T cell immunity in liver disease Öffentlichkeit
Tedesco, Dana Christine (2017)
Published
Abstract
The liver critically participates in a multitude of metabolic functions required for human life. Due to shared blood flow with the gastrointestinal (GI) tract, the liver is perpetually bombarded with antigen rich intestinal blood, oxidative stress, and metabolites, yet maintains order amidst this antigenic chaos. Fibrosis, reversible liver scarring, is one of several mechanisms contributing to preservation of the liver microenvironment. Fibrosis is thought to shunt insults from healthy tissue such that the liver may function unscathed. Once the insult is resolved, fibrosis reverses as healthy tissue replaces scar tissue.
Central to the process fibrosis are activated hepatic stellate cells (HSCs), which upon activation initiate the liver wound healing process. Activated HSC-derived all-trans retinoic acid (ATRA) induces Foxp3 expression on CD4+ T cells. These "regulatory" T cells (Tregs) protect the liver from immune mediated injury by CD8+ T cells and other effectors. While beneficial for preservation of the liver microenvironment, these Tregs are implicated in suppressing antiviral responses and permitting chronic hepatotropic infections such as hepatitis C (HCV). Despite dampened CD8+ T cell immunity, chronic liver disease can manifest systemically as antibody mediated disorders due to aberrant B cell functions. These opposing yet co-existent features suggest that fibrosis-driven alterations of intrahepatic CD4+ T cell-help yield extrahepatic consequences. Surprisingly, we found that a subpopulation of fibrosis-elicited Tregs expressing CD40L and therefore represents one mechanism driving the extrahepatic sequelae of chronic liver disease.
Given the peripheral consequences of liver-specific events, it is entirely plausible that peripheral events can influence the liver. Persistent liver injury results in destruction of the liver architecture; this is associated with digestive perturbations such as defective shuttling of bile. Blockages in bile flow, cholestasis, has been linked to intestinal abnormalities, translocation of microbes to the periphery and imbalances in commensal flora. In the clinic, transient improvement in liver functional tests have been reported following antibiotic treatment of patients suffering from choleostatic liver disorders. Although these strategies are not curative, the outcomes suggest that events in GI tract have the potential to augment intrahepatic processes. Here, we found that microbial translocation from the GI tract to the liver augments disease pathology through interaction with γδ-T cells, a non-conventional lymphocyte population selectively enriched and expanded in the liver.
The studies carried out in this dissertation propose that the events in the liver have extrahepatic consequences. Additionally, this work begins to address the effects of extrahepatic events on intrahepatic processes. Overall, deviations associated with chronic liver disease emphasize the liver's remarkable capacity to maintain a balance between tolerance and inflammatory responses while simultaneously inundated with panoply of antigenic stimuli.
Table of Contents
Table of Contents
Chapter 1: Consequences of intrahepatic environmental cues on T cell functions: a comprehensive review of the literature 1
Introduction: Meet the liver 2
I. Liver-specific signals differentially instruct CD4+ T cell
responses 7
CD4+ T cell priming by liver-resident APCs 8
II. Hepatic CD8+ T cell responses 14
Intrahepatic CD8+ T cell priming 14
Memory responses, activated T cell sink, and immune-mediated injury 16
III. Non-conventional T cell populations 20
gd-T cell subsets 20
NK and NKT subsets 22
IV. Liver transplantation highlights intrinsic management of T cell activation 24
V. Concluding remarks and therapeutic implications 26
Chapter 2: CD4+ Foxp3+ T cells promote aberrant IgG production and maintain CD8+ T cell suppression during chronic liver disease 31
I. Abstract 32
II. Introduction 33
III. Materials and Methods 35
IV. Results 42
Aberrant IgG production during hepatic fibrosis requires CD4+ T cells 42
Fibrosis-elicited CD4+Foxp3+ T cells do not suppress B cell activity 45
Fibrosis-elicited CD4+Foxp3+ T cells suppress CD8+ T cell responses 48
Fibrotic liver CD4+ Foxp3+ T cells up-regulate CD40L, CD69 and PD-1 Expression 50
CD40L expression is localized to CD4+Foxp3+CXCR5-ICOS- T cells 52
In vivo CD40L blockade during liver injury attenuates IgG aberrations 54
Accumulation of CD4+Foxp3+CD40L+ T cells in explanted HCV patients livers 56
Aberrant IgG production correlated with frequency of CD4+Foxp3+ T cells in explanted HCV patient livers 58
V. Discussion 60
VI. Supplemental Data 64
Chapter 3: Gut dysbiosis propels pathogenic IL-17A+ Vγ6Jγ1-γδ T cells during chronic liver disease 73
I. Abstract 74
II. Introduction 75
III. Materials and Methods 78
IV. Results 83
Intrahepatic gd T Cells are a predominant source of IL-17a during chronic choleostatic hepatic fibrogenesis 83
