Gene expression profiling of epithelium-associated FcRL4+ B cells in primary Sjögren's syndrome reveals a pathogenic signature

Gwenny M Verstappen; John A Ice; Hendrika Bootsma; Sarah Pringle; Erlin A Haacke; Kim de Lange; Gerben B van der Vries; Peter Hickey; Arjan Vissink; Frederik K L Spijkervet; Christopher J Lessard; Frans G M Kroese

doi:10.1016/j.jaut.2020.102439

Gene expression profiling of epithelium-associated FcRL4⁺ B cells in primary Sjögren's syndrome reveals a pathogenic signature

J Autoimmun. 2020 May:109:102439. doi: 10.1016/j.jaut.2020.102439. Epub 2020 Mar 20.

Affiliations

¹ Department of Rheumatology and Clinical Immunology, University of Groningen, University Medical Center Groningen, the Netherlands. Electronic address: G.M.P.J.Verstappen@umcg.nl.
² Genes and Human Disease Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA.
³ Department of Rheumatology and Clinical Immunology, University of Groningen, University Medical Center Groningen, the Netherlands.
⁴ Department of Rheumatology and Clinical Immunology, University of Groningen, University Medical Center Groningen, the Netherlands; Department of Pathology and Medical Biology, University of Groningen, University Medical Center Groningen, the Netherlands.
⁵ Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.
⁶ Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands; Genomics Coordination Center, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.
⁷ The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Melbourne, VIC, 3052, Australia; Department of Medical Biology, University of Melbourne, Melbourne, VIC, 3010, Australia.
⁸ Department of Oral and Maxillofacial Surgery, University of Groningen, University Medical Center Groningen, the Netherlands.
⁹ Genes and Human Disease Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA; Department of Pathology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.

Abstract

In primary Sjögren's syndrome (pSS), FcRL4⁺ B cells are present in inflamed salivary gland tissue, within or in close proximity to ductal epithelium. FcRL4 is also expressed by nearly all pSS-related mucosa-associated lymphoid tissue (MALT) B cell lymphomas, linking FcRL4 expression to lymphomagenesis. Whether glandular FcRL4⁺ B cells are pathogenic, how these cells originate, and how they functionally differ from FcRL4^- B cells in pSS is unclear. This study aimed to investigate the phenotype and function of FcRL4⁺ B cells in the periphery and parotid gland tissue of patients with pSS. First, circulating FcRL4⁺ B cells from 44 pSS and 54 non-SS-sicca patients were analyzed by flow cytometry. Additionally, RNA sequencing of FcRL4⁺ B cells sorted from parotid gland cell suspensions of 6 pSS patients was performed. B cells were sorted from cell suspensions as mini bulk (5 cells/well) based on the following definitions: CD19⁺CD27^-FcRL4^- ('naive'), CD19⁺CD27⁺FcRL4^- ('memory'), and CD19⁺FcRL4⁺ B cells. We found that, although FcRL4⁺ B cells were not enriched in blood in pSS compared with non-SS sicca patients, these cells generally exhibited a pro-inflammatory phenotype. Genes coding for CD11c (ITGAX), T-bet (TBX21), TACI (TNFRSF13B), Src tyrosine kinases and NF-κB pathway-related genes were, among others, significantly upregulated in glandular FcRL4⁺ B cells versus FcRL4^- B cells. Pathway analysis showed upregulation of B cell activation, cell cycle and metabolic pathways. Thus, FcRL4⁺ B cells in pSS exhibit many characteristics of chronically activated, pro-inflammatory B cells and their gene expression profile suggests increased risk of lymphomagenesis. We postulate that these cells contribute significantly to the epithelial damage seen in the glandular tissue and that FcRL4⁺ B cells are an important treatment target in pSS.

Keywords: Autoimmunity; B lymphocytes; Epithelium; MALT lymphoma; RNA sequencing; Salivary gland; Sjögren's syndrome.

Publication types

Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

MeSH terms

Aged
B-Lymphocytes / immunology*
B-Lymphocytes / metabolism*
Biomarkers
Disease Susceptibility
Epithelium / immunology*
Epithelium / metabolism*
Female
Gene Expression Profiling*
Gene Expression Regulation
Humans
Immunohistochemistry
Immunophenotyping
Male
Middle Aged
Receptors, Fc / genetics
Receptors, Fc / metabolism*
Salivary Glands / immunology
Salivary Glands / metabolism
Signal Transduction
Sjogren's Syndrome / etiology*
Sjogren's Syndrome / metabolism
Sjogren's Syndrome / pathology
Transcriptome*

Substances

Biomarkers
FCRL4 protein, human
Receptors, Fc