Key words : Antibody-mediated rejection, Basiliximab, Intravenous immunoglobulin, Rituximab

Introduction

Liver transplantation is the therapeutic option of choice for patients with end-stage liver disease and early hepatocellular carcinoma. However, the limited supply of deceased donor organs has prompted efforts to enlarge the donor pool via living donor liver transplantation. Furthermore, persistent organ shortages have led to the use of ABO-incompatible donors for living donor liver transplant, which was previously considered a barrier to transplant.¹

Starzl and colleagues described ABO-incompatible liver transplant in 1979 and proposed that the liver is an “immune-privileged” organ.² However, the graft survival rate was low, and the acute humoral rejection due to the portal tracts’ hemorrhagic infiltration was high.^3,4 Advances in ABO-incompatible kidney transplant have guided the development of diverse strategies to overcome ABO incompatibility in liver transplant, including plasma exchange, local graft infusion, splenectomy, immunosuppressive agents, and monoclonal antibodies (eg, rituximab).^5-7

ABO-incompatible living donor liver transplant is currently being performed in many centers, and results for ABO-incompatible liver transplant have been shown to be similar to those of ABO-compatible liver transplant.⁸ However, reports on ABO-incom­patible liver transplant have focused on short-term results, and data on long-term results are limited. Furthermore, there is no consensus regarding the desensitization regimen, and desensitization approach methods have varied according to the center's prefe­rence and experience.^7,9,10 Here, we have reported our experience with 20 consecutive patients who under­went ABO-incompatible living donor liver transplant and who received a simplified desensitization and immunosuppression regimen.

Materials and Methods

Patients
This retrospective study evaluated patients who underwent ABO-incompatible living donor liver transplant at a single institution between August 2015 and July 2019. The surgical procedures were performed in the usual manner, that is, the same as for ABO-compatible living donor liver transplant procedures, and all patients completed the same ABO-incompatible living donor liver transplant protocol. No patients underwent simultaneous splenectomy or local graft infusion. Patient medical records were retrospectively reviewed to collect data on demo­graphic characteristics, Model for End-stage Liver Disease score, blood group, surgery duration, graft-to-recipient weight ratio, postoperative complications, and follow-up information. This study was approved by the Institutional Review Board of Pusan National University Yangsan Hospital (05-2020-227).

Donor hepatectomy
The abdomen was entered through a right subcostal incision with a vertical midline extension. After a thorough examination of the liver’s morphology, size, and texture, a biopsy was performed at the liver border on both lobes. After dissection of the ligaments around the liver and cholecystectomy, attention was shifted to the hepatic hilum. The bifurcations of the hepatic duct, portal vein, and hepatic artery were identified after gentle dissection of the hepato­duodenal ligament, and the interlobar line was demarcated via unilateral temporary clamping of the hepatic artery and portal vein. Intraoperative ultraso­nography was performed along the demarcated line to identify the intraparenchymal hepatic vein. The parenchyma was transected with a Cavitronic ultraso­nograph aspirator (Valleylab), without hepatic inflow or outflow occlusion, and the hanging maneuver was used in all cases prior to the parenchymal transection. The bile duct was transected after the parenchymal dissection was completed. The hepatic artery, portal vein, and hepatic vein were divided, and the graft liver was delivered to the table and flushed with histidine-tryptophan-ketoglutarate solution (Custodial, JeniceParm). The remnant stumps of the bile duct were closed using continuous 6-0 absorbable surgical sutures without narrowing. Routine assessments were performed, including injection of methylene blue through the cystic duct to identify bile leakage. After meticulous hemostasis, closed suction drainage was placed before wound closure.

Recipient procedure
Recipient hepatectomy was performed through a reverse L incision in the right upper quadrant. The midline incision was extended to the xiphoid process, which exposed the suprahepatic vena cava. The ligaments of liver attachments, such as right and left triangular, coronary, and hepatogastric ligaments, were then dissected to mobilize the liver in its entirety. Perihilar dissection was performed after isolation of the hepatic arteries, with transection of the right anterior hepatic artery, the right posterior hepatic artery, and the left hepatic artery. Minimal dissection has been shown to reduce biliary stricture, and periductal blood supply can be preserved using various techniques, such as encircling of the hilar plate. The bile duct was isolated and divided near the hilar plate, and the portal vein was isolated and transected distal to the bifurcation. If portal vein thrombosis was observed during the preoperative examination, thrombectomy was performed after severing the portal vein. The right hepatic vein and the middle vein were clamped and resected close to the hepatic parenchyma.

