Exposure to environmental bacteria may have differing effects on tumour necrosis factor‐α and interleukin‐6‐producing capacity in infancy

Abstract

Exposure to Gram-negative bacteria and their components may be associated with down-regulated immune responses in early infancy, indicated as an impaired production of pro-inflammatory cytokines following mitogen stimulation. Gram-positive bacteria and their constituents seem to have opposite effects. Of the measured markers, exposure to bioactive endotoxin appears to have the strongest impact on T-helper type 1 responses.

The occupant as a source of house dust bacteria

“…In addition to bioactive LPS, 3-hydroxy fatty acids with carbon chain length from 10 to 18 [3-OH FAs (C 10:0 -C 18:0 )] can be measured to assess the amount of LPS. 11 Another microbial cell wall component recently introduced as a bacterial marker is N-acetylmuramic acid, [12][13][14][15] which is considered a marker for grampositive bacteria. Other microbial markers, such as ergosterol, extracellular polysaccharides, or b-1,3 glucans, have been analyzed to assess fungal exposure.…”

High Indoor Microbial Levels Are Associated with Reduced Th1 Cytokine Secretion Capacity in Infancy

“…In the present study, the levels of 3-OH FAs (C 10: ₀–C 14: ₀) in floor dust did not have a consistent influence on the cytokine secretion capacity at birth or at the age of 1 year. Similarly, no associations were found between the levels of floor dust 3-OH FAs (C 10: ₀–C 14: ₀) and cytokine responses (IFN-γ, TNF-α and IL-6) at the age of 3 months in our earlier study [13], but instead there was an inverse association between bed dust 3-OH FA concentrations and proinflammatory cytokine responses. The divergent findings between bed dust and floor dust samples may be due to different sources of bacteria; 86% of the Gram-negative bacteria in bed dust originate from human sources, whereas 79% of floor dust Gram-negative bacterial species are from environmental sources [34].…”

“…Similarly to the qPCR results, some U-shaped associations were detected between the levels of ergosterol (marker for fungal biomass) and immune responses at birth but not at 1 year of age. Furthermore, exposure to ergosterol has not been linked to the production of cytokines at birth [13], at 3 months of age [13], at 1 year of age [36] or at 3 years of age [36]. However, even though the results were not very consistent, recent findings from the PASTURE core study do indicate that the levels of fungal extracellular polysaccharides measured from smooth floor may be associated with increased cord blood TNF-α responses [37].…”

“…Chemical marker concentrations, namely ergosterol as a marker of fungal biomass, 3-hydroxy fatty acids with a carbon chain length from 10 to 14 [3-OH FAs (C 10: ₀–C 14: ₀)], indicating the presence of Gram-negative bacteria, and muramic acid, used to reflect the presence of Gram-positive bacteria, were determined from house dust using GC-MS-MS. Sample preparation of the chemical markers and the GC-MS-MS method for ergosterol were based on our previously described methods [13], but for analyses of muramic acid and 3-OH FAs, GC-MS-MS methods were modified to improve repeatability. …”

“…Our previous study indicated that exposure to house dust Gram-negative bacteria was inversely associated with the proinflammatory cytokine responses at the age of 3 months, whereas Gram-positive bacterial exposures seemed to have opposite effects on these cytokines [13]. This formed the basis for this series of investigations in which we have evaluated these respective associations in a larger number of subjects and explored whether other possible microbial groups may be associated with early immune development.…”