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192 Disparities of B-cell type I interferon production and responses in SLE
  1. W Winn Chatham,
  2. Hui-Chen Hsu,
  3. John Mountz,
  4. Qi Wu,
  5. Alex Essman,
  6. Oluwagbemiga Ojo,
  7. Shanrun Liu,
  8. PingAr Yang,
  9. Bao Luo and
  10. Jennie Hamilton
  1. University of Alabama at Birmingham

Abstract

Background Dysregulated responses to type I interferons (IFNs) is a hallmark of autoreactive B-cell development in SLE. This study investigated the source of IFN, the major type I IFN responsive B cells, and the disparities associated with B-cell IFN production and type I IFN responses.

Methods IFN 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 4287 high-throughput PEPperPrint Autoimmune Epitope Microarray and a conventional ELISA analysis.

Results IFN was analyzed in B cells, CD4 T cells and pDCs in PBMCs of SLE patients and healthy controls (HCs). Endogenous IFN was significantly increased in transitional (Tr), mature naïve, and memory B cells of SLE patients compared to HCs. Endogenous IFN in B cells was equivalent to that in pDCs. B-cell endogenous IFN was highly correlated with renal disease, anti-dsDNA, anti-Sm and anti-SSA. Strikingly, the highest correlation of IFN 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 9 G4 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.

Funding Source(s): R01-AI-071110, R01 AI134023, LRA Distinguished Innovator Award and Novel Research Award, VA Merit Review Award I01B × 004049, Immunology T32 Training Grant 2T32AI007051-39, the LFA Finzi Summer Fellowship.

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