Acute, Chronic, and Humoral Rejection: Pathologic Features Under Current Immunosuppressive Regimes

Pre-transplant Use of Immune Checkpoint Inhibitors for Hepatocellular Carcinoma: A Multicenter, Retrospective Cohort Study

Immune checkpoint inhibitors (ICIs) as a downstaging or bridging therapy for liver transplantation (LT) in hepatocellular carcinoma (HCC) patients is rapidly increasing. However, the evidence about the feasibility and safety of pre-LT ICIs therapy is limited and controversial. To this end, a multicenter, retrospective cohort study was conducted in 11 Chinese centers. The results showed that 83 recipients received pre-LT ICIs therapy during the study period. The median post-LT follow up was 8.1 (interquartile range [IQR] 3.3-14.6) months. During the short follow-up, 23 (27.7%) recipients developed allograft rejection, and 7 of them (30.4%) was diagnosed by liver biopsy. Multivariate logistics regression analysis showed that time interval between the last administration of ICIs therapy and LT (TLAT) ≥ 30 days was an independent protective factor for allograft rejection (OR = 0.096, 95%CI 0.026-0.357; P < 0.001). Multivariate Cox analysis showed that allograft rejection was an independent risk factor for overall survival (OS) (HR = 9.960, 95%CI 1.006-98.610; P = 0.043). We conclude that patients who receive a pre-LT ICIs therapy with a TLAT shorter than 30 days have a much higher risk of allograft rejection than those with a TLAT longer than 30 days. The presence of rejection episodes might be associated with a higher post-LT mortality.

Boosting regulatory T cell-dependent immune tolerance by activation of p53

Regulatory T cells (Tregs) have critical roles in maintaining immune hemostasis and have important anti-inflammatory functions in diseases. Recently, we identified that CX-5461 (a selective RNA polymerase I inhibitor and p53 activator) acted as a potent immunosuppressive agent, which prevented allogeneic acute rejection in animal models via a molecular mechanism distinct from all those of conventional immunosuppressive drugs. Unexpectedly, we discovered that CX-5461 could promote Treg differentiation. In this review, we have summarized the evidence for a potential role of p53 in mediating Treg differentiation and its possible mechanisms, including regulation of FoxP3 transcription, regulation of the expression of PTEN (phosphatase and tensin homolog), as well as protein-protein interaction with the transcription factor STAT5 (signal transducer and activator of transcription 5). Evidence also suggests that pharmacological p53 activators may potentially be used to boost Treg-mediated immune tolerance. Based on these data, we argue that novel p53 activators such as CX-5461 may represent a distinct class of immunosuppressants that repress conventional T cell-mediated alloimmunity with concomitant boosting of Treg-dependent immune tolerance.

Application of Immune Checkpoint Inhibitors in Solid Organ Transplantation Recipients: A Systematic Review

BACKGROUND

Solid organ transplantation (SOT) is a treatment method for end-stage organ diseases and improve their life quality, while using long-term immunosuppressant drugs (ISD) is needed to suppress the function of the immune system. Immune checkpoint inhibitors (ICIs) are a class of anti-tumor drugs that kill tumors by activating the autoimmune system. The primary objective of our systematic review is to investigate the risk factors for organ rejection and the efficacy of ICIs in solid organ transplantation recipients (SOTRs).

METHODS

We searched four databases to find relevant articles up to January 2021. A total of 61 articles involving 106 SOTRs met the screening criteria and were included in our systematic review. The collected data were statistical described, and the risk factors were analyzed by logistic regression.

RESULTS

Forty-four patients (41.5%) developed host-versus-graft response (HVGR) after ICIs. mTOR inhibitors (pre-ICIs) (p = 0.069, OR = 0.377, 95% CI 0.132-1.078) and calcineurin inhibitors (post-ICIs) (p = 0.056, OR = 0.375, 95%CI 0.137-1.025) may help reduce the incidence of HVGR. Hormones (pre-ICIs) (p = 0.026, OR = 3.150, 95%CI 1.150-8.628) and anti-metabolites (pre-ICIs) (p = 0.022, OR = 3.214, 95%CI 1.185-8.720) may adversely affect the efficacy of ICIs. Only 35.6% of patients both responded well to ICIs treatment and did not develop HVGR.

CONCLUSIONS

Our systematic review summarizes the use of ICIs in SOTRs and evaluates the efficacy of ICIs and the risk factors that induce HVGR. Through risk factor analysis, we found that mTOR inhibitors and calcineurin inhibitors may help to reduce the occurrence of HVGR; hormones and anti-metabolic drugs may have adverse effects on the efficacy of ICIs. In addition, there is a contradictory relationship between the occurrence of HVGR and the efficacy of ICIs.

