Identification of pediatric activated T-cell hepatitis using clinical immune studies.

BACKGROUND AND AIMS: The majority of indeterminate pediatric acute liver failure (PALF) cases are secondary to immune dysregulation, labeled activated T-cell hepatitis (TCHep). We aimed to describe a cohort of children with acute severe hepatitis and PALF and define how clinical immune labs may help identify the TCHep group. METHODS: Retrospective review of children with acute hepatitis and PALF between March 2020 and August 2022. Patients were classified as known diagnosis, indeterminate hepatitis (IND-Hep), or TCHep (defined by liver biopsy with predominant CD8 T-cell inflammation or development of aplastic anemia). RESULTS: 124 patients were identified: 83 with known diagnoses, 16 with TCHep, and 25 with IND-Hep. Patients with TCHep had significantly increased median total bilirubin levels (7.5 mg/dL (IQR 6.8-8.9) vs 1.5 mg/dL (IQR 1.0-3.6), p < 0.0001), soluble interleukin-2 receptor levels (4512 IU/mL (IQR 4073-5771) vs 2997 IU/mL (IQR 1957-3237), p = 0.02), and percent of CD8+ T-cells expressing perforin (14.5 % (IQR 8.0-20.0) vs 1.0 % (IQR 0.8-1.0), p = 0.004) and granzyme (37.5 % (IQR 15.8-54.8) vs 4.0 % (IQR 2.5-5.5), p = 0.004) compared to IND-Hep patients. Clinical flow cytometry showed that TCHep patients had significantly increased percent CD8+ T cells (29.0 % (IQR 24.5-33.5) vs 23.6 % (IQR 19.8-25.8), p = 0.04) and HLA-DR+ (16.0 % (IQR 14.5-24.5) vs 2.7 (1.8-5.3), p < 0.001) compared to IND-Hep patients indicative of increase in CD8+ T cells that are activated. CONCLUSIONS: Peripheral blood clinical immune studies demonstrate increased markers of CD8 T-cell activation, proliferation, and cytotoxic function for TCHep patients. These readily available immune function labs can be used to help distinguish patients with TCHep from those with other causes. This provides a non-invasive tool for early detection of potential TCHep before progression to liver failure.

"Where Did This Come From?": Antibiotic Prophylaxis in Biliary Atresia After Kasai Procedure.

For patients with Biliary atresia, antibiotic prophylaxis after Kasai portoenterostomy is a common practice. Societal guidelines often cite one reference as supportive evidence for this practice. In this paper, we go back to review the quality of this evidence and suggest more research is required to demonstrate the efficacy of antibiotic prophylaxis in this population.

Immunosuppression minimization is safe and associated with good long-term success in pediatric recipients of liver transplant.

Immunosuppression reduction after liver transplant is an important strategy to mitigate long-term medication side effects. We describe our center's experience with immunosuppression minimization to once-daily calcineurin inhibitor dosing. Success was defined as continuing daily calcineurin inhibitor monotherapy with normal transaminases and no rejection. We performed a retrospective review of eligible children who received a liver transplant between 2009 and 2016, had a surveillance biopsy, and were on twice-daily calcineurin inhibitor monotherapy. Twenty-eight of 51 eligible patients were minimized to daily calcineurin inhibitor with goal 12-hour trough detectable. Nineteen patients (68%) had 1-year success, and 17 (61%) had long-term success at a median follow-up of 5.0 years (interquartile range (IQR): 2.9-6.6). Minimization failure occurred at a median of 0.6 years (IQR: 0.3-1.0) after dose reduction. Patients with long-term success had lower aspartate aminotransferase levels prior to minimization compared to those who failed with a median of 28.0 IU/L (IQR: 20.5-32.0) versus 32.0 IU/L (IQR: 30.0-37.0), p = 0.047. The long-term success group demonstrated a trend toward greater recipients of liver transplant from living donors (53% vs. 18%, p = 0.07). At the time of the last follow-up at a median of 5.0 years (IQR: 2.9-6.1) after surveillance biopsy, most (73%) patients who failed had returned to twice-daily calcineurin inhibitor monotherapy, all had liver enzymes <2 times the upper limit of normal, and there were no patient deaths or graft losses. In conclusion, immunosuppression minimization is safe in pediatric recipients of liver transplant and should be considered to reduce long-term medication side effects and improve patient quality of life. Future studies are necessary to follow long-term outcomes and develop biomarkers to predict minimization success.

