Complement component 4d immunostaining in liver allografts of patients with de novo immune hepatitis

Recurrent Autoimmune Hepatitis and De Novo Autoimmune Hepatitis in the Liver Allograft

OBJECTIVES

Autoimmune hepatitis (AIH) is a form of severe hepatitis that can recur after orthotopic liver transplant (OLT). Presentation of AIH in patients with OLT who do not have a history of AIH is called de novo AIH (DNAIH). We evaluated the clinicopathologic characteristics of AIH and DNAIH.

METHODS

Clinicopathologic and outcome measures of 11 patients with recurrent AIH (RAIH) and 22 with DNAIH identified between 2000 and 2017 were compared.

RESULTS

Both cohorts showed female predominance. The mean clinical follow-up was 13 and 7.8 years in the in the RAIH and DNAIH groups, respectively (P = .1). Moderate portal inflammation was more common in patients with RAIH (64% vs 27%, P = .043). A trend was observed for more cases of DNAIH showing severe inflammation (36% vs 9%, P = .09) and submassive necrosis compared with RAIH (23% vs 0%, P = .086). A trend for more advanced fibrosis was also noted in the RAIH group (27% vs 5%, P = .059). Three patients with RAIH lost their grafts because of RAIH. Five-year disease-specific graft survival (GS) (P = .012) and overall GS (P = .015) were worse in patients with RAIH. Complement component 4d immunohistochemistry was positive in 2 patients with RAIH and 3 with DNAIH but showed no correlation with GS or other parameters.

CONCLUSIONS

RAIH seems to have a more aggressive clinical course than DNAIH and warrants closer clinical follow-up and aggressive treatment.

Glutathione S-Transferase T1 Mismatch Is a Risk Factor for Chronic Ductopenic Rejection of Liver Allografts

The underlying causes of chronic rejection (CR) after liver transplantation (LT) are not completely known. The main aim of this study was to explore the involvement of the minor histocompatibility antigen glutathione S-transferase T1 (GSTT1) in CR. We retrospectively studied 611 patients who underwent LTs at University Hospital Virgen del Rocío between 2003 and 2016 with a median follow-up of 7.4 ± 4.2 years. The GSTT1 genotype was determined by polymerase chain reaction. We defined GSTT1 mismatch as a specific donor/recipient combination in which a recipient who was homozygous for the deletion allele received a transplant from a positive donor. The prevalence of CR in our whole cohort was 11.6% (71/611), and the prevalence in the GSTT1-mismatched group was 18.8% (16/85) versus 10.5% (55/526) in the GSTT1-matched group. In the cyclosporine A (CsA) group, the prevalence was 26.3% (26/99), much higher than the 8.8% (45/512) observed in the tacrolimus (Tac) group. For statistical analysis, the patients were distributed into 2 groups: group 1, regarded as GSTT1 mismatched, which included the donor (D)+/recipient (R)- allelic combination; and group 2, regarded as GSTT1 matched, which included the other allelic combinations of D+/R+, D-/R-, and D-/R+. All relevant clinical information was collected, and a diagnosis of CR was always confirmed by liver biopsy. GSTT1 mismatch (hazard ratio [HR], 1.99; 95% confidence interval [CI], 1.08-3.66; P = 0.03) and use of CsA/Tac (P < 0.001) were independent risk factors for CR. CR increased the risk of mortality (HR, 2; 95% CI, 1.2-3.6; P = 0.01). Out of the 71 CR patients, 12 (16.9%) needed retransplantation. In conclusion, the GSTT1 D+/R- allelic mismatch is an independent risk factor for CR. A long follow-up of LT patients is recommended because the incidence of CR in adults seems to be underestimated.

