DataSheet_1_Mice Plasmacytoid Dendritic Cells Were Activated by Lipopolysaccharides Through Toll-Like Receptor 4/Myeloid Differentiation Factor 2.docx

Plasmacytoid dendritic cells (pDCs) are known to respond to viral infections. However, the activation of pDCs by bacterial components such as lipopolysaccharides (LPS) has not been well studied. Here, we found that pDCs, conventional dendritic cells (cDCs), and B cells express high levels of toll-like receptor 4 (TLR4), a receptor for LPS. Moreover, LPS could effectively bind to not only cDCs but also pDCs and B cells. Intraperitoneal administration of LPS promoted activation of splenic pDCs and cDCs. LPS treatment led to upregulation of interferon regulatory factor 7 (IRF7) and induced production of interferon-alpha (IFN-α) in splenic pDCs. Furthermore, LPS-dependent upregulation of co-stimulatory molecules in pDCs did not require the assistance of other immune cells, such as cDCs. However, the production levels of IFN-α were decreased in cDC-depleted splenocytes, indicating that cDCs may contribute to the enhancement of IFN-α production in pDCs. Finally, we showed that activation of pDCs by LPS requires the TLR4 and myeloid differentiation factor 2 (MD2) signaling pathways. Thus, these results demonstrate that the gram-negative component LPS can directly stimulate pDCs via TLR4/MD2 stimulation in mice.

浆细胞样树突状细胞（pDCs）已知对病毒感染产生反应。然而，由细菌成分如脂多糖（LPS）引起的pDCs激活尚未得到充分研究。在本研究中，我们发现pDCs、常规树突状细胞（cDCs）和B细胞均表达高水平的TLR4（脂多糖受体），且LPS能够有效结合cDCs、pDCs和B细胞。腹腔内注射LPS促进了脾脏pDCs和cDCs的激活。LPS处理导致脾脏pDCs中干扰素调节因子7（IRF7）的上调，并诱导产生干扰素-α（IFN-α）。此外，pDCs上共刺激分子的LPS依赖性上调无需其他免疫细胞，如cDCs的辅助。然而，在cDCs耗竭的脾细胞中，IFN-α的产生水平降低，这表明cDCs可能有助于增强pDCs中IFN-α的产生。最后，我们证实LPS通过TLR4/MD2信号通路激活pDCs的过程。因此，这些研究结果证明了革兰氏阴性成分LPS可以通过TLR4/MD2刺激直接刺激小鼠中的pDCs。