There are 4 types of human blood: A, B, AB, O. The difference is due to proteins found both on the red blood cells and in the blood plasma. The proteins on the red blood cells act as antigens and the proteins in the plasma act as antibodies. Type A blood has A antigens on the surface of the red blood cells and B antibodies (anti-B) in the blood plasma. Type B blood has B antigens on the surface of the red blood cells and A antibodies (anti-A) in the blood plasma. Type AB blood has both A and B antigens on the surface of the red blood cells, but no plasma antibodies. Type O blood has no antigens on the surface of the red blood cells, and has both A and B antibodies in the blood plasma. .
Mixing blood types has serious consequences. For example, when type A blood is mixed with type B blood, the antigens on the type A red blood cells react with the serum antibodies of type B blood. This antibody antigen reaction causes severe clumping (agglutination) of the red blood cells. This tends to block blood vessels, resulting in brain and kidney damage and, ultimately, death. Those with type O blood are called universal donors. Although blood type O contains plasma antibodies against blood types A and B, it can sometimes be used in emergency transfusions as a donor to these blood types since the antibodies in this blood plasma become so diluted in the recipient's plasma that the amount of clumping does not reach lethal levels. The O blood cells are not attacked by the anti-A and/or anti-B in the recipient because the O cells do not contain any A or B antigens. Those with type AB blood are called universal recipients since they have no plasma antibodies to react with the antigens found on A, B, and O types of red blood cells.
In the lab experiment, we used the aforementioned information to determine the type of the blood by using a certain anti-serum.
Hypothesis.
If the blood mixes fully with the respective anti-serum, then the blood is of the type of the corresponding serum.
