Constitutive Activation of Natural Killer Cells in Primary Biliary Cholangitis.

Theresa J Hydes,Matthew D Blunt,Salim I Khakoo,Jennifer Naftel,Marta E Polak,Grégory Seumois,Alice Wang,Andres F Vallejo,Pandurangan Vijayanand

doi:10.3389/fimmu.2019.02633

Abstract

Natural killer (NK) cells are innate immune cells that interface with the adaptive immune system to generate a pro-inflammatory immune environment. Primary Biliary Cholangitis (PBC) is a hepatic autoimmune disorder with extrahepatic associations including systemic sclerosis, Sjogren's syndrome and thyroiditis. Immunogenetic studies have identified polymorphisms of the IL-12/STAT4 pathway as being associated with PBC. As this pathway is important for NK cell function we investigated NK cells in PBC. Circulating NK cells from individuals with PBC were constitutively activated, with higher levels of CD49a and the liver-homing marker, CXCR6, compared to participants with non-autoimmune chronic liver disease and healthy controls. Stimulation with minimal amounts of IL-12 (0.005 ng/ml) led to significant upregulation of CXCR6 (p < 0.005), and enhanced IFNγ production (p < 0.02) on NK cells from PBC patients compared to individuals with non-autoimmune chronic liver disease, indicating dysregulation of the IL-12/STAT4 axis. In RNAseq studies, resting NK cells from PBC patients had a constitutively activated transcriptional profile and upregulation of genes associated with IL-12/STAT4 signaling and metabolic reprogramming. Consistent with these findings, resting NK cells from PBC patients expressed higher levels of pSTAT4 compared to control groups (p < 0.001 vs. healthy controls and p < 0.05 vs. liver disease controls). In conclusion NK cells in PBC are sensitive to minute quantities of IL-12 and have a “primed” phenotype. We therefore propose that peripheral priming of NK cells to express tissue-homing markers may contribute to the pathophysiology of PBC.

Highlights

Primary Biliary Cholangitis (PBC) affects 1 in 1,000 women over 40 and is common indication for liver transplantation [1]
We have identified that Natural killer (NK) cells in PBC are activated, as determined by both phenotypic and functional analysis
The observation that CD49a can be upregulated with low dose IL-12 in individuals with other chronic liver diseases, could be related to differences in transcriptional regulation between CXCR6 and CD49a, in that CD49a expression on NK cells appears more sensitive to short term culture with IL-12 than CXCR6

Summary

Introduction

Primary Biliary Cholangitis (PBC) affects 1 in 1,000 women over 40 and is common indication for liver transplantation [1]. PBC predominantly affects the liver, but is associated with a number of other conditions including Sjogren’s syndrome, scleroderma, thyroid disease, and autoimmune diabetes [2]. It can be considered a syswtemic disease. Natural killer (NK) cells produce IFNγ and are being increasingly recognized for their role in adaptive immunity and having trained immunological memory [14, 15]. They have been demonstrated to modulate tumor microenvironments toward inducing cytotoxic T-cell responses [16]. Consistent with a role in interfacing with the adaptive immune system, NK cells may potentiate CD4 T-cell responses in PBC [21]

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