Gram-Positive and Gram-Negative Bacteria Induce Different Patterns of Cytokine Production in Human Mononuclear Cells Irrespective of Taxonomic Relatedness

Abstract

Upon bacterial stimulation, tissue macrophages produce a variety of cytokines that orchestrate the immune response that clears the infection. We have shown that Gram-positives induce higher levels of interleukin-12 (IL-12), interferon-gamma (IFN-gamma), and tumor necrosis factor (TNF) from human peripheral blood mononuclear cells (PBMCs) than do Gram-negatives, which instead induce more of IL-6, IL-8, and IL-10. Here, we study whether these patterns follows or crosses taxonomic borders. PBMCs from blood donors were incubated with UV-inactivated bacteria representing 37 species from five phyla. IL-12, TNF, IL-1beta, IL-6, IL-8, and IL-10 were measured in the supernatants after 24 h and IFN-gamma after 5 days. Irrespective of phylogenetic position, Gram-positive bacteria induced much more IL-12 (nine times more on average) and IFN-gamma (seven times), more TNF (three times), and slightly more IL-1beta (1.5 times) than did Gram-negatives, which instead induced more IL-6 (1.5 times), IL-8 (1.9 times), and IL-10 (3.3 times) than did Gram-positives. A notable exception was the Gram-positive Listeria monocytogenes, which induced very little IL-12, IFN-gamma, and TNF. The results confirm the fundamental difference in innate immune responses to Gram-positive and Gram-negative bacteria, which crosses taxonomic borders and probably reflects differences in cell wall structure.

NK Cells Are Required for Dendritic Cell–Based Immunotherapy at the Time of Tumor Challenge

“…In our study, both intact Gram-positive bacteria and LTA components were found to be the more effective adjuvants for DC vaccination in a therapeutic setting compared with other TLR agonists. The enhanced adjuvant effect of Gram-positive preparations in our study and that of others (55,56) may reflect the superior induction of inflammatory cytokines by Gram-positive bacteria, without the induction of IL-10 observed with Gram-negative bacteria (33,57).…”

“…Superior induction of IFN-g from splenocyte cocultures was achieved with Gram-positive preparations, and the activity was shown to be dependent on NK cells (34). The particular strain of S. salivarius selected to enhance DC activation for tumor immunotherapy has the additional advantage of a lack of mammalian toxin sequences, a demonstrated lack of pathogenicity, and is widely used in humans as an oral probiotic (52), yet is a potent inducer of IL-12 and IFN-g in human and murine leukocytes (33,34). Although bacteria induce potent activation of DC enabling optimal T cell stimulation (53, 54), we cannot rule out that host responses to bacterial products associated with S. salivarius-matured DC may also contribute to the potency of the observed immune response.…”

“…Streptococcus salivarius was selected for this study as it has previously been shown to induce the highest amount of IL-12 in human PBMC from a panel of 37 taxonomically diverse bacteria tested. S. salivarius induces high-level IFNg expression in both human PBMCs (33) and murine NK cells (34). Using a therapeutic tumor model, we found that in vivo depletion of NK cells completely abolished the benefit of the bacteria-stimulated DC immunotherapy.…”

Inflammatory molecules expression pattern for identifying pathogen species in febrile patient serum

“…It is reported that procalcitonin, but not CRP and WBC counts, is associated with gram-negative bacteria (28). Due to the different components of the cell (29,30). Therefore, we hypothesized that inflammatory molecules in the serum may provide information for identifying bacterial species.…”

“…Therefore, we hypothesized that inflammatory molecules in the serum may provide information for identifying bacterial species. Gram-negative bacteria induce higher levels of IL-6, IL-10 and IL-8 compared with gram-positive bacteria in human monocytes (29)(30)(31). To the best of our knowledge, there are few studies reporting whether cytokines or chemokines could be markers to distinguish infection of gram-positive or gram-negative bacteria in patient serum.…”