Rethinking de novo immune hepatitis, an old concept for liver allograft rejection: Relevance of glutathione S-transferase T1 mismatch

Antibody-mediated rejection (AMR) in liver transplantation has long been underestimated. The concept of the liver as an organ susceptible to AMR has emerged in recent years, not only in the context of the major histocompatibility complex with the presence of HLA donor-specific antibodies, but also with antigens regarded as “minor”, whose role in AMR has been demonstrated. Among them, antibodies against glutathione S-transferase T1 have been found in 100% of patients with de novo autoimmune hepatitis (dnAIH) when studied. In its latest update, the Banff Working Group for liver allograft pathology proposed replacing the term dnAIH with plasma cell (PC)-rich rejection. Antibodies to glutathione S-transferase T1 (GSTT1) in null recipients of GSTT1 positive donors have been included as a contributory but nonessential feature of the diagnosis of PC-rich rejection. Also in this update, non-organ-specific anti-nuclear or smooth muscle autoantibodies are no longer included as diagnostic criteria. Although initially found in a proportion of patients with PC-rich rejection, the presence of autoantibodies is misleading since they are not disease-specific and appear in many different contexts as bystanders. The cellular types and proportions of the inflammatory infiltrates in diagnostic biopsies have been studied in detail very recently. PC-rich rejection biopsies present a characteristic cellular profile with a predominance of T lymphocytes and a high proportion of PCs, close to 30%, of which 16.48% are IgG4⁺. New data on the relevance of GSTT1-specific T lymphocytes to PC-rich rejection will be discussed in this review.

Antibody-mediated rejection: what is the clinical relevance?

PURPOSE OF REVIEW

The review outlines the diagnosis, clinical implications, and treatment strategies for acute and chronic antibody-mediated rejection (AMR) after orthotopic liver transplantation (OLT).

RECENT FINDINGS

A combination of clinical work-up, histopathology, C4d staining, and donor-specific antibody (DSA) should be used to diagnose AMR. The differential diagnosis for idiopathic fibrosis now includes chronic AMR. Characterization of pathogenic DSA continues to progress. De-novo and persistent DSA, particularly of the IgG3 subtype, are associated with inferior long-term outcomes.The liver allograft may confer long-term immunologic benefits to the kidney allograft after simultaneous liver-kidney transplant.The more widespread use of rituximab has improved outcomes in ABO-incompatible OLT.Although larger long-term studies of treatment options are needed, compliance with tacrolimus-based immunosuppression and transfusion minimization are agreed upon preventive strategies.

SUMMARY

AMR has evolved into an established pathology in OLT recipients. Acute AMR may lead to early graft loss whereas chronic AMR results in progressive fibrosis if unrecognized. DSAs, likely in the setting of predisposing environmental factors, appear to play a role in T cell-mediated rejection and long-term graft outcomes.

Antibody-Mediated Rejection After Liver Transplant

Antibody-mediated rejection (AMR) in liver transplants is a field in its infancy compared with its allograft cohorts of the kidney and lung. Acute AMR is diagnosed based on specific clinical and histopathologic criteria: serum donor specific antibodies, C4d staining, histopathologic findings on liver biopsy, and exclusion of other entities. In contrast, the histologic features of chronic AMR are not as specific and it is a more challenging diagnosis to make. Treatments of acute and chronic AMR include some combination of steroids, immune-modulating agents, intravenous immunoglobulin, plasmapheresis, and proteasome inhibitors.

Autoimmune Hepatitis in the Liver Transplant Graft

Recurrent autoimmune hepatitis (AIH) and de novo AIH are 2 important causes of late graft failure after liver transplantation (LT). Recurrent AIH occurs in patients who undergo LT for AIH. De novo AIH occurs in patients who are transplanted for etiologies other than AIH. Although typically treated with standard treatment for AIH, including corticosteroids and azathioprine, both recurrent and de novo AIH may progress to end-stage liver disease requiring retransplantation.