Implantation was initiated by anastomosing the graft’s right hepatic vein with the recipient’s vein. Longitudinal incisions were made on the upper and lower sides of the right hepatic vein to increase primary outflow. The graft’s right hepatic vein was anastomosed with a widened recipient hepatic vein. If the inferior right hepatic vein was preserved in the graft, it was anastomosed to the side of the recipient’s retrohepatic vena cava. A Satinsky vascular clamp was used to partially clamp the vena cava sidewall for anastomosis of the accessory short right hepatic veins, without using active bypass.

After completion of venous outflow reconstruction, the portal vein was flushed to remove any thrombi and to evaluate the portal flow. If the portal vein flow was weak, we ligated the coronal vein or left renal vein. Any redundant or excess length of the native portal vein was excised and trimmed to avoid portal vein kinking. The anastomosis was performed with a continuous suture over the anterior and posterior walls, and then polytetrafluoroethylene interposition vein grafts were anastomosed to the recipient’s middle or left hepatic vein stumps. The hepatic artery anastomosis was performed under surgical loupes, and Doppler ultrasonography was performed imme­diately after the anastomosis to ensure good patency.

The final step involved biliary reconstruction, and the specific technique was selected according to the number and size of graft duct openings and the anatomical variation of the biliary system. Duct-to-duct anastomosis was preferred if possible. After posterior wall anastomosis with interrupted sutures, an internal stent was inserted and fixed to the bile duct wall.

Desensitization and immunosuppression protocol
All ABO-incompatible living donor liver transplant procedures were conducted under our simplified protocol (Figure 1). First, patients received a single dose of rituximab (375 mg/m2) at 2 to 3 weeks before transplant. Second, plasma exchange was performed repeatedly starting 1 week before the living donor liver transplant, using AB fresh frozen plasma to lower the anti-ABO antibody titer to ≤1:8. If the patient’s anti-ABO titer did not reach ≤1:8, a single dose of bortezomib (1.3 mg/m2) was administered. Third, intravenous immunoglobulin (IVIG; 2 g/day) was administered after transplant for 1 week. The immunosuppression protocol involved high-dose methylprednisolone (500 mg) during surgery. Moreover, tacrolimus, mycophenolate mofetil, and a combination of corticosteroids were administered after transplant. Basiliximab was also administered as induction therapy (20 mg on the day of surgery and on postoperative day 4). Tacrolimus treatment was started 6 hours after transplant, with a target of 8 to 12 ng/mL during the first month after surgery and titration to 5 to 8 ng/mL over the next few months. After 1 year, a tacrolimus trough level was maintained at approximately 5 ng/mL. Mycophenolate mofetil treatment (0.5-1.0 g/day) was started when the patient began to take sips of water after the living donor liver transplant, with a mycophenolate mofetil dose reduction when the white blood cell count decreased to <2000/μL. Mycophenolate mofetil treatment was stopped if the absolute neutrophil count reached <500/μL; treatment was also tapered or stopped based on symptom severity if the patient developed digestive symptoms, including indigestion, abdominal pain, or diarrhea. Methylprednisolone was tapered from 200 to 80 mg/day over the first 4 postoperative days, with the patient then switched to oral prednisolone (20 mg/day); this was stopped within 3 months after transplant.

Antibiotic prophylaxis
Perioperative infection prevention protocols were in line with those for ABO-compatible living donor liver transplant. Patients received broad-spectrum antibiotics (ceftazidime/moxifloxacin) for 7 days, an antifungal agent (amphotericin B) for 5 days, and trimethoprim-sulfamethoxazole for 3 months. Cytomegalovirus prophylaxis using ganciclovir was routinely administered for 5 days. Patients were tested once per week until discharge to identify cytomegalovirus antigenemia, with subsequent testing once per month for 3 months and then once every 3 months. Diagnosis of cytomegalovirus infection was based on a positive polymerase chain reaction result, regardless of symptoms, and ganciclovir (5 mg/kg every 12 h for 2 weeks) was administered until a negative polymerase chain reaction result was observed.

Monitoring for anti-ABO antibody titers, cluster of differentiation 19+ B-lymphocyte count, and rejection
Basal values from before rituximab administration were determined for the anti-ABO antibody titer and cluster of differentiation 19 (CD19+) B-lymphocyte count. Serial measurements were also performed after initiation of plasmapheresis. After ABO-incompatible living donor liver transplant, the isoagglutinin titer was checked daily for 1 week, once per week until discharge, and then monthly for the next 6 months. Plasma exchange was only performed if a patient’s anti-ABO antibody titer increased to >1:32 during the first 2 weeks posttransplant. The effect of rituximab was confirmed based on the serum CD19+ lymphocyte count before living donor liver transplant, and weekly counts were performed until discharge.

