TO THE EDITOR
Liver transplantation (LT) stands as the curative gold standard for end-stage liver disease and select hepatic malignancies, yet the immunological complexity of the procedure continues to shape post-transplant outcomes in profound ways[1]. The liver has long been recognized as unique among solid organs for its relative resistance to antibody-mediated injury, but this resistance is far from absolute: It is context-dependent, and mounting clinical evidence confirms that pre-formed donor-specific antibodies (DSAs)-especially high-titer, complement-binding variants-and positive donor-recipient crossmatches drive increased risks of acute rejection, graft dysfunction, and mortality in transplant recipients[2-4]. Hyperimmunization affects a clinically significant subset of liver transplant candidates, typically stemming from prior sensitizing events such as blood transfusions, pregnancy, or previous solid organ transplantation[5-7].
The management of hyperimmunized liver transplant recipients remains one of the field’s most contentious areas, with particular debate surrounding the role and optimal composition of induction immunosuppression. While induction therapy is a well-established cornerstone of kidney transplantation care, its use in LT has been inconsistent and heterogeneous across centers, rooted in valid concerns about infection, malignancy, and the risks of over-immunosuppression in a population already vulnerable to post-transplant complications[7,8]. EL-Domiaty et al[9] published in the World Journal of Hepatology address this long-unresolved clinical gap by evaluating a combined induction regimen of rabbit anti-T-lymphocyte globulin (rATLG) and intravenous immunoglobulin (IVIG) in hyperimmunized liver transplant recipients, offering critical, practice-changing insights into risk mitigation strategies for this high-risk group in contemporary LT.
Methods
EL-Domiaty et al’s study[9] was conducted at a high-volume liver transplant center using a retrospective 1:1 exact matched case-control design, pairing 46 hyperimmunized liver transplant recipients with 46 non-immunized controls. Matching was strictly based on age, sex, primary transplant indication, and model for end-stage liver disease score, with post-matching balance diagnostics confirming well-balanced baseline characteristics between the two cohorts-an essential step in minimizing confounding bias in retrospective analyses. Hyperimmunization was defined by the presence of DSAs with a mean fluorescence intensity ≥ 5000 (the center’s established clinical threshold for high-titer DSAs) and/or a positive complement-dependent cytotoxicity crossmatch at the time of transplantation; no additional complement-binding assays (e.g., C1q or C3d) were performed as part of the study’s inclusion criteria.
High-risk hyperimmunized recipients received a standardized induction therapy regimen of rATLG (1.5 mg/kg/day for 3 consecutive days, initiated intraoperatively) combined with high-dose IVIG (2 g/kg total dose, administered in two divided doses in the first week post-transplant), followed by center-standard maintenance immunosuppression (tacrolimus-based triple therapy with mycophenolate mofetil and prednisone). In contrast, non-immunized control patients did not receive any induction immunosuppression and were managed with the identical maintenance regimen alone.
Clinical, immunological, and histopathological outcomes were systematically collected and adjudicated, with acute rejection classified strictly according to the 2016 Banff Working Group criteria for liver allograft pathology[10]. Graft and patient survival were analyzed using Kaplan-Meier curves, with standardized statistical comparisons (including log-rank tests and Cox proportional hazards models) employed to evaluate between-group differences. This rigorous analytical approach ensured methodological robustness, even within the constraints of the study’s retrospective design.
Key findings
Despite their markedly higher baseline immunological risk, hyperimmunized recipients who received the rATLG/IVIG induction regimen exhibited rates of biopsy-proven acute T-cell–mediated rejection that were nearly identical to those of non-immunized controls. Most notably, no graft losses were attributed to acute rejection in either cohort over the study follow-up period. While acute antibody-mediated rejection occurred exclusively in the hyperimmunized group, these episodes were rare, clinically mild, and readily managed with targeted immunosuppressive interventions-with no subsequent impact on long-term graft survival.
Graft and patient survival at 1 and 3 years were comparable between the two groups, with a borderline statistical trend favoring non-immunized recipients (log-rank P = 0.048 for 3-year graft survival; P = 0.051 for 3-year patient survival). This subtle statistical finding is best interpreted as a reflection of the study’s limited sample size (46 pairs) rather than a clinically meaningful disparity in outcomes, as the absolute survival differences between groups were minimal (≤ 3% at all time points).
Notably, the rATLG/IVIG induction regimen was well-tolerated in this high-risk cohort: Severe infectious complications (defined as life-threatening infections requiring ICU admission, intravenous antimicrobial therapy for ≥ 14 days, or associated with organ dysfunction) occurred in 8.7% of hyperimmunized recipients vs 6.5% of controls (P = 0.68), with no cases of induction-related severe infection (e.g., early opportunistic infection within the first month post-transplant). No new-onset malignancy was diagnosed in either group during the follow-up period, and induction-related adverse events (e.g., infusion reactions, cytopenias) were mild, transient, and managed with supportive care alone-no recipients required discontinuation of induction therapy for adverse events. These findings strongly support the favorable safety profile of this induction strategy in hyperimmunized liver transplant recipients.
Critical appraisal
The findings of EL-Domiaty et al’s study[9] align closely with and extend the growing body of research demonstrating that antibody-mediated mechanisms are clinically impactful drivers of outcomes in LT-contrary to the historical view of the liver as uniformly resistant to AMR[2,6,11]. Earlier studies have consistently linked pre-formed DSAs, and particularly high-titer class II HLA antibodies, to elevated risks of acute rejection and early mortality in liver transplant recipients[3,4,12-14]. The low incidence of severe acute rejection (both T-cell-mediated and antibody-mediated) and the complete absence of rejection-related graft loss in the hyperimmunized cohort of this study stand in stark contrast to historical data, which report rejection rates ranging from 23% to 65% in sensitized liver transplant recipients without targeted induction therapy-underscoring the clinical efficacy of the rATLG/IVIG regimen[11,15-17].
