Abstract
Innate immune surveillance in the blood is executed mostly by circulating monocytes, which recognize conserved bacterial molecules such as peptidoglycan and lipopolysaccharide. Toll-like receptors (TLR) play a central role in microbe-associated molecular pattern detection. The aim of this study was to compare the differences in TLR expression and cytokine production after stimulation of peripheral blood cells with heat-killed gram-negative and gram-positive human pathogens: Neisseria meningitidis, Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae. We found that TLR2 expression is up-regulated on monocytes after stimulation with S. aureus, S. pneumoniae, E. coli, and N. meningitidis. Moreover, TLR2 up-regulation was positively associated with increasing concentrations of gram-positive bacteria, whereas higher concentrations of gram-negative bacteria, especially E. coli, caused a milder TLR2 expression increase when compared to low doses. Cytokines were produced in similar dose-dependent profiles regardless of the stimulatory pathogen; however, gram-negative pathogens induced higher cytokine levels when compared to gram-positive bacteria at the same density. These results indicate that gram-positive and gram-negative bacteria differ in their dose-dependent patterns of induction of TLR2 and TLR4, but not cytokine expression.
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Acknowledgments
This study was supported by the grants IGA NR/9316-3 from the Ministry of Health, Czech Republic, MSM 0021620806 and SVV-2010-260506 from the Ministry of Education, Youth and Sports. The authors thank Dr. Alice Gabrielová (Department of Clinical Microbiology, University Hospital Bulovka, Prague) and Dr. Jitka Kalmusová (National Institute of Public Health, National Reference Laboratory for Meningococcal Infections, Prague) for help with bacterial suspension preparation, and Dr. Robert S. Munford (National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA) for critical review of the manuscript.
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Beran, O., Potměšil, R. & Holub, M. Differences in Toll-like receptor expression and cytokine production after stimulation with heat-killed gram-positive and gram-negative bacteria. Folia Microbiol 56, 138–142 (2011). https://doi.org/10.1007/s12223-011-0001-9
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DOI: https://doi.org/10.1007/s12223-011-0001-9