STAT2 is required for TLR-induced cross-presentation (APP3P.109)

Abstract

Abstract Type I Interferons (IFNs) are one of the principal mediators in cross-presentation of exogenous antigens to prime CD8+ T cells. Toll-like receptor (TLR) stimulation enhances cross-presentation in dendritic cells (DCs), however, the molecular mediators involved in TLR-induced cross-presentation remain to be elucidated. Since STAT2 is a critical signaling component in the canonical signaling pathway downstream of type I IFN receptor, we hypothesized that TLR-induced cross-presentation may require STAT2. We generated an in vitro model of murine conventional DCs, the bone marrow derived DCs (BMDCs) from WT and STAT2KO mice, and found that STAT2 deficiency did not affect GMCSF-dependent DC development in vitro. Yet upon TLR stimulation, we found STAT2 deficiency impaired the type I IFN response as postulated, including reduction in costimulatory molecules (MHC Class I and CD86), and in the up-regulation of IFN-stimulated genes. Furthermore, STAT2KO DCs were impaired in their expression of signal 3 cytokines, such as IL-12, upon TLR stimuli. To complement our findings, we performed in vitro cross-presentation assays using OT-I TCR transgenic (Tg) T cells, and found that both proliferation and IFN-γ production of CD8+ Tg T cells were reduced when primed with LPS- or CpG-induced STAT2KO BMDCs cross-presenting OVA. Hence, our current data demonstrate that STAT2/type I IFNs axis is essential for TLR4 and 9-induced cross-presentation.