HERV1-env Induces Unfolded Protein Response Activation in Autoimmune Liver Disease: A Potential Mechanism for Regulatory T Cell Dysfunction.

Regulatory T cells (Tregs) are not terminally differentiated but can acquire effector properties. Here we report an increased expression of human endogenous retrovirus 1 (HERV1-env) proteins in Tregs of patients with de novo autoimmune hepatitis and autoimmune hepatitis, which induces endoplasmic reticulum (ER) stress. HERV1-env-triggered ER stress activates all three branches (IRE1, ATF6, and PERK) of the unfolded protein response (UPR). Our coimmunoprecipitation studies show an interaction between HERV1-env proteins and the ATF6 branch of the UPR. The activated form of ATF6α activates the expression of RORC and STAT3 by binding to promoter sequences and induces IL-17A production. Silencing of HERV1-env results in recovery of Treg suppressive function. These findings identify ER stress and UPR activation as key factors driving Treg plasticity (species: human).

Evaluation of pediatric patients for intestinal transplantation in the modern era.

OBJECTIVES: To review recent evaluations of pediatric patients with intestinal failure (IF) for intestinal transplantation (ITx), waiting list decisions, and outcomes of patients listed and not listed for ITx at our center. METHODS: Retrospective chart review of 97 patients evaluated for ITx from January 2014 to December 2021 including data from referring institutions and protocol laboratory testing, body imaging, endoscopy, and liver biopsy in selected cases. Survival analysis used Kaplan-Meier estimates and Cox proportional hazards regression. RESULTS: Patients were referred almost entirely from outside institutions, one-third because of intestinal failure-associated liver disease (IFALD), two-thirds because of repeated infective and non-IFALD complications under minimally successful intestinal rehabilitation, and a single patient because of lost central vein access. The majority had short bowel syndrome (SBS). Waiting list placement was offered to 67 (69%) patients, 40 of whom for IFALD. The IFALD group was generally younger and more likely to have SBS, have received more parenteral nutrition, have demonstrated more evidence of chronic inflammation and have inferior kidney function compared to those offered ITx for non-IFALD complications and those not listed. ITx was performed in 53 patients. Superior postevaluation survival was independently associated with higher serum creatinine (hazard ratio [HR] 15.410, p = 014), whereas inferior postevaluation survival was associated with ITx (HR 0.515, p = 0.035) and higher serum fibrinogen (HR 0.994, p = 0.005). CONCLUSIONS: Despite recent improvements in IF management, IFALD remains a prominent reason for ITx referral. Complications of IF inherent to ITx candidacy influence postevaluation and post-ITx survival.

Epidemiology and outcomes of surgical site infections among pediatric liver transplant recipients.

INTRODUCTION: Surgical site infections (SSI) are a significant cause of morbidity in liver transplant recipients, and the current data in the pediatric population are limited. The goal of this study was to identify the incidence, classification, risk factors, and outcomes of SSIs among children undergoing liver transplantation (LT). METHODS: A single-center, retrospective descriptive analysis was performed of patients age ≤18 years undergoing LT between September 2007 and April 2017. SSI identified within the first 30 days were analyzed. Primary endpoints included incidence, classification, risk factors, and outcomes associated with SSIs. RESULTS: We included 86 patients, eight patients (9.3%) developed SSIs. Among segmental grafts (SG) recipients, 7/61 (11.4%) developed SSI. Among whole grafts recipients, 1/25 (4%) developed SSI. SSIs were associated with the presence of biliary complications (35% vs. 3%, p < .01; odds ratios 24, 95% CI: 3.41-487.37, p<.01). There were no differences in long term graft or patient survival associated with SSI. Patients who developed SSI were more likely to undergo reoperation (50% vs. 16.7%, p = .045) and had an increased total number of hospital days in the first 60 days post-transplant (30.5 vs. 12.5 days, p = .001). CONCLUSIONS: SSIs after pediatric LT was less frequent than what has been previously reported in literature. SSIs were associated with the presence of biliary complications without an increase in mortality. SG had an increased rate of biliary complications without an association to SSIs but, considering its positive impact on organ shortage barriers, should not be a deterrent to the utilization of SGs.

