Postoperative flow cytometry crossmatch in living donor liver transplantation: clinical significance of humoral immunity in acute rejection

Clinical Relevance of Isoagglutinin Rebound in Adult ABO-Incompatible Living Donor Liver Transplantation

ABO-incompatible (ABO-I) living donor liver transplantation (LDLT) can be performed successfully. However, anti-ABO isoagglutinin rebound may cause antibody-mediated rejection (AMR) and graft loss. The risk threshold of isoagglutinin rebound is still not defined. 76 ABO-I LDLT recipients were divided into group A (n = 56) with low isoagglutinin titers (<1:256), and group B (n = 20) with high isoagglutinin titers (≥1:256), at initial assessment for liver transplantation. The last 12 patients in group B received a modified desensitization regimen by adding bortezomib to deplete plasma cells. Six (10.7%) patients in group A and 10 (50.0%) patients in group B had postoperative isoagglutinin rebound (p < 0.001). Three patients (5.54%) in group A and two patients (10%) in group B developed clinical AMR (p = 0.602). The cutoff value of postoperative isoagglutinin rebound to cause clinical AMR was ≥1:1024. Among the 12 patients in group B with bortezomib administration, isoagglutinin rebounded up to 1:128 only, and no clinical AMR occurred. In conclusion, the patients with high isoagglutinin titers had a higher rate of postoperative isoagglutinin rebound. Isoagglutinin rebound ≥1:1024 is risky for developing clinical AMR. Adding bortezomib into the desensitization regimen may mitigate isoagglutinin rebound, and avoid clinical AMR.

ABO-Incompatible Adult Living Donor Liver Transplantation in the Era of Rituximab: A Systematic Review and Meta-Analysis

Aim

The primary aim of this study is to compare the short- and long-term outcomes between ABO-incompatible (ABOi) adult living donor liver transplantation (ALDLT) with rituximab prophylaxis and ABO-compatible (ABOc) ALDLT.

Background

The strategy of ABOi liver transplantation (LT) was originated initially to increase the donor pool and to enable liver transplantation in emergency conditions. However, ABOi ALDLT remains a controversial approach in comparison to ABOc ALDLT.

Methods

PubMed, Embase, and the Cochrane Library study search were accomplished to recognize studies comparing ABOi and ABOc ALDLT. Meta-analyses were conducted based on the evaluation of heterogeneity using a fixed-effect model and a random-effect model to assess the short- and long-term outcomes following ABOi ALDLT with rituximab prophylaxis.

Results

Nine studies comprising a total of 3,922 patients (ABOi = 671 and ABOc = 3,251) were identified. There was no significant difference between ABOi and ABOc groups for 1-year, 3-year, and 5-year OS and graft survival, respectively. Moreover, 1-year and 3-year OS and DFS were similar between both groups for HCC patients. However, ABOi ALDLT had higher incidences of CMV infection, AMR, overall biliary complications, and biliary stricture than ABOc ALDLT and had other comparable postoperative complications.

Conclusion

Our meta-analysis included studies comparing ABOi and ABOc ALDLT after the introduction of rituximab in a desensitization protocol for ABOi ALDLT. The results of ABOi ALDLT were comparable with those of ABOc ALDLT. However, biliary complications, CMV infection, and AMR remain a concern in the era of rituximab.

Long-term Outcomes of ABO-incompatible Pediatric Living Donor Liver Transplantation

BACKGROUND

ABO-incompatible (ABOi) living donor liver transplantation (LDLT) has been performed to compensate for donor shortage. To date, few studies have reported detailed B-cell desensitization protocols and long-term outcomes of ABOi pediatric LDLT.

METHODS

Twenty-nine pediatric ABOi LDLT recipients were retrospectively analyzed. We compared the clinical outcomes between ABOi (n = 29) and non-ABOi (n = 131) pediatric LDLT recipients. Furthermore, we evaluated the safety and efficacy of our rituximab-based regimen for ABOi pediatric LDLT (2 ≤ age < 18; n = 10).

RESULTS

There were no significant differences in the incidence of infection, vascular complications, biliary complications, and acute cellular rejection between ABOi and non-ABOi groups. The cumulative graft survival rate at 1, 3, and 5 years for non-ABOi group were 92.1%, 87.0%, and 86.1%, and those for ABOi group were 82.8%, 82.8%, and 78.2%, respectively. Rituximab-based desensitization protocol could be performed safely, and reduced CD19+ lymphocyte counts effectively. Although rituximab-treated ABOi group showed comparable clinical outcomes and graft survival rate, 2 patients developed antibody-mediated rejection.

CONCLUSIONS

ABOi LDLT is a feasible option for pediatric end-stage liver disease patients. However, it should be noted that current desensitization protocol does not completely prevent the onset of antibody-mediated rejection in several cases.

Impact of Antibodies That React With Liver Tissue and Donor-Specific Anti-HLA Antibodies in Pediatric Idiopathic Posttransplantation Hepatitis

Background

The cause of late graft dysfunction has not been elucidated. Although an antibody-mediated reaction is suspected as a potential mechanism, the target antigens have not been clarified.

Methods

To clarify the etiology of idiopathic posttransplantation hepatitis (IPTH), we simultaneously examined the presence of antibodies that react with liver tissue (ARLT) by means of indirect immunofluorescence staining, as well as the presence of donor-specific anti-human leukocyte antigen antibodies (HLA-DSA). A subanalysis of the IPTH group was also performed. Within the IPTH group, the correlation between ARLT titer and clinical data were analyzed.

Results

In the sera of patients with IPTH (30 patients), ARLT were found at a significantly higher frequency than in patients without IPTH (42 patients; P < 0.001). Moreover, the ARLT titer appeared to be correlated with the severity of hepatitis or hepatic injury. In contrast, the frequency of HLA-DSA was significantly lower in patients with IPTH than in patients without IPTH (P = 0.001).

Conclusion

Our findings indicate that ARLT, and not HLA-DSA, profoundly influence the etiology of IPTH.

The authors show that antibodies that react with liver tissue and not donor-specific anti-human leukocyte antigen antibodies, profoundly influence the etiology of idiopathic posttransplantation hepatitis in children providing a rationale for therapy.

Significant association between FOXP3 gene polymorphism and steroid-resistant acute rejection in living donor liver transplantation

Previous studies have found that preferential accumulation of regulatory T (Treg) cells in liver allografts during acute cellular rejection (ACR) is associated with less severe rejection, suggesting a role of Treg cells in preventing excessive progress of ACR. We investigated the impact of single nucleotide polymorphisms (SNPs) in the Forkhead box P3 (FOXP3) gene, a master regulator gene of Treg cells, on ACR severity in liver transplant (LT) recipients. In total, 102 living donor LT patients were enrolled in this study and categorized into no rejection (n = 86), steroid-sensitive acute rejection (SSAR; n = 11), and steroid-resistant acute rejection (SRAR; n = 5). FOXP3 SNPs -3499 A/G (rs3761547), -3279 A/C (rs3761548), and -924 A/G (rs2232365) were genotyped using the polymerase chain reaction restriction fragment length polymorphism technique. T-cell responses to allostimulation were evaluated by the mixed lymphocyte reaction assay. We found no statistical association between the FOXP3 SNP genotype frequencies and ACR incidence. However, significantly higher incidence of SRAR was observed in LT patients with the FOXP3 rs3761548 A/C+A/A genotype than in those with the C/C genotype (A/C+A/A versus C/C; no rejection, SSAR, SRAR, 85.71%, 0%, 14.29% versus 83.58%, 16.42%, 0%, respectively; P =  0.0005). The mixed lymphocyte reaction assay performed at the time of ACR diagnosis showed higher anti-donor CD4+ T-cell responses in patients carrying rs3761548 A/C+A/A than in those with the C/C genotype (P =  0.019). No significant association was observed between the incidence of SRAR and either rs3761547A/G or rs2232365 A/G. Infectious complications and overall survival were not related to FOXP3 SNPs. Conclusion: Our findings indicate that FOXP3 SNP rs3761548 A/C might be a predisposing factor for SRAR after liver transplantation. (Hepatology Communications 2017;1:406-420).