2016 Comprehensive Update of the Banff Working Group on Liver Allograft Pathology: Introduction of Antibody-Mediated Rejection

The Banff Working Group on Liver Allograft Pathology reviewed and discussed literature evidence regarding antibody-mediated liver allograft rejection at the 11th (Paris, France, June 5-10, 2011), 12th (Comandatuba, Brazil, August 19-23, 2013), and 13th (Vancouver, British Columbia, Canada, October 5-10, 2015) meetings of the Banff Conference on Allograft Pathology. Discussion continued online. The primary goal was to introduce guidelines and consensus criteria for the diagnosis of liver allograft antibody-mediated rejection and provide a comprehensive update of all Banff Schema recommendations. Included are new recommendations for complement component 4d tissue staining and interpretation, staging liver allograft fibrosis, and findings related to immunosuppression minimization. In an effort to create a single reference document, previous unchanged criteria are also included.

Prevention and treatment of liver allograft antibody-mediated rejection and the role of the 'two-hit hypothesis'

PURPOSE OF REVIEW

The review outlines the diagnosis, prevention strategies, and possible treatment options for acute and chronic antibody-mediated rejection (AMR).

RECENT FINDINGS

Although rare, severe acute AMR (aAMR) usually occurs in patients with high mean fluorescence intensity despite serial dilutions or high-titer preformed class I donor-specific alloantibodies (DSA). The diagnosis is suspected when allograft dysfunction occurs with DSA, diffuse C4d staining, and a microvascular injury, and may be aided by the aAMR score. However, the incidence of and treatment approach to combined T-cell-mediated rejection (TCMR) with DSA present and some but not all features of AMR is yet to be determined. Chronic liver allograft AMR is characterized by low-grade chronic inflammation and progressive fibrosis with DSA, the chronic AMR (cAMR) score may facilitate diagnosis. The 'two-hit' hypothesis, whereby a coexistent insult upregulates human leukocyte antigen class II target antigens on the microvascular endothelium, may explain why suboptimal donors with lower sensitization levels might suffer from acute AMR and those with chronic complications (e.g., recurrent original disease) might be more susceptible to chronic AMR. Although treatment algorithms are needed, prevention is preferable and at a minimum includes transfusion minimization, and medication adherence.

SUMMARY

Severe acute AMR is rare but diagnosable, and there is need to determine the incidence of and optimal therapy for less severe combined AMR and TCMR. Chronic AMR is likely more common and of significant relevance to long-term allograft survival improvement. The two-hit hypothesis may help to explain the rarity of both findings and shed insight onto future prevention and treatment strategies.

Donor-Specific HLA Antibodies in Living Versus Deceased Donor Liver Transplant Recipients

With less ischemia, improved donor selection and controlled procedures, living donor liver transplantation (LDLT) might lead to less HLA donor-specific antibody (DSA) formation or fewer adverse outcomes than deceased donor liver transplantation (DDLT). Using the multicenter A2ALL (Adult-to-Adult Living Donor Liver Transplantation Cohort Study) biorepository, we compared the incidence and outcomes of preformed and de novo DSAs between LDLT and DDLT. In total, 129 LDLT and 66 DDLT recipients were identified as having serial samples. The prevalence of preformed and de novo DSAs was not different between DDLT and LDLT recipients (p = 0.93). There was no association between patient survival and the timing (preformed vs. de novo), class (I vs. II) and relative levels of DSA between the groups; however, preformed DSA was associated with higher graft failure only in DDLT recipients (p = 0.01). De novo DSA was associated with graft failure regardless of liver transplant type (p = 0.005) but with rejection only in DDLT (p = 0.0001). On multivariate analysis, DSA was an independent risk factor for graft failure regardless of liver transplant type (p = 0.017, preformed; p = 0.002, de novo). In conclusion, although similar in prevalence, DSA may have more impact in DDLT than LDLT recipients. Although our findings need further validation, future research should more robustly test the effect of donor type and strategies to mitigate the impact of DSA.

Autoimmune Liver Disease Post-Liver Transplantation: A Summary and Proposed Areas for Future Research

Autoimmune liver diseases (AILD) are rare diseases with a reported prevalence of less than 50 per 100 000 population. As the research landscape and our understanding of AILDs and liver transplantation evolves, there remain areas of unmet needs. One of these areas of unmet needs is prevention of disease recurrence after liver transplantation. Disease recurrence is not an insignificant event because allograft loss with the need for retransplantation can occur. Patients transplanted for AILD are more likely to experience acute rejection compared to those transplanted for non-AILD, and the reason(s) behind this observation is unclear. Tasks for the future include a better understanding of the pathogenesis of AILD, definition of the precise pathogenetic mechanisms of recurrent AILD, and development of strategies that can identify recipients at risk for disease recurrence. Importantly, the role of crosstalk between alloimmune responses and autoimmune responses in AILD is an important area that needs further study.

