Allergic Sensitization to Bovine β-Lactoglobulin: Comparison between Germ-Free and Conventional BALB/c Mice

Abstract

Background: The ‘hygiene hypothesis’ suggests that high hygienic standards met in western countries lead to a lack of microbial exposure, thus promoting the development of atopy by preventing the proper maturation of the immune system. Germ-free animals are deprived of the immune stimulation that occurs during postnatal gut colonization by commensal bacteria. Germ-free mice could thereby provide an attractive model for studying the impact of gut microbiota on the development of Th2-mediated disorders such as allergy. Methods: Germ-free and conventional BALB/c mice were sensitized to β-lactoglobulin (BLG), a major cow’s milk allergen, by means of intraperitoneal injections in the presence of incomplete Freund’s adjuvant. Time courses of serum and fecal BLG-specific antibody responses were monitored and cytokine production was assayed in BLG-reactivated splenocytes. Results: Serum BLG-specific IgG1 and IgE concentrations were significantly higher in germ-free mice during the primary immune response and IgE production persisted longer in germ-free mice. Furthermore, secretion of BLG-specific IgA was evidenced only in feces from germ-free mice while, in contrast, fecal IgG1 concentrations were at least 3-fold higher in conventional mice than in germ-free mice. Production of IL-5, IL-10 and IFN-γ was 3-fold enhanced in BLG-reactivated splenocytes from germ-free mice. Conclusion: The absence of gut microbiota significantly affects the BLG-specific immune response in BALB/c mice, thus suggesting that this model might be of interest for further studies exploring the influence of gut colonization by different bacterial strains on the development of an allergic-type sensitization.

Intestinal commensal bacteria promote T cell hyporesponsiveness and down-regulate the serum antibody responses induced by dietary antigen

“…Previous studies have also suggested that GF mice are more susceptible to allergic sensitization than CV mice [9,10]. Our present study, using a model in which the antigen was exclusively fed, without any systemic sensitization by intraperitoneal or intraveneous administration, has revealed that higher serum antibody responses (OVA-specific IgE, IgG1 and IgG2a) are induced in GF mice than in CV animals (Fig.…”

“…As a consequence, germ-free (GF) animals, which lack indigenous bacteria in their gastrointestinal tract, provide valuable tools for analyzing the direct modulation of the immune system by such bacteria. Indeed, when such mice are intraperitoneally immunized with an antigen plus adjuvant, more antigen-specific antibodies are produced in the serum of GF mice than in that of specific-pathogen free (SPF) animals [9,10]. In addition, it has been reported that oral administration of various antigens prior to immunization with those same antigens induces oral tolerance in conventional (CV) mice but not in GF mice [1,9,11].…”

“…One hypothesis for the dysregulation of the induction of oral tolerance or allergic sensitization in GF 0165-2478/$ -see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.imlet.2010.05.007 mice is that there is a Th2-skewed immune response in these animals [9,10]. It has also been suggested that the reduction in T cells observed in Peyer's patches (PP) [1] and the impaired function of regulatory T cells in mesenteric lymph nodes (MLN) [11] contribute to the impaired induction of oral tolerance in GF mice.…”

Pathophysiology of Food Allergy

“…In mice, experiments using germ-free or antibiotic-treated mice have demonstrated an increased food-allergen sensitivity, elevated serum-specific IgE, and increased levels of circulating basophils. 54,55 In humans, differences in the intestinal flora of allergic versus nonallergic children have been noted. 56 Investigators have identified certain microbes that promote the development of Tregs and certain microbes that promote the skewing toward allergic sensitization.…”

Gut microbes and adverse food reactions: Focus on gluten related disorders

“…41 Many recent studies have suggested that the microbiota may be a disease promoting factor in food intolerances or sensitivities. Evidence from animal models show that germ-free mice are more susceptible to oral sensitization to cow's milk protein, 42,43 and OVA-induced allergy. 44 Oral sensitization to OVA led to altered intestinal microbial composition in genetically susceptible mice, which was not evident in wild-type (WT) mice.…”