Application of CD8+ Cells Count as a Guide of Immunosuppressive Regimen Introduction for Very Sick Patients Undergoing Liver Transplantation

BACKGROUND

Immunosuppression (IS) protocols should be individualized according to the individual recipient's immunity to minimize adverse effects. The aim of this study was to determine whether preoperative levels of CD8+ T lymphocytes could be used as a guide for the introduction of IS.

METHODS

Sixteen adult liver transplantations in our institute were retrospectively analyzed. The immunosuppressive agents were temporarily withheld for 8 patients with a lower (<10%) preoperative percentage of CD8+ cells after transplant (classified as group A). In this group, postoperative immunosuppressive agents had never been used until acute rejection was suspected. Another 8 patients receiving classic IS were classified as group B. We collected their demographic features and analyzed the clinical courses.

RESULTS

The postoperative IS-free period of group A was 5 to 120 days (median, 31 days). Our data showed an inverse correlation between CD8+ levels and the severity of liver disease. Although the IS-free protocol did not present a lower incidence of infection-related events, most of them were effectively treated with antibiotics. The 1-, 3-, and 5-year overall patient survival rates were not different between those with a short-term IS-free period and those with regular IS (87.5% vs 100%, 75% vs 100%, and 62.5% vs 87.5%; P = .468). No patient died of graft failure due to acute rejection.

CONCLUSIONS

Postoperative immunosuppressive agents can be safely withheld for a period of time to preserve proper immune responses against infections in very sick recipients guided by using the CD8+ levels.

Donor-specific HLA Antibodies Are Associated With Late Allograft Dysfunction After Pediatric Liver Transplantation

BACKGROUND

The role of donor-specific HLA antibodies (DSA) after pediatric liver transplantation (LTx) is not clearly established. We completed a cross-sectional study to characterize DSA in long-term survivors of pediatric LTx and assess the impact of C1q-binding DSA on allograft outcomes.

METHODS

Serum samples were collected at routine clinic visits from 50 pediatric LTx recipients classified into 3 clinical phenotypes: nontolerant (n = 18) with de novo autoimmune hepatitis (DAIH) and/or late acute cellular rejection (ACR); stable (n = 25) on maintenance tacrolimus; operationally tolerant (n = 7). Samples were blinded, and antibody detection was performed using Luminex single antigen class I and II beads. Patients with positive DSA were tested for C1q-binding DSA.

RESULTS

DSA were detected in 54% (n = 27) of the patients, with the majority directed at HLA class II antigens (DR, 41%; DQ, 53%). Patients with DSA were younger at the time of LTx (P = 0.016) and time of study (P = 0.024). Mean aspartate aminotransferase, alanine aminotransferase, total bilirubin, and gamma glutamyl transferase were higher in DSA-positive patients, though did not reach statistical significance. Nontolerant patients were significantly more likely to have DQ DSA (61%) compared to stable (20%) and tolerant (29%) patients (P = 0.021). The nontolerant phenotype was associated with DSA and C1q-binding DSA, with odds ratios of 13 (P = 0.015) and 8.6 (P = 0.006), respectively. The presence of DQ DSA was associated with DAIH and late ACR, with odds ratios of 12.5 (P = 0.004) and 10.8 (P = 0.006), respectively.

CONCLUSIONS

Allograft dysfunction is not always evident in patients with DSA, but DQ DSA are strongly associated with DAIH, late ACR, and chronic rejection.

Adult Living Donor Liver Transplantation Across ABO-Incompatibility

The objective of this study was to evaluate the results of adult ABO-incompatible living donor liver transplantation (LDLT).ABO-incompatible LDLT is an aggressive treatment that crosses the blood-typing barrier for saving lives from liver diseases. Although graft and patient survival have been improved recently by various treatments, the results of adult ABO-incompatible LDLT require further evaluation.Two regimens were designed based on isoagglutinin IgG and IgM titers and the time course of immunological reactions at this institute. When isoagglutinin IgG and IgM titers were ≤64, liver transplantation was directly performed and rituximab (375 mg/m) was administrated on postoperative day 1 (regimen I). When isoagglutinin titers were >64, rituximab (375 mg/m) was administered preoperatively with or without plasmapheresis and boosted on postoperative day 1 (regimen II). Immunosuppression was achieved by administration of mycophenolate mofetil, tacrolimus, and steroids.Forty-six adult ABO-incompatible and 340 ABO-compatible LDLTs were performed from 2006 to 2013. The Model for End-Stage Liver Disease scores for ABO-incompatible recipients ranged from 7 to 40, with a median of 14. The graft-to-recipient weight ratio ranged from 0.61% to 1.61% with a median of 0.91%. The 1-, 3-, and 5-year survival rates were 81.7%, 75.7%, and 71.0%, respectively, for ABO-incompatible LDLT recipients, compared to 81.0%, 75.2%, and 71.5% for ABO-C recipients (P = 0.912). The biliary complication rate was higher in ABO-incompatible LDLT recipients than in the ABO-compatible recipients (50.0% vs 29.7%, P = 0.009).In the rituximab era, the blood type barrier can be crossed to achieve adult ABO-incompatible LDLT with survival rates comparable to those of ABO-compatible LDLT, but with more biliary complications.

Pathologic sequelae of allosensitization in liver transplantation

The long-term impact of allosensitization between ABO compatible donor/recipient pairs in liver transplantation is unclear. Accumulating clinical evidence suggests that donor-specific antibody formation may lead to antibody-mediated rejection and is causally linked to pathologic injury, graft loss, and death. Although this immune-mediated graft dysfunction is increasingly being associated with poor outcomes, the specific pathologic sequelae are not defined. Herein, we examine the relationship between allosensitization, antibody-mediated rejection, and subsequent graft pathology.

Effects of converting tacrolimus formulation from twice-daily to once-daily in liver transplantation recipients

Typically, tacrolimus is administrated twice daily. Prolonged-release tacrolimus is the once-daily formulation and may be more convenient for patients. Experience with the administration of the once-daily formulation is still limited. This study enrolled 210 liver transplant recipients who had stable liver function and converted tacrolimus from a twice-daily to once-daily formulation on a 1 mg to 1 mg basis. Among 210 patients, seven patients (3.3%) were withdrawn from the once-daily formulation due to allergy and fatigue. For the other patients, the trough concentration after converting to the once-daily formulation was lower than that of the twice-daily formulation. Liver enzymes were mildly elevated in 3 months after formulation conversion and serum creatinine and uric acid were mildly decreased. Seven patients (3.4%) had clinical suspicion of acute rejection after the formulation conversion and three of them were caused by nonadherence. 155 patients (76.4%) experienced a more convenient life with an increase of social activity. Forty-seven patients (23.2%) experienced the convenience of once-daily formulation during overseas trips. In conclusion, tacrolimus can be safely converted from the twice-daily to the once-daily formulation for most stable liver recipients. Acute rejection may occur in a minority of patients during formulation conversion and should be carefully monitored.