Mismatch epitope load predicts de novo-DSA-free survival in pediatric liver transplantation.

BACKGROUND: Our knowledge of de novo anti-HLA donor-specific antibodies (dnDSA) in liver transplantation continues to be defined. We hypothesized that differences of HLA-DR/DQ mismatches can improve precision in alloimmune risk categorization and be applied to tailor immunosuppression. METHODS: A retrospective chart review of 244 pediatric patients consecutively transplanted at our center between 2003 and 2019 was performed to identify patients tested for dnDSA. Records were queried for: demographics, pre-transplant diagnosis, biopsy-proven T-cell-mediated rejection (TCMR), radiology proven biliary complications, tacrolimus trough levels, dnDSA characteristics, and HLA typing. The eplet mismatch analyses were performed using HLAMatchmaker™ 3.1. All statistical analyses were conducted using R software version 3.40. RESULTS: There were 99 dnDSA-negative patients and 73 dnDSA-positive patients (n = 70 against class II and n = 3 against class I and II). ROC analysis identified optimal cutoff of eplet mismatch load for dnDSA and defined risk groups for an alloimmune outcome. Kaplan-Meier curves and log-rank tests showed high eplet mismatch load was associated with shorter dnDSA-free survival (log-rank p = .001). Multivariable Cox regression models showed that tacrolimus coefficient of variation and tacrolimus mean levels were significantly associated with dnDSA-free survival (p < .001 and p = .036). Fisher's exact test showed that dnDSA was associated with an increased likelihood of TCMR (OR 14.94; 95% CI 3.65 - 61.19; p < .001). Patients without TCMR were more likely to have dnDSA to HLA-DQ7 and less likely to have dnDSA to HLA-DQ2 (p = .03, p = .080). CONCLUSIONS: Mismatched epitope load predicts dnDSA-free survival in pediatric liver transplant, while dnDSA specificity may determine alloimmune outcome.

SARS-CoV-2 Infection in Pediatric Solid Organ Transplant Recipients: A Single Center Observation.

OBJECTIVES: This is a descriptive study to characterize rates of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in pediatric solid organ transplant (SOT) recipients during the early days of the pandemic. We hypothesized that asymptomatic infection may represent a large proportion of SARS-CoV-2 infection in pediatric SOT recipients. METHODS: We queried Organ Transplant Tracking Record (OTTR) for all pediatric SOT recipients followed at our center and reviewed medical records to identify patients tested for SARS-CoV-2 between March 15, 2020 and June 30, 2021. Patients were tested by polymerase chain reaction (PCR): prior to planned procedures or because of symptoms; OR: tested by measurement of IgG to spike protein with their routine labs q 2-monthly. A positive PCR was called acute infection. A positive IgG with negative PCR was called convalescence. For immunologic studies, blood was obtained when the PCR or IgG was positive. Statistical comparisons were made between (1) acute infection versus convalescence; (2) acute infection versus SOT recipients without infection (called healthy controls); (3) liver transplant (LT) versus small bowel (SB)/multivisceral transplant (MVT); (4) positive versus negative test result. RESULTS: Of 257 LT recipients, 99 were tested: 6 were PCR positive, 13 were antibody positive. Of 150 SB/MVT recipients, 55 were tested: 4 were PCR positive, 6 were antibody positive. Of 8 simultaneous liver, kidney transplant recipients, 3 were tested: 1 was PCR positive. Symptoms when present were mostly mild. Patients with a positive test result were younger (6.3 vs 10.0 years; P = 0.017). We observed a rapid decline in viral load within 96 hours without a change in immunosuppression. Antibody lasted >8 months beyond the time it was monitored. Acute infection was associated with increased CD4 and CD8 T EM cell frequency ( P = 0.04, P = 0.03, respectively), decreased interferon (IFN)-γ production from T-cells (2.8% vs 11.3%; P = 0.006), and decreased CD8 TEMRA frequency (4.56% vs 11.70%; P = 0.006). CONCLUSIONS: Early in the pandemic, COVID-19 disease was mostly mild in pediatric SOT recipients with no rejection, patient death, or graft loss observed.

Anti-plasma cell treatment in refractory autoimmune hemolytic anemia in a child with multivisceral transplant.

BACKGROUND: Warm-antibody AIHA is known to complicate solid organ (SOT) and HSCT, the disease maybe refractory to standard therapy. Immunosuppressive therapies as well as IVIG, and rituximab have been the main stay of treatment. Over the past decade, B-lymphocyte targeted, anti-CD-20 antibody has been recognized in the treatment of autoimmune diseases and utilized in AIHA. Bortezomib, a proteasome inhibitor that causes apoptosis of plasma cells, is an appealing targeted therapy in secondary AIHA and has demonstrated efficacy in HSCT patients. From our experience, we advocate for early targeted therapy that combines B cell with plasma cell depletion. CASE REPORT: We describe a 4-year-old-girl with stage III neuroblastoma, complicated with intestinal necrosis needing multivisceral transplant developed warm AIHA 1-year after transplantation, and following an adenovirus infection. She received immunoglobulin therapy, rituximab, sirolimus, plasmapheresis, and long-term prednisolone with no sustained benefit while developing spinal fractures related to the latter therapy. She received bortezomib for intractable AIHA in combination with rituximab with no appreciable adverse effects. Three years later the child remains in remission with normal reticulocyte and recovered B cells. In the interim, she required chelation therapy for iron overload related to blood transfusion requirement during the treatment of AIHA. CONCLUSION: We propose early targeted anti-plasma cell therapy with steroid burst, IVIG, rituximab, and possible plasmapheresis may reduce morbidity in secondary refractory w-AIHA.

20- to 25-year patient and graft survival following a single pediatric liver transplant-Analysis of the United Network of Organ Sharing database: Where to go from here.

To understand factors contributing to liver graft loss and patient death, we queried a national database designed to follow pediatric patients transplanted between 1987 and 1995 till adulthood. A comparison was made to a cohort transplanted between 2000 and 2014. The 5-, 10-, 15-, 20-, and 25-year patient survival and graft survival were 95.5%, 93.7%, 89.1%, 80.8%, and 73.1%, and 92.5%, 86.7%, 77.6%, 68.7%, and 62.2%, respectively. The twenty-year patient/graft survival was significantly worse in those transplanted between 5 and 17 years of age compared to those transplanted at <5 years of age (P < 0.001). For the modern era cohort, the 3-year patient survival was significantly lower in children transplanted at 16-17 years of age compared to those transplanted at <5 and 11-15 years of age (P ≤ 0.02). The 3-year graft survival was similarly lower in children transplanted at 16-17 years of age compared to those transplanted at <5, 5-10, and 11-15 years of age (P ≤ 0.001). Infection as a cause of death occurred either early or >15 years post-transplant. Chronic rejection remained the leading cause of graft loss in both cohorts and the commonest indication for retransplantation 20-25 years following primary transplant. Further research is required to identify modifiable factors contributing to development of chronic rejection.

Five-year histological and serological follow-up of operationally tolerant pediatric liver transplant recipients enrolled in WISP-R.

Pediatric liver transplant recipients arguably have the most to gain and the most to lose from discontinuing immunosuppression (IS). Whereas IS undoubtedly exerts a cumulative toll, there is concern that insufficient or no IS may contribute to allograft deterioration. Twelve pediatric recipients of parental living donor liver grafts, identified as operationally tolerant through complete IS withdrawal (WISP-R; NCT00320606), were followed for a total of 5 years (1 year of IS withdrawal and 4 years off IS) with serial liver tests and autoantibody and alloantibody assessments. Liver biopsies were performed 2 and 4 years off IS, and, at these time points, immunoglobulin G (IgG) subclass and C1q binding activity for donor-specific antibodies (DSAs) were determined. There were no cases of chronic rejection, graft loss, or death. Allografts did not exhibit progressive increase in inflammation or fibrosis. Smooth-muscle actin expression by stellate cells and CD34 expression by liver sinusoidal endothelial cells remained stable, consistent with the absence of progressive graft injury. Three subjects never exhibited DSA. However, 3 subjects showed intermittent de novo class I DSA, 4 subjects showed persistent de novo class II DSA, and 5 subjects showed persistent preexisting class II DSA. Class II DSA was predominantly against donor DQ antigens, often of high mean fluorescence intensity, rarely of the IgG3 subclass, and often capable of binding C1q. CONCLUSION: Operationally tolerant pediatric liver transplant recipients maintain generally stable allograft histology in spite of apparently active humoral allo-immune responses. The absence of increased inflammation or progressive fibrosis suggests that a subset of liver allografts seem resistant to the chronic injury that is characteristic of antibody-mediated damage. (Hepatology 2017;65:647-660).

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.

Biliary drainage as treatment for allograft steatosis following liver transplantation for PFIC-1 disease: A single-center experience.

Development of macrovesicular steatosis post-LT in patients with PFIC-1 is increasingly being observed, with the etiology not fully understood. We highlight successful and effective EBD for reversal of allograft steatosis in 2 patients with PFIC-1 disease and discuss our experience with internal biliary diversion in this patient population.

Long-term outcomes of de novo autoimmune hepatitis in pediatric liver transplant recipients.

The long-term course and outcome of DAIH is unknown. A retrospective multicenter study assessing associations and long-term consequences of DAIH developing in a transplanted allograft is presented. Children with DAIH were followed from diagnosis until death, re-LT, or transfer of care and for a minimum of 1 year. A total of 31 patients of 1833 (1.7%) LT were identified; 29 followed for a median of 7.1 years (range, 1.6-15); 52% had no rejection preceding diagnosis of DAIH. Transaminases fell following treatment with steroids and antimetabolites (ALT 108 vs 39 U/L (P=.002); AST 112 vs 52 U/L (P=.003); GGT 72 vs 36 U/L (P=.03), but this was not universally sustained. Transaminases >2X ULN observed in 38% of patients at last follow-up; commonly GGT, attributed to bile duct injury and ductopenia. Portal hypertension (PHT) was seen in four patients and associated with severe fibrosis and cirrhosis. Re-LT occurred in two patients for chronic rejection (CR) and uncontrolled PHT with gastrointestinal bleeding, respectively. No deaths from DAIH were reported. DAIH is an uncommon complication following pediatric LT requiring prolonged and augmented immunosuppression. It is associated with continued allograft dysfunction and may lead to bile duct injury, CR, and PHT necessitating re-LT.

Hepatic Issues and Complications Associated With Inflammatory Bowel Disease: A Clinical Report From the NASPGHAN Inflammatory Bowel Disease and Hepatology Committees.

Hepatobiliary disorders are common in patients with inflammatory bowel disease (IBD), and persistent abnormal liver function tests are found in approximately 20% to 30% of individuals with IBD. In most cases, the cause of these elevations will fall into 1 of 3 main categories. They can be as a result of extraintestinal manifestations of the disease process, related to medication toxicity, or the result of an underlying primary hepatic disorder unrelated to IBD. This latter possibility is beyond the scope of this review article, but does need to be considered in anyone with elevated liver function tests. This review is provided as a clinical summary of some of the major hepatic issues that may occur in patients with IBD.

Extended follow-up of pediatric liver transplantation patients receiving once daily calcineurin inhibitor.

We describe longitudinal results in a cohort of pediatric liver transplant patients successfully minimized to once daily CNI monotherapy for longer than five yr and assess changes in liver biochemistries and liver histology. A retrospective chart review of all pediatric liver transplant patients at a single center was performed. Biopsies and serum biochemistries (AST, ALT, total bilirubin, direct bilirubin, INR, creatinine) are reported at time points: PM, five-yr, seven-yr, and nine-yr post-minimization. Biopsies were assessed for inflammation and fibrosis using Ishak and Batts grading systems. Successful minimization to daily CNI monotherapy was defined as normal liver enzymes with no episodes of rejection. Thirty-three patients have successfully remained on once daily CNI for >5 yr, and 19/33 of these patients have serial liver biopsies available for review. We report on the clinical and histological findings of these 19 patients. All 19 patients continue to have normal liver biochemistries. On post-minimization biopsies, fibrosis progressed by ≥2 stages in one patient (5.3%) despite normal liver biochemistries. Carefully selected patients can tolerate minimization to once daily CNI monotherapy as few have progression of fibrosis.

Non-fatal outcomes of COVID-19 disease in pediatric organ transplantation associates with down-regulation of senescence pathways.

This is a cross-sectional study examining kinetics and durability of immune response in children with solid organ transplants (SOTs) who had COVID-19 disease between November 2020 through June 2022, who were followed for 60-days at a single transplant center. Blood was collected between 1-14 (acute infection), and 15-60 days of a positive PCR (convalescence). SOT children with peripheral blood mononuclear cells (PBMC) cryopreserved before 2019 were non-infected controls (ctrls). PBMCs stimulated with 15-mer peptides from spike protein and anti-CD49d/anti-CD28. Testing done included mass cytometry, mi-RNA sequencing with confirmatory qPCR. 38 children formed the study cohort, 10 in the acute phase and 8 in the convalescence phase. 20 subjects were non-infected controls. Two subjects had severe disease. Subjects in the acute and convalescent phases were different subjects. The median age and tacrolimus level at blood draw was not significantly different. There was no death, and no subject was lost to follow-up. During acute infection CD57 expression was low in NKT, Th17 effector memory, memory Treg, CD4-CD8-, and γδT cells (p = 0.01, p = 0.04, p = 0.03, p = 0.03, p = 0.004 respectively). The frequencies of NK and Th2 effector memory cells increased (p = 0.01, p = 0.02) during acute infection. Non-switched memory B and CD8 central memory cell frequencies were decreased during acute infection (p = 0.02; p = 0.02), but the decrease in CD8 central memory cells did not persist. CD4-CD8- and CD14 monocyte frequencies increased during recovery (p = 0.03; p = 0.007). Our observations suggest down regulation of CD57 with absence of NK cell contraction protect against death from COVID-19 disease in children with SOTs.

Rituximab as therapy for the recurrence of bile salt export pump deficiency after liver transplantation.

Progressive familial intrahepatic cholestasis type 2 (PFIC2) results from recessive mutations in the adenosine triphosphate-binding cassette B11 gene, which encodes for bile salt export pump (BSEP). Liver transplantation (LT) is offered to PFIC2 patients with end-stage liver disease. Reports have described recurrent cholestasis in PFIC2 patients after transplantation, and this has been associated with immunoglobulin G antibodies to BSEP. High-titer anti-BSEP antibodies appear to correlate with episodes of cholestatic graft dysfunction. There is no established paradigm for treating antibody-mediated posttransplant BSEP disease. It appears to be refractory to changes in immunosuppressant medications that would typically be effective in treating allograft rejection. Taking what is known about its pathophysiology, we designed a treatment consisting of rituximab, a chimeric monoclonal anti-CD20 antibody, in combination with intravenous immunoglobulin and plasmapheresis. Using this approach, we report the successful management of 2 patients with antibody-mediated recurrence of PFIC2 after LT.

The SPLIT research agenda 2013.

This review focuses on active clinical research in pediatric liver transplantation with special emphasis on areas that could benefit from studies utilizing the SPLIT infrastructure and data repository. Ideas were solicited by members of the SPLIT Research Committee and sections were drafted by members of the committee with expertise in those given areas. This review is intended to highlight priorities for clinical research that could successfully be conducted through the SPLIT collaborative and would have significant impact in pediatric liver transplantation.

COVID-19 Disease in Pediatric Solid Organ Transplantation from Alpha to Omicron: A High Monocyte Count in the Preceding Three Months Portends a Risk for Severe Disease.

