Regulation of NF-κB- and STAT1-mediated plasmacytoid dendritic cell functions by A20.

Pham Ngoc Duy,Nguyen Thi Hong Van,Bui Kieu Trang,Nguyen Thi Xuan,Nguyen Thu Thuy,Nguyen Hoang Giang,Martin E Rottenberg

doi:10.1371/journal.pone.0222697

Abstract

Dendritic cells (DCs) are professional antigen presenting cells involved in the induction of T cell-mediated adaptive immunity. Plasmacytoid DCs (pDCs) originate from lymphoid precursors and produce type I interferons (IFNs) in response to pathogens. A20 is considered as a negative regulator of toll-like receptor (TLR) signaling pathways, in which Toxoplasma gondii- derived profilin (TgPRF) is a TLR11/12 ligand recognised by DCs to stimulate their maturation/activation. Little is known about contributions of A20 to changes in biological properties of pDCs. The present study, therefore, explored whether pDC functions are influenced by A20. To this end, bone marrow cells were isolated and cultured with Flt3L to attain CD8DCs, CD11bDCs and pDCs and followed by challenge with TgPRP in the presence or absence of A20 siRNA. Expression of maturation markers were analysed by flow cytometry, and secretion of inflammatory cytokines by ELISA, cell migration by a transwell migration assay and expression of signalling molecules by western blotting. As a result, treatment with A20 siRNA enhanced activations of IκB-α and STAT-1, leading to increases in expressions of maturation markers and cytokine productions as well as migration of TgPRP-treated pDCs, while mature CD11bDCs produced at higher levels of TNF-α and IL-6 only. In addition, functions of CD8DCs remained unaltered following A20 silencing. The effects of A20 on pDC maturation and activation were completely abolished by IKK inhibitor and partially blunted by fludarabine. In conclusion, the inhibitory effects of A20 on pDC functions are expected to affect the immune response in T. gondii infection.

Highlights

Dendritic cells (DCs) are professional antigen-presenting cells (APCs) originated from a common bone marrow progenitor and involved in the induction of T cell-mediated adaptive immunity
We showed for the first time that downregulation of A20 expression resulted in increases in plasmacytoid DCs (pDCs) maturation/activation and inflammatory reaction in CD11bDCs in response to Toxoplasma gondii- derived profilin (TgPRF)
Similar to previous reports [8, 10, 24, 25], we illustrate that expressions of the maturation markers are increased in TgPRP-stimulated CD8DCs and pDCs and unaltered in TgPRP-stimulated CD11bDCs

Summary

Introduction

Dendritic cells (DCs) are professional antigen-presenting cells (APCs) originated from a common bone marrow progenitor and involved in the induction of T cell-mediated adaptive immunity. The two major subsets of DCs including plasmacytoid DCs (pDCs) and conventional DCs (cDCs, subdivided into CD8DCs and CD11bDCs) express different toll-like. Roles of A20 in regulating plasmacytoid dendritic cell functions receptors (TLRs), play distinct roles in immunity regarding their interaction with pathogens [1]. The cDCs (CD11c+ cells) exhibit antigen recognition, cytokine production, and antigen presentation, at levels higher than pDCs and are potent inducers of effector T cells in response to infection, whereas pDCs tend to mediate immune tolerance rather than immunity [2]. PDCs originated from lymphoid precursors are CD11clow B220high expressing cells and the main producers of type I interferons (IFNs) in response to pathogens [3]. Recruitment of pDCs is frequently seen in viral infections and autoimmune disease such as systemic lupus erythematosus [5]

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Conclusion