The microbial origins of food allergy.

Food allergy (FA) is a significant public health issue, propelled by its rapidly increasing prevalence. Its sharp rise into prominence has focused attention on causative environmental factors and their interplay with the immune system in disease pathogenesis. In that regard, there is now substantial evidence that alterations in the gut microbiome early in life imprint the host gut mucosal immunity and may play a critical role in precipitating FA. These changes may impact key steps in the development of the infant gut microbiome, including its shaping by maternal factors and upon the introduction of solid food (the weaning reaction). These early-life changes may have long-range effects on host immunity that manifest later in time as disease pathology. Experimental studies have shown that resetting the host intestinal immune responses by treatment with either a healthy fecal microbiota transplantation or defined commensal bacterial taxa can prevent or treat FA. The mechanisms by which these interventions suppress FA include restoration of gut immune regulatory checkpoints, notably the retinoic orphan receptor gamma T regulatory T cells, the epithelial barrier, and healthy immunoglobulin A responses to the gut commensals. These findings inform human studies currently in progress that evaluate the role of microbial therapies in FA.