfusions, also called a universal donor.
Blood Type | Antigens on Surface | Antibodies made |
|---|---|---|
A | A antigens | Anti-B |
B | B antigens | Anti-A |
AB | A and B antigens | None |
O | none | Anti-A and Anti-B |
The Rh Factor:
Among the four basic blood types, further organization is made, splitting each type into a positive and negative branch. This is derived from a third antigen present in red blood cells, called the D antigen. The presence of this antigen, or lack thereof, coordinates blood types into the two branches by their Rhesus (Rh) factor. The existence of D antigens on red blood cells classifies blood types as Rh positive, such as O+ or A+. The lack of D antigens on red blood cells classifies blood types as Rh negative, such as O- or A-. The Rh factor of an individual can help determine which blood types he/she can recieve or donate to in a blood transfusion, as seen in the next section.
Type A: A can recieve from A types and O types, but will react to B antigens. It can donate to both A types and AB types, since AB has A antigens naturally.
Type B: B can recieve from B types and O types, but will react to A antigens. It can donate to both B types and AB types, since AB has B antigens naturally.
Type AB: AB is a universal acceptor since it can recieve blood from any type. This is due to the presence of both A and B antigens, meaning AB does not producing anti-A or anti-B antibodies. However, because AB has both types of antigens, it can only donate to other AB types.
Type O: O can only accept blood from other O types since it contains both anti-A and anti-B antibodies that will react to any other blood type. However, type O's lack of antigens means that it will not react when donated to other blood types, making it a universal donor.
Blood Type Compatibility:
Because of the A and B antigens and antibodies, certain blood types can interact with each other without causing a problem in transfusions, while other may be incompatible and even kill the recipient of the transfusion. When an incompatible blood type is introduced to a body, the antibodies produced by red blood cells quickly attach to the antigen they are specified for (ex. anti-A attaches to A antigens). This causes the blood to clot while the antibodies destroy the incompatible blood cells, causing an allergic reaction that can be quite severe, even fatal. Take a look at the picture above to see which blood types are compatible with each other.Type A: A can recieve from A types and O types, but will react to B antigens. It can donate to both A types and AB types, since AB has A antigens naturally.
Type B: B can recieve from B types and O types, but will react to A antigens. It can donate to both B types and AB types, since AB has B antigens naturally.
Type AB: AB is a universal acceptor since it can recieve blood from any type. This is due to the presence of both A and B antigens, meaning AB does not producing anti-A or anti-B antibodies. However, because AB has both types of antigens, it can only donate to other AB types.
Type O: O can only accept blood from other O types since it contains both anti-A and anti-B antibodies that will react to any other blood type. However, type O's lack of antigens means that it will not react when donated to other blood types, making it a universal donor.
