Although B cells expressing the IFNgR or the IFNg-inducible transcription factor T-bet drive autoimmunity in Systemic Lupus Erythematosus (SLE)-prone mouse models, the role for IFNg signaling in human antibody responses is unknown. We show that elevated levels of IFNg in SLE patients correlate with expansion of the T-bet expressing IgDnegCD27negCD11c+CXCR5neg (DN2) pre-antibody secreting cell (pre-ASC) subset. We demonstrate that naïve B cells form T-bethi pre-ASCs following stimulation with either Th1 cells or with IFNg, IL-2, anti-Ig and TLR7/8 ligand and that IL-21 dependent ASC formation is significantly enhanced by IFNg or IFNg-producing T cells. IFNg promotes ASC development by synergizing with IL-2 and TLR7/8 ligands to induce genome-wide epigenetic reprogramming of B cells, which results in increased chromatin accessibility surrounding IRF4 and BLIMP1 binding motifs and epigenetic remodeling of IL21R and PRDM1 loci. Finally, we show that IFNg signals poise B cells to differentiate by increasing their responsiveness to IL-21.
Sequencing data have been deposited in GEO under accession codes GSE95282 and GSE118984. All data generated or analyzed during this study are included in the manuscript and supporting files. Source data files for sequencing analysis are included as Supplementary Files 1 and 2 (excel files).
Chromatin accessibility of ex vivo derived Be-g2 cellsNCBI Gene Expression Omnibus, GSE119726.
Be1 and Be2 B cells are transcriptionally distinctNCBI Gene Expression Omnibus, GSE95282.
Gene expression studies of lupus and healthy B cell subsets through RNA sequencingNCBI Gene Expression Omnibus, GSE92387.
Molecular Signatures Database (MSigDB)Molecular Signatures Database.
- Travis Ptacek
- Trenton R Schoeb
- Frances E Lund
- Frances E Lund
- Jeremy Boss
- Jeremy M Boss
- Sanz Inaki
- Sanz Inaki
- Sara L Stone
- Maria I Danila
- Frances E Lund
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Animal experimentation: All procedures involving animals were approved by the UAB Institutional Animal Care and Use Committee and were conducted in accordance with the principles outlined by the National Research Council. UAB IACUC approval IACUC-09648 and IACUC-21203.
Human subjects: All subjects gave written informed consent for participation and provided peripheral blood for analysis. The UAB and Emory Human Subjects Institutional Review Board approved all study protocols for healthy donors and SLE patients. IRB protocols 160301002, X020805006, X140213002, and N140102003 for UAB and 58515 for Emory.
- Facundo D Batista, Ragon Institute of MGH, MIT and Harvard, United States
© 2019, Zumaquero et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
During obesity and high fat-diet (HFD) feeding in mice, sustained low-grade inflammation includes not only increased pro-inflammatory macrophages in the expanding adipose tissue, but also bone marrow (BM) production of invasive Ly6Chigh monocytes. As BM adiposity also accrues with HFD, we explored the relationship between the gains in BM white adipocytes and invasive Ly6Chigh monocytes by in vivo and ex vivo paradigms. We find a temporal and causal link between BM adipocyte whitening and the Ly6Chigh monocyte surge, preceding the adipose tissue macrophage rise during HFD in mice. Phenocopying this, ex vivo treatment of BM cells with conditioned media from BM adipocytes or bona fide white adipocytes favoured Ly6Chigh monocyte preponderance. Notably, Ly6Chigh skewing was preceded by monocyte metabolic reprogramming towards glycolysis, reduced oxidative potential and increased mitochondrial fission. In sum, short-term HFD changes BM cellularity, resulting in local adipocyte whitening driving a gradual increase and activation of invasive Ly6Chigh monocytes.
The type VI secretion system (T6SS) is used by bacteria to deliver toxic effectors directly into target cells. Most T6SSs mediate antibacterial activities, whereas the potential anti-eukaryotic role of T6SS remains understudied. Here, we found a Vibrio T6SS that delivers two novel effectors into mammalian host immune cells. We showed that these effectors induce a pyroptotic cell death in a phagocytosis-dependent manner; we identified the NLRP3 inflammasome as being the underlying mechanism leading to the T6SS-induced pyroptosis. Moreover, we identified a compensatory T6SS-induced pathway that is activated upon inhibition of the canonical pyroptosis pathway. Genetic analyses revealed possible horizontal spread of this T6SS and its anti-eukaryotic effectors into emerging pathogens in the marine environment. Our findings reveal novel T6SS effectors that activate the host inflammasome and possibly contribute to virulence and to the emergence of bacterial pathogens.