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, 69 (3), 654-665

Human Liver Infiltrating γδ T Cells Are Composed of Clonally Expanded Circulating and Tissue-Resident Populations

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Human Liver Infiltrating γδ T Cells Are Composed of Clonally Expanded Circulating and Tissue-Resident Populations

Stuart Hunter et al. J Hepatol.

Abstract

Background & aims: γδ T cells comprise a substantial proportion of tissue-associated lymphocytes. However, our current understanding of human γδ T cells is primarily based on peripheral blood subsets, while the immunobiology of tissue-associated subsets remains largely unclear. Therefore, we aimed to elucidate the T cell receptor (TCR) diversity, immunophenotype and function of γδ T cells in the human liver.

Methods: We characterised the TCR repertoire, immunophenotype and function of human liver infiltrating γδ T cells, by TCR sequencing analysis, flow cytometry, in situ hybridisation and immunohistochemistry. We focussed on the predominant tissue-associated Vδ2- γδ subset, which is implicated in liver immunopathology.

Results: Intrahepatic Vδ2- γδ T cells were highly clonally focussed, with single expanded clonotypes featuring complex, private TCR rearrangements frequently dominating the compartment. Such T cells were predominantly CD27lo/- effector lymphocytes, whereas naïve CD27hi, TCR-diverse populations present in matched blood were generally absent in the liver. Furthermore, while a CD45RAhi Vδ2- γδ effector subset present in both liver and peripheral blood contained overlapping TCR clonotypes, the liver Vδ2- γδ T cell pool also included a phenotypically distinct CD45RAlo effector compartment that was enriched for expression of the tissue tropism marker CD69, the hepatic homing chemokine receptors CXCR3 and CXCR6, and liver-restricted TCR clonotypes, suggestive of intrahepatic tissue residency. Liver infiltrating Vδ2- γδ cells were capable of polyfunctional cytokine secretion, and unlike peripheral blood subsets, were responsive to both TCR and innate stimuli.

Conclusion: These findings suggest that the ability of Vδ2- γδ T cells to undergo clonotypic expansion and differentiation is crucial in permitting access to solid tissues, such as the liver, which results in functionally distinct peripheral and liver-resident memory γδ T cell subsets. They also highlight the inherent functional plasticity within the Vδ2- γδ T cell compartment and provide information that could be used for the design of cellular therapies that suppress liver inflammation or combat liver cancer.

Lay summary: γδ T cells are frequently enriched in many solid tissues, however the immunobiology of such tissue-associated subsets in humans has remained unclear. We show that intrahepatic γδ T cells are enriched for clonally expanded effector T cells, whereas naïve γδ T cells are largely excluded. Moreover, whereas a distinct proportion of circulating T cell clonotypes was present in both the liver tissue and peripheral blood, a functionally and clonotypically distinct population of liver-resident γδ T cells was also evident. Our findings suggest that factors triggering γδ T cell clonal selection and differentiation, such as infection, can drive enrichment of γδ T cells into liver tissue, allowing the development of functionally distinct tissue-restricted memory populations specialised in local hepatic immunosurveillance.

Keywords: Gamma delta T cells; Human liver; Immunological memory; Liver immune surveillance; Liver-resident T cells; T cell receptor.

Figures

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Fig. 1
Fig. 1
Normal liver parenchyma is enriched for γδ T cells. (A) Comparison of γδ TCR+ proportion of CD3+ T cells identified by IHC in normal (n = 21) and diseased (n = 62) liver tissue (left) and in CD3+ T cells identified by IHC in normal (n = 21), PSC (n = 13), PBC (n = 13), ALD (n = 12), NASH (n = 12) and viral hepatitis (n = 12) liver tissue (right). (B) Representative staining for CD3+ (left) and γδ TCR+ (right) cells on sequential FFPE sections from NASH liver tissue viewed at 40× magnification. (C) Densities of CD3+ and γδ TCR+ cells in normal (n = 21) and diseased (n = 62) liver tissue. (D) Comparison of the γδ TCR+ proportion of CD3+ T cells identified by IHC in parenchymal and portal areas of normal (n = 15) and diseased (n = 30) liver tissue. (E) Comparison of the γδ TCR+ proportion of CD3+ T cells identified by flow cytometry in normal (n = 15) and diseased (n = 42) liver cell suspensions. (F) Comparison of the γδ TCR+ proportion of CD3+ T cells identified by flow cytometry in normal (n = 15) and diseased liver cell suspensions of various aetiologies. (G) Comparison of Vδ2+ and Vδ2 proportions in γδ TCR+ cells identified by flow cytometry from normal (n = 15) and diseased (n = 42) liver cell suspensions. (H) Comparison of Vδ1+ and Vδ1 proportions in Vδ2 cells from liver cell suspensions (n = 16). (I) Comparison of Vδ2+ (left) and Vδ1+ (right) proportion of CD3+ T cells in CMV (n = 11) and CMV+ donors (n = 6) from diseased livers. Error bars indicate mean ± SEM; data analysed by Kruskal-Wallis ANOVA with Dunn’s post-test comparisons, n.s. p >0.05, **p <0.01, ***p <0.001 and ****p <0.0001. ALD, alcoholic liver disease; CMV, cytomegalovirus; FFPE, formalin-fixed paraffin embedded; IHC, immunohistochemistry; NASH, non-alcoholic steatohepatitis; PBC, primary biliary cholangitis; PSC, primary sclerosing cholangitis; TCR, T cell receptor. (This figure appears in colour on the web.)
Fig. 2
Fig. 2
Intrahepatic Vδ2 γδ T cells are formed of clonally focussed TCR repertoires. (A) Representative tree maps show CDR3 clonotype usage in relation to repertoire size (each CDR3 colour is chosen randomly and does not match between plots) in TCRδ and TCRγ repertoires from αβ TCR Vδ2 T cells sorted from normal (n = 5) and diseased livers (n = 5). Proportion of the total (B) TCRδ and (C) TCRγ repertoire occupied by the 50 most prevalent CDR3 sequences from sorted Vδ2 T cells for each sorted liver sample (n = 10). The dashed black line denotes the percentage of the repertoire occupied by the ten most frequent clonotypes. (D) Analysis of inter-donor diversity by D75 (percentage of clonotypes required to occupy 75% of the total TCR repertoire) from TCRδ repertoire analyses from 12 healthy donors (Vδ1+), 5 cord blood donors (Vδ1+) and 7 liver samples (Vδ2) and lowest quartile range plotted (dashed line). (E) Vδ and (F) Vγ chain usage by the 50 most prevalent γδ TCR CDR3 sequences from sorted Vδ2 T cells from normal and diseased livers with summary plots. Error bars indicate mean ± SEM. CDR3, complementarity determining region 3; TCR, T cell receptor. (This figure appears in colour on the web.)
Fig. 3
Fig. 3
Single-cell TCR sequencing reveals clonal focussing in Vδ2 γδ T cells. Clonal focussing of intrahepatic (A) Vδ1+ and (B) Vδ3+ cells determined by single-cell TCR sequencing analysis of CDR3δ. Each colour represents an individual CDR3δ, with clonal sequences labelled beside each chart (from 16–42 single cells per population, as indicated; with each pie chart representing an independent donor). CDR3, complementarity determining region 3; TCR, T cell receptor. (This figure appears in colour on the web.)
Fig. 4
Fig. 4
Intrahepatic Vδ1+ T cells are phenotypically distinct from those in matched blood. Representative flow cytometry plots and summary data of the enrichment of (A) γδ TCR+ and (B) CD8+ cells in donor matched liver and peripheral blood samples (n = 8). (C) Representative flow cytometry plots and summary data of the enrichment of Vδ1+ and Vδ1Vδ2 or contraction of Vδ2+ T cells in liver (lower plots) and donor matched peripheral blood (upper plots) (n = 8). (D) Representative histograms and summary data of the frequency of CD27hi Vδ1+ T cells derived from donor matched liver and peripheral blood samples (n = 7). (E) Representative flow cytometry plots and summary data of CD27lo/− CD45RAhi and CD45RAlo populations within donor matched liver (lower panels) and peripheral blood (upper panels) Vδ1+ T cells (n = 8). Data analysed by Mann-Whitney U test, **p <0.01. TCR, T cell receptor. (This figure appears in colour on the web.)
Fig. 5
Fig. 5
Intrahepatic Vδ1 T cells contain clonotypes both distinct and overlapping with the blood. (A) Clonal focussing of intrahepatic Vδ1+ CD27lo/− CD45RAlo (n = 11 single cells) and CD27lo/− CD45RAhi (n = 24 single cells) cells determined by single-cell TCR sequencing analysis of CDR3δ. Each colour represents an individual CDR3δ, with clonal amino acid sequences labelled below the chart. Total Vδ1+: TCR sequence data was combined with flow cytometry data to generate the two layered pie, linking clonotype (inner pie chart) to phenotype (outer pie chart). (B) Assessment of clonality by single-cell TCR sequencing analysis of CD27lo/− CD45RAlo, CD27loCD45RAhi and CD27hi Vδ1+ T cells sorted from liver and donor matched blood (n = 8). (C) Comparison of the relationship between phenotype (outer pie chart) and clonality (inner pie chart) determined by phenotype-linked indexed single-cell TCR sequencing analysis, in donor matched peripheral blood (upper) and liver (lower) Vδ1+ T cells, classified according to clone presence within liver and/or blood compartments. Error bars indicate mean ± SEM; data analysed by Mann-Whitney U test, ***p <0.001. CDR3, complementarity determining region 3; TCR, T cell receptor. (This figure appears in colour on the web.)
Fig. 6
Fig. 6
Intrahepatic Vδ1+ T cells segregate into cytokine producing and cytotoxic subsets. (A) Representative histograms from one donor and summary data of CD69 surface expression by CD45RAlo (orange) and CD45RAhi (grey) intrahepatic Vδ1+ and CD8+ T cells (n = 8). (B) As in (A), but displaying representative histograms and summary data for CXCR3, CXCR6 and CX3CR1 surface expression by intrahepatic Vδ1+ and CD8+ T cells (n = 6). (C) Representative histograms and summary data from sorted intrahepatic CD3+ T cells were incubated with indicated medium, cytokines or anti-CD3/CD28 beads for 72 h. CD45RAlo (orange) and CD45RAhi (grey) Vδ1+ T cells were then assessed for the upregulation of the T cell activation marker CD25 (n = 5–6). (D) Representative histograms and summary data for intracellular granzyme B and perforin expression by CD45RAlo (orange) and CD45RAhi (grey) intrahepatic Vδ1+ and CD8+ T cells (n = 5–6). (E) Representative flow cytometry plot and summary data of intrahepatic CD3+ T cells stimulated with PMA/Ionomycin and assessed for the production of intracellular IFNγ and TNFα in CD45RAlo (orange) and CD45RAhi (grey) Vδ1+ and CD8+ cells (n = 6). Error bars indicate mean ± SEM; data analysed by Kruskal-Wallis ANOVA with Dunn’s post-test comparisons, n.s. p >0.05, *p <0.05, **p <0.01 and ***p <0.001. (A–E) Disease aetiologies analysed included ALD, NASH, PSC, and normal liver no significant differences were observed between different individual disease groups in any of the comparisons highlighted. ALD, alcoholic liver disease; IFN, interferon; NASH, non-alcoholic steatohepatitis; PSC, primary sclerosing cholangitis; TNFα, tumour necrosis factor alpha. (This figure appears in colour on the web.)

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