This article reviews the relevant literature of de novo autoimmune hepatitis, recurrent autoimmune hepatitis, recurrent primary sclerosing cholangitis, and recurrent primary biliary cirrhosis in terms of the clinical entity, the scientific advancements, and future scientific goals to enhance our understanding of these diseases.

A review of the relevant literature of de novo autoimmune hepatitis, recurrent autoimmune hepatitis, recurrent primary sclerosing cholangitis, and recurrent primary biliary cirrhosis in terms of the clinical entity, the scientific advancements and future scientific goals to enhance our understanding of these diseases.

Production of Proinflammatory Cytokines by Monocytes in Liver-Transplanted Recipients with De Novo Autoimmune Hepatitis Is Enhanced and Induces TH1-like Regulatory T Cells

A subset of human regulatory T cells (Tregs) can secrete IFN-γ or IL-17, and thus share features of TH1 or TH17 effector cells and lose suppressive function. The main factors driving this differentiation of Tregs toward a proinflammatory phenotype include IL-12 for TH1-like and IL-6 for TH17-type Tregs. In this study we show that Tregs of patients with de novo autoimmune hepatitis (dAIH) display increased frequencies of proinflammatory IFN-γ and IL-17 cytokines. Irrespective of a fully demethylated FOXP3 locus, Tregs of subjects with dAIH are functionally impaired. In line with the observed Treg phenotype, we detected the presence of two dominant cytokines (IL-12 and IL-6) clustering with CD68(+) monocyte/macrophage cells in livers of subjects with dAIH, and isolated monocytes of subjects with dAIH secrete high levels of proinflammatory IL-12 and IL-6, suggesting that this inflammatory milieu is key for functional impairment of Tregs. Importantly, the blockade of IFN-γ partially restores suppressive function of Tregs of subjects with dAIH, indicating that monocyte/macrophage-derived triggers might play a central role in Treg dysfunction and pathogenesis of dAIH.

De novo autoimmune hepatitis in liver transplant: State-of-the-art review

In the two past decades, a number of communications, case-control studies, and retrospective reports have appeared in the literature with concerns about the development of a complex set of clinical, laboratory and histological characteristics of a liver graft dysfunction that is compatible with autoimmune hepatitis. The de novo prefix was added to distinguish this entity from a pre-transplant primary autoimmune hepatitis, but the globally accepted criteria for the diagnosis of autoimmune hepatitis have been adopted in the diagnostic algorithm. Indeed, de novo autoimmune hepatitis is characterized by the typical liver necro-inflammation that is rich in plasma cells, the presence of interface hepatitis and the consequent laboratory findings of elevations in liver enzymes, increases in serum gamma globulin and the appearance of non-organ specific auto-antibodies. Still, the overall features of de novo autoimmune hepatitis appear not to be attributable to a univocal patho-physiological pathway because they can develop in the patients who have undergone liver transplantation due to different etiologies. Specifically, in subjects with hepatitis C virus recurrence, an interferon-containing antiviral treatment has been indicated as a potential inception of immune system derangement. Herein, we attempt to review the currently available knowledge about de novo liver autoimmunity and its clinical management.

ABO-compatible liver allograft antibody-mediated rejection: an update

PURPOSE OF REVIEW

Liver allograft antibody-mediated rejection (AMR) studies have lagged behind parallel efforts in kidney and heart because of a comparative inherent hepatic resistance to AMR. Three developments, however, have increased interest: first, solid phase antibody testing enabled more precise antibody characterization; second, increased expectations for long-term, morbidity-free survival; and third, immunosuppression minimization trials.