Rejection and complications
Biopsy was not routinely performed to identify rejection and was only performed if imaging revealed no abnormal results and liver function tests revealed postoperative serum concentrations of aspartate aminotransferase, alanine aminotransferase, and total bilirubin that were 2-fold or 3-fold higher than the upper limit of normal. If necessary, transjugular liver biopsy was performed during the first 3 months after transplant to reduce the bleeding risk and prevent any potential liver capsule damage.11 When liver biopsy confirmed acute cellular rejection, methylprednisolone (500 mg) was administered intravenously for 3 days, with daily dose reductions of 40 mg/day for the next 4 days. Biopsy was also performed if antibody-mediated rejection was suspected based on a simultaneous increase in liver enzymes and the isoagglutinin titer increasing to >4-fold the value from the day of surgery or to >1:32 during the first 2 weeks after transplant. The treatment plan for biopsy-proven antibody-mediated rejection involved high-dose IVIG (1 g/kg/day), steroid pulse therapy, and plasma exchange.

Transplant-related complications were evaluated, which included biliary complications, infectious complications, and incidences of antibody-mediated rejection and acute cellular rejection. Biliary complications were considered meaningful when surgical, endoscopic, or radiologic interventions were required (Clavien-Dindo grade ≥IIIa).

Statistical analyses
All data were analyzed using Statistical Package for the Social Sciences statistical software (version 21.0; IBM Corp.). Normally distributed continuous variables were presented as means ± standard deviations and nonnormally distributed variables were presented as medians (ranges). Overall survival rate was evaluated by the Kaplan-Meier method and log-rank test.

Results

Recipient characteristics
The 20 adult patients included 18 men and 2 women who underwent ABO-incompatible living donor liver transplant between 2015 and 2019. The mean age of the recipients was 55.4 ± 6.3 years. Liver disease etiology included hepatitis B and C virus-associated liver cirrhosis (n = 1, 5%), alcoholic cirrhosis (n = 2, 10%), and polycystic liver disease (n = 1, 5%). Fourteen patients (70%) had hepatocellular carcinoma, including 8 patients who fulfilled the Milan criteria and 6 patients who did not fulfill the Milan criteria. The mean Model for End-stage Liver Disease score was 14.7 ± 7.7 (median of 14; range, 6-40), the mean operative time was 602.0 ± 112.6 min, and the mean red blood cell transfusion requirement was 7.0 ± 5.5 packs. Patient characteristics are summarized in Tables 1 and 2.

Graft and donor characteristics
The 20 cases of ABO-incompatible living donor liver transplant involved the modified right lobe (18 patients), the right posterior lobe (1 patient), or the left lobe (1 patient). Donor mean age was 28.3 ± 9.7 years, and 15 donors (75%) were male patients. The mean graft weight-to-recipient weight ratio was 1.07 ± 0.2%. The ABO blood group mismatches between donors and recipients are shown in Table 2.

Isoagglutinin titers, plasma exchange, rituximab, and CD19+ profiles
The median initial values for anti-ABO isoagglutinin titers were 1:16 for immunoglobulin M (IgM; range, 1:2 to 1:256) and 1:48 for immunoglobulin G (IgG; range, 1:4 to 1:>2048) (Table 1). After several plasma exchange sessions (median 2; range, 0-12), median titers before living donor liver transplant were 1:2 for IgM (range, 1:1 to 1:16) and 1:8 for IgG (range, 1:1 to 1:64). The isoagglutinin titers decreased even more after transplant, with median values of 1:2 for IgM (range, negative to 1:8) and 1:4 for IgG (range, negative to 1:128). The anti-ABO isoagglutinin titer was extremely high (>1:1024) in 5 patients and did not decrease to the target titer despite repeated plasma exchange in 2 patients (cases 1 and 10). One patient (case 16) also had initial titers of 1:64 for IgM and 1:128 for IgG, which did not decrease after 3 plasma exchange sessions. These patients (cases 1, 10, and 16) received a single dose of bortezomib (1.3 mg/m²) and continued the plasma exchange sessions, achieving anti-ABO isoagglutinin titers of 1:32 before transplant (Table 3).