Antibody-mediated rejection in liver transplantation: current controversies and future directions

Interest in the role of donor-specific human leukocyte antibodies in liver transplantation has been rekindled recently. Emerging evidence suggests that these antibodies may cause injury to the liver allograft. Here we review the clinical literature, highlight controversial results, and propose a path forward for the definition and better understanding of antibody-mediated injury to the liver.

De novo donor-specific HLA antibodies decrease patient and graft survival in liver transplant recipients

The role of de novo donor-specific HLA antibodies (DSA) in liver transplantation remains unknown as most of the previous studies have only focused on preformed HLA antibodies. To understand the significance of de novo DSA, we designed a retrospective cohort study of 749 adult liver transplant recipients with pre- and posttransplant serum samples that were analyzed for DSA. We found that 8.1% of patients developed de novo DSA 1 year after transplant; almost all de novo DSAs were against HLA class II antigens, and the majority were against DQ antigens. In multivariable modeling, the use of cyclosporine (as opposed to tacrolimus) and low calcineurin inhibitor levels increased the risk of de novo DSA formation, while a calculated MELD score >15 at transplant and recipient age >60 years old reduced the risk. Multivariable analysis also demonstrated that patients with de novo DSA at 1-year had significantly lower patient and graft survival. In conclusion, we demonstrate that de novo DSA development after liver transplantation is an independent risk factor for patient death and graft loss.

Liver transplantation with a strongly positive crossmatch: case study and literature review

A positive crossmatch has been associated with increased risk in liver transplantation. To study the clinical significance of preformed donor-specific human leukocyte antigen antibodies (DSAs) in liver transplantation, we reviewed patients who underwent liver transplantation with a strongly positive flow cytometry crossmatch. DSAs were evaluated with a Luminex solid phase assay. The complement-fixing ability of DSAs was tested with a complement component 1q (C1q) assay. Using an assay correlation between complement-dependent cytotoxicity crossmatch, flow cytometry crossmatch, and DSA results, we reviewed the effects of DSAs on the outcomes of our patients as well as reported cases in the literature. Five of 69 liver recipients had a strongly positive crossmatch: 4 had a positive T cell crossmatch [median channel shift (MCS) = 383.5 ± 38.9], and 5 had a positive B cell crossmatch (MCS = 408.8 ± 52.3). The DSAs were class I only in 1 patient, class I and II in 3 patients, and class II only in 1 patient. Cholestasis, acute rejection, or both were observed in 3 of the 4 patients with a positive T cell crossmatch with an MCS approximately greater than 300. The C1q assay was positive for 3 patients. Two had either persistent cholestasis or early acute rejection. One patient who was treated with preemptive intravenous immunoglobulin had an unremarkable outcome despite a positive C1q result. One of the 2 patients with a negative C1q assay experienced persistent cholestasis and early and recurrent acute rejection; the other had an unremarkable outcome. None of the patients died or lost a graft within the first year of transplantation. Our study suggests that human leukocyte antigen antibody screening, flow cytometry crossmatch MCS levels, DSA mean fluorescent intensity levels, and C1q assays may be useful in assessing the risk of antibody-mediated rejection and timely interventions in liver transplantation.

De novo donor-specific HLA antibodies decrease patient and graft survival in liver transplant recipients

The role of de novo donor-specific HLA antibodies (DSA) in liver transplantation remains unknown as most of the previous studies have only focused on preformed HLA antibodies. To understand the significance of de novo DSA, we designed a retrospective cohort study of 749 adult liver transplant recipients with pre- and posttransplant serum samples that were analyzed for DSA. We found that 8.1% of patients developed de novo DSA 1 year after transplant; almost all de novo DSAs were against HLA class II antigens, and the majority were against DQ antigens. In multivariable modeling, the use of cyclosporine (as opposed to tacrolimus) and low calcineurin inhibitor levels increased the risk of de novo DSA formation, while a calculated MELD score >15 at transplant and recipient age >60 years old reduced the risk. Multivariable analysis also demonstrated that patients with de novo DSA at 1-year had significantly lower patient and graft survival. In conclusion, we demonstrate that de novo DSA development after liver transplantation is an independent risk factor for patient death and graft loss.

Predicting operational tolerance in pediatric living-donor liver transplantation by absence of HLA antibodies

BACKGROUND

The role of anti-human leukocyte antigen (HLA) antibodies in operational tolerance (OT) after pediatric living-donor liver transplantation (LDLT) remains inconclusive. We investigated whether the presence of HLA antibodies impeded the development of OT.

METHODS

We retrospectively examined the prevalence of anti-HLA antibodies in pediatric LDLT recipients before transplantation and at 3 weeks after transplantation and analyzed the significance of those antibodies in relation to later OT. Forty pediatric LDLTs were performed between April 1996 and December 2000 and followed up through July 2011, with sera available for measurement of HLA antibodies. Seventeen patients achieved OT (mean follow-up, 4571.9±544.7 days) and 23 patients did not achieve OT (mean follow-up, 4532.0±425.4 days). Protocol liver biopsy was done for 14 OT patients and 16 non-OT patients. Their sera were tested for anti-HLA class I and II antibodies using the LABScreen single antigen beads test, in which a 1000 mean fluorescence value was considered positive.

RESULTS

The prevalence of antibodies after transplantation in non-OT patients was higher than in OT patients (95.2% vs. 73.3%; P<0.001). The highest mean fluorescence intensity of antibodies was significantly higher in non-OT patients than in OT patients. The prevalence of HLA-B, HLA-C, HLA-DQ, and HLA-DR antibodies was significantly higher in non-OT patients than in OT patients. The highest mean fluorescence intensity of HLA-A, HLA-B, and HLA-DQ observed in non-OT patients was significantly higher than those in OT patients.

CONCLUSIONS

In our study, posttransplantation HLA antibodies were associated with the future absence of OT. A prospective study with more patients is necessary to confirm the predictive value of HLA antibodies for OT.

Progressive graft fibrosis and donor-specific human leukocyte antigen antibodies in pediatric late liver allografts

The role of donor-specific anti-human leukocyte antigen antibodies (DSAs) that develop late after living donor liver transplantation is unknown. Seventy-nine pediatric recipients who had good graft function and underwent protocol liver biopsy more than 5 years after transplantation (median = 11 years, range = 5-20 years) were reviewed. DSAs were determined with the Luminex single-antigen bead assay at the time of the last biopsy, and complement component 4d (C4d) immunostaining was assessed at the times of the last biopsy and the previous biopsy. The donor specificity of antibodies could be identified in 67 patients: DSAs were detected in 32 patients (48%), and they were usually against human leukocyte antigen class II (30 cases) but were rarely against class I (2 cases). These patients had a higher frequency of bridging fibrosis or cirrhosis (28/32 or 88%) than DSA-negative patients (6/35 or 17%, P < 0.001). Fibrosis was likely to be centrilobular-based. DSA-positive patients, in comparison with DSA-negative patients, had higher frequencies of diffuse/focal endothelial C4d staining (P < 0.001) and mild/indeterminate acute rejection [15/32 (47%) versus 5/35 (14%), P = 0.004]. Four DSA-negative patients were off immunosuppression, whereas no patients in the DSA-positive group were (P = 0.048). In conclusion, the high prevalence of graft fibrosis and anti-class II DSAs in late protocol biopsy samples suggests that humoral alloreactivity may contribute to the process of unexplained graft fibrosis late after liver transplantation.