RECENT FINDINGS

Two overlapping liver allograft AMR phenotypic expressions are beginning to emerge: acute and chronic AMR. Acute AMR usually occurs within the several weeks after transplantation and characterized clinically by donor-specific antibodies (DSA) persistence, allograft dysfunction, thrombocytopenia, and hypocomplementemia. Acute AMR appears histopathologically similar to acute AMR in other organs: diffuse microvascular endothelial cell hypertrophy, C4d deposits, neutrophilic, eosinophilic, and macrophag-mediated microvasculitis/capillaritis, along with liver-specific ductular reaction, centrilobular hepatocyte swelling, and hepatocanalicular cholestasis often combined with T-cell-mediated rejection (TCMR). Chronic AMR is less well defined, but strongly linked to serum class II DSA and associated with late-onset acute TCMR, fibrosis, chronic rejection, and decreased survival. Unlike acute AMR, chronic AMR is a slowly evolving insult with a number of potential manifestations, but most commonly appears as low-grade lymphoplasmacytic portal and perivenular inflammation accompanied by unusual fibrosis patterns and variable microvascular C4d deposition; capillaritis can be more difficult to identify than in acute AMR.

SUMMARY

More precise DSA characterization, increasing expectations for long-term survival, and immunosuppression weaning precipitated a re-emergence of liver allograft AMR interest. Pathophysiological similarities exist between heart, kidney, and liver allografts, but liver-specific considerations may prove critical to our ultimate understanding of all solid organ AMR.

Quantification of C4d deposition and hepatitis C virus RNA in tissue in cases of graft rejection and hepatitis C recurrence after liver transplantation

Histology is the gold standard for diagnosing acute rejection and hepatitis C recurrence after liver transplantation. However, differential diagnosis between the two can be difficult. We evaluated the role of C4d staining and quantification of hepatitis C virus (HCV) RNA levels in liver tissue. This was a retrospective study of 98 liver biopsy samples divided into four groups by histological diagnosis: acute rejection in patients undergoing liver transplant for hepatitis C (RejHCV+), HCV recurrence in patients undergoing liver transplant for hepatitis C (HCVTx+), acute rejection in patients undergoing liver transplant for reasons other than hepatitis C and chronic hepatitis C not transplanted (HCVTx-). All samples were submitted for immunohistochemical staining for C4d and HCV RNA quantification. Immunoexpression of C4d was observed in the portal vessels and was highest in the HCVTx- group. There was no difference in C4d expression between the RejHCV+ and HCVTx+ groups. However, tissue HCV RNA levels were higher in the HCVTx+ group samples than in the RejHCV+ group samples. Additionally, there was a significant correlation between tissue and serum levels of HCV RNA. The quantification of HCV RNA in liver tissue might prove to be an efficient diagnostic test for the recurrence of HCV infection.

Positive C4d staining of the portal vein endothelium in the liver of patients with biliary atresia: a role of humoral immunity in ongoing liver fibrosis

PURPOSE

This study aimed to clarify the role of complement activation in fibrogenesis in BA.

METHODS

In total, 27 paraffin-embedded liver biopsy samples were immunohistochemically analyzed using C4d polyclonal antibody, vascular cell adhesion molecule-1 (VCAM-1), and CD45. The liver samples were obtained from 25 patients during Kasai operation, and two additional specimens were obtained from 2 patients by needle biopsy later at the time of liver function deterioration. The degree of liver fibrosis was histologically graded 1-3.

RESULTS

Among the 25 samples, 9 showed C4d-positive immunostaining localized on the endothelia of a few portal veins in the portal tract. The degree of fibrosis was correlated with C4d staining (p = 0.025). The age at Kasai operation correlated with the degree of fibrosis and the C4d positivity. Two needle biopsy samples were positive for C4d. Among 13 samples submitted for VCAM-1 staining, 2 negative samples were C4d negative and all positive C4d samples were VCAM-1 positive with CD45 mononuclear cell infiltration.