Effector memory CD8 T-cells as a novel peripheral blood biomarker for activated T-cell pediatric acute liver failure.

A distinct phenotype of pediatric acute liver failure (PALF) has been identified, labeled activated T-cell hepatitis. These patients, previously included within the indeterminate group, have evidence of systemic immune activation and liver biopsy specimens with dense infiltration of CD8+ T-cells. We aimed to evaluate the peripheral blood T-cell phenotype in PALF patients with activated T-cell hepatitis compared to indeterminate cause. PALF patients with unknown etiology age 1-17 years were prospectively enrolled between 2017-2020. Within the unknown group, patients were classified as either activated T-cell hepatitis if they had a liver biopsy with dense or moderate CD8 staining and an elevated soluble interleukin-2 receptor level, or they were classified as indeterminate if they did not meet these criteria. Whole blood was collected for flow cytometry and T-cell phenotyping. Four patients with activated T-cell hepatitis and 4 patients with indeterminate PALF were enrolled. Activated T-cell hepatitis patients had significantly greater percentage of CD8 T-cells that were effector memory (TEM) phenotype compared to indeterminate PALF patients (median 66.8% (IQR 57.4-68.7) vs 19.1% (IQR 13.4-25.2), P = 0.03). In addition, CD8+ TEM cells in activated T-cell hepatitis patients were significantly more likely to be CD103 positive, a marker of tissue resident memory T-cells, compared to indeterminate PALF patients (median 12.4% (IQR 9.5-14.7) vs 4.7% (IQR 4.5-5.3), P = 0.03). We found patients with activated T-cell hepatitis can be identified by the unique pattern of increased percentage of peripheral blood effector memory CD8+ CD103+ T-cells. These findings will guide future studies exploring the T-cell phenotype for these patients and whether they may respond to directed immunosuppressive therapies.

Adenovirus is Not Detected in Liver Tissue From a Historical Multicenter Cohort of Children With Acute Liver Failure.

There has been a recent surge in cases of pediatric acute hepatitis and pediatric acute liver failure (PALF) of unknown cause. Several reports have described clusters of these children who were positive for adenovirus (AdV) DNA, primarily in peripheral blood but some in liver tissue. We tested archived liver tissue specimens from a historical cohort of 44 children with PALF who were enrolled in a multicenter biorepository between 2007 and 2014 for AdV 40/41 using quantitative polymerase chain reaction. Most children had final diagnosis indeterminate. All samples were negative. Our findings suggest that AdV was unlikely to be an unidentified cause of indeterminate PALF during this past era. The significance of AdV viremia in contemporary cohorts of children with PALF remains unknown and requires further study.

Fluid balance in pediatric postoperative liver transplant recipients.

BACKGROUND: Positive fluid balance (FB) is associated with poor outcomes in critically ill children but has not been studied in pediatric liver transplant (LT) recipients. Our goal is to investigate the relationship between postoperative FB and outcomes in pediatric LT recipients. METHODS: We performed a retrospective cohort study of first-time pediatric LT recipients at a quaternary care children's hospital. Patients were stratified into three groups based on their FB in the first 72 h postoperatively: <10%, 10-20%, and > 20%. Outcomes were pediatric intensive care unit (PICU) and hospital length of stay, ventilator-free days (VFD) at 28 days, day 3 severe acute kidney injury, and postoperative complications. Multivariate analyses were adjusted for age, preoperative admission status, and Pediatric Risk of Mortality (PRISM)-III score. RESULTS: We included 129 patients with median PRISM-III score of 9 (interquartile range, IQR 7-15) and calculated Pediatric End-stage Liver Disease score of 15 (IQR 2-23). A total of 37 patients (28.7%) had 10-20% FB, and 26 (20.2%) had >20% FB. Greater than 20% FB was associated with an increased likelihood of an additional PICU day (adjusted incident rate ratio [aIRR] 1.62, 95% CI: 1.18-2.24), an additional hospital day (aIRR 1.39, 95% CI: 1.10-1.77), and lower likelihood of a VFD at 28 days (aIRR 0.85, 95% CI: 0.74-0.97). There were no differences between groups in the likelihood of postoperative complications. CONCLUSIONS: In pediatric LT recipients, >20% FB at 72 h postoperatively is associated with increased morbidities, independent of age and severity of illness. Additional studies are needed to explore the impact of fluid management strategies on outcomes.

