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

Abstract

Objective: Patients 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. Methods: Peripheral 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. Results: Type 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%. Conclusions: Type 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.

Comparison of Surrogate Markers of the Type I Interferon Response and Their Ability to Mirror Disease Activity in Systemic Lupus Erythematosus

“…Measurement of protein levels of IFN-α in serum is a less sensitive assay than the IGS, herein detecting IFN-α in only 22% of the SLE cases. This could possibly be explained by the fact that patients were well controlled and used antimalarial agents to a high extent ( 30 ). Still, and in line with the report by Matsuoka et al, levels of galectin-9, as well as CXCL10, CCL2, and CCL19, were significantly higher among those with detectable serum IFN-α than among the others.…”

“…Our in vitro experiments revealed different responses of IC induced versus TLR7/8-induced production of cytokines and galectin-9. This may indicate a complexity of IC induced responses in a mixed cell culture that, on one hand, activates TLR-7 and type I IFN regulated genes (30), but on the other hand stimulates chemokine production independent of TLR-7/8 activation. Another explanation could be that TLR7/8 activation results in different inflammatory profiles depending on the agonist, previously shown by Berggren et al (39).…”

Interferon lambda in inflammation and autoimmune rheumatic diseases

“…These cells accumulate in the skin of mice with lupus and produce IFNλs in response to TLR7 agonists 35 . In humans, RNA-containing immune complexes can induce the production of type III interferons in a subset of pDCs that also produce type I interferons 77 . The production of IFNλs by pDCs in vitro was attenuated in the presence of hydroxychloroquine or an IL-1 receptor associated kinase 4 (IRAK4) inhibitor, indicating that RNA-containing immune complexes induce the production of IFNλs through the endosomal TLR–myeloid differentiation primary response protein (MyD88) system.…”

“…In addition to biologic agents that target BDCA2 or LILRA4, a variety of drugs can inhibit interferon production by other means. Antimalarial drugs such as hydroxychloroquine are commonly used to treat SLE and can inhibit type I and type III interferon production by pDCs in response to TLR7 or TLR9 stimulation 77 , 148 . Other TLR inhibitors are currently in various stages of development 149 .…”

Phenotypical Diversification of Early IFNα-Producing Human Plasmacytoid Dendritic Cells Using Droplet-Based Microfluidics

“…Inside these droplets, cells receive their input while being excluded from any kind of interaction with other cells, thereby revealing their intrinsic behaviors upon single-cell activation. This change in approach revealed that upon single-cell activation only fractions of 1-3% produce IFN-Is, which is a phenomenon that has been observed in multiple different settings, for different types of immune cells, both in vitro and in vivo ( 17 – 21 ). Additionally, IFN-I priming revealed the crucial role of paracrine signaling in amplifying the TLR-induced IFN-I response by increasing the fraction of IFN-producing pDCs up to 40%, which comes to a halt upon the administration of neutralizing antibodies ( 16 ).…”