Microbial regulation of allergic responses to food

Abstract

The incidence of food allergy in developed countries is rising at a rate that cannot be attributed to genetic variation alone. In this review we discuss the environmental factors that may contribute to the increasing prevalence of potentially fatal anaphylactic responses to food. Decreased exposure to enteric infections due to advances in vaccination and sanitation, along with the adoption of high-fat (Western) diets, antibiotic use, Caesarian birth, and formula feeding of infants, have all been implicated in altering the enteric microbiome away from its ancestral state. This collection of resident commensal microbes performs many important physiological functions and plays a central role in the development of the immune system. We hypothesize that alterations in the microbiome interfere with immune system maturation, resulting in impairment of IgA production, reduced abundance of regulatory T cells, and Th2-skewing of baseline immune responses which drive aberrant responses to innocuous (food) antigens.

Regulatory T cells in allergic diseases

“…Emerging studies emphasize the interaction of environmental factors, including diet, antibiotic usage and others, with components of the immune system, affecting their function and modify the outcome of the immune response 8 . They also support the idea that the commensal bacteria play a central role in the regulation of allergic diseases and that they dynamically interact with host genetic background and environmental factors to promote or disrupt oral tolerance 9-11 . Genetic and immunological evidence also reinforce the idea of a pivotal role for regulatory T (T Reg ) cells in promoting tolerance to allergens and preventing allergic disorder 12-16 .…”

Cellular and molecular pathways through which commensal bacteria modulate sensitization to dietary antigens

“…The composition of the microbiota is dynamic and strongly influenced by the external environment. It can be dramatically altered by diet, antibiotic use, mode of birth, formula feeding, vaccination and exposure to pathogens (reviewed in [3]). It is now hypothesized that changes in the composition of the microbiota, called dysbiosis, lead to a loss of protective bacterial signals, which can cause both allergic and inflammatory disease.…”

Commensal bacteria protect against food allergen sensitization

“…Rising disease prevalence over a short period cannot be explained by genetic variation alone, renewing interest in the role of the environment in shaping allergic sensitization to food (2,3). First proposed more than 20 years ago, the hygiene hypothesis suggested that societal efforts to reduce exposure to infectious microbes early in life have deprived the immune system of immunoregulatory stimulation necessary for protection against allergic disease (4).…”