Heart rate variability is associated with encephalopathy and outcomes in pediatric acute liver failure.

BACKGROUND: More than half of children with pediatric acute liver failure (PALF) experience hepatic encephalopathy (HE), which is related to poor outcomes; however, HE is difficult to diagnose in children. The objective of this study was to evaluate if heart rate variability (HRV), a continuous measure of autonomic nervous system function, was related to the presence and severity of HE as well as clinical outcomes in children with PALF. METHODS: We conducted a retrospective observational cohort study of 38 critically ill children with PALF to examine the association between HRV and HE severity and clinical outcome. HRV was estimated using the integer HRV (HRVi). Categorical variables were compared using the Fisher Exact test and continuous variables were compared using Kruskal-Wallis tests. Associations between grades of HE and minimum and median HRVi were evaluated with Pearson's correlation, with p values <0.05 considered significant. RESULTS: A more negative median and minimum HRVi, indicating poorer autonomic nervous system function, was significantly associated with abnormal EEG findings, presence of HE, and poor outcomes (death or listing for transplant). CONCLUSIONS: Heart rate variability may hold promise to predict outcomes in children with PALF, but these findings should be replicated in a larger sample. IMPACT: The findings of our study suggest that heart rate variability is associated with clinical outcomes in children with acute liver failure, a cohort for which prognostics are challenging, especially in young children and infants. Use of heart rate variability in the clinical setting may facilitate earlier detection of children with pediatric acute liver failure (PALF) at high risk for severe hepatic encephalopathy and poor outcomes. Identification of children with PALF at high risk of decompensation may assist clinicians in making decisions about liver transplantation, an important, but resource-limited, treatment of PALF.

RNA-Sequencing Analysis Identifies Etiology Specific Transcriptional Signatures in Neonatal Acute Liver Failure.

OBJECTIVE: To assess hepatic transcriptional signatures in infants with gestational alloimmune liver disease (GALD) compared with other etiologies of neonatal acute liver failure (ALF) and older pediatric patients with ALF. STUDY DESIGN: Neonates with ALF (international normalized ratio ≥2 within 30 days of life) and deceased neonates without liver disease (<30 days of age) with available liver tissue between 2010 and 2021 were identified at Ann & Robert H. Lurie Children's Hospital of Chicago. Clinical information, liver histology, and data from RNA-sequencing analysis was compared between neonates with GALD, non-GALD etiologies of neonatal ALF, and nondiseased neonatal liver. RESULTS: Quantification of trichrome staining showed an increase in fibrosis in patients with GALD vs those with non-GALD neonatal ALF (P = .012); however, quantification of α-cytokeratin 19-positive ductules did not differ between groups (P = .244). Gene set enrichment analysis of RNA-sequencing data identified the pathways of complement activation, fibrosis, and organogenesis to be upregulated in patients with GALD with ALF. In contrast, patients with non-GALD causes of neonatal ALF had increased gene expression for interferon-driven immune pathways. Individual genes upregulated in GALD included matrix metallopeptidase 7, hepatocyte growth factor, and chemokine ligand 14. CONCLUSIONS: We have identified distinct pathways that are significantly upregulated in patients with GALD and potential disease-specific diagnostic biomarkers. Future studies will aim to validate these findings and help identify GALD-specific diagnostic biomarkers to improve diagnostic accuracy and reduce GALD-associated patient mortality.

An Update on Pediatric Acute Liver Failure: Emerging Understanding of the Impact of Immune Dysregulation and Novel Opportunities for Intervention.

Pediatric acute liver failure (PALF) is a complex, unpredictable, often rapidly progressive, potentially devastating clinical syndrome that occurs in infants, children, and adolescents without pre-existing liver disease. PALF is characterized by acute onset of hepatocellular injury and liver-based coagulopathy, frequently accompanied by hepatic encephalopathy. Etiologies include drug and toxin exposures, metabolic and genetic disorders, infections, and immune-mediated disease. PALF management primarily involves early contact with and consideration of transfer to a pediatric liver transplant center and intensive supportive multidisciplinary clinical care, with targeted therapies available for a subset of causes. Outcomes include survival with native liver, death, and liver transplantation. Efforts to develop reliable clinical prognostic tools to predict PALF outcomes early in the course of disease have not yet been fulfilled, and the possibility remains that some transplanted PALF patients might have survived without transplantation.