Donor-specific human leukocyte antigen antibodies of the immunoglobulin G3 subclass are associated with chronic rejection and graft loss after liver transplantation

In a previous study, we found that 92% of patients with chronic rejection had donor-specific human leukocyte antigen antibodies (DSAs), but surprisingly, 61% of comparator patients without rejection also had DSAs. We hypothesized that immunoglobulin G (IgG) subclasses were differentially distributed between the 2 groups. A modified single-antigen bead assay was used to detect the presence of individual IgG subclasses against human leukocyte antigen in 39 chronic rejection patients and 66 comparator patients. DSAs of the IgG1 subclass were most common and were found in 45% of all patients; they were followed by IgG3 DSAs (21%), IgG4 DSAs (14%), and IgG2 DSAs (13%). The percentage of patients with multiple IgG subclasses was significantly higher in the chronic rejection group versus the comparator group (50% versus 14%, P < 0.001). Patients with normal graft function in the presence of DSAs mostly had isolated IgG1, whereas patients with chronic rejection had a combination of IgG subclasses. Patients who developed DSAs of the IgG3 subclass showed an increased risk of graft loss (hazard ratio = 3.35, 95% confidence interval = 1.39-8.05) in comparison with patients with DSAs of other IgG subclasses or without DSAs. Although further study is needed, the determination of the IgG subclass in DSA-positive patients may help us to identify patients with a higher risk of chronic rejection and graft loss.

High mean fluorescence intensity donor-specific anti-HLA antibodies associated with chronic rejection Postliver transplant

In contrast to kidney transplantation where donor-specific anti-HLA antibodies (DSA) negatively impact graft survival, correlation of DSA with clinical outcomes in patients after orthotopic liver transplantation (OLT) has not been clearly established. We hypothesized that DSA are present in patients who develop chronic rejection after OLT. Prospectively collected serial serum samples on 39 primary OLT patients with biopsy-proven chronic rejection and 39 comparator patients were blinded and analyzed for DSA using LABScreen(®) single antigen beads test, where a 1000 mean fluorescence value was considered positive. In study patients, the median graft survival was 15 months, 74% received ≥ one retransplant, 20% remain alive and 87% had ≥ one episode of acute rejection. This is in contrast to comparator patients where 69% remain alive, and no patient needed retransplant or experienced rejection. Thirty-six chronic rejection patients (92%) and 24 (61%) comparator patients had DSA (p = 0.003). Chronic rejection versus comparator patients had higher mean fluorescence intensity (MFI) DSA. Although a further study with larger numbers of patients is needed to identify clinically significant thresholds, there is an association of high-MFI DSA with chronic rejection after OLT.

Liver allograft antibody-mediated rejection with demonstration of sinusoidal C4d staining and circulating donor-specific antibodies

The importance of antibody-mediated rejection (AMR) in ABO-compatible liver transplantation is controversial. Here we report a prospective series of liver recipients with a preoperative positive crossmatch. To establish the diagnosis of AMR in liver recipients, the criteria described for kidney allografts were adopted. In approximately 10% of 197 liver transplants, we observed a positive T and B cell flow crossmatch before transplantation. Fifteen of 19 patients converted to negative crossmatches early after transplantation and displayed normal liver function while they were on routine immunosuppression. Four patients maintained positive crossmatches. Three of the 4 met the criteria for AMR and showed evidence of graft dysfunction, the presence of donor-specific antibodies (DSAs), morphological tissue destruction with positive C4d linear staining on the graft sinusoidal endothelium, and improved function with attempts to eliminate DSAs. A persistently positive crossmatch after liver transplantation may lead to early, severe AMR and liver failure. C4d staining in the liver sinusoidal endothelium should alert one to the possibility of AMR. In our experience, patients with a positive crossmatch should have it repeated at 2 weeks and, if it is positive, again at 3 to 5 weeks. Recipients with an unknown preoperative crossmatch who develop early cholestasis of unclear etiology should be crossmatched or tested for the presence of DSAs to evaluate for AMR.

Flexible and individualized treatment to achieve sustained viral response for recurrent hepatitis C in liver transplant recipients

Hepatitis C recurrence after liver transplantation is universal and is a major cause of long-term graft failure. Improving the effectiveness of recurrent hepatitis C treatment is extremely important. We studied 35 anti-hepatitis C virus (HCV)-positive patients who underwent liver transplantation. Among the 35 patients, 25 patients had recurrent hepatitis C and received antiviral treatment. HCV RNA load after liver transplantation was increased by 3.68-fold. The antiviral treatment regimen comprised pegylated-interferon (180 μg) every 2 weeks and ribavirin at a dose of 200-400 mg every day. The treatment duration was flexible and individualized, and depended on viral response to treatment. The dosage of tacrolimus was decreased gradually to minimize immunocompromise. Median (interquartile) serum level of tacrolimus was 6.9 (6-8.9) ng/mL at initiation of treatment and 3.8 (3.6-5) ng/mL at the end of treatment. One patient (4.0%) was withdrawn from the study, and three patients (12%) died of infection during treatment. At end of treatment, 18 of 25 patients (72%) were negative for serum HCV RNA. After an additional 6 months following the end of treatment, 16 of the 25 patients (64%) had sustained viral response (SVR) and only two patients had HCV relapse. The 1-year, 3-year and 5-year survival rates were 91.4%, 84.5% and 84.5% for all patients and 88.0%, 82.8% and 82.8% for the 25 patients who received antiviral therapy. In conclusion, recurrent HCV infection is an important issue in liver transplantation. The flexible regimen of antiviral therapy and individualized immunosuppressive agents that was applied in this study achieved a SVR rate of 64%.

Indirect immunohistochemical evaluation of graft fibrosis and interface hepatitis after pediatric liver transplantation

Fibrosis or IH following pediatric liver transplantation is recognized as major causes of graft loss, but the etiology remains unclear. To determine this issue, we used an indirect immunohistochemistry technique with post-transplant serum samples from recipients and normal human liver tissues from living liver donors, and the association between occult antibody reaction to the liver and the occurrence of fibrosis or IH was evaluated. Forty-three recipients were evaluated, and both hepatocytes and biliary epithelial cells were evaluated for staining intensity. Fibrosis and IH occurred in 13 and six patients, respectively. According to staining results for the hepatocytes and biliary epithelial cells, 18 and 11 patients, respectively, were classified into the positive group. According to log-rank analysis, positive reaction for hepatocytes was associated with increased rates of fibrosis and IH (p = 0.002 and 0.048, respectively), while positive reaction for biliary epithelial cells was associated with an increased rate of fibrosis (p = 0.014). Multivariate analysis revealed that positive reaction for hepatocytes and biliary epithelial cells was independently associated with fibrosis occurrence (p = 0.020 and 0.047, respectively). In conclusion, immune-mediated reactions by occult antibodies may underlie the pathogeneses of fibrosis and IH.