CONCLUSION

These findings suggest that ongoing cirrhosis could be a result of progressive "vasculopathy" of the portal vein caused by humoral and cell-mediated immune interaction.

Long term outcomes after pediatric liver transplantation

Long term outcomes after liver transplantation are major determinants of quality of life and of the value of this heroic treatment. As short term outcomes are excellent, our community is turning to take a harder look at long term outcomes. The purpose of this paper is to review these outcomes, and highlight proposed treatments, as well as pressing topics needing to be studied. A systemic review of the English literature was carried in PubMed, covering all papers addressing long term outcomes in pediatric liver transplant from 2000-2013. Late outcomes after pediatric liver transplant affect the liver graft in the form of chronic liver dysfunction. The causes include rejection particularly humoral rejection, but also de novo autoimmune hepatitis, and recurrent disease. The metabolic syndrome is a major factor in long term cardiovascular complication risk. Secondary infections, kidney dysfunction and malignancy remain a reality of those patients. There is growing evidence of late cognitive and executive function delays affecting daily life productivity as well as likely adherence. Finally, despite a good health status, quality of life measures are comparable to those of children with chronic diseases. Long term outcomes are the new frontier in pediatric liver transplantation. Much is needed to improve graft survival, but also to avoid systemic morbidities from long term immunosuppression. Quality of life is a new inclusive measure that will require interventions and innovative approaches respectful not only on the patients but also of their social circle.

Clinical relevance of human leukocyte antigen antibodies in liver, heart, lung and intestine transplantation

PURPOSE OF REVIEW

Solid phase assays identify human leukocyte antigen (HLA) antibodies with a great sensitivity. Whether to accept or decline an organ if the virtual crossmatch is positive, when to monitor and whether to treat de-novo donor-specific antibody (DSA) posttransplant remain challenging issues for the transplant clinician.

RECENT FINDINGS

Technologies that can differentiate which antibodies pose the greatest risk for antibody-mediated rejection (AMR) are evolving. Complement fixing luminex assays have been used to predict high-risk antibodies, but using these assays alone will miss some preformed antibodies. How these technologies fit into the laboratory's testing algorithm will likely need to be individualized. Posttransplant de-novo DSAs are associated with inferior outcomes. In hearts, similar to renal transplantation, acute rejection is a risk factor for developing de-novo DSA. Further data are needed to determine whether other risk factors are similar to those reported for renal transplants. Antibodies to self-antigens are increasingly recognized posttransplant and how the alloimmune response contributes to altered autoregulation is a current research focus.

SUMMARY

Identification of DSA enables the clinician to make informed decisions regarding whether or not to accept an organ and if augmented immunosuppression is indicated. Monitoring for DSA posttransplant identifies recipients at a greater risk for AMR and can guide management. However, the best approach to dealing with de-novo DSA remains unclear.

Impact of donor-specific antibodies on results of liver transplantation

PURPOSE OF REVIEW

To critically examine the recent literature evaluating the importance of HLA donor-specific antibody (DSA) impact on liver transplant and simultaneous liver-kidney transplant (SLKT) outcomes.

RECENT FINDINGS

Many preformed DSAs, especially of low mean fluorescence intensity (MFI), are absorbed by the liver at transplant. However, patients with post-liver transplant DSA, especially of higher MFI, are at increased risk of acute and chronic rejection. C4d staining, when positive, may be helpful but lacks sensitivity especially in formalin tissue. SLKT recipients may need close follow-up when class II DSA is found, as the liver protects the kidney from hyperacute rejection, but can still cause early renal antibody-mediated rejection, liver allograft rejection, and impair patient, liver allograft, and renal allograft survival.

SUMMARY

Some DSAs are relevant in liver transplant and can lead to acute and chronic allograft rejection. However, before clinical practice patterns can change we must create unified diagnostic criteria, define the pathologic potential of different DSAs, and improve the specificity of current testing.