Severe Hepatitis in Pediatric Coronavirus Disease 2019.

ABSTRACT: Hepatic involvement in coronavirus disease 2019 (COVID-19) is typically characterized as mild hepatitis with preserved synthetic function in children. Severe hepatitis is a rare complication of COVID-19 infection that has not been extensively described in the pediatric population. We report a case series of four previously healthy children who presented with significant hepatitis as the primary manifestation of COVID-19 infection. Two of these patients met criteria for acute liver failure. None of the patients had respiratory symptoms. One patient was found to have complement dysfunction resulting in microangiopathic features and was treated successfully with eculizumab. This case is in line with adult post-mortem data showing that more severe cases of hepatic dysfunction secondary to COVID-19 infection may be associated with complement activation and microangiopathic features. Liver function should be evaluated in cases of severe COVID-19, and severe acute respiratory syndrome coronavirus 2 infection should be considered as a cause of acute severe hepatitis even in patients without significant respiratory or other systemic symptoms.

Transcriptional Analysis of Liver Tissue Identifies Distinct Phenotypes of Indeterminate Pediatric Acute Liver Failure.

Many patients with indeterminate pediatric acute liver failure (PALF) have evidence of T-cell driven immune injury; however, the precise inflammatory pathways are not well defined. We have characterized the hepatic cytokine and transcriptional signatures of patients with PALF. A retrospective review was performed on 22 children presenting with indeterminate (IND-PALF; n = 17) or other known diagnoses (DX-PALF; n = 6) with available archived liver tissue. Specimens were stained for clusters of differentiation 8 (CD8) T cells and scored as dense, moderate, or minimal. Measurement of immune analytes and RNA sequencing (RNA-seq) was performed on whole-liver tissue. Immune analyte data were analyzed by principal component analysis, and RNA-seq was analyzed by unsupervised hierarchical clustering, differential gene expression, and gene-set enrichment analysis. Most patients with IND-PALF (94%) had dense/moderate CD8 staining and were characterized by Th1 immune analytes including tumor necrosis factor α, interferon γ (IFN-γ), interleukin (IL) 1ß, IL-12, C-X-C motif chemokine ligand (CXCL) 9, and CXCL12. Transcriptional analyses identified two transcriptional PALF phenotypes. Most patients in group 1 (91%) had IND-PALF and dense/moderate CD8 staining. This group was characterized by increased expression of genes and cell subset-specific signatures related to innate inflammation, T-cell activation, and antigen stimulation. Group 1 expressed significantly higher levels of gene signatures for regulatory T cells, macrophages, Th1 cells, T effector memory cells, cytotoxic T cells, and activated dendritic cells (adjusted P < 0.05). In contrast, patients in group 2 exhibited increased expression for genes involved in metabolic processes. Conclusion: Patients with IND-PALF have evidence of a Th1-mediated inflammatory response driven by IFN-γ. Transcriptional analyses suggest that a complex immune network may regulate an immune-driven PALF phenotype with less evidence of metabolic processes. These findings provide insight into mechanisms of hepatic injury in PALF, areas for future research, and potential therapeutic targets.

Four Biomarkers Linked to Activation of Cluster of Differentiation 8-Positive Lymphocytes Predict Clinical Outcomes in Pediatric Acute Liver Failure.

BACKGROUND AND AIMS: Immune dysregulation contributes to the pathogenesis of pediatric acute liver failure (PALF). Our aim was to identify immune activation markers (IAMs) in PALF that are associated with a distinct clinical phenotype and outcome. APPROACH AND RESULTS: Among 47 PALF study participants, 12 IAMs collected ≤6 days after enrollment were measured by flow cytometry and IMMULITE assay on blood natural killer and cluster of differentiation 8-positive (CD8+ ) lymphocytes and subjected to unsupervised hierarchical analyses. A derivation cohort using 4 of 12 IAMs which were available in all participants (percent perforin-positive and percent granzyme-positive CD8 cells, absolute number of CD8 cells, soluble interleukin-2 receptor level) were sufficient to define high (n = 10), medium (n = 15), and low IAM (n = 22) cohorts. High IAM was more frequent among those with indeterminate etiology than those with defined diagnoses (80% versus 20%, P < 0.001). High IAM was associated with higher peak serum total bilirubin levels than low IAM (median peak 21.7 versus 4.8 mg/dL, P < 0.001) and peak coma grades. The 21-day outcomes differed between groups, with liver transplantation more frequent in high IAM participants (62.5%) than those with medium (28.2%) or low IAM (4.8%) (P = 0.002); no deaths were reported. In an independent validation cohort (n = 71) enrolled in a prior study, segregation of IAM groups by etiology, initial biochemistries, and short-term outcomes was similar, although not statistically significant. High serum aminotransferases, total bilirubin levels, and leukopenia at study entry predicted a high immune activation profile. CONCLUSION: Four circulating T-lymphocyte activation markers identify a subgroup of PALF participants with evidence of immune activation associated with a distinct clinical phenotype and liver transplantation; these biomarkers may identify PALF participants eligible for future clinical trials of early targeted immunosuppression.

