Open AccessNucleic acids of Enterococcus faecalis strain EC‐12 are potent Toll‐like receptor 7 and 9 ligands inducing interleukin‐12 production from murine splenocytes and murine macrophage cell line J774.1
Author(s) -
Inoue Ryo,
Nagino Takayuki,
Hoshino Go,
Ushida Kazunari
Publication year - 2011
Publication title -
fems immunology & medical microbiology
Language(s) - English
Resource type - Journals
eISSN - 1574-695X
pISSN - 0928-8244
DOI - 10.1111/j.1574-695x.2010.00752.x
Subject(s) - enterococcus faecalis , splenocyte , tlr2 , microbiology and biotechnology , biology , lactobacillus gasseri , tlr4 , toll like receptor , lactobacillus , receptor , bacteria , immune system , biochemistry , staphylococcus aureus , immunology , innate immune system , fermentation , genetics
In experiment 1 of this study, the interleukin‐12 (IL‐12)‐inducing ability of six Enterococcus strains was evaluated in comparison with that of five Lactobacillus strains using murine splenocytes. At the same time, the involvement of Toll‐like receptor (TLR) ligands in IL‐12‐inducing ability was assessed using splenocytes from TLR2‐, TLR4‐ and MyD88‐deficient mice. Most Enterococcus strains, especially Enterococcus faecalis strain EC‐12, exerted higher IL‐12‐inducing ability compared with the Lactobacillus strains evaluated. Almost the same amount of IL‐12 protein was produced by all lactic acid bacteria strains in splenocytes from TLR2‐ and TLR4‐deficient mice, whereas splenocytes from MyD88‐deficient mice showed no IL‐12 production against all bacteria evaluated. In experiment 2, the role of TLR7, 8 and 9 ligands of E. faecalis strain EC‐12 in the induction of IL‐12 production was evaluated using murine macrophage cell line J774.1. A drastic decrease in IL‐12‐inducing ability was observed when heat‐killed E. faecalis strain EC‐12 was treated with nuclease, particularly RNase. In addition, less than one‐tenth of IL‐12 was produced by heat‐killed E. faecalis strain EC‐12 when both TLR7 and 9 were antagonized. These facts indicate that the nucleic acids of E. faecalis strain EC‐12, particularly its RNA, are the potent TLR7 and 9 ligands that induce IL‐12 production from antigen‐presenting cells.