Lymphocytotoxic crossmatch in pediatric living donor liver transplantation

To investigate the relationship between the pretransplant LCT results and the outcome after pediatric LDLT in a single center. The clinical data of 76 children undergoing 79 LDLTs including three retransplantations from May 2001 to January 2006 were retrospectively analyzed. All of the children had end-stage liver disease, and their median age was 1.4 yr (range, six months to 16.5 yr). Immunosuppressive therapy consisted of cyclosporine- or FK-based regimens with steroids. The children were classified into two groups (positive or negative) according to the pretransplant LCT results. The incidences of post-transplant surgical complications and of rejection episodes were compared. The relationship between the pretransplant LCT results and patient and graft survival rates was also analyzed. Seventy-nine pretransplant crossmatch tests were done; 13 (16.5%) were positive, and 66 (83.5%) were negative. No significant difference was found in the pretransplant clinical factors between two crossmatch groups. There was no significant difference between the groups in the incidence of vascular and biliary tract complications, in the rate of early or steroid-resistant cellular rejections, or in one- and three-yr patient (91.7%, 91.7%, respectively, in the positive group, 93.5%, 93.5%, respectively, in the negative group, p = 0.80) and graft (92.3%, 92.3%, respectively, in the positive group, 88.8%, 86.4%, respectively, in the negative group, p = 0.63) survival. The present study demonstrates that there is no reason to do pretransplant LCT to select the living donor for pediatric LDLT.

Significance of C4d staining in ABO-identical/compatible liver transplantation

Complement degradation product C4d has become an important marker of humoral or antibody-mediated rejection in renal and heart allograft biopsies. Although there have been several reports on the detection of C4d in liver allografts, the significance of C4d in liver transplantation and its relationship with humoral rejection are still not clear. We investigated the frequency and pattern of C4d staining in liver allograft biopsies with reference to preoperative lymphocyte crossmatch tests, which detect donor-reactive lymphocyte antibody. Survival rates at 5 years were 77% for crossmatch-negative patients and 53% for crossmatch-positive patients (P=0.009). In crossmatch-negative patients, reproducible positive staining was obtained in 28 of 86 (33%) biopsies taken within 90 days after transplantation and 33 of 96 (34%) biopsies 90 days or after transplantation. Most C4d staining was observed in the portal areas, and no clear correlation was observed between C4d positivity and histological diagnosis. In crossmatch-positive patients, 9 of 11 (82%) biopsies showed positivity for C4d. C4d stained perivenular areas as well as portal areas. Histology of crossmatch-positive patients included acute rejection and cholangitis, but did not include periportal changes that were seen in humoral rejection in ABO-incompatible liver transplantation. In summary, focal C4d deposition was seen in various types of liver allograft injury and had little clinical impact on crossmatch-negative patients, but extensive C4d staining in crossmatch-positive patients may be associated with humoral rejection and poor graft survival.

Antidonor antibody in patients receiving ABO-identical and HLA-mismatched living donor liver transplants: effect on survival

We retrospectively determined the correlation of results of lymphocyte crossmatch tests by direct complement-dependent cytotoxicity, to the outcomes of 585 consecutive ABO-identical and human leukocyte antigen (HLA)-mismatched living donor liver transplants (LDLTs) (male:female=276:309; median age, 18 years). Crossmatch test results were positive in 14 recipients (2.4%). Patient survival at eight years in the crossmatch-positive group was significantly lower than in the crossmatch-negative group (positive group, 56.3%; negative group, 77.6%; P=0.014). The survival at five years of the crossmatch-positive group was significantly lower than the negative group in both older recipients (>or=18 years of age: positive group, 41.7%; negative group, 76.4%; P=0.0065), and female recipients (positive group, 37.5%; negative group, 81.9%; P=3.3x10). We conclude that antidonor antibodies have adverse effects on the clinical outcome of LDLTs, and that being female and/or older aged (>or=18 years of age) are risk factors for LDLT.

A synergistic effect between PG490-88 and tacrolimus prolongs renal allograft survival in monkeys

This study was undertaken to determine if PG490-88 and tacrolimus (Tac) act synergistically to prevent renal allograft rejection in monkeys and to explore possible mechanisms of synergy between these agents. MHC-mismatched renal allografts were transplanted into cynomolgus monkeys after bilateral nephrectomy. Recipients were divided into the following groups: (i) no treatment; (ii) PG490-88 (0.03 mg/kg); (iii) Tac (1 mg/kg); (iv) PG490-88 (0.01 mg/kg) + Tac (1 mg/kg) and (v) PG490-88 (0.03 mg/kg) + Tac (1 mg/kg). Through synergy PG490-88 and Tac inhibited anti-CD3/PMA-induced T-cell proliferation and IFN-gamma expression in vitro. Tac monotherapy only marginally prolonged survival (27 +/- 3.2 days), while the combination of PG490-88 and Tac significantly prolonged graft survival to a median of 99 days (PG490-88 at 0.03 mg) and 38.5 days (PG490-88 at 0.01 mg/kg). Prolonged survival correlated with inhibited IgM production as well as reduced T-cell infiltration, IL-2 protein expression and NF-AT/NF-kappaB activity. We conclude that PG490-88 and a subtherapeutic dose of Tac significantly prolong renal allograft survival in monkeys through the synergistic inhibition of T-cell activation and a decrease in IFN-gamma production and NF-AT/NF-kappaB activity.

Influence of HLA compatibility and lymphocyte cross-matching on acute cellular rejection following living donor adult liver transplantation

BACKGROUND

Reports on the relevance of immunogenetic factors in living donor adult liver transplantation (LDALT) are often conflicting or inconclusive. We therefore investigated the human leukocyte antigen (HLA) mismatches, lymphocyte crossmatch positivity, and the reactivity in mixed lymphocyte culture (MLC) in a series of LDALT.

METHODS

A total of 104 LDALT patients were studied. The minimum follow-up was 12 months, and the graft survival rates were assessed. The incidence of the most common complications was analyzed. And the influence of HLA, the flow cytometric analysis findings, enhanced cytotoxic cross-matching and MLC on graft survival, and acute rejection was also investigated.

RESULTS

As a result, 96 negative cross-matching and eight positive cross-matching cases were identified. Positive cytotoxic cross-matching had a significant effect on graft survival (P<0.05), while flow cytometric cross-matching also had an additional effect on acute rejection (P<0.05). The MLC of the patients with three HLA mismatches was significantly higher than the MLC of patients with zero HLA mismatches. The incidence of acute cellular rejection (ACR) was higher in the patients with three mismatches than in the other patients, and moderate rejection only occurred in the patients with three mismatches.

CONCLUSION

HLA mismatching was not statistically associated with the overall graft survival after LDALT. The graft failure rates were higher in the positive cross-matching cases and therefore a strong immuosuppressant might be needed for positive cross-matching cases.

Equal overall rejection rate in pre-transplant flow-cytometric cross-match negative and positive adult recipients in liver transplantation

T cell IgG flow-cytometric cross-matches (FCXM) using 48 stored pre-transplant patient serum samples and 40 stored serum samples collected 3 wk after liver transplantation and frozen spleen cells of cadaveric donors in 48 consecutive liver transplantations were performed retrospectively. T cell IgG FCXM using pre-transplant serum samples was compared with 46 complement-dependent lymphocytotoxic cross-matches (CDCXM) performed at the time of transplantation. Clinical relevance of these tests was evaluated in relation to acute rejection, 1-, 3- and 5-yr graft and patient survival. The incidence of positive FCXM was 33% (16 of 48) and 13% (six of 46) by CDCXM. The median time of acute rejection was 29 d after transplantation in FCXM positive group (range 13-101 d) and 22 d in FCXM negative group (range 7-157 d, NS). Rejection rate was similar in 16 pre-transplant FCXM positive patients (eight of 16, 50%) compared with six pre-transplant CDCXM positive patients (three of six, 50%; NS). Recipients having graft rejection tended to be more often pre-transplant FCXM positive (eight of 21, 38%) than CDCXM positive (three of 21, 14%), but the difference was not significant (p > 0.1). No difference was found in the positive predictive value in relation to acute rejection between positive FCXM and CDCXM (69% vs. 50%; NS). Furthermore there was no correlation between post-transplant positive FCXM and acute rejection. No difference was found between pre-transplant T cell IgG FCXM positive and negative recipients in relation to graft or patient survival. Our findings are supportive for little risk associated with preformed donor-specific antibodies in liver transplantation.

