Accuri C6 Flow Cytometer System
Originally published online as doi:10.1189/jlb.1206737 on July 14, 2008

Published online before print July 14, 2008
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(Journal of Leukocyte Biology. 2008;84:1092-1100.)
© 2008 by Society for Leukocyte Biology

Live Lactobacillus rhamnosus and Streptococcus pyogenes differentially regulate Toll-like receptor (TLR) gene expression in human primary macrophages

Minja Miettinen1, Ville Veckman, Sinikka Latvala, Timo Sareneva, Sampsa Matikainen and Ilkka Julkunen

Department of Viral Diseases and Immunology, National Public Health Institute, Helsinki, Finland

1 Correspondence: Department of Viral Diseases and Immunology, National Public Health Institute, Mannerheimintie 166, 00300 Helsinki, Finland. E-mail: minja.miettinen{at}gmail.com

Macrophages are phagocytes that recognize bacteria and subsequently activate appropriate innate and adaptive immune responses. TLRs are essential in identifying conserved bacterial structures and in initiating and mediating innate immune responses. In this work, we have characterized TLR gene expression in human monocyte-derived macrophages in response to stimulation with two live Gram-positive bacteria, a human commensal and probiotic Lactobacillus rhamnosus GG (LGG), and an important human pathogen Streptococcus pyogenes. LGG and S. pyogenes enhanced TLR2 expression in macrophages. LGG and S. pyogenes also required TLR2 for NF-{kappa}B activation. Only pathogenic S. pyogenes was able to up-regulate TLR3 and TLR7 gene expression. This up-regulation was dependent on IFN-{alpha}/β, as neutralizing anti-IFN-{alpha}/β antibodies reduced S. pyogenes-induced TLR3 and TLR7 mRNA expression. Our results show that despite similarities, TLR responses of macrophages differ for a Gram-positive probiotic and a pathogen. Our data suggest that macrophages can discriminate between probiotic and pathogenic bacteria by IFN-mediated TLR gene regulation.

Key Words: Gram-positive bacteria • innate immunity