IRF5 genetic risk variants drive myeloid-specific IRF5 hyperactivation and presymptomatic SLE
Dan Li, … , Peter Linsley, Betsy J. Barnes
Dan Li, … , Peter Linsley, Betsy J. Barnes
Published December 26, 2019
Citation Information: JCI Insight. 2020;5(2):e124020. https://doi.org/10.1172/jci.insight.124020.
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Research Article Genetics Immunology

IRF5 genetic risk variants drive myeloid-specific IRF5 hyperactivation and presymptomatic SLE

Abstract

Genetic variants within or near the interferon regulatory factor 5 (IRF5) locus associate with systemic lupus erythematosus (SLE) across ancestral groups. The major IRF5-SLE risk haplotype is common across populations, yet immune functions for the risk haplotype are undefined. We characterized the global immune phenotype of healthy donors homozygous for the major risk and nonrisk haplotypes and identified cell lineage–specific alterations that mimic presymptomatic SLE. Contrary to previous studies in B lymphoblastoid cell lines and SLE immune cells, IRF5 genetic variants had little effect on IRF5 protein levels in healthy donors. Instead, we detected basal IRF5 hyperactivation in the myeloid compartment of risk donors that drives the SLE immune phenotype. Risk donors were anti-nuclear antibody positive with anti-Ro and -MPO specificity, had increased circulating plasma cells and plasmacytoid dendritic cells, and had enhanced spontaneous NETosis. The IRF5-SLE immune phenotype was conserved over time and probed mechanistically by ex vivo coculture, indicating that risk neutrophils are drivers of the global immune phenotype. RNA-Seq of risk neutrophils revealed increased IRF5 transcript expression, IFN pathway enrichment, and decreased expression of ROS pathway genes. Altogether, the data support that individuals carrying the IRF5-SLE risk haplotype are more susceptible to environmental/stochastic influences that trigger chronic immune activation, predisposing to the development of clinical SLE.

Authors

Dan Li, Bharati Matta, Su Song, Victoria Nelson, Kirsten Diggins, Kim R. Simpfendorfer, Peter K. Gregersen, Peter Linsley, Betsy J. Barnes

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Figure 6

SLE NETs are an antigenic source that drives IRF5 activation in pDCs, pDC activation and expansion, and PB differentiation.

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SLE NETs are an antigenic source that drives IRF5 activation in pDCs, pD...
(A–G) As in Figure 4E, neutrophils from patients with SLE (S-N) were isolated and plated on poly-l-lysine coverslips for 4 hours in a 24-well plate before addition of healthy donor PBMCs (H-P). Cocultures consisted of healthy donor 1 PBMCs (H1-P) plated alone, neutrophils (N) from healthy donor 1 plated with matched PBMCs (H1-N + H1-P), neutrophils from healthy donor 2 plated with healthy donor 1 PBMCs (H2-N + H1-P), and SLE neutrophils plated with healthy donor 1 PBMCs (S-N + H1-P). (A) Cells were harvested after 4 hours’ coculture to examine IRF5 activation in pDCs by imaging flow cytometry (1-way ANOVA with Tukey’s multiple-comparisons test; n = 4 healthy and SLE donors). A second time point was harvested after overnight coculture to examine pDC numbers (B and C) and activation via CD40 surface expression by flow cytometry (D and E) (1-way ANOVA with Tukey’s multiple-comparisons test; n = 5 healthy donors, n = 4 SLE). B is pregated on CD45+ cells and D on CD45+CD123+BDCA2+ cells. A third time point was harvested after 7 days of coculture where PB differentiation was analyzed by flow cytometry (F). (G) Representative dot plots and summarized data are shown for the 4 conditions (1-way ANOVA with Tukey’s multiple-comparisons test; n = 5 healthy and SLE donor). Experiments were repeated 3 or more times. Single data points represent cells from individual donors. Data are presented as mean ± SEM. *P ≤ 0.05; **P ≤ 0.01.