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Translational
Abstract Submission
W Winn Chatham, MD
Professor of Medicine, Clinical Immunology and Rheumatology
University of Alabama at Birmingham
Hui-Chen Hsu, PhD
Associate Professor
UAB
John Mountz, MD, PhD
Professor of Medicine, Clinical Immunology and Rheumatology
University of Alabama at Birmingham
Qi Wu, PhD
Research Associate
University of Alabama at Birmingham
Alex Essman, BS
Researcher II
University of Alabama at Birmingham
Oluwagbemiga Ojo, BS
Graduate Student
University of Alabama at Birmingham
Shanrun Liu, PhD
Scientist I
University of Alabama at Birmingham
PingAr Yang, PhD
Research Associate
University of Alabama at Birmingham
Bao Luo, PhD
Research Associate
University of Alabama at Birmingham
Jennie Hamilton, PhD
Research Associate
University of Alabama at Birmingham
Background : Dysregulated responses to type I interferons (IFNs) is a hallmark of autoreactive B-cell development in SLE. This study investigated the source of IFNβ, the major type I IFN responsive B cells, and the disparities associated with B-cell IFNβ production and type I IFN responses.
Methods : IFNβ expression in B, CD4 T and plasmacytoid dendritic cells (pDCs) in PBMCs were analyzed by flow cytometry. Single cell gene expression analysis was carried out using the Fluidigm/BioMark system for targeted expression of low abundance genes, and the 10x Chromium platform for unbiased transcriptome and BCR V(D)J analysis of approximately 2,000 B cells per subject. Autoantigen epitope targets were analyzed using a 4,287 high-throughput PEPperPrint Autoimmune Epitope Microarray and a conventional ELISA analysis.
Results : IFNβ was analyzed in B cells, CD4 T cells and pDCs in PBMCs of SLE patients and healthy controls (HCs). Endogenous IFNβ was significantly increased in transitional (Tr), mature naïve, and memory B cells of SLE patients compared to HCs. Endogenous IFNβ in B cells was equivalent to that in pDCs. B-cell endogenous IFNβ was highly correlated with renal disease, anti-dsDNA, anti-Sm and anti-SSA. Strikingly, the highest correlation of IFNβ with clinical manifestations was observed in African-American (AA) patients with IgG autoAbs against snRNP323-339, U1snRNP-C97-113. At the single cell transcriptome levels, Tr B cells could be divided into type I IFN expressing (IFN+) or type I IFN stimulated gene (ISG+) subpopulations. TLR7 and TLR3 were mainly expressed by IFN+ cells whereas TLR9 was mainly expressed by ISG+ B cells. Unbiased single cells analysis of B cells indicated highly expressed ISG gene set in IGHM+, IGHD+, and IGHG+ B cells in AA patients with autoantibodies and renal disease. Further, ISG highly expressing SLE B cells exhibited unique heavy- and light-chain repertoires including expression of the autoreactive IGHV4-34 gene, targeted with the 9G4 anti-idiotype antibody that recognizes DNA- and RBP-autoreactive B cells.
Conclusions : (i) B cells are an important source of type I IFNs in modulating TLR and BCR responses in SLE; (ii) there are well-orchestrated distinct programs in type I IFN expression and response genes in subsets of B cells, (iii) distinct pathways of autoreactive B cell survival and activation are effected by combined signaling through BCR, TLR, and IFNAR with resultant distinct BCR heavy- and light-chain repertoire.