Abstract
Germ-free animals have been used to define the vital role of commensal bacteria on the maturation of the host immune system. However, the role of bacterial residues in diet in this setting is poorly understood. Here we investigated the effect of bacterial contamination in sterile diet on the level of allergic sensitization in germ-free mice. Sterile grain-based diets ST1 and R03 were tested for the level of bacterial contamination. ST1 contained higher amount of bacterial DNA, approximately ten times more endotoxin, and induced higher, TLR4-dependent, cytokine production in dendritic cells compared to R03. In a germ-free mouse model of sensitization to the major birch pollen allergen Bet v 1, feeding on ST1 for at least two generations was associated with decreased production of allergen-specific IgE and IgG1 antibodies in sera in comparison to R03. Furthermore, reduced levels of allergen-specific and ConA-induced cytokines IL-4, IL-5 and IL-13 accompanied by increased levels of IFN-γ were detected in splenocytes cultures of these mice. Our results show that contamination of experimental diet with bacterial residues, such as endotoxin, significantly affects the development of allergic sensitization in germ-free mice. Therefore, careful selection of sterile food is critical for the outcomes of germ-free or gnotobiotic experimental models of immune-deviated diseases.
Highlights
Reduced exposure to exogenous stimuli and/or altered composition of intestinal microbiota due to the overuse of antibiotics, western diet, and reduced prevalence of infection diseases during childhood are feasible factors of increasing prevalence of allergic disorders [1,2,3]
We tested the presence of bacterial material in two different diets which are routinely used in gnotobiotic breeding facilities
Germ-free animals provide an attractive model for studying the host-microbiota interactions and they are extensively used in investigating the impact of gut microbiota on the maturation and function of the host immune system [20,35]
Summary
Reduced exposure to exogenous stimuli and/or altered composition of intestinal microbiota due to the overuse of antibiotics, western diet, and reduced prevalence of infection diseases during childhood are feasible factors of increasing prevalence of allergic disorders [1,2,3]. This concept was first put forth by the hygiene hypothesis and suggested a causal link between allergy and western lifestyle, where the limited exposure to microbes can lead to compromised regulation of the immune responses [4]. One example of such microbe-derived environmental factor is lipopolysaccharide (LPS), ubiquitously present cell wall component of Gram-
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