Liver-specific alterations to the gd T Cell compartment during choleostatic liver disease 86
Fibrosis drives expansion of Vγ6Jγ1-γδ T cells 88
Increased gut permeability and dysbiosis favor microbial translocation and enrichment in fibrotic liver 91
Intrahepatic γδ T cells produce IL-17 in response to translocated gut microbiota 95
Administration of Mdr2-/- liver-derived Lactobacillus induces IL-17 responses in WT mice 97
Antibody-mediated blockade of the γδ TCR attenuates fibrosis 99
V. Discussion 101
VI. Supplemental Data 105
Chapter 4: Discussion 114
I. When a "Treg" is not really a "Treg": intrahepatic environmental cues can tip the balance between tolerance and immune responses 115
II. Gut-Liver Axis is disrupted during liver diseases: implications on pathologic outcomes 118
III. The liver does not exist in a vacuum 121
Appendices 124
Appendix 1: References 124
Appendix 2: Reprint licensure information for "CD4+ Foxp3+ T cells promote aberrant IgG production and maintain CD8+ T cell suppression during chronic liver disease" courtesy of John Wiley and Sons and Copyright Clearance Center 143
Appendix 3: Unpublished supplemental data figures 144
List of Tables and FiguresChapter 2: CD4+ Foxp3+ T cells promote aberrant IgG production and maintain CD8+ T cell suppression during chronic liver disease 31
Figure 2-1: Aberrant IgG-production during hepatic fibrosis requires CD4+ T cells 44
Figure 2-2: Fibrosis-elicited CD4+Foxp3+T cells do not suppress
B cell activity 47
Figure 2-3: Fibrotic liver CD4+Foxp3+ T cells suppress CD8+ T cell
response 49
Figure 2-4: Fibrotic liver CD4+Foxp3+ T cells up-regulate CD69,
PD-1 and CD40L 53
Figure 2-5: CD40L is primarily expressed on CXCR5 and ICOS double
negative CD4+Foxp3+ T cells 53
Figure 2-6: In vivo blockade of CD40L attenuates Ig-mediated
manifestations of liver fibrosis 55
Figure 2-7: Phenotypic analysis of CD4+Foxp3+ T cells in explanted
liver from HCV patients 57
Figure 2-8: Aberrant IgG production correlates with frequency of
CD4+Foxp3+ T cells in explanted HCV patient livers 59
Chapter 2: Supplemental Data 64
Figure S2-1: Antibody mediated depletion of CD4+ T cells in C57BL6/J treated with CCl4 64
Figure S2-2: CCl4 treatment primarily alters the
hepatic B cell compartment 65
Figure S2-3: Increased B cell activation and survival during liver
fibrosis 66
Figure S2-4: CD25 negative CD4+ T cell interaction with B cells is
not influenced by fibrosis 67
Figure S2-5: Phenotypic analysis of splenic CD4+Foxp3+ T cells
68
Figure S2-6: Intrahepatic accumulation of CD4+Foxp3+ T cells and
incidence of spontaneous IgG production are independent of HCV
viral load 70
Table S2-1: Fibrosis Lesion Scoring analysis Rubric and Findings
71
Table S2-2: Clinical Characteristics of HCV patients in this study
72
Table S2-3: Clinical characteristics of non-fibrotic control
subjects in this study 72
Chapter 3: Gut dysbiosis propels pathogenic IL-17A+ Vγ6Jγ1-γδ T cells during chronic liver disease 73
Figure 3-1: Intrahepatic γδ -T cells are a predominant source of IL-17A during chronic liver disease 85
Figure 3-2: Fibrotic liver γδ-T cell compartment is
altered in favor of IL-17 producing subsets 87
Figure 3-3: Fibrosis drives expansion of IL-17A+ invariant
Vγ6Jγ1 γδ -T cells 90
Figure 3-4: Increased gut permeability and dysbiosis favor
microbial translocation and enrichment of lactobacillus in
fibrotic liver 93
Figure 3-5: Intrahepatic γδ -T cells produce IL-17 in
response to translocated gut microbiota 96
Figure 3-6: Administration of Lactobacillus can induce
hepatic inflammation and increase serum IL-17 in wild-type FVB/N
mice98
Figure 3-7: Antibody-mediated blockade of the γδ TCR
attenuates hepatic fibrosis 100
Chapter 3: Supplemental Data 105
Figure S3-1: Neutralization of IL-17A attenuates hepatic inflammation in Mdr2-/- mice 105
Figure S3-2: In vivo administration of anti- γδ
TCR (Clone UC7-13D5) preferentially targets IL-17 producing subsets
106
Figure S3-3: Accumulation of intrahepatic in vivo bound
anti-TCR + corresponds with increased serum IL-17A levels in
Mdr2-/-
mice 107
Figure S3-4: Gut microbial composition is altered in 8-wk-old
Mdr2-/- mice 108
Figure S3-5: Identification of culture isolates 109
Figure S3-6: Increased IL-17A in FVB/N mice inoculated with
Lactobacillus 110
Figure S3-7: Blockade of TCR results in reduced intrahepatic
expansion of IL-17+ population and corresponds to reduced
neutrophilic infiltration 111
Figure S3-8: Fibrosis scores in control Mdr2-/- vs.
anti-IL-17A treated and anti-TCR treated mice 112
Table S3-1: Fibrosis scoring criteria and representative
findings 113
Chapter 4: Discussion 114
Figure 4-1: The fibrotic liver microenvironment promotes aberrant CD4+ T cell functions 117
Appendix 3: Unpublished supplemental data figures 144
Figure A3-1: ANA-assay of naive splenic B cell supernatants co-cultured with the indicated total CD4+ T cell source. 144
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