Portal capillary C4d deposits and increased infiltration by macrophages indicate humorally mediated mechanisms in acute cellular liver allograft rejection

Almost no data exist concerning the role of antibody-mediated mechanisms in human acute cellular liver allograft rejection (ACR). Therefore, the aim of this study was to determine whether ACR is associated with depositions of complement split products and increased infiltration by B-lymphocytes, plasma cells and macrophages. A total of 35 liver biopsy specimens (ACR n=22, controls n=13) were analyzed by immunohistochemical single and double staining. The average numbers of CD 20(+), CD 38(+) and CD 68(+) cells per portal tract were established while the presence of C4d and C3d deposits was evaluated semiquantitatively. Significantly greater numbers of CD 20(+) (P=0.029) and CD 38(+) (P=0.014) cells were found in the ACR specimens than in the control specimens. Additionally, 50% of patients diagnosed with ACR showed C4d deposits along portal capillaries, which was associated with a significantly increased portal infiltration by macrophages (P=0.007). Taken together these results support the involvement of humorally mediated mechanisms in some cases of ACR.

Interferon-alpha therapy in liver transplant recipients: lack of association with increased production of anti-HLA antibodies

Interferon-alpha (IFN) is a useful treatment for active HCV infection. In kidney transplantation, IFN has been shown to trigger acute rejection with de novo anti-HLA antibodies. Interferon-alpha has not been reported to enhance the risk of acute rejection in HCV-positive liver transplant recipients (LTRs). Sera were collected from 44 LTRs greater than 6 months post-transplant. Sera were tested with ELISA for the presence and the specificity of anti-HLA antibodies. The prevalence of anti-HLA antibodies was 11% and was not significantly different in 13 HCV-positive recipients who received IFN, compared with 10 who did not receive IFN (8% vs. 20%), or with 21 HCV-negative recipients (10%). None of the patients had an acute rejection after starting IFN. In this study, LTRs receiving IFN did not have an increased frequency of anti-HLA antibodies. This may partially explain the safety of IFN previously reported in LTRs requiring antiviral therapy.

Immunoglobulin-G subclass antidonor reactivity in transplant recipients

Outcomes may differ after kidney transplantation compared to combined liver-kidney transplantation. In animal models, distinct patterns of antidonor immunoglobulin (Ig) G subclasses are associated with either rejection or transplant tolerance. Flow cytometry has increased the sensitivity of antidonor immunoglobulin detection. We compared antidonor IgG subclass responses in kidney transplant recipients to those in recipients of liver or multiorgan grafts. In this study of 19 organ (kidney, liver, pancreas) transplantations, recipient serum incubated with donor splenocytes was tested by flow cytometry for the presence of IgM, IgG, or IgG subclass 1-4. Sera before transplantation and 10 days and 100 days after transplantation were used. No differences were seen in antidonor IgM, IgG, or IgG subclass antibodies among recipients of kidney transplants and liver grafts or combination grafts, either before or after transplantation. IgG4 gradually but significantly increased after transplantation in all groups. High levels of antidonor IgG3 either before transplantation or produced after it were found in 3 kidney recipients who experienced acute rejection. No other patients experienced rejection, and no other increase in IgG3 was seen. In conclusion, antidonor IgG subclass profiles may be useful to distinguish populations at risk of rejection but they do not differentiate the immunological response after kidney transplantation from that after liver or combined transplantation. A late rise in antidonor IgG4 is consistent with decreased antidonor reactivity thought to occur late after transplantation.

Significant changes in the alloantibody after lung transplantation in the cyclosporine treated rat model

BACKGROUND

The diagnosis of acute rejection after organ transplantation is often complicated by other possibilities, such as infection. Despite many attempts to identify rejection episodes after transplantation, only the detection of the humoral anti-human leukocyte antigen antibody has been effective in measuring alloimmunization, especially detected with flow cytometry cross-match (FCXM). As an initial step towards gaining a better understanding of the correlation between humoral responses and graft rejection in an immunosuppressant recipient, we investigated responses of alloantibodies (allo-Abs) after lung transplantation (LTx) in a rat model treated with adequate or inadequate cyclosporine A (CsA) therapy.

METHODS

Orthotopic LTx was performed using a major histocompatibility complex fully incompatible combination (Brown Norway to Lewis rat). CsA was given subcutaneously to recipients at an optimal or a sub-optimal dosage for 3 days after transplantation. A FCXM technique was used to determine the time-course of changes in titers of allo-Abs in serum. The allo-Ab deposition in the grafted lung was detected with an immunofluorescent staining method.

RESULTS

Circulating IgM allo-Ab levels were significantly elevated on day 4 in both groups when histological findings revealed early stage of acute rejection. IgM levels in the sub-optimal dosage group were maximal and significantly higher than those in the optimal dosage group on day 4, and levels then decreased after day 8. IgG allo-Ab levels increased significantly on day 8 and continued to increase throughout the observation period.

CONCLUSIONS

Our data suggest that the monitoring IgM allo-Abs might be effective for identifying acute rejection in recipients with inadequate immunosuppression therapy.

The role of B cells and alloantibody in the host response to human organ allografts

Some human organ transplants deteriorate slowly over a period of years, often developing characteristic syndromes: transplant glomerulopathy (TG) in kidneys, bronchiolitis obliterans in lungs, and coronary artery disease in hearts. In the past, we attributed late graft deterioration to "chronic rejection", a distinct but mysterious immunologic process different from conventional rejection. However, it is likely that much of chronic rejection is explained by conventional T-cell-mediated rejection (TMR), antibody-mediated rejection (AMR), and other insults. Recently, criteria have emerged to now permit us to diagnose AMR in kidney transplants, particularly C4d deposition in peritubular capillaries and circulating antibody against donor human leukocyte antigens (HLA). Some cases with AMR develop TG, although the relationship of TG to AMR is complex. Thus, a specific diagnosis of AMR in kidney can now be made, based on graft damage, C4d deposition, and donor-specific alloantibodies. Criteria for AMR in other organs must be defined. Not all late rejections are AMR; some deteriorating organs probably have smoldering TMR. The diagnosis of late ongoing AMR raises the possibility of treatment to suppress the alloantibody, but efficacy of the available treatments requires further study.