The induction strategy evaluated here mirrors promising approaches previously explored in crossmatch-positive LT, including thymoglobulin-based regimens combined with B-cell-directed therapies[12], but offers a key advantage in its use of rATLG over thymoglobulin. While direct head-to-head comparative data of rATLG and thymoglobulin specifically in LT remain limited, multiple studies in solid organ transplantation (including kidney and heart transplantation) have demonstrated that rATLG confers a more favorable safety profile-with lower rates of severe cytopenia and opportunistic infection-while maintaining equivalent immunosuppressive efficacy[18-20]. This is a critical distinction for LT, where recipients are inherently immunocompromised due to underlying liver dysfunction and at high risk of post-transplant infection[21-23].
Equally important, EL-Domiaty et al’s study[9] demonstrates that standard maintenance immunosuppression levels are sufficient to maintain graft tolerance in hyperimmunized recipients who receive effective induction therapy. This finding challenges the historical practice of intensifying long-term immunosuppression in high-risk sensitized recipients-a strategy that often increases the risk of infection and malignancy without meaningful improvements in graft survival. Instead, the study supports a more nuanced approach: Front-loading immunosuppression with a short, targeted induction course to mitigate early immunological risk, followed by standard maintenance therapy to balance long-term graft protection and patient safety.
Of course, the study is not without limitations, which must be acknowledged to avoid overinterpretation of its findings. The retrospective, single-center design and relatively small sample size limit the generalizability of the results and preclude definitive conclusions about the regimen’s efficacy in broader patient populations. Additionally, the study did not include systematic post-transplant DSA monitoring, which limits mechanistic insights into DSA kinetics, antibody decline, and the potential for subclinical AMR-an area increasingly recognized as a key driver of long-term graft fibrosis and dysfunction in LT[6,24,25]. Future studies addressing these gaps will be essential to refining this induction strategy for clinical practice.
Future perspectives
EL-Domiaty et al’s work[9] reinforces a central tenet of modern transplant medicine: The need for individualized immunosuppressive strategies in LT, and particularly for hyperimmunized recipients who have long been underserved by a one-size-fits-all approach. Prospective, multicenter randomized controlled trials are urgently warranted to validate the efficacy and safety of the rATLG/IVIG induction regimen in larger, more diverse cohorts of hyperimmunized liver transplant recipients. These trials should incorporate pre-transplant stratification of patients based on DSA specificity, class, and titer (including complement-binding status via C1q/C3d assays) to define optimal patient selection criteria-ensuring that the regimen is targeted to those who will derive the greatest clinical benefit.
To further refine risk stratification and improve long-term outcomes, future clinical practice should integrate routine post-transplant DSA surveillance (at 1, 3, 6, and 12 months post-transplant, and annually thereafter) with protocol liver biopsies in hyperimmunized recipients. This integrated approach will enable early detection of subclinical AMR and antibody-mediated graft injury, allowing for timely, targeted interventions (e.g., IVIG, plasma exchange, or B-cell depletion) before irreversible graft damage occurs-a critical step in preserving long-term graft function.
Advances in immunological profiling-including high-dimensional flow cytometry to characterize T-cell/B-cell subsets, immune cell activation status, and cytokine profiles-also open the door to tailoring induction regimens to the distinct immunological phenotypes of individual hyperimmunized recipients. For example, recipients with high levels of circulating memory B cells and plasma cells may benefit from the addition of B-cell depletion therapy (e.g., rituximab) to the rATLG/IVIG backbone, while those with predominant T-cell sensitization may thrive with the standard regimen alone. This precision immunology approach will allow clinicians to balance rejection prevention against the inherent risks of immunosuppression (infection, malignancy, cardiovascular disease)-a delicate rebalancing act that is the core of optimal transplant care[7,8].
Notably, future research should prioritize the generation of direct head-to-head comparative data between rATLG and thymoglobulin in LT, to formally validate the safety and efficacy advantages of rATLG suggested by solid organ transplantation data. This research will fill a key evidence gap and provide clinicians with clear, evidence-based guidance for induction agent selection in hyperimmunized recipients.
CONCLUSION
EL-Domiaty et al’s study[9] delivers a landmark contribution to the field of LT, providing robust clinical evidence that a short-course induction regimen combining rATLG and high-dose IVIG can effectively mitigate immunological risk in hyperimmunized liver transplant recipients. By achieving rejection rates and graft/patient survival outcomes comparable to those of non-immunized patients-without excessive toxicity or an increased risk of severe infection or malignancy-this strategy represents a meaningful step forward in the shift from universal to personalized immunosuppression in LT.
This work addresses a long-standing clinical unmet need, offering clinicians a pragmatic, evidence-based approach to managing one of the most challenging subsets of liver transplant candidates. Continued investigation through larger, prospective, multicenter studies-incorporating immunological phenotyping, routine DSA surveillance, and protocol biopsies-will be essential to confirm these findings, refine the regimen, and optimize long-term care for hyperimmunized liver transplant recipients. Ultimately, this work paves the way for a more precise, patient-centered approach to immunosuppression in LT, where immunological risk is balanced with graft protection to achieve the best possible outcomes for every recipient.