Tissue biopsy monitoring of operational tolerance in liver allograft recipients

PURPOSE OF REVIEW

Highly selected, long-surviving, liver allograft recipients with normal/near normal liver injury tests can be weaned from immunosuppression. Baseline biopsies document changes before weaning and can help stratify risk of rejection or dysfunction after weaning; biopsies after weaning are used to study mechanisms of operational tolerance and to monitor for subclinical events.

RECENT FINDINGS

Clinicopathological features associated with successful weaning include a lack of sensitization [negative donor-specific antibodies (DSA) and lack of tissue C4d deposits]; 'inexperienced' recipient immune system with limited potential for cross-reactivity (less immunological memory; infant recipients); noninflamed allograft in those with nonviral, nonimmunological original diseases; upregulation of liver genes associated with iron metabolism; allograft colonization with 'immunosuppressive' cells (Treg and γδ-1>γδ-2); and longer time on immunosuppression, which might signal slow clonal deletion or silencing. The differential diagnosis of histopathological findings detected before and after weaning includes emerging infections, typical and atypical cellular rejection, indolent antibody-mediated rejection, 'autoimmunity', and other causes of progressive fibrosis.

SUMMARY

Operationally tolerant liver allograft recipients can be successfully managed with very low, and sometimes no immunosuppression, but challenges exist. Newer approaches to tissue pathology and tissue, serum, and cross-platform analytics are needed to predict successful weaning and to monitor for subclinical events.

Plasma cell hepatitis (de-novo autoimmune hepatitis) developing post liver transplantation

PURPOSE OF REVIEW

Cases of de-novo autoimmune hepatitis/plasma cell hepatitis (PCH) are increasingly being diagnosed by liver transplant centers. Its pathogenesis is poorly understood but this entity appears to be a variant of rejection. Herein, we review recent clinical reports of patients developing PCH.

RECENT FINDINGS

Histologically, PCH is a challenging diagnosis, especially in the setting of recurrent hepatitis C and, in some cases, can be mistaken for acute cellular rejection. Recent case reports and case-control studies have shown that interferon appears to trigger PCH in hepatitis C posttransplant patients. Optimization of the immunosuppression regimen was found to prevent the development of PCH. In the nonhepatitis C posttransplant patient, tacrolimus-based immunosuppression appears to have some protective effect from PCH development. A combination therapy of cyclosporine and everolimus has also been shown to be effective in treating PCH.

SUMMARY

PCH is a variant of rejection and is a cause of late graft loss post liver transplantation, especially in patients with hepatitis C. It should be part of the differential diagnosis of abnormal liver enzyme tests occurring in the post-liver transplant setting.

Antibody-mediated rejection in the liver allograft

PURPOSE OF REVIEW

There is increasing evidence to suggest that antibody-mediated mechanisms play a role in the pathogenesis of liver allograft rejection. This article will review the pathology of antibody-mediated rejection (AMR) focusing on recent studies which have improved our understanding of the clinicopathological features and diagnostic approaches.

RECENT FINDINGS

Recent studies have investigated the patterns of immunohistochemical staining for C4d as a tissue marker of AMR in posttransplant biopsies, and have correlated these findings with other histopathological changes and with the presence of donor-specific antibodies (DSAs). These studies have highlighted the diagnostic applications and limitations of C4d immunostaining. They have also emphasized the importance of using strict criteria for defining 'pure' AMR in the liver allograft - that is, graft dysfunction associated with compatible histological findings (typically resembling biliary obstruction), the presence of DSAs and diffusely positive staining for C4d.

SUMMARY

Pure AMR is relatively uncommon in ABO-compatible grafts - it should be diagnosed on the basis of strict criteria and requires treatment with antibody-depleting immunosuppression. C4d immunostaining in isolation has limited diagnostic value. However, the presence of diffuse C4d immunostaining (involving endothelium or stroma in >50% of portal tracts or sinusoids) suggests a significant component of antibody-mediated graft damage. In a person with suggestive histological features, this finding should prompt testing for DSAs. Even in the absence of typical histological features of AMR, the combined presence of DSAs and diffuse C4d positivity is associated with more frequent or severe acute and chronic rejection, which may also warrant treatment with antibody-depleting immunosuppression.