Plasmapheresis as rescue therapy in accelerated acute humoral rejection

Accelerated acute humoral rejection (AHR) continues to occur in renal transplantation despite improved crossmatching, with potentially devastating consequences. Between 1 June 1998 and 31 December 2000, 440 renal transplants were performed in our center. AHR was diagnosed by the demonstration of typical pathological features on renal histology and positive direct immunofluorescence or detection of anti-HLA antibodies in serum. AHR developed in 20 (4.5%) of our renal transplant recipients, nine male and eleven female at an average of 16.3 days post transplantation. All of these patients had a negative current cytotoxic crossmatch prior to transplantation. The median serum creatinine at diagnosis was 5.96 mg/dL, and 83% of these individuals developed oliguric renal failure requiring dialysis after having initially attained good graft function (median of best serum creatinine before AHR was 2.64 mg/dL). The 18 recipients who had not infarcted their grafts at the time of diagnosis of AHR received plasmapheresis in conjunction with intensification of their immunosuppressive regimen. This regimen was successful in reversing AHR in 78% of those treated with apheresis. In the 14 responders, graft survival at 6 months was 100% and at 12 months was 91%. Median serum creatinine at 6 and 12 months was 1.26 and 1.33 mg/dL, respectively. Patients received an average of 8.1 plasma exchanges. However, responders received a significantly higher frequency of plasmapheresis (P =.0053), despite undergoing a similar number of exchanges overall. Plasmapheresis appears to be an effective modality for reversing AHR and maintaining graft function.

Humoral theory of transplantation

According to the humoral theory of transplantation, antibodies cause allograft rejection. Publications are cited showing that antibodies: (1). cause hyperacute kidney rejection, (2). lead to C4d deposits associated with early kidney graft failures, (3). are a good indicator of presensitization leading to early acute rejections, (4). were present in 96% of 826 patients who rejected a kidney graft, (5). are associated with chronic rejection in 33 studies of kidney, heart, lung and liver grafts, and (6). in three studies, appeared in the circulation BEFORE evidence of bronchiolitis obliterans in lung transplants, and BEFORE kidney rejection. In addition, a prospective cooperative study of 1629 patients in 24 centers demonstrated that antibodies foretold subsequent failures after a follow-up period of 6 months (p = 0.05). The specificity of antibodies detected in the serum of rejecting patients were often not donor specific, presumably because they were absorbed by the rejecting organ. If the humoral theory is accepted, even provisionally, transplanted patients who have antibodies could be treated with immunosuppression until the antibodies disappear to determine whether chronic rejection can be blocked. If successful, in patients who do not have antibodies, immunosuppression could be reduced until antibodies appear.

Humoral immune responses during acute rejection in rat lung transplantation

The detailed responses of humoral immunity during acute rejection remain obscure in lung transplantation (LTx). In order to clarify the reactions of alloantibodies (allo-Abs) during acute rejection, we demonstrated the time-course of changes in anti-donor Ab reaction in the peripheral blood and deposition in the grafts using a rat LTx model. Lewis (LEW) rats served as recipients for Brown Norway (BN) lung allografts (MHC fully incompatible combination). The left lung was transplanted orthotopically using a cuff technique. Syngeneic transplants (LEW to LEW) served as control. No immunosuppression therapy was administered in this model. We evaluated the alloreactivity against donor in rat recipients by detecting allo-Abs with a flow cytometric cross-match (FCXM) technique. Recipient serum samples were incubated with donor lymphocytes and stained with anti-rat immunoglobulin (Ig), to determine the titers of circulating allo-Abs in the peripheral blood with a three-color FCXM technique. We also examined the deposition of anti-donor Abs (IgG and IgM) in the grafts with an immunofluorescent method. All allografts were completely rejected and lost their aeration within 6 days after LTx. Strong allo-Abs responses of both IgG and IgM were observed in the peripheral blood during acute rejection. The level of IgM allo-Abs had already significantly increased on day 2 at the time of mild rejection; however, IgG Abs did not elevate until day 6, when the grade of rejection was severe. Circulating IgM levels started decreasing on day 8, whereas IgG Abs continued elevating. On the other hand, no evident deposition of allo-Abs in the grafts was observed until day 6. We have shown in this study that circulating IgM allo-Abs was detected at the time of mild allograft rejection, interestingly, before evident deposition in the graft. It might be suggested that allograft rejection progressed without antibody deposition until severe rejection.

Role of HLA compatibility in pediatric living-related liver transplantation

BACKGROUND

Human leukocyte antigen (HLA) matching is, at present, not used for the allocation of cadaveric hepatic allografts because the liver is generally believed to be less susceptible to HLA-mediated rejection. However, the exact role of HLA compatibility in the long-term outcome of liver transplantation is not yet clearly defined. One of the advantages of living-related liver transplantation (LRLT) could be a better histocompatibility between donor and recipient. This study aimed at an assessment of the influence of HLA compatibility in a large series of LRLTs.

METHODS

A total of 321 pediatric patients who underwent ABO-identical or ABO-compatible primary LRLT from the parental donors in the period between June 1990 and August 2000 were involved in the study. Graft survival, rejection episodes, and immunosuppression were evaluated from the viewpoint of HLA compatibility.

RESULTS

The overall 1- and 5-year graft survivals were 85.7% and 84.1%, respectively. The cumulative 5-year graft survivals in HLA 0-, 1-, 2- and 3-mismatch groups (A, B, and DR) were 100% (n=10), 78.9% (n=19), 86.2% (n=87), and 82.9% (n=205), respectively (P=0.525). The overall incidence of rejection during the follow-up period (median 66 months, range 16-139 months) was 46.1%. No significant difference was found in the incidence of rejection and rejection-free survival among the four groups. However, steroid-resistant rejection that necessitated OKT3 treatment (n=6) and chronic rejection (n=2) were recognized only in the 3-mismatch group. The whole-blood trough level of tacrolimus and the duration of steroid administration were not significantly different among the groups. The rate of the patients who succeeded in withdrawal from immunosuppression was also similar among the groups. However, the trough level of tacrolimus needed for maintenance of an acceptable liver function test during the chronic phase tended to be lower in well-matched pairs, and a high percentage of immunosuppressant-free patients were found in the 0-mismatch group. Fatal graft-versus-host disease developed in one patient with a complete one-way HLA-matched transplant.

CONCLUSION

We could not find any supportive evidence of beneficial effects of HLA-matching in pediatric LRLT. The potential benefit of HLA-matching for the reduction protocol for immunosuppressants may play a role in the withdrawal program. It appears unnecessary to pay attention to HLA compatibility in donor selection in LRLT, except for one-way HLA matching, or to adjust immunosuppression according to HLA compatibility.

Is presensitization relevant to liver transplantation outcome?

The impact of anti-HLA antibodies and crossmatch (CM) on liver transplantation (LT) outcome is still controversial. In this retrospective study we analyzed LT outcome according to pretransplant pre-formed anti-HLA antibodies and CM status. Serum anti-HLA antibodies were screened by ELISA assay, utilizing One Lambda antigen tray-mixed (LAT-M). CMs were performed by the complement dependent cytotoxicity test using Dithiotreitol treated sera. Anti-HLA antibodies were studied in 80 recipients; 56/80 had positive LAT-M tests (PLAT-M), whereas the remaining 24 recipients tested negative for both classes I and II (NLAT-M). Rejection episodes were more frequent in PLAT-M compared with NLAT-M group in post-LT intervals of <1 week (p = 0.05), 1 week-3 months (p = 0.035), and 3-12 months (p = 0.076). Graft and patient survival rates were better, albeit not significantly, in the NLAT-M compared with PLAT-M recipients. CM status was investigated in 62/80 recipients, 18/62 recipients had positive CM (PCM), and 44 had negative CM (NCM). Five of 18 PCM recipients (28%) experienced early graft loss compared with 1/44 (2%) with NCM (p = 0.006). Rejection episodes were more frequent within first 3 months post-LT in PCM recipients compared with NCM (p = 0.015). One-year graft survival rate was better in NCM, compared with PCM recipients (graft loss of 2/44 vs 5/18). NCM PLAT-M had a higher incidence of rejection episodes compared with the NCM NLAT-M group (p = 0.031). The presence of anti-HLA antibodies suggests a deleterious effect on LT outcome, and was associated with an increased incidence of early graft loss and rejection episodes.