The median peripheral CD19+ count before rituximab administration was 17.5% (range, 4.3%-53.3%). The patients received a single dose of rituximab (375 mg/m2) at 2 to 3 weeks before transplant, which reduced the median CD19+ count to 0.1% (range, 0%-0.5%).

Overall survival and complications after ABO-incompatible living donor liver transplant
Overall survival rates were 90.0% at 1 year, 79.1% at 3 years, and 79.1% at 5 years (Figure 2). The mean follow-up period was 33.7 months (median of 33 months; range, 2-59 months), and 4 deaths were identified. The causes of death were sepsis in 1 patient, graft-versus-host disease in 1 patient, and hepato­cellular carcinoma recurrence in 2 patients (both patients did not fulfill the Milan criteria). One patient experienced relapse in the lungs and peritoneum at 6 months after living donor liver transplant, and the other patient experienced recurrence in the liver graft at 8 months after transplant. One patient (case 14) experienced fever, skin rash, and diarrhea and was treated for suspected drug eruption and cytomegalovirus colitis on postoperative day 39. Endoscopic stomach biopsy and skin biopsy revealed histopathological features of graft-versus-host disease, which was treated with tacrolimus and a 5-day course of thymoglobulin treatment (75 mg/day). The patient also received prophylactic treatment that included antibiotics, antiviral agents, and antifungal agents; however, the patient subsequently developed septicemia and pancytopenia and ultimately died because of multiorgan failure.

Biliary complications occurred in 9 patients, and all 9 patients exhibited biliary stricture. A duct-to-duct anastomosis was performed in 6 patients, and 3 patients underwent hepaticojejunostomy. Two patients underwent endoscopic retrograde cholangiography. Three patients underwent failed endoscopic retrograde cholangiography and subsequently underwent percu­ta­neous transhepatic biliary drainage. Four patients underwent initial treatment using percutaneous transhepatic biliary drainage.

We identified 1 patient (case 16) with diffuse intrahepatic biliary stricture. The patient was seen at the hospital at 2 months after discharge because of abdominal discomfort. Computed tomography revealed that the diameter of the right intrahepatic bile duct had increased, and there appeared to be a new thrombus in the suprahepatic inferior vena cava. Blood tests revealed normal values for liver enzymes, total bilirubin, and prothrombin time, although the anti-ABO isoagglutinin titers had increased to 1:256 for IgM and 1:1024 for IgG. Magnetic resonance cholangiopancreatography also revealed multifocal stricture in the right intrahepatic duct and bile leakage at the anastomosis site. A transabdominal liver biopsy was performed but did not confirm the presence of antibody-mediated rejection. Nevertheless, based on a clinical suspicion of antibody-mediated rejection, high-dose IVIG (0.5 kg/day) was administered after plasma exchange was performed to diminish the anti-ABO isoagglutinin titer. The patient also received 2 injections of bortezomib (1.3 mg/m2) as treatment for suspected antibody-mediated rejection. The biloma was managed using percutaneous catheter drainage and endoscopic retrograde biliary drainage. The patient currently has a dilated right intrahepatic duct, which is filled with cast material, although the percutaneous catheter drainage and endoscopic retrograde biliary drainage had been removed. The patient’s liver enzyme and jaundice levels have continued to be normal, and there were no infection-related complications (Figure 3).

None of the patients had biopsy-confirmed antibody-mediated rejection. One patient had clinically suspected acute cellular rejection, based on liver enzymes and total bilirubin levels that were >2-fold to 6-fold the upper limit of normal, although liver biopsy was not performed. The patient had an excellent response to steroid pulse therapy. Ten patients had positive results for cytomegalovirus infection, which was treated using ganciclovir, and all patients had recovered.

Discussion
Early animal experiments conducted by Starzl and associates² indicated that the liver might be an “immunologically privileged organ,” with excellent resistance to hyperacute rejection (versus the kidney or heart). Based on this understanding, Starzl and associates broke the ABO blood group barriers, which was necessary particularly in emergency settings, when there was no choice but to proceed with the first available organ.¹² However, the liver was quickly found to not be “immunologically privileged” in terms of ABO incompatibility, as several early studies of ABO-incompatible living donor liver transplant revealed a high incidence of early graft loss and low patient survival. Therefore, ABO-incompatible transplant was considered a contraindication because of the high incidence of acute rejection, biliary and vascular complications, and decreased survival after ABO-incompatible living donor liver transplant. These facts led to ABO-incompatible living donor liver transplant only being performed in emergencies when ABO-compatible grafts were unavailable.¹³

