ABO Blood Group Compatibility in Liver Transplantation

ABO Blood Groups – The Basics

ABO antigens are sugars on the surface of red blood cells and many tissues, including the vascular endothelium and bile ducts—so they matter for transfusion and organ transplantation.[1,2]

• Four main blood groups exist: A, B, AB, and O, defined by A and/or B antigens on the cell surface.[1]
• People naturally make antibodies (isoagglutinins) against the A or B antigens they do not have—for example, group O patients have both anti-A and anti-B antibodies.[1,2]
• These antibodies can bind donor cells or graft endothelium, causing hemolysis or antibody-mediated rejection (AMR) if ABO barriers are ignored.[2,3]
• Transplant organizations such as UNOS/OPTN require accurate, independent blood typing for both donors and recipients before matching.[2,3]

Who Can Receive Which Liver? (Biologic ABO Compatibility)

In general, the liver follows the same ABO compatibility rules used for other solid organs, though special exceptions may be made in pediatrics and emergencies.[2–5]

Below is a simplified biologic compatibility chart (not a full statement of policy). Actual allocation rules depend on OPTN/UNOS policies, local practices, and clinical judgment.[3,4]

The transplant team also considers donor/recipient size, urgency, HLA antibodies, and logistics. ABO-nonidentical, but biologically compatible, grafts may be used to reduce mortality on the waiting list while maintaining acceptable outcomes.[4–6]

ABO-Nonidentical and ABO-Incompatible Liver Transplantation

Historically, outcomes were best with ABO-identical grafts, and early experiences with ABO-incompatible liver transplantation showed higher rejection and biliary complications.[5,6]

• Large series from the 1980s–1990s demonstrated that survival was significantly better with ABO-identical grafts, leading many centers to avoid ABO-incompatible liver transplants except in life-saving emergencies.[5,6]
• Meta-analyses and registry studies confirm that ABO-incompatible (ABOi) liver transplants have historically carried higher risks of early graft loss, hepatic artery thrombosis, and biliary problems—but these gaps have narrowed with modern protocols.[6–9]
• Carefully selected ABO-nonidentical transplants (for example, O donor into A or B recipient) can expand access for blood-type B and AB candidates without clearly worsening outcomes when policies are thoughtfully designed.[4]
• Current reviews emphasize that the “penalty” for ABOi liver transplant is much smaller than it once was, especially in experienced centers using rituximab-based desensitization and titer-guided therapy.[7–9]

Most adult programs still prefer ABO-identical or compatible grafts whenever possible, but ABO-incompatible options may be considered for highly urgent cases, re-transplantation, or specific living-donor scenarios when the alternative is death on the waiting list.[6–9]

Modern Desensitization Protocols for ABO-Incompatible LT

Advances in immunosuppression have transformed ABO-incompatible liver transplantation from an experimental, high-risk option into a viable strategy in many centers.[7–10]

• Modern protocols typically include B-cell depletion (often with rituximab), peri-operative plasma exchange or immunoadsorption to lower anti-A/B titers, and potent maintenance immunosuppression.[7–10]
• Contemporary series of living-donor ABOi liver transplantation report graft and patient survival approaching those of ABO-compatible cases when desensitization is carefully applied and anti-A/B titers are controlled.[7–9]
• Some centers individualize the intensity of desensitization based on starting antibody titers, age, and comorbidities to reduce infectious and hematologic complications.[9,10]
• Emerging data suggest that in certain low-titer or pediatric situations, less intensive rituximab-based regimens may be sufficient, but protocols remain center-specific.[9,10]

For patients and families, the key message is that ABO-incompatible transplant is no longer an automatic “last resort.” In selected circumstances, it can be a planned, protocol-driven option that meaningfully increases access to life-saving surgery.[7–10]

ABO-Incompatible Liver Transplantation in Children

Infants and young children are “special cases” because their immune systems are still developing, and anti-A/B antibodies may be absent or very low.[1,7,11–14]

• Multiple pediatric series and meta-analyses now show excellent outcomes for ABO-incompatible liver transplantation in infants, especially those with high PELD scores or acute liver failure.[11–14]
• Long-term graft and patient survival for pediatric ABOi recipients who survive the early post-operative period can approximate those of ABO-compatible transplants, particularly in experienced centers.[11–13]
• Some guidelines and expert reviews suggest liberalizing indications for ABOi pediatric liver transplantation to prevent wait-list deaths and irreversible deterioration in critically ill children.[11–14]
• Children may “accommodate” the ABO-mismatched graft over time, with a fall in anti-A/B titers and reduced risk of late antibody-mediated injury compared with adults.[7,11–13]

For parents, this means that an ABO-incompatible liver may be offered as a medically sound, guideline-supported option when compatible organs are not available quickly enough—and that long-term outcomes can be very favorable in this context.[11–14]

Key Questions to Ask Your Transplant Team

Understanding how your blood type affects transplant options can help you make informed, shared decisions with your team.

• “What is my blood type, and how does it affect my place on the waiting list and expected waiting time?”
• “Will my transplant be ABO-identical, compatible, nonidentical, or ABO-incompatible? Why are you recommending this option for me?”
• “If you are considering an ABO-incompatible transplant, what desensitization protocol will you use, and what are the added risks and benefits in my situation?”
• “How do outcomes with ABO-nonidentical or incompatible grafts at this center compare with ABO-identical grafts, especially for patients like me?”
• “Are there special considerations for my child’s age, diagnosis, or urgency that make ABO-incompatible transplantation more appropriate?”
• “How will you monitor for antibody-mediated rejection or biliary complications after an ABO-nonidentical or incompatible transplant?”