Toll‐like receptor‐induced innate immune responses in non‐parenchymal liver cells are cell type‐specific

TLDR

"Kupffer cells produce TNF‑α/IL‑6 in response to all TLR ligands, IFN‑β to TLR3/4, up‑regulate MHC II and costimulatory molecules to TLR1/8, and stimulate T‑cell proliferation and IFN‑γ in MLR via TLR1,2,4,6; liver sinusoidal endothelial cells produce TNF‑α to TLR1‑4,6,8,9, IL‑6 to TLR3/4, IFN‑β to TLR3, and can stimulate allogeneic T cells in MLR despite limited MHC II up‑regulation, indicating that NPC have a restricted TLR‑mediated activation profile relative to classical APCs, which may underlie their tolerogenic role." That's long but still one sentence. Might be too long but acceptable. Let's craft a shorter sentence: "Kupffer cells produce TNF‑α/IL‑6 to all TLR ligands, IFN‑β to TLR3/4, up‑regulate MHC II and costimulatory molecules to TLR1/8, and stimulate T‑cell proliferation and IFN‑γ in MLR via TLR1,2,4,6, whereas liver sinusoidal endothelial cells produce TNF‑α to TLR1‑4,6,8,9, IL‑6 to TLR3/4, IFN‑β to TLR3, and can stimulate allogeneic T cells in MLR despite limited MHC II up‑regulation, showing that NPC have a restricted TLR‑mediated activation profile compared with classical APCs, which may explain their tolerogenic function." That's still one sentence. Might be okay.

Abstract

Little is known of how the Toll-like receptor (TLR) system can modulate the function of non-parenchymal liver cells (NPC) as a major component of the innate and adaptive immune system of the liver. To investigate the diversification of TLR signalling pathways in NPC, we isolated Kupffer cells (KC) and liver sinusoidal endothelial cells (LSEC) from wild-type C57BL/6 mice and examined their responses to TLR1 to TLR9 agonists. The data show that KC respond to all TLR ligands by producing tumour necrosis factor-alpha (TNF-alpha) or interleukin-6 (IL-6), to TLR3 and TLR4 ligands only by producing interferon-beta (IFN-beta), to TLR1 and TLR8 ligands by significantly up-regulating major histocompatibility complex (MHC) class II and costimulatory molecules, and to TLR1, -2, -4 and -6 ligands by inducing high levels of T-cell proliferation and IFN-gamma production in the mixed lymphocyte reaction (MLR). Similarly, LSEC respond to TLR1 to -4, -6, -8 and -9 ligands by producing TNF-alpha, to TLR3 and -4 ligands by producing IL-6, and to TLR3 ligands by producing IFN-beta. Interestingly, despite significant up-regulation of MHC class II and co-stimulatory molecules in response to TLR8 ligands, LSEC stimulated by TLR1, -2 or -6 could stimulate allogeneic T cells as assessed by MLR. By contrast, myeloid dendritic cells, used as positive control for classical antigen-presenting cells, respond to TLR1, -2, -4 and -9 ligands by both up-regulation of CD40 and activation of allogeneic T cells. In conclusion, NPC display a restricted TLR-mediated activation profile when compared with 'classical' antigen-presenting cells which may, at least in part, explain their tolerogenic function in the liver.