Damage to ABO-incompatible liver grafts is initiated by preformed anti-ABO isoagglutinin and enhanced by B-cell proliferation, activated by ABO antigens in the donor graft. The main targets are endothelial cells of the graft vascular system and the epithelial cells in the bile duct.¹⁴ Different desensitization therapies have been proposed to prevent these anti-ABO isoagglutinin-mediated graft injuries. These protocols have 3 main aims: (1) reduction of anti-ABO isoagglutinin titers before transplant, (2) elimination of B-cell activity, and (3) reduction of local inflammation.¹⁴

Tanabe and colleagues (Keio University School of Medicine)¹⁵ initially introduced local infusion therapy to reduce local inflammation in the graft. This method involves injection of anti-inflammatory agents, such as methylprednisolone, prostaglandins, or protease inhibitors, directly into the donor graft through a catheter that is placed in the hepatic artery or portal vein. Pathological findings from failed ABO-incompatible liver grafts revealed features of hepatic disseminated intravascular coagulation, and this provided the theoretical background for the use of local infusion therapy.¹⁶ Although local infusion therapy has improved survival rates among patients undergoing ABO-incompatible living donor liver transplant, it does not block antibody-mediated rejection.¹⁵ Furthermore, local infusion therapy can negatively affect outcomes after ABO-incompatible living donor liver transplant, as this treatment is associated with an increased risk of catheter-related complications, such as vascular thrombosis, infection, hemorrhage, and catheter displacement.¹⁵ Ikegami and colleagues (Kyushu university group) were the first to report a successful protocol that did not involve local infusion therapy for patients undergoing ABO-incompatible living donor liver transplant,⁶ and recent reports have also described successful desensitization protocols for ABO-incompatible living donor liver transplant that did not involve local infusion therapy.^8,9,14

The effects of IVIG treatment in this setting may involve blocking Fc receptors on mononuclear phagocytes, directly neutralizing alloantibodies, suppressing CD19 on activated B cells, suppressing complement, and suppressing alloreactive T cells.^8,10,17 In addition, IVIG is used for emergency ABO-incompatible transplant procedures, such as in cases of acute hepatic failure when early rituximab injection is not possible, and as rescue therapy for antibody-mediated rejection.⁶ The use of IVIG with rituximab should result in better outcomes, as the early administration of rituximab can suppress humoral reactions.¹⁸ Our results suggest that IVIG admin­istration synergistically improved outcomes by suppressing humoral reactions with rituximab, without splenectomy, local infusion therapy, and preoperative mycophenolate mofetil. Furthermore, IVIG is able to neutralize bacterial toxins and promote phagocytosis, which can deactivate bacterial endo­toxins and exotoxins, promote leukocytosis, and accelerate serum bactericidal activity. It is used to treat septicemia. In ABO-incompatible living donor liver transplant recipients, the use of rituximab, plasmapheresis, splenectomy, and aggressive immunosuppression can significantly increase the postoperative risks of bacterial, fungal, and viral infections.⁷ However, we did not identify any patients with bacterial or fungal infections after ABO-incompatible living donor liver transplant, and 10 patients with cytomegalovirus infections recovered after ganciclovir treatment. Therefore, IVIG may help prevent antibody-mediated rejection and postop­erative infections in recipients of ABO-incompatible living donor liver transplant without splenectomy and local graft infusion.

Splenectomy has been an essential part of the desensitization regimen for ABO-incompatible living donor liver transplant in many centers. The rationale for this practice is that the spleen was considered the maturational site of B cells and the antibody manufacturer site; thus splenectomy aimed to eliminate the place of origin of new antibodies of ABO antigens.^7,12 However, the spleen is not the sole secreting apparatus for anti-ABO isoagglutinin, and splenectomy is associated with various complications, including portal vein thrombosis, pancreatic fistula, hemorrhage, and septicemia.¹⁹ In contrast, rituximab is a chimeric monoclonal antibody targeted against the pan-B-cell marker cluster of differentiation 20 (CD20), which diminishes B cells via direct signaling of apoptosis, complement activation, and cell-mediated cytotoxicity; CD20 is expressed in all stages of B-cell development, except stem cells, early pro-B cells, and plasma cells. Our institution uses CD19 as an alternative marker for patients who receive rituximab because CD19 reflects CD20 expression and is expressed on a range of cells from pro-B cells to memory B cells, excluding stem cells and plasma cells. Furthermore, rituximab functions by depleting CD20+ B cells from the circulation and lymphoid tissues, including the spleen, which acts as a form of “chemical splenectomy.”²⁰ Raut and associates¹⁹ concluded that ABO-incompatible living donor liver transplant recipients who underwent splenectomy do not gain any immunological merit, and a multicenter Japanese study identified significantly improved outcomes for ABO-incompatible living donor liver transplant after the introduction of rituximab.²¹ However, there is no consensus on the optimal timing and dosage of rituximab treatment. Our group currently uses a single dose of rituximab (375 mg/m²) at 2 to 3 weeks before ABO-incompatible living donor liver transplant. Other centers have also used rituximab doses of 375 mg/m² at 10 days before surgery,10 375 mg/m² at 2 weeks before surgery,²⁰ and 300 mg/m2 at least 7 days before surgery.⁸