Low-dose steroids associated with milder histological changes after pediatric liver transplantation

Controversy remains about the role of protocol liver biopsy for symptom-free recipients and about the long-term use of low-dose steroids after pediatric liver transplantation (LT). We conducted a national cross-sectional study of pediatric recipients who underwent LT between 1987 and 2007. Liver biopsy samples were taken from 54 patients (82% of survivors) after a median posttransplant follow-up of 11 years, and they were reviewed by 2 pathologists blinded to the clinical data. Biopsy samples from 18 patients (33%) showed nearly normal histology with no inflammation, fibrosis, or steatosis. Portal inflammation was detected in 14 samples (26%), showed no correlation with anti-nuclear antibodies, and was less frequent in the 35 patients whose immunosuppression included steroids (14% versus 47% of patients not using steroids, P = 0.008). Fibrosis was present in 21 biopsy samples (39%). According to the Metavir classification, 16 were stage 1, 3 were stage 2, and 2 were stage 3. The fibrosis stage correlated negatively with serum prealbumin levels (r = -0.364, P = 0.007) and positively with chronic cholestasis (cytokeratin 7 staining; r = 0.529, P < 0.001) and portal inflammation (r = 0.350, P = 0.01). Microvesicular steatosis was found in 23 biopsy samples (43% of patients in 5%-80% of hepatocytes), and it correlated with the body mass index (r = 0.458, P < 0.001) but not with steroid use. The age of the allograft (donor age plus follow-up time) correlated with higher serum gamma-glutamyltransferase (r = 0.472, P < 0.001) and conjugated bilirubin levels (r = 0.420, P = 0.002) as well as chronic cholestasis (r = 0.299, P = 0.03). The biopsy findings led to treatment changes in 10 patients (19%), whereas only 1 complication (subcapsular hematoma) was encountered. In conclusion, continuing low-dose steroids indefinitely after pediatric LT may have a positive effect on the long-term histological state of the liver graft. Allograft aging may lead to chronic cholestasis and thus contribute to the development of liver fibrosis.

Sinusoidal C4d deposits in liver allografts indicate an antibody-mediated response: diagnostic considerations in the evaluation of liver allografts

There is a paucity of data concerning the correlation of complement component 4d (C4d) staining in liver allografts and antibody-mediated rejection. Data about the location and character of C4d deposits in native and allograft liver tissues are inconsistent. We performed C4d immunofluorescence (IF) on 141 fresh-frozen liver allograft biopsy samples and native livers, documented the pattern of C4d IF staining, and correlated the findings with the presence of donor-specific alloantibodies (DSAs). A linear/granular sinusoidal pattern of C4d IF was noted in 18 of 28 biopsy samples obtained after transplantation from patients with positive crossmatch and detectable donor-specific alloantibody (pos-XM/DSA) findings. None of the 59 tested biopsy samples from patients with negative crossmatch and detectable donor-specific alloantibody (neg-XM/DSA) findings were C4d-positive (P < 0.001). No significant association was found between pos-XM/DSA and C4d IF staining in other nonsinusoidal liver compartments. To compare the results of sinusoidal C4d staining with IF and 2 immunohistochemistry (IHC) techniques, C4d IHC was performed on 19 liver allograft biopsy samples in which a sinusoidal pattern of C4d IF had been noted. Sinusoidal C4d IHC findings were negative for 17 of the 19 biopsy samples; 2 showed weak and focal staining, and both patients had pos-XM/DSA findings. Portal vein endothelium staining was present in only 1 IF-stained biopsy sample (pos-XM/DSA) but in 11 IHC-stained biopsy samples (2 of the 11 samples had neg-XM/DSA findings). We conclude that sinusoidal C4d deposits detected by IF in frozen tissue samples from liver allograft recipients correlate with the presence of DSAs and an antibody-mediated alloresponse. These observations are similar to findings reported for other solid organ transplants and can provide relevant information for patient management. Further validation of IHC techniques for C4d detection in liver allograft tissue is required.