Chronic Airway Inflammation Provides a Unique Environment for B Cell Activation and Antibody Production

Abstract

Background

B cells play many roles in health and disease. However, little is known about the mechanisms that drive B cell responses in the airways, especially in humans. Chronic rhinosinusitis (CRS) is an inflammatory disease of the upper airways that affects 10% of Europeans and Americans. A subset of CRS patients develop nasal polyps (NP), which are characterized by type 2 inflammation, eosinophils and group 2 innate lymphoid cells (ILC2). We have reported that NP contain elevated levels of B cells and antibodies, making NP an ideal system for studying B cells in the airways.

Objective

We sought to determine the mechanisms that drive B cell activation and antibody production during chronic airway inflammation.

Methods

We analyzed B cells from NP or tonsil, or after ILC2 co-culture, by flow cytometry. Antibody production from tissue was measured using Luminex assays, and the frequency of antibody-secreting cells by ELISpot. Formation of B cell clusters was assessed using immunohistochemistry. Expression of genes associated with B cell activation and class switch recombination was measured by qRT-PCR.

Results

NP contained significantly elevated frequencies of plasmablasts, especially those that expressed the extra follicular marker Epstein-Barr virus-induced protein 2 (EBI2), but significantly fewer germinal center (GC) B cells compared to tonsil. Antibody production and the frequency of antibody-secreting cells were significantly elevated in NP, and there was evidence for local class switch recombination in NP. Finally, ILC2s directly induced EBI2 expression on B cells in vitro.

Conclusions and Clinical Relevance

Our data suggest there is a unique B cell activation environment within NP that is distinct from classic GC-mediated mechanisms. We show for the first time that ILC2s directly induce EBI2 expression on B cells, indicating that ILC2s may play an important role in B cell responses. B cell-targeted therapies may provide new treatment options for CRSwNP.

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