There is also no consensus regarding the target anti-ABO isoagglutinin titer or the ideal number of plasma exchanges. We target a pretransplant anti-ABO isoagglutinin titer of ≤1:8, although other reports have described targets of 1:161 and 1:32.^8,10 A study by Kim and colleagues²² involved delaying transplant if a target of 1:8 was not achieved, with plasma exchange continued until the target titer was achieved. Three patients in our study did not complete the target anti-ABO isoagglutinin titer, despite several plasma exchange sessions, and subsequently received a single dose of bortezomib (1.3 mg/m²) followed by more plasma exchange sessions. In this context, the high-titer isoagglutinin rebound could be related to plasma cells, and bortezomib is a proteasome inhibitor that induces plasma cell apoptosis via inhibition of the nuclear factor KB pathway, which prevents potential alloantibody production. Bortezomib has been used to treat antibody-mediated rejection and acute cellular rejection²³ and may reduce or eliminate donor-specific antihuman leukocyte antigen antibodies via depletion of plasma cells.^24,25 Jeong and associates²⁶ evaluated 23 patients who received bortezomib, rituximab, and IVIG as desensitization, which successfully decreased the target anti-ABO isoagglutinin titers in high-sensitized and ABO-incompatible kidney transplant. However, we are not aware of any studies regarding bortezomib treatment for patients with ABO-incompatible living donor liver transplant that involved high anti-ABO isoagglutinin titers. Although bortezomib may be useful for preparing these patients for ABO-incompatible living donor liver transplant, a well-designed clinical trial is needed to evaluate this possibility.

Bile complications are considered the Achilles heel of liver transplant, with reported rates of 10% to 30%.²⁷ These complications are related to acute or chronic rejection, cytomegalovirus infection, hepatic artery stenosis or thrombosis, ABO-incompatible living donor liver transplant, positive human leukocyte antigen cross-reaction, and primary biliary sclerosis. Under the same anatomical conditions, ABO-incompatible living donor liver transplant may also be a risk factor for development of biliary stenosis. Song and associates²⁷ confirmed that, among ABO-incompatible living donor liver transplant recipients, an initial IgG titer of ≥1:128 was associated with a 3.38-fold risk of biliary stenosis (versus initial titers of <1:128). Therefore, immune-related ABO incompatibility may be associated with the incidence of biliary tract injury and subsequent stenosis to some extent. Furthermore, the change in anti-ABO isoagglutinin titers should be carefully observed to reduce the incidence of biliary stenosis in ABO-incompatible living donor liver transplant, even if the liver function test results are normal after transplant. Plasma exchange or B-lymphocyte suppression may be useful for depleting anti-ABO isoagglutinin. Egawa and associates²¹ argued that biliary stricture in ABO-incompatible living donor liver transplant recipients involves the same mechanism as graft damage caused by antibody-mediated rejection. In one of our patients (case 16), liver biopsy did not identify antibody-mediated rejection, although we still selected antibody-mediated rejection treatment based on the high anti-ABO titer and clots in the blood vessels. Although diffuse intrabiliary stricture is not always fatal, it often causes refractory cholangitis leading to sepsis and graft failure, and, in most cases, diffuse intrabiliary stricture cannot be resolved using conventional biliary interventions. However, this patient achieved control of the diffuse intrabiliary stricture after biliary intervention and did not require retransplant, despite retransplant being the only proven effective treatment for diffuse intrabiliary stricture.

