From the Guidelines
The ABO reaction works through a process of specific recognition and binding between antibodies and antigens, where antibodies against A or B antigens can trigger an immune response, leading to hemolysis, particularly in patients receiving incompatible plasma from platelet transfusions, as highlighted in the context of transfusion medicine 1. When considering the ABO blood group system, it's essential to understand that individuals with type A blood have A antigens on their red cells and anti-B antibodies in their plasma, while those with type B blood have B antigens and anti-A antibodies. This inherent incompatibility is crucial in the context of blood transfusions, where mismatched blood types can lead to severe reactions, including hemolysis, as noted in the guidelines for platelet transfusion 1. The process of antibody-antigen binding is fundamental to understanding how ABO reactions occur. Antibodies are Y-shaped proteins that recognize and bind to specific antigens, in this case, the A or B antigens present on red blood cells. This binding can activate the complement system, leading to the destruction of the incompatible red blood cells. The importance of ABO compatibility in transfusions is underscored by guidelines that recommend providing ABO-compatible products whenever possible to minimize the risk of hemolysis, especially in vulnerable populations like children 1. In the context of transfusion medicine, extending the red cell antigen profile beyond ABO/RhD typing can help identify and manage patients at risk of alloimmization, as discussed in guidelines for sickle cell disease management 1. However, the primary concern with ABO reactions remains the immediate and potentially life-threatening consequences of mismatched blood transfusions, emphasizing the need for strict adherence to ABO compatibility in transfusion practices. Key points to consider in managing ABO reactions include:
- The importance of ABO compatibility in blood transfusions to prevent hemolysis 1.
- The role of extended red cell antigen profiling in managing patients with a positive antibody screen or history of transfusion reactions 1.
- The need for careful consideration of plasma compatibility in platelet transfusions to minimize the risk of hemolysis, particularly in children 1.
From the Research
ABO Reaction Mechanism
The ABO reaction is a complex process involving the immune system's response to incompatible blood types. The key factors involved in this reaction are:
- Preformed immunoglobulin M (IgM) and IgG antibodies to ABO blood group antigens (isohemagglutinins) present in everyone except group AB individuals 2
- Complement-mediated lysis of red blood cells, which can occur in the setting of red cell transfusion, hematopoietic and solid organ transplantation, hemolytic disease of the newborn, and intravenous immunoglobulin infusion 2
Hemolytic Transfusion Reactions
Hemolytic transfusion reactions (HTR) are systemic reactions provoked by immunologic red blood cell (RBC) incompatibility. These reactions proceed through phases of:
- Humoral immune reaction
- Activation of phagocytes
- Production of cytokine mediators
- Wide-ranging cellular responses 3 HTR have many features in common with the systemic inflammatory response syndrome (SIRS) 3
ABO Incompatibility and Hemolysis
ABO incompatibility can cause hemolysis, which is a major concern in transfusion medicine. The risk of hemolysis due to ABO incompatible plasma-containing components is a significant concern, particularly in the setting of whole blood transfusion 4. The lowest anti-A titre reported to cause haemolysis was 32 (IgG), while for anti-B it was 512 (IgG and IgM) for adults 4.
Clinical Implications
The ABO reaction can have severe clinical implications, including: