Chronic graft-versus-host disease (cGVHD) is a major cause of late mortality following allogeneic bone marrow transplantation (BMT) and is characterized by tissue fibrosis manifesting as scleroderma ...and bronchiolitis obliterans. The development of acute GVHD (aGVHD) is a powerful clinical predictor of subsequent cGVHD, suggesting that aGVHD may invoke the immunologic pathways responsible for cGVHD. In preclinical models in which sclerodermatous cGVHD develops after a preceding period of mild aGVHD, we show that antigen presentation within major histocompatibility complex (MHC) class II of donor dendritic cells (DCs) is markedly impaired early after BMT. This is associated with a failure of regulatory T-cell (Treg) homeostasis and cGVHD. Donor DC-restricted deletion of MHC class II phenocopied this Treg deficiency and cGVHD. Moreover, specific depletion of donor Tregs after BMT also induced cGVHD, whereas adoptive transfer of Tregs ameliorated it. These data demonstrate that the defect in Treg homeostasis seen in cGVHD is a causative lesion and is downstream of defective antigen presentation within MHC class II that is induced by aGVHD.
•Acute GVHD leads to defective MHC class II antigen presentation by donor DC, leading to a failure of peripheral Treg homeostasis.•Impaired Treg homeostasis results in chronic GVHD directly and can be alleviated by adoptive Treg transfer.
Natural regulatory T cells (nTregs) play an important role in tolerance; however, the small numbers of cells obtainable potentially limit the feasibility of clinical adoptive transfer. Therefore, we ...studied the feasibility and efficacy of using murine-induced regulatory T cells (iTregs) for the induction of tolerance after bone marrow transplantation. iTregs could be induced in large numbers from conventional donor CD4 and CD8 T cells within 1 wk and were highly suppressive. During graft-versus-host disease (GVHD), CD4 and CD8 iTregs suppressed the proliferation of effector T cells and the production of proinflammatory cytokines. However, unlike nTregs, both iTreg populations lost Foxp3 expression within 3 wk in vivo, reverted to effector T cells, and exacerbated GVHD. The loss of Foxp3 in iTregs followed homeostatic and/or alloantigen-driven proliferation and was unrelated to GVHD. However, the concurrent administration of rapamycin, with or without IL-2/anti-IL-2 Ab complexes, to the transplant recipients significantly improved Foxp3 stability in CD4 iTregs (and, to a lesser extent, CD8 iTregs), such that they remained detectable 12 wk after transfer. Strikingly, CD4, but not CD8, iTregs could then suppress Teff proliferation and proinflammatory cytokine production and prevent GVHD in an equivalent fashion to nTregs. However, at high numbers and when used as GVHD prophylaxis, Tregs potently suppress graft-versus-leukemia effects and so may be most appropriate as a therapeutic modality to treat GVHD. These data demonstrate that CD4 iTregs can be produced rapidly in large, clinically relevant numbers and, when transferred in the presence of systemic rapamycin and IL-2, induce tolerance in transplant recipients.
Liver biopsies have consistently contributed to our understanding of the pathogenesis and aetiologies of acute liver disease. As other diagnostic modalities have been developed and refined, the role ...of biopsy in the management of patients with acute liver failure (ALF), acute‐on‐chronic liver failure (ACLF) and acute hepatitis, including acute liver injury (ALI), has changed. Liver biopsy remains particularly valuable when first‐line diagnostic algorithms fail to determine aetiology. Despite not being identified as a mandatory diagnostic tool in recent clinical guidelines for the management of ALF or ACLF, many centres continue to undertake biopsies given the relative safety of transjugular biopsy in this setting. Several studies have demonstrated that liver biopsy can provide prognostic information, particularly in the context of so‐called indeterminate hepatitis, and is extremely useful in excluding conditions such as metastatic tumours that would preclude transplantation. In addition, its widespread use of percutaneous biopsies in cases of less severe acute liver injury, for example in the establishment of a diagnosis of acute presentation of autoimmune hepatitis or confirmation of a probable or definite drug‐induced liver injury (DILI), has meant that many centres have seen a shift in the ratio of specimens they are receiving from patients with chronic to acute liver disease. Histopathologists therefore need to be equipped to deal with these challenging specimens. This overview provides an insight into the contemporary role of biopsies (as well as explant and autopsy material) in diagnosing acute liver disease. It outlines up‐to‐date clinical definitions of liver injury and considers recent recommendations for the diagnosis of AIH and drug‐induced, autoimmune‐like hepatitis (DI‐AIH).
This overview provides an insight into the contemporary role of biopsies (as well as explant and autopsy material) in diagnosing acute liver disease. It outlines up‐to‐date clinical definitions of liver injury and considers recent recommendations for the diagnosis of AIH and drug‐induced, autoimmune‐like hepatitis (DI‐AIH).
Background & Aims: Portal fibrosis and linkage is a key feature of progressive disease in nonalcoholic steatohepatitis (NASH), but not simple steatosis. It is underappreciated and poorly understood. ...Fatty liver has impaired regeneration that induces a secondary replicative pathway using bipotential, periportal, hepatic progenitor cells (HPCs). We propose that activation of this pathway, with increased cell injury in NASH, also induces a periportal ductular reaction (DR) that could produce a profibrogenic stimulus. Methods: Biopsy specimens from 107 patients with nonalcoholic fatty liver disease and 11 controls were immunostained with cytokeratin-7 to quantify the DR and HPCs, and with p21 to assess hepatocyte replicative arrest. These results were correlated with clinicopathologic variables. Results: Patients with nonalcoholic fatty liver disease had expansion of HPCs, with a strong association between HPCs and the DR (rs = 0.582, P < .0001). In those with NASH (n = 69) there was an increased DR compared with simple steatosis, which correlated with the stage of fibrosis (rs = 0.510, P < .0001). The DR increased with the grade of NASH activity (rs = 0.478, P < .0001), grade of portal inflammation (rs = 0.445, P < .0001), and extent of hepatocyte replicative arrest (rs = 0.446, P < .0001). Replicative arrest was in turn associated with insulin resistance (rs = 0.450, P < .0001) and NASH activity (rs = 0.452, P < .0001). By multivariate analysis, the extent of DR (odds ratio OR = 17.9, P = .016), hepatocyte ballooning (OR = 8.1, P < .0001), and portal inflammation (OR = 3.3, P = .005) were associated independently with fibrosis. Conclusions: These findings suggest that an altered replication pathway in active NASH promotes a periportal DR, which in turn may provoke progressive periportal fibrogenesis.
Resident and recruited macrophages control the development and proliferation of the liver. We have previously shown in multiple species that treatment with a macrophage colony stimulating factor ...(CSF1)-Fc fusion protein initiated hepatocyte proliferation and promoted repair in models of acute hepatic injury in mice. Here, we investigated the impact of CSF1-Fc on resolution of advanced fibrosis and liver regeneration, using a non-resolving toxin-induced model of chronic liver injury and fibrosis in C57BL/6J mice. Co-administration of CSF1-Fc with exposure to thioacetamide (TAA) exacerbated inflammation consistent with monocyte contributions to initiation of pathology. After removal of TAA, either acute or chronic CSF1-Fc treatment promoted liver growth, prevented progression and promoted resolution of fibrosis. Acute CSF1-Fc treatment was also anti-fibrotic and pro-regenerative in a model of partial hepatectomy in mice with established fibrosis. The beneficial impacts of CSF1-Fc treatment were associated with monocyte-macrophage recruitment and increased expression of remodelling enzymes and growth factors. These studies indicate that CSF1-dependent macrophages contribute to both initiation and resolution of fibrotic injury and that CSF1-Fc has therapeutic potential in human liver disease.
Endothelial function and integrity are compromised after allogeneic bone marrow transplantation (BMT), but how this affects immune responses broadly remains unknown. Using a preclinical model of CMV ...reactivation after BMT, we found compromised antiviral humoral responses induced by IL-6 signaling. IL-6 signaling in T cells maintained Th1 cells, resulting in sustained IFN-γ secretion, which promoted endothelial cell (EC) injury, loss of the neonatal Fc receptor (FcRn) responsible for IgG recycling, and rapid IgG loss. T cell-specific deletion of IL-6R led to persistence of recipient-derived, CMV-specific IgG and inhibited CMV reactivation. Deletion of IFN-γ in donor T cells also eliminated EC injury and FcRn loss. In a phase III clinical trial, blockade of IL-6R with tocilizumab promoted CMV-specific IgG persistence and significantly attenuated early HCMV reactivation. In sum, IL-6 invoked IFN-γ-dependent EC injury and consequent IgG loss, leading to CMV reactivation. Hence, cytokine inhibition represents a logical strategy to prevent endothelial injury, thereby preserving humoral immunity after immunotherapy.
Endoplasmic reticulum (ER) stress is an important pathogenic mechanism for alcoholic (ALD) and nonalcoholic fatty liver disease (NAFLD). Iron overload is an important cofactor for liver injury in ALD ...and NAFLD, but its role in ER stress and associated stress signaling pathways is unclear. To investigate this, we developed a murine model of combined liver injury by co-feeding the mildly iron overloaded, the hemochromatosis gene-null (Hfe(-/)) mouse ad libitum with ethanol and a high-fat diet (HFD) for 8 weeks. This co-feeding led to profound steatohepatitis, significant fibrosis, and increased apoptosis in the Hfe(-/-) mice as compared with wild-type (WT) controls. Iron overload also led to induction of unfolded protein response (XBP1 splicing, activation of IRE-1α and PERK, as well as sequestration of GRP78) and ER stress (increased CHOP protein expression) following HFD and ethanol. This is associated with a muted autophagic response including reduced LC3-I expression and impaired conjugation to LC3-II, reduced beclin-1 protein, and failure of induction of autophagy-related proteins (Atg) 3, 5, 7, and 12. As a result of the impaired autophagy, levels of the sequestosome protein p62 were most elevated in the Hfe(-/-) group co-fed ethanol and HFD. Iron overload reduces the activation of adenosine monophosphate protein kinase associated with ethanol and HFD feeding. We conclude that iron toxicity may modulate hepatic stress signaling pathways by impairing adaptive cellular compensatory mechanisms in alcohol- and obesity-induced liver injury.
The recent shift to the use of stem cells mobilized by granulocyte colony-stimulating factor (G-CSF) for hematopoietic transplantation has increased chronic graftversus-host disease (GVHD), although ...the mechanisms of this are unclear. We have found that G-CSF invokes potent type 17 rather than type 1 or type 2 differentiation. The amplification of interleukin-17 (IL-17) production by G-CSF occurs in both CD4 and CD8 conventional T cells and is dependent on, and downstream of, G-CSF–induced IL-21 signaling. Importantly, donor IL-17A controls the infiltration of macrophages into skin and cutaneous fibrosis, manifesting late after transplantation as scleroderma. Interestingly, donor CD8 T cells were the predominant source of IL-17A after transplantation and could mediate scleroderma independently of CD4 T cells. This study provides a logical explanation for the propensity of allogeneic stem cell transplantation to invoke sclerodermatous GVHD and suggests a therapeutic strategy for intervention.
FoxP3+ confers suppressive properties and is confined to regulatory T cells (Treg) that potently inhibit autoreactive immune responses. In the transplant setting, natural CD4+ Treg are critical in ...controlling alloreactivity and the establishment of tolerance. We now identify an important CD8+ population of FoxP3+ Treg that convert from CD8+ conventional donor T cells after allogeneic but not syngeneic bone marrow transplantation. These CD8+ Treg undergo conversion in the mesenteric lymph nodes under the influence of recipient dendritic cells and TGF-β. Importantly, this population is as important for protection from GVHD as the well-studied natural CD4+FoxP3+ population and is more potent in exerting class I–restricted and antigen-specific suppression in vitro and in vivo. Critically, CD8+FoxP3+ Treg are exquisitely sensitive to inhibition by cyclosporine but can be massively and specifically expanded in vivo to prevent GVHD by coadministering rapamycin and IL-2 antibody complexes. CD8+FoxP3+ Treg thus represent a new regulatory population with considerable potential to preferentially subvert MHC class I–restricted T-cell responses after bone marrow transplantation.
Donor T cells play pivotal roles in graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL) effects following bone marrow transplantation (BMT). DNAX accessory molecule 1 (DNAM-1) is a ...costimulatory and adhesion molecule, expressed mainly by natural killer cells and CD8+ T cells at steady state to promote adhesion to ligand-expressing targets and enhance cytolysis. We have analyzed the role of this pathway in GVHD and GVL. The absence of DNAM-1 on the donor graft attenuated GVHD in major histocompatibility complex (MHC)-mismatched and MHC-matched BMT following conditioning with lethal and sublethal irradiation. In contrast, DNAM-1 was not critical for GVL effects against ligand (CD155) expressing and nonexpressing leukemia. The effects on GVHD following myeloablative conditioning were independent of CD8+ T cells and dependent on CD4+ T cells, and specifically donor FoxP3+ regulatory T cells (Treg). The absence of DNAM-1 promoted the expansion and suppressive function of Treg after BMT. These findings provide support for therapeutic DNAM-1 inhibition to promote tolerance in relevant inflammatory-based diseases characterized by T-cell activation.
•The DNAM-1 adhesion and costimulatory pathway promotes GVHD via effects on regulatory T cells.•Effective GVL can still occur in the absence of DNAM-1, making the pathway an attractive therapeutic target.
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