Blood transfusions in the ABO blood group system:

Blood transfusion is the process of transferring blood or blood-based products from one person into the circulatory system of another.

Requirement of Blood transfusions:

Blood transfusions can be life-saving in some situations, such as massive blood loss due to injury, or can be used to replace blood lost during surgery. People suffering from anemia, hemophilia, thalassemia, or sickle-cell disease may require frequent blood transfusions.

Cross Matching for Blood transfusions:

Transfusion of blood is done after confirming that no agglutination results in the blood of the recipient.

Agglutination:

Agglutination leads to the clumping of cells and clumped cells cannot pass through capillaries. For the confirmation of no agglutination, blood samples of donor and recipient are crossed-matched for compatibility. Antibodies of the recipient's blood may destroy the corresponding antigen-containing RBCes of the donor or the antibodies of the donor's blood may destroy the antigen-containing RBCes of the recipient.