Our protocol varies from those used in other centers. First, our desensitization protocol involves lower doses of IVIG (2 g/day) than doses used in other centers (0.6-0.8 g/kg/day). However, our results in terms of infection, acute cellular rejection, and antibody-mediated rejection were not substantially different from those reported by other centers.^8,9,22 Second, we did not use preoperative mycophenolate mofetil and the immunosuppression regimen was the same as for ABO-compatible living donor liver transplant. Third, patients with persistently high anti-ABO isoagglutinin titers received bortezomib to facilitate ABO-incompatible living donor liver transplant. Thus, patients with high anti-ABO isoagglutinin titers were still able to undergo the surgery without delay, and the incidence of antibody-mediated rejection was remarkably low. However, the present study also had several limitations. First, we only evaluated a small number of ABO-incompatible living donor liver transplant cases, which precluded broad conclusions regarding our protocol. Second, we only considered patients with ABO-incompatible living donor liver transplant and did not compare the outcomes with those in patients with ABO-compatible living donor liver transplant. Therefore, large well-designed randomized studies with a standard desensitization protocol and long-term follow-up are needed to confirm the effectiveness of desensitization strategies for ABO-incompatible living donor liver transplant.

Conclusions

Our simplified ABO-incompatible living donor liver transplant protocol involved rituximab, plasma exchange, low-dose IVIG, and immunosuppressant therapy equivalent to that used in ABO-compatible living donor liver transplant, without local infusion or splenectomy. This protocol may be a safe and effective way to overcome antibody-mediated rejection and other complications after ABO-incom­patible living donor liver transplant.

References:

1. Lee SH, Choi HJ, You YK, Kim DG, Na GH. ABO incompatible living donor liver transplantation: a single center experience. J Korean Soc Transplant. 2018;32(4):84-91. doi:10.4285/jkstn.2018.32.4.84
   CrossRef - PubMed
   
2. Starzl TE, Koep LJ, Halgrimson CG, et al. Fifteen years of clinical liver transplantation. Gastroenterology. 1979;77(2):375-388
   CrossRef - PubMed
   
3. Gugenheim J, Samuel D, Reynes M, Bismuth H. Liver transplantation across ABO blood group barriers. Lancet. 1990;336(8714):519-523. doi:10.1016/0140-6736(90)92082-s
   CrossRef - PubMed
   
4. Rego J, Prevost F, Rumeau JL, et al. Hyperacute rejection after ABO-incompatible orthotopic liver transplantation. Transplant Proc. 1987;19(6):4589-4590
   CrossRef - PubMed
   
5. Urbani L, Mazzoni A, Bianco I, et al. The role of immunomodulation in ABO-incompatible adult liver transplant recipients. J Clin Apher. 2008;23(2):55-62. doi:10.1002/jca.20156
   CrossRef - PubMed
   
6. Ikegami T, Taketomi A, Soejima Y, et al. Rituximab, IVIG, and plasma exchange without graft local infusion treatment: a new protocol in ABO incompatible living donor liver transplantation. Transplantation. 2009;88(3):303-307. doi:10.1097/TP.0b013e3181adcae6
   CrossRef - PubMed
   
7. Egawa H, Teramukai S, Haga H, Tanabe M, Fukushima M, Shimazu M. Present status of ABO-incompatible living donor liver transplantation in Japan. Hepatology. 2008;47(1):143-152. doi:10.1002/hep.21928
   CrossRef - PubMed
   
8. Kim JD, Choi DL, Kim SG, Lee AJ. Single-center experience of ABO-incompatible living-donor liver transplantation with a new simplified intravenous immunoglobulin protocol: a propensity score-matching analysis. Transplant Proc. 2016;48(4):1134-1138. doi:10.1016/j.transproceed.2016.02.040
   CrossRef - PubMed
   
9. Song GW, Lee SG, Hwang S, et al. Successful experiences of ABO-incompatible adult living donor liver transplantation in a single institute: no immunological failure in 10 consecutive cases. Transplant Proc. 2013;45(1):272-275. doi:10.1016/j.transproceed.2012.06.079
   CrossRef - PubMed
   
10. Lee J, Lee JG, Lee JJ, et al. Results of ABO-incompatible liver transplantation using a simplified protocol at a single institution. Transplant Proc. 2015;47(3):723-726. doi:10.1016/j.transproceed.2015.02.004
    CrossRef - PubMed
    
11. Kim KR, Ko GY, Sung KB, et al. Transjugular liver biopsy in patients with living donor liver transplantation: comparison with percutaneous biopsy. Liver Transpl. 2008;14(7):971-979. doi:10.1002/lt.21448
    CrossRef - PubMed
    
