Immuno-Hematologic Complexity of ABO-Incompatible Allogeneic HSC Transplantation

Area of Science:

• Immunology
• Hematology
• Transplantation Science

Background:

• ABO incompatibility is a frequent challenge in hematopoietic stem cell transplantation (HSCT), affecting up to 50% of unrelated donor transplants.
• While not an absolute contraindication, ABO mismatch necessitates meticulous immuno-hematologic assessment and management strategies.
• Potential complications include immediate hemolysis and delayed issues like passenger lymphocyte syndrome and pure red cell aplasia.

Purpose of the Study:

• To review the immuno-hematologic challenges and management strategies for ABO-incompatible HSCT.
• To highlight the current lack of standardized methods for isohemagglutinin titration and definitive treatment protocols.
• To emphasize the importance of tailored transfusion strategies until successful engraftment and ABO conversion.

Main Methods:

• Pre-HSCT immuno-hematologic investigations to assess donor/recipient ABO mismatch and anti-A/B isohemagglutinin (IHA) titers.
• Evaluation of preventive measures including decision-making algorithms based on IHA titration.
• Consideration of protocols for IHA reduction (e.g., plasma exchange, immunoadsorption) and product manipulation (e.g., RBC/plasma depletion).

Main Results:

• ABO-incompatible HSCT requires careful monitoring of IHAs and consideration of various reduction techniques.
• Standardization of IHA titration methods and definitive management guidelines are currently lacking.
• Transfusion strategies must account for both donor and recipient blood groups until confirmed RBC engraftment and ABO conversion.

Conclusions:

• ABO incompatibility in HSCT presents a significant immuno-hematologic challenge requiring proactive management.
• A definitive expert consensus or solid evidence-based approach for ABO-incompatible HSCT is yet to be established.
• Appropriate selection of ABO blood components for transfusion is crucial for successful outcomes.