Clinical implications of flow cytometry crossmatch with T or B cells in living donor liver transplantation

BACKGROUND

Acute allograft rejection (AR) in solid organ transplantation is generally regarded to develop through cell-mediated immune response following activation of helper T cells. Since production of antibodies is also mediated by helper T cells, humoral immunity may play some roles in AR. Although flow cytometry crossmatch (FCXM) is reported as a useful method for the detection of antibodies against donor antigen, specific role of T- or B-cell FCXM and its sensitivity for AR is controversial.

METHODS

T- and B-cell FCXM using fresh donor peripheral lymphocytes were performed before and after blood-type compatible living donor liver transplantation in 47 patients. IgM and IgG anti-donor antibodies were analyzed in relation to clinical AR.

RESULTS

Positive pre-transplant T-cell FCXM was associated with a high incidence of positive post-transplant T-cell FCXM (p=0.017). Four of five cases (80%) with positive pre-transplant T-cell FCXM experienced earlier AR (day 8.0+/-4.4, mean+/-SD) than 16 of 42 cases (31%) with negative pre-transplant T-cell FCXM (17.3+/-6.8; p=0.016). In addition, higher dose of steroids was given to treat AR episodes in cases with positive pre-transplant T-cell FCXM (79.9+/-10.3 mg/kg/month) than in those with negative pre-transplant T-cell FCXM (47.1+/-26.6; p=0.039). In the first month after transplantation, 13 episodes of positive post-transplant T-cell FCXM were all concomitant with or preceded clinical AR compared with seven ARs in T-cell FCXM-negative cases (p<0.0001). T-cell FCXM between positive sera and third parties revealed some crossreactions. In contrast, detection of antibodies by B-cell FCXM in pre- and post-transplant phases was scarcely associated with AR, and no correlation was found between T- and B-cell FCXM before and after transplantation.

CONCLUSIONS

Positive T-cell FCXM is closely related with AR and that before transplantation is a predictor of early and refractory AR as well as post-transplant FCXM. In contrast, not a few detections of antibodies irrelevant to AR are observed in B-cell FCXM, suggesting its low specificity.

Improved flow cytometric detection of HLA alloantibodies using pronase: potential implications in renal transplantation

BACKGROUND

Flow cytomeric crossmatch (FCXM) has grown in popularity and has become the "standard of practice" in many programs. Although FCXM is the most sensitive method for detecting alloantibody, the B cell FCXM has been problematic. Difficulties with the B cell FCXMs have been centered around high nonspecific fluorescence background owing to Fc-receptors present on the B cells and autoantibodies. To improve the specificity and sensitivity of the B cell FCXM, we utilized the proteolytic enzyme pronase to remove Fc receptors from lymphocytes before their use in FCXM.

METHODS

Lymphocytes isolated from peripheral blood, spleen, or lymph nodes were treated with pronase and then used in a three-color FCXM. A total of 167 T- and B cell FCXMs using pronase-treated and untreated cells were performed. Testing used serial dilutions of HLA allosera (22 class I and 6 class II), with the titer of each antibody at one dilution past the titer at which the complement-mediated cytotoxicity anti-human globulin crossmatch became negative.

RESULTS

After pronase treatment, the actual channel values of the negative control in both T cell and B cell FCXMs declined from 78+/-10 to 57+/-4 (P<0.05) and 107+/-11 to 49+/-3 (P<0.00001), respectively. Pronase treatment resulted in improved sensitivity of the T and B cell FCXM in detecting class I antibody by 20% and 80%, respectively. In no instance was a false-positive reaction observed. In this study, pronase treatment improved the specificity of B cell FCXM for detecting class II antibodies from 75% to 100% (P=0.03). In no instance was a false-negative reaction recorded. Lastly, on the basis of these observations we re-evaluated three primary transplant recipients who lost their allografts because of accelerated rejection. One of the patients was transplanted across negative T and B cell FCXM, whereas the other two patients were transplanted across a positive T cell, but negative B cell, FCXM. After pronase treatment, T and B cell FCXMs of each patient became strongly positive, and donor-specific anti-HLA class I antibody was identi. fied in each case.

CONCLUSION

Utilization of pronase-treated lymphocytes improves both the sensitivity and specificity of the FCXM.

A 12-day course of FK506 allows long-term acceptance of semi-identical liver allograft in inbred miniature swine

BACKGROUND

Spontaneous tolerance to liver allograft has been reported previously in outbred pig models, but the lack of genetic background did not allow to analyze the impact of the major histocompatibility complex (MHC) on tolerance induction. A model of semi-identical liver allograft was therefore developed in inbred miniature swine in order to mimic the clinical situation of living related liver transplant (parent into infant) and to study a protocol for inducing tolerance to liver allograft.

METHODS

SLAdd (class Id/d, class IId/d) pigs received orthotopic liver allograft from heterozygous SLAcd (class Ic/d, class IIc/d) miniature swine. Eight animals did not receive immunosuppression. Fourteen SLAdd animals had a 12-day course of FK506 and were divided in two subgroups. In subgroup FK-1, six pigs received a daily intramuscular injection of FK506 at 0.1-0.4 mg/kg, in order to reach daily trough levels between 7 and 20 ng/ml; in subgroup FK-2, eight additional animals received two daily injections of FK506 at 0.05 mg/kg regardless of the daily trough levels. Graft survival, liver biological tests, histology, cellular and humoral immune responses, as well as detection of microchimerism were assessed in all groups.

RESULTS

All untreated animals rejected their allograft and died within 28.1 +/- 9.5 days. These rejector animals developed a significant anti-donor cellular and humoral immune response. No peripheral or lymphoid tissue microchimerism was detected in this group. In contrast, long-term survival was obtained in five FK-treated animals (112, 154, 406, 413, and 440 days), whereas several pigs died with a normal allograft function from either overimmunosuppression or intercurrent causes. All FK-treated pigs developed a specific anti-donor unresponsiveness in both cell mediated lymphocytotoxicity and mixed lymphocyte reaction and did not develop anti-donor alloantibodies. The study of the anti-donor immune response by mixed lymphocyte reaction, during the first postoperative week, demonstrated a specific anti-donor unresponsiveness in the peripheral blood from the first posttransplant day. Although microchimerism was detectable in the peripheral blood for several postoperative weeks (maximum 10 weeks) in FK-treated animals, donor cells or DNA were not detected during the long-term follow-up in peripheral blood or lymphoid tissues.

CONCLUSIONS

Spontaneous tolerance to semi-identical orthotopic liver allograft did not occur, whereas a 12-day course of FK506 allowed long-term graft acceptance. All FK-treated animals developed in vitro signs of specific immune unresponsiveness and transient peripheral microchimerism. The specific anti-donor cellular unresponsiveness occurred on the first postoperative day after surgery and was of long-term duration. The study of the early immunological events in this model could be of major importance regarding clinical living related liver transplantation.