University Alabama Birmingham Birmingham, AL, United States
John Mountz, Min Gao, Shanrun Lui, Walter Chatham and Hui-Chen Hsu, University of Alabama at Birmingham, Birmingham, AL
Background/Purpose: Factors that promote B-cell quiescence and homeostasis at the transitional (Tr) and naive stages of B cells to prevent excessive TLR7 and type I interferon (IFN) stimulation are less studied. We determined the transcriptomic program maintaining Tr and naïve B cell quiescence that is disrupted in SLE patients.
Methods: Adult SLE patients (N=47) were recruited. Differentially expressed genes and B-cell developmental trajectories in SLE and healthy controls (HC) were determined by single cell RNA-sequencing (scRNA-seq) analysis. In vitro culture was used to determine IFNβ and/or IL-4 modulation of TLR7 plus IFNɣ and IL-21-mediated development of T-bet+CD11c+ IgD−CD27− (DN2) B cells, PC, and classical memory B cells. B-cell subsets and transcription factors (TFs) expression was measured by FACS analysis of intra-nuclear expression. Autoantibodies were measured by ELISA; disease activity was assessed by SLEDAI at time of blood draw and historical presence/absence of nephritis.
Results: Seventeen genes upregulated in IGHD+ naïve B cells in SLE compared to healthy controls (HC) share common TFs including HESX1, IRF9, ZNFX1, ZBP1, STAT2, SP110, PARP12, ZC3HAV1, IRF7, and IRF1. Genes that have been found in DN2 B cells including FCRL3, FCRL5, and ZEB2 were also upregulated in activated naive B (aNAV) cells in SLE. In contrast, genes upregulated in Tr B cells and naive B cells of HC included IL-4 receptor (IL-4R) pathways genes, IL4R, FCER2 (CD23), and IL2RG. IKAROS was identified as the top TF that is associated with the upregulated genes in HC IGHD+ B cells. Genes upregulated in IL4R+ versus ISG15+ in FACS sorted Tr B cells include IKZF1 (the gene encoding IKAROS), BACH2, MEF2C, and FCER2. Flow cytometry confirmed that the percentage of IL-4R+IFNβ- B cells at the Tr and naïve B-cell stage were correlated with low SLEDAI score. Higher percentages of IL-4R+IFNβ− Tr B cells were negatively correlated with aNAV B cells. A higher percentage of IL-4R+IFNβ− Tr B cells was found in patients who were seronegative for anti-Sm, anti-DNA, and renal disease. Pre-treatment of B cells with IL-4 significantly suppressed the percentages of T-bet+CD11c+ aNAV and DN2 B cells and IFNβ-induced IRF7.
Conclusion: The IL-4R/IKAROS transcriptome network including MEF2CBACH2, IGHD, and FCER2 exists in opposition to the FCRL3, FCRL5, ZEB2, and ISG network and can maintain B cells at the quiescent status starting at the Tr stage of development. Our results suggest that the IL-4R/IKAROS integrated transcriptomics program acts together at the Tr and naïve stages of normal B-cell development to safeguard against type I IFN and TLR7 stimulation and thereby enable B-cell quiescence and resistance to SLE.
Disclosures: J. Mountz, None; M. Gao, None; S. Lui, None; W. Chatham, None; H. Hsu, None.