12. Raut V, Uemoto S. Management of ABO-incompatible living-donor liver transplantation: past and present trends. Surg Today. 2011;41(3):317-322. doi:10.1007/s00595-010-4437-3
    CrossRef - PubMed
    
13. Tanabe M, Kawachi S, Obara H, et al. Current progress in ABO-incompatible liver transplantation. Eur J Clin Invest. 2010;40(10):943-949. doi:10.1111/j.1365-2362.2010.02339.x
    CrossRef - PubMed
    
14. Song GW, Lee SG, Hwang S, et al. Section 15. A desensitizing protocol without local graft infusion therapy and splenectomy is a safe and effective method in ABO-incompatible adult LDLT. Transplantation. 2014;97 Suppl 8:S59-66. doi:10.1097/01.tp.0000446279.81922.dd
    CrossRef - PubMed
    
15. Tanabe M, Shimazu M, Wakabayashi G, et al. Intraportal infusion therapy as a novel approach to adult ABO-incompatible liver transplantation. Transplantation. 2002;73(12):1959-1961. doi:10.1097/00007890-200206270-00021
    CrossRef - PubMed
    
16. Kawagishi N, Satomi S. ABO-incompatible living donor liver transplantation: new insights into clinical relevance. Transplantation. 2008;85(11):1523-1525. doi:10.1097/TP.0b013e318173a70e
    CrossRef - PubMed
    
17. Lee SD, Kim SH, Kong SY, Kim YK, Lee SA, Park SJ. ABO-incompatible living donor liver transplantation without graft local infusion and splenectomy. HPB (Oxford). 2014;16(9):807-813. doi:10.1111/hpb.12215
    CrossRef - PubMed
    
18. Egawa H, Ohmori K, Haga H, et al. B-cell surface marker analysis for improvement of rituximab prophylaxis in ABO-incompatible adult living donor liver transplantation. Liver Transpl. 2007;13(4):579-588. doi:10.1002/lt.21092
    CrossRef - PubMed
    
19. Raut V, Mori A, Kaido T, et al. Splenectomy does not offer immunological benefits in ABO-incompatible liver transplantation with a preoperative rituximab. Transplantation. 2012;93(1):99-105. doi:10.1097/TP.0b013e318239e8e4
    CrossRef - PubMed
    
20. Pescovitz MD. Rituximab, an anti-cd20 monoclonal antibody: history and mechanism of action. Am J Transplant. 2006;6(5 Pt 1):859-866. doi:10.1111/j.1600-6143.2006.01288.x
    CrossRef - PubMed
    
21. Egawa H, Teramukai S, Haga H, et al. Impact of rituximab desensitization on blood-type-incompatible adult living donor liver transplantation:a Japanese multicenter study. Am J Transplant. 2014;14(1):102-114. doi:10.1111/ajt.12520
    CrossRef - PubMed
    
22. Kim JM, Kwon CH, Joh JW, et al. ABO-incompatible living donor liver transplantation is suitable in patients without ABO-matched donor. J Hepatol. 2013;59(6):1215-1222. doi:10.1016/j.jhep.2013.07.035
    CrossRef - PubMed
    
23. Everly MJ, Everly JJ, Susskind B, et al. Bortezomib provides effective therapy for antibody- and cell-mediated acute rejection. Transplantation. 2008;86(12):1754-1761. doi:10.1097/TP.0b013e318190af83
    CrossRef - PubMed
    
24. Perry DK, Burns JM, Pollinger HS, et al. Proteasome inhibition causes apoptosis of normal human plasma cells preventing alloantibody production. Am J Transplant. 2009;9(1):201-209. doi:10.1111/j.1600-6143.2008.02461.x
    CrossRef - PubMed
    
25. Everly MJ, Everly JJ, Susskind B, et al. Proteasome inhibition reduces donor-specific antibody levels. Transplant Proc. 2009;41(1):105-107. doi:10.1016/j.transproceed.2008.10.073
    CrossRef - PubMed
    
26. Jeong JC, Jambaldorj E, Kwon HY, et al. Desensitization using bortezomib and high-dose immunoglobulin increases rate of deceased donor kidney transplantation. Medicine (Baltimore). 2016;95(5):e2635. doi:10.1097/MD.0000000000002635
    CrossRef - PubMed
    
27. Song GW, Lee SG, Hwang S, et al. Biliary stricture is the only concern in ABO-incompatible adult living donor liver transplantation in the rituximab era. J Hepatol. 2014;61(3):575-582. doi:10.1016/j.jhep.2014.04.039
    CrossRef - PubMed