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Although intestinal flora are crucial in maintaining immune homeostasis of the intestine, the role of intestinal flora in immune responses at other mucosal surfaces remains less clear. Here, we show that intestinal flora composition critically regulates the toll-like receptor 7 (TLR7) signaling pathway following respiratory influenza virus infection. TLR7 ligands rescued the immune impairment in antibiotic-treated mice. Intact microbiota provided signals leading to the expression of mRNA for TLR7, MyD88, IRAK4, TRAF6, and NF-κB at steady state. Significant changes in the composition of culturable commensal bacteria reduced the expression levels of components of the TLR7 signaling pathway. Our results reveal the importance of intestinal flora in regulating immunity in the respiratory mucosa through the upregulation of the TLR7 signaling pathway for the proper activation of inflammasomes.

Patchouli alcohol (PA) is a kind of methanol extracted from traditional Chinese medicine Pogostemonis Herba. Our research aimed to observe the anti-influenza virus role of PA in vitro. 16HBE (human respiratory epithelial cell) was infected by H1N1 (A/FM1/1/47) to set the cell model. Then the 16HBE was co-cultivated with three kinds of immune cells: dendritic cells, macrophages, and monocytes, PA (the concentration is 10 μg/mL) was added as a treatment intervention for 24 h. The immune cells and the supernate were collected for RT-PCR and ELISA detection related to RLH (RIG-1-like helicases) pathway. Results showed that the IL-4 and IFN-γ in supernate were increased after H1N1 infection, and the PA treatment suppressed the expression of cytokines and the mRNA of RLH pathway. PA anti-influenza virus may through regulate the RLH singal pathway.