Immunostaining Patterns of Posttransplant Liver Biopsies Using 2 Anti-C4d Antibodies

Histopathologic diagnosis of antibody-mediated rejection in posttransplant liver biopsies is challenging. The recently proposed diagnostic criteria by the Banff Working Group on Liver Allograft Pathology require positive C4d immunohistochemical staining to establish the diagnosis. However, the reported C4d staining patterns vary widely in different studies. One potential explanation may be due to different antibody preparations used by different investigators. In this study, posttransplant liver biopsies from 69 patients histopathologically diagnosed with acute cellular rejection, chronic rejection, or recurrent hepatitis C were immunohistochemically stained using 2 polyclonal anti-C4d antibodies. On the basis of the distribution of C4d immunoreactivity, 5 different staining patterns were observed: portal vein and capillary, hepatic artery, portal stroma, central vein, and sinusoids. The frequency, extent, and intensity of positive C4d staining with the 2 antibody preparations differed significantly for portal veins/capillaries and central veins, but not for hepatic arteries and portal stroma. Positive sinusoidal staining was seen in only 1 case. There were no significant differences in the frequency, extent, and intensity of positive C4d staining among the acute cellular rejection, chronic rejection, and recurrent hepatitis C groups with the 2 anti-C4d antibodies. These data show that different anti-C4d antibodies can show different staining patterns, which may lead to different interpretation. Caution is thus needed when selecting C4d antibodies for clinical use to aid in the diagnosis of antibody-mediated rejection.

Recipient risk factors for acute cellular rejection after orthotopic liver transplant - a single-center, retrospective study

The use of model for end-stage liver disease (MELD) score for liver allocation has resulted in transplanting sicker patients. As such, it is unclear whether the risk factors and severity of acute cellular rejection (ACR) have changed. To identify ACR characteristics where average MELD score at transplant is higher than previously published studies. This is a single-center, retrospective study designed to assess risk factors associated with ACR after adult orthotopic liver transplant (OLT) using a steroid sparing regimen. This study included 174 OLT patients transplanted from 2008 to 2013 at a single tertiary care center. Recipient demographics, preoperative clinical, and laboratory data were recorded for each transplant. Univariate and multivariate regression analyses were performed to identify variables that are significant predictors for ACR. The median MELD at transplantation was 29.5. The average time from transplant to ACR diagnosis was 283.9 days and a majority of ACR episodes were mild to moderate. Serum creatinine, primary sclerosing cholangitis etiology, and tacrolimus use were significant predictors for ACR (P < 0.05). This study confirmed a change in timing and severity of ACR in the MELD era. Recipient characteristics may affect the risk for developing ACR and should be considered when managing immunosuppression.

[Liver transplantation. Current aspects of pretransplantation diagnosis and rejection]

Liver transplantation is an established treatment option for patients with end-stage liver disease. The therapy management of these patients is interdisciplinary and requires pathologists to have both clinical and immunological knowledge. Continuous advances in treatment and increasing clinical experience are accompanied by the further development of pathological transplant diagnostics. This article presents and discusses the latest classification of T‑cell-mediated rejection (TCMR), antibody-mediated rejection (AMR), and aspects of pretransplant diagnostics.

Intrahepatic Microdialysis for Monitoring of Metabolic Markers to Detect Rejection Early After Liver Transplantation

OBJECTIVES

The clinical and biochemical manifestations of acute rejection after liver transplantation are nonspecific, and a liver biopsy is often needed to verify the diagnosis. This may delay treatment. The aim of this study was to evaluate whether monitoring of intrahepatic glucose, lactate, pyruvate, and glycerol by microdialysis can be used to predict rejection early after liver transplantation.

METHODS

Seventy-one patients undergoing liver transplantation were included in the study. The patients were monitored using microdialysis for up to 6 days postoperatively. Patients who developed acute rejection within 1 month were identified according to standard protocol. Area under the curve (AUC) was calculated for 12-hour intervals for glucose, lactate, pyruvate, glycerol, and lactate/pyruvate ratio. Patients with and without rejection were compared with respect to these parameters, as well as standard liver blood investigations and time-zero biopsies.

RESULTS

The lactate/pyruvate ratio was higher at 0 to 12 hours in the group with rejection as compared to the group without rejection. Glucose was lower in the group with rejection at 24 to 48 hours. Also, the intrahepatic lactate levels at 48 to 72 hours and pyruvate levels at 60 to 72 hours after liver transplantation, were higher in the rejection group. The lactate/pyruvate ratio at 0 to 12 hours and lactate at 60 to 72 hours were two independent risk factors for rejection within the first month after liver transplantation. No significant differences in glycerol levels could be detected between the two patient groups.

CONCLUSIONS

Microdialysis monitoring following liver transplantation may be useful in the detection of the metabolic events that precede rejection. The metabolic patterns detected by microdialysis early after transplantation indicate a possible relation between primary ischemia-reperfusion injury and the development of rejection. Identifying these patterns may help to identify patients at risk for the development of acute rejection and may help select those who may benefit from higher dose of immunosuppression early after liver transplantation.

A review of the use of transient elastography in the assessment of fibrosis and steatosis in the post-liver transplant patient

Liver biopsy is considered the gold standard method for diagnosing and staging liver disease, particularly in the post-liver transplant setting. Given the invasive nature of biopsy, alternate means for accurately assessing liver fibrosis and steatosis are preferred especially as the number of patients with fatty liver disease is increasing. Transient elastography has been validated as a useful tool for evaluation of liver fibrosis, as has controlled attenuation parameter index as a tool for assessing steatosis. It is a non-invasive, rapid, and highly reproducible approach to demonstrate the presence of fibrosis among non-transplant patients with chronic liver disease of various etiologies. However, it has not yet found wide acceptance in liver transplant recipients. There are few published studies evaluating the merits and applicability of transient elastography to assess allografts after liver transplantation. We review the published data on the use of transient elastography with concurrent controlled attenuation parameter in liver transplant recipients and recommend its greater use to follow allograft function over time.