Activated CD8 T-cell Hepatitis in Children With Indeterminate Acute Liver Failure: Results From a Multicenter Cohort.

OBJECTIVES: In many pediatric acute liver failure (PALF) cases, a diagnosis is not identified, and the etiology is indeterminate (IND-PALF). Our pilot study found dense CD8 T-cell infiltrates and increased T-cell clonality in liver specimens from IND-PALF patients. We aimed to validate these findings in a multicenter cohort with investigators blinded to diagnosis. METHODS: PALF Study Group registry subjects with IND-PALF (n = 37) and known diagnoses (DX-PALF) (n = 18), ages 1 to 17 years, with archived liver tissue were included. Liver tissue slides were stained for T cells (CD8 and CD4), B cells (CD20), macrophages (CD163), perforin, and tissue resident-memory T cells (Trm, CD103), and scored as minimal, moderate, or dense. Lymphocytes were isolated from frozen liver tissue for T-cell receptor beta (TCRß) sequencing. RESULTS: Dense hepatic CD8 staining was found in significantly more IND-PALF (n = 29, 78%) compared with DX-PALF subjects (n = 5, 28%) (P = 0.001). IND-PALF subjects were more likely to have dense or moderate perforin (88% vs 50%, P = 0.03) and CD103 (82% vs 40%, P = 0.02) staining compared with DX-PALF subjects. TCRß sequencing of 15 IND-PALF cases demonstrated increased clonal overlap compared with 6 DX-PALF cases (P = 0.002). CONCLUSIONS: Dense infiltration of effector Trm CD8 T cells characterizes liver tissue from IND-PALF subjects. Increased clonality suggests the T-cell expansion is antigen(s)-driven as opposed to a nonspecific inflammatory response. These findings support CD8 staining as a new biomarker of the activated CD8 T-cell PALF phenotype. Future studies are needed to characterize potential antigens, host risk factors, and inflammatory pathways with the goal of developing targeted therapies.

Corticosteroid Therapy for Indeterminate Pediatric Acute Liver Failure and Aplastic Anemia with Acute Hepatitis.

OBJECTIVE: To examine the characteristics and outcomes of a multicenter patient cohort with indeterminate pediatric acute liver failure (IND-PALF) and with aplastic anemia with acute hepatitis treated with corticosteroids. STUDY DESIGN: Retrospective study of patients age 1-17 years with IND-PALF and aplastic anemia with acute hepatitis who presented between 2009 and 2018 to 1 of 4 institutions and were treated with corticosteroids for presumed immune dysregulation. RESULTS: Of 28 patients with IND-PALF (median of 4.0 years of age [range 1-16] and 71% male) 71% (n = 20) were treated with 0.5-4 mg/kg/day of intravenous methylprednisolone, and 8 patients received 10 mg/kg/day followed by a taper. By 21 days postcorticosteroid initiation, 14 patients (50%) underwent liver transplantation, 13 patients (46%) recovered with their native liver, and 1 patient (4%) died. Patients who recovered with their native liver received a median of 139 days (range 19-749) of corticosteroid therapy, with a median of 12 days (range 1-240) to international normalized ratio ≤1.2. Patients with aplastic anemia with acute hepatitis (n = 6; median of 9.5 years of age [range 1-12], 83% male), received 1-2 mg/kg/day of methylprednisolone for a median of 100 days (range 63-183), and all recovered with their native liver. One patient with IND-PALF and 2 patients with aplastic anemia with acute hepatitis developed a serious infection within 90 days postcorticosteroid initiation. CONCLUSIONS: Many patients with IND-PALF or aplastic anemia with acute hepatitis that were treated with corticosteroids improved, but survival with native liver may not be different from historical reports. A randomized controlled trial exploring the benefits and risks of steroid therapy is needed before it is adopted broadly.

