Why is it important to have compatible donor and recipient blood types in transfusions?

In blood transfusions, having compatible donor and recipient blood types is crucial to prevent potentially fatal complications. When transfusing blood, the recipient's immune system reacts to the transfused blood components. Mismatched blood types can lead to severe immune responses, such as:

1. Hemolysis: This is the destruction of transfused red blood cells (RBCs) by the recipient's immune system. Mismatched RBC antigens (such as A, B, AB, or O blood group antigens) can trigger the recipient's antibodies to attack and destroy the donor RBCs. This process releases hemoglobin, which can damage kidneys and cause a condition called hemoglobinuria.

2. Transfusion-Related Acute Lung Injury (TRALI): TRALI is a severe complication that can occur when incompatible plasma or white blood cells are transfused. It is characterized by acute respiratory distress, fever, chills, and hypotension. TRALI can lead to respiratory failure and is associated with high mortality rates.

3. Febrile Non-Hemolytic Transfusion Reactions (FNHTR): FNHTRs are common but less severe reactions to transfused blood. They are caused by antibodies in the recipient's plasma that react with antigens on donor white blood cells or platelets. FNHTRs typically manifest as fever, chills, and discomfort during or shortly after the transfusion.

4. Delayed Hemolytic Transfusion Reactions (DHTR): DHTRs occur several days to weeks after a transfusion and are caused by antibodies that develop in response to foreign RBC antigens. These antibodies can attack and destroy transfused RBCs, leading to anemia.

5. Graft-versus-Host Disease (GVHD): GVHD is a rare but life-threatening complication that can occur when transfused lymphocytes (a type of white blood cell) attack the recipient's tissues. GVHD affects various organs and causes severe damage, leading to a high risk of mortality.

To prevent these complications, blood transfusions are performed with careful matching of blood types between donors and recipients. This matching includes ABO blood group compatibility (A, B, AB, or O), Rh factor compatibility (positive or negative), and, in some cases, additional minor antigen matching. Modern blood banking practices and pre-transfusion testing protocols ensure that blood transfusions are as safe as possible, significantly reducing the risk of adverse reactions and complications in recipients.