PolyI:C plus IL‐2 or IL‐12 induce IFN‐γ production by human NK cells via autocrine IFN‐β

Abstract

NK lymphocytes and type I IFN (IFN-a/b) are major actors of the innate anti-viral response that also influence adaptive immune responses. We evaluated type I IFN production by human NK cells in response to polyI:C, a potent type I IFN-inducing TLR3 agonist. PolyI:C plus IL-2/IL-12 induced IFN-b (but not IFN-a) mRNA expression and protein production by highly pure human NK cells and by the human NK cell line NK92. Neutralizing anti-IFNAR1 or anti-IFN-b Ab prevented the production of IFN-c induced by polyI:C plus IL-2/IL-12. Similarly, IFN-c production induced by polyI:C plus IL-12 was reduced in NK cells isolated from IFNAR1 À/À compared with WT mice. The ability of polyI:C plus IL-12 to induce IFN-c production was related to an increase of TLR3, Mda5 and IFNAR expression and by an increase of STAT1 and STAT4 phosphorylation. Collectively, these data demonstrate that NK cells, in response to polyI:C plus IL-2/IL-12, produce IFN-b that induce, in an autocrine manner, the production of IFN-c and thereby highlight that NK cells may control the outcome of protective or injurious immune responses through type I IFN secretion.Key words: IFN-g . NK cells . PolyI:C . Type I IFN IntroductionType I IFN is a multi-member cytokine family, in which IFN-a and -b are the main types of interest from an immunological perspective [1,2]. They are involved in anti-viral immunity and in some immune disorders (such as autoimmune diseases). In addition to directly interfering with viral replication, type I IFN have anti-proliferative and immunoregulatory properties. They bridge innate and adaptive immune responses by inducing DC maturation and favoring antigen cross-presentation [3]. They also act directly on CD8 1 T cells to favor the generation of effector and memory T cells [4]. The expression of type I IFN is induced early upon recognition of viruses or viral moieties by some innate receptors of the TLR or RIG-1-like receptor families [5]. IFN-a is mainly secreted by plasmacytoid DC in response to viral nucleic acids recognized by TLR7 and 9 [6]. IFN-b mRNA expression is induced in numerous cell types by TLR stimulation [7,8]. IFN-b has a short half-time, is difficult to quantify, and its secretion is mainly evidenced indirectly by neutralizing its activity in in vitro assay [9]. Owing to the central role of type I IFN in the [11]. These cells kill virally infected cells and tumoral cells in the absence of prior activation [11,12]. NK-cell cytotoxic activity is tightly regulated by inhibitory and activatory receptors [13]. Consequently, NK cells are important during the early phases of viral infection, while antigen-specific T-and B-cell responses are generated. In addition to cytotoxic properties, NK cells have immunoregulatory functions. Through the expression of cell surface molecules and the secretion of cytokines such as IFN-g, they directly modulate macrophages, B and T lymphocyte and DC functions [11,12,14,15]. Consequently, in addition to a protective role in anti-tumor and antiviral immunity, it is now suggested that NK c...

Improved host defense against septic peritonitis in mice lacking MyD88 and TRIF is linked to a normal interferon response

“…Although IL-12 is considered important for the induction of IFN-␥, it has been shown previously that IFN-␥ may also be induced by alternative pathways, including type I IFNs and IL-15 [35][36][37]. Notably, we found that Myd88 Ϫ/Ϫ ;Trif Lps2/Lps2 mice up-regulate Ifnb to a substantial extent during septic peritonitis and that IFN-regulated genes as well as IL-15 are induced normally.…”

“…5A), and expression of IL-15 was not altered in the absence of MyD88/ TRIF signaling (Fig. 5B), suggesting that these pathways may contribute to IFN-␥ production in septic peritonitis [35][36][37].…”

Critical role of Toll-like receptor signaling in NK cell activation

“…As expected, poly I : C directly induced the secretion of IFN-, as well as pro-inflammatory cytokine IL-6 and IL-8 by NK cells in a dose-dependent manner without the help of other cytokines [44]. And NK cells showed a up-regulation of CD69 expression and enhanced cytotoxicity targeting K562 tumor cells [44,45]. Similarly, poly I : C also directly activated human NK cell lines, NK92, YTCl2 and YTS, which all had a notable TLR3 expression [43].…”

“…Similarly, poly I : C also directly activated human NK cell lines, NK92, YTCl2 and YTS, which all had a notable TLR3 expression [43]. Poly I : C stimulation up-regulated the cytotoxic activity of NK cells targeting K562 and 721.221 cell lines, promoted the secretion of IFN- and induced the CXCL10 mRNA without additional cytokines or cell assist [44,45]. Further study proved that the TLR3 stimulation can directly induce the activation of TRIF/TICAM-1-dependent transcription factor IRF-3 and p38 MAPK in these human NK cell lines, and activation of p38 MAPK was essential for the activation of NK cells [43].…”

Poly(I:C) Treatment Leads to Interferon-Dependent Clearance of Hepatitis B Virus in a Hydrodynamic Injection Mouse Model

“…4B) can also induce NK activity (37). Activated DCs and KCs secrete IL-6, IL-12, and TNF-␣, which stimulate NK (38,39) and NKT (40) cells to produce IFN-␥. In turn, IFN-␥ upregulates NKmediated lysis of HBV-infected cells, enhances the cytokine response of KC, and recruits HBV-specific T cells (41).…”