The regulation and pharmacological modulation of immune complex induced type III IFN production by plasmacytoid dendritic cells

Karin Hjorton,Niklas Hagberg,Pascal Pucholt,Lars Rönnblom,Maija-Leena Eloranta

doi:10.1186/s13075-020-02186-z

Abstract

ObjectivePatients with systemic lupus erythematosus (SLE) have an ongoing interferon (IFN) production due to an activation of plasmacytoid dendritic cells (pDCs), which can be triggered to type I IFN synthesis by RNA containing immune complexes (RNA-IC). Considering emerging data suggesting a role of type III IFN in the SLE disease process, we asked if RNA-IC can induce type III IFN production in pDC and how this production can be regulated.MethodsPeripheral blood mononuclear cells (PBMCs) or immune cell subsets were isolated from healthy blood donors or SLE patients and stimulated with IC containing U1 snRNP and SLE-IgG (RNA-IC). Hydroxychloroquine (HCQ) and an interleukin receptor 1-associated kinase 4 inhibitor (IRAK4i) were added to cell cultures. Cytokine mRNA levels were determined with a microarray and protein levels with immunoassays. Single-cell RNA sequencing of pDCs using ddSEQ technology was performed.ResultsType III IFN mRNA and protein was induced in RNA-IC-stimulated pDC-NK and pDC-B cell co-cultures. A subset of activated pDCs (3%) expressed both type III and type I IFN mRNA. IFN-λ2, IFN-α2b, interleukin (IL)-3, IL-6, or granulocyte-macrophage colony-stimulating factor (GM-CSF) enhanced IFN-λ1/3 production 2–5-fold. HCQ and an IRAK4i blocked the RNA-IC-triggered IFN-λ1/3 production (p < 0.01). IFN-α2b and GM-CSF increased the proportion of SLE patients producing IFN-λ1/3 in response to RNA-IC from 11 to 33%.ConclusionsType III IFN production is triggered by RNA-IC in pDCs in a TLR-MyD88-dependent manner, enhanced by NK and B cells as well as several pro-inflammatory cytokines. These results support a contributing role for both type I and type III IFNs in SLE, which needs to be considered when targeting the IFN system in this disease.

Highlights

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by the presence of autoantibodies and immune complex (IC) formation
Type III IFN is induced in co-cultures of Plasmacytoid dendritic cell (pDC) and Natural killer (NK) cells or B cells stimulated with RNA containing immune complexes (RNA-IC) To clarify if RNA-ICs trigger the expression of type III IFN in immune cells from healthy blood donors, we performed a microarray analysis of RNA-IC-stimulated pDCs, NK cells, or B cells, as well as pDC-NK or pDC-B cell co-cultures
Observing a more prominent increase in the type III IFN expression by pDC-NK cells compared to pDC-B cell cocultures, we proceeded to focus on the co-cultures of pDCs and NK cells

Summary

Introduction

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by the presence of autoantibodies and immune complex (IC) formation. Via Toll-like receptors (TLRs), ICs can trigger the activation of the interferon (IFN) system, an important feature of SLE [1, 2]. A majority of SLE patients display an increased expression of IFN-regulated genes, an IFN signature, which contributes to the activation of immune cells, a sustained immune reaction, and several disease manifestations [3, 4]. Type I IFNs are mainly responsible for the IFN signature, but both type II and type III IFNs can be measured in a proportion of SLE patients and could contribute to the IFN signature [6]. The exact role of type III IFNs in the generation of the IFN signature and in the SLE disease process is, to a large extent, unknown

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