Cirrhosis and Portal Hypertension in the Pediatric Population.

Cirrhosis is a complex process in which the architecture of the liver is replaced by structurally abnormal nodules due to cirrhosis. Cirrhosis frequently leads to the development of portal hypertension. In children, portal hypertension may be caused by a wide range of etiologies, including extrahepatic portal vein obstruction, biliary atresia, alpha 1 antitrypsin deficiency, and autoimmune hepatitis. Gastroesophageal varices and ascites are two of the complications of portal hypertension likely to cause morbidity and mortality. This review also discusses extrahepatic manifestations of portal hypertension and treatment options.

Liver Biopsy Can Be Safely Performed in Pediatric Acute Liver Failure to Aid in Diagnosis and Management.

OBJECTIVES: Liver biopsy can be a valuable tool to help determine the etiology of pediatric acute liver failure (PALF), but is often not performed due to safety concerns. The primary aim was to describe the incidence of major complications after liver biopsy performed in the setting of PALF. METHODS: Medical records from 2006 to 2016 were reviewed. Patients age 0 to 17 years, who met criteria for PALF, and had a liver biopsy performed while their international normalized ratio (INR) was ≥1.5 were included. RESULTS: A total of 26 cases of liver biopsy in the setting of PALF were identified. The majority (n = 22, 85%) of patients had primary liver disease. Most biopsies (n = 17, 65%) were performed by the transjugular route, with 5 (19%) performed percutaneously under ultrasound guidance and 4 (15%) during a surgical procedure. Median INR before biopsy was 2.1 (IQR = 1.73-2.9). Blood products were given before or during the procedure in 23 (88%) cases. One patient (3.8%) had a major complication of biopsy-associated bleeding requiring a blood transfusion. An additional 3 patients had a hemoglobin decrease of 2.1 to 2.9 g/dL post-biopsy that was attributed to the procedure but no interventions were necessary. Biopsy results contributed to establishing a diagnosis in 62% (n = 16) of cases, and influenced treatment decisions in 9 of those cases. CONCLUSIONS: Liver biopsy is safe in the majority of patients with PALF and associated with infrequent major complications. Clinicians should consider performing liver biopsy in this setting, especially when the transjugular approach is feasible, since findings may guide diagnosis and therapy.

Indeterminate pediatric acute liver failure is uniquely characterized by a CD103+ CD8+ T-cell infiltrate.

The cause of pediatric acute liver failure (PALF) is unknown in up to 40% of cases. Evidence suggests that aberrant immune system activation may play a role. We hypothesized that indeterminate PALF cases would exhibit a unique pattern of hepatic inflammation. This was a retrospective and prospective study of PALF cases due to indeterminate (iPALF), autoimmune hepatitis, or known diagnosis (dPALF) etiology. Liver tissue sections were stained with immunohistochemical markers for cytotoxic T-cells (cluster of differentiation 8 [CD8]), perforin, and tissue resident memory T-cells (CD103) and scored as minimal, moderate, or dense. Lymphocytes were isolated from liver tissue for T-cell receptor beta sequencing and flow-cytometric studies. Thirty-three iPALF, 9 autoimmune hepatitis, and 14 dPALF cases were included. Dense hepatic infiltrates of CD8+ T-cells were found in 27 (82%) iPALF cases compared to 1 (7%) dPALF case (P < 0.0001). Perforin staining was dense or moderate in 19 (73%) of 26 iPALF cases compared to minimal in all 7 dPALF cases (P = 0.004); 16 (62%) of 26 iPALF cases had dense CD103 staining compared to none of the 6 dPALF cases (P = 0.001). T-cell receptor beta sequencing of iPALF cases demonstrated increased clonality compared to dPALF and control cases. Flow cytometry and immunohistochemistry revealed that iPALF intrahepatic leukocytes were predominantly tissue resident memory CD8+ T-cells. CONCLUSION: Indeterminate PALF is characterized by a dense CD8+ T-cell hepatic infiltrate consistent with expansion of a tissue resident memory T-cell phenotype; CD8+ T-cells are a biomarker of immune dysregulation in iPALF and may be used to better identify and define this group. (Hepatology 2018).