IMPORTANCE: Planning for future resurgences in SARS-CoV-2 infection is necessary for providers who care for immunocompromised patients. OBJECTIVE: to determine factors associated with COVID-19 disease severity in immunosuppressed children. DESIGN: a case series of children with solid organ transplants diagnosed with SARS-CoV-2 infection between 15 March 2020 and 31 March 2023. SETTING: a single pediatric transplant center. PARTICIPANTS: all children with a composite transplant (liver, pancreas, intestine), isolated intestine transplant (IT), isolated liver transplant LT), or simultaneous liver kidney transplant (SLK) with a positive PCR for SARS-CoV-2. EXPOSURE: SARS-CoV-2 infection. MAIN OUTCOME AND MEASURES: We hypothesized that children on the most immunosuppression, defined by the number of immunosuppressive medications and usage of steroids, would have the most severe disease course and that differential white blood cell count in the months preceding infection would be associated with likelihood of having severe disease. The hypothesis being tested was formulated during data collection. The primary study outcome measurement was disease severity defined using WHO criteria. RESULTS: 77 children (50 LT, 24 intestine, 3 SLK) were infected with SARS-CoV-2, 57.4 months from transplant (IQR 19.7-87.2). 17% were ≤1 year post transplant at infection. 55% were male, 58% were symptomatic and ~29% had severe disease. A high absolute lymphocyte count at diagnosis decreased the odds of having severe COVID-19 disease (OR 0.29; CI 0.11-0.60; p = 0.004). Conversely, patients with a high absolute monocyte count in the three months preceding infection had increased odds of having severe disease (OR 30.49; CI 1.68-1027.77; p = 0.033). Steroid use, higher tacrolimus level, and number of immunosuppressive medications at infection did not increase the odds of having severe disease. CONCLUSIONS AND RELEVANCE: The significance of a high monocyte count as predictor of severe disease potentially confirms the importance of monocytic inflammasome-driven inflammation in COVID-19 pathogenesis. Our data do not support reducing immunosuppression in the setting of infection. Our observations may have important ramifications in resource management as vaccine- and infection-induced immunity wanes.

Idiopathic Ileal Ulceration After Intestinal Transplantation.

Background: Idiopathic ileal ulceration after intestinal transplantation (ITx) has been discussed infrequently and has an uncertain natural history and relation to graft rejection. Herein, we review our experience with this pathology. Methods: We retrospectively reviewed 225 ITx in 217 patients with minimum 1 y graft survival. Routine graft endoscopy was conducted up to twice weekly within the first 90 d after ITx, gradually decreasing to once yearly. Risks for ulceration over time were evaluated using Cox regression. Results: Of 93 (41%) patients with ulcers, 50 were found within 90 d after ITx mostly via ileoscopy; delayed healing after biopsy appeared causal in the majority. Of the remaining 43 patients with ulcers found >90 d after ITx, 36 were after ileostomy closure. Multivariable modeling demonstrated within 90-d ulcer associations with increasing patient age (hazard ratio [HR], 1.027; P < 0.001) and loop ileostomy (versus Santulli ileostomy; HR, 0.271; P < 0.001). For ulcers appearing after ileostomy closure, their sole association was with absence of graft colon (HR, 7.232; P < 0.001). For ulcers requiring extended anti-microbial and anti-inflammatory therapy, associations included de novo donor-specific antibodies (HR, 3.222; P < 0.007) and nucleotide oligomerization domain mutations (HR, 2.772; P < 0.016). Whole-cohort post-ITx ulceration was not associated with either graft rejection (P = 0.161) or graft failure (P = 0.410). Conclusions: Idiopathic ulceration after ITx is relatively common but has little independent influence on outcome; risks include ileostomy construction, colon-free ITx, immunologic mutation, and donor sensitization.

Successful resolution of inflammation and increased regulatory T cells in sirolimus-treated post-transplant allograft hepatitis.

This retrospective case series reviews our center's experience with sirolimus and a CNI as alternative therapy for the treatment of PTAH. It also characterizes regulatory T cells (Tregs) in PTAH. LT recipients with PTAH who had received or were receiving treatment with sirolimus were retrospectively identified (n = 12). Liver enzymes, immunohistochemistry, and histology were compared in all 12 patients. Immunophenotyping for Tregs in peripheral blood mononuclear cells was performed on LT recipients with PTAH on conventional therapy with CNI, azathioprine ± prednisone (CT) (n = 11), recipients with PTAH on sirolimus, CNI ± prednisone (n = 8), recipients without PTAH (n = 25), and pre-transplant patients (n = 5). Severity of necro-inflammatory changes markedly improved with sirolimus. Treg frequency and number were significantly lower in recipients with PTAH on CT compared to (i) those on sirolimus (p = 0.002 and p = 0.01, respectively), and (ii) recipients without PTAH (p = 0.07 and p = 0.009, respectively). Treg frequency was significantly higher in recipients with PTAH on sirolimus compared to recipients without PTAH under CNI therapy (p = 0.027). Sirolimus in addition to a CNI is successful in reversing inflammation in LT recipients with PTAH. This is associated with significantly higher circulating Tregs.