Mast Cells: Linking Allergy and Microbiome

It is now widely accepted that there is a relationship between the microbiota and development and severity of allergic disease. In investigating the mechanisms underlying microbiota modulation of allergic disease the focus has been on the induction phase of the disease; alterations in the phenotype and function of antigen presenting cells, induction of regulatory T cells and shifts in Th1/Th2 balance. However there is evidence that microbes can influence the effector phase of allergic disease. The position of mast cells on the frontline of defence against pathogens also suggests they may play an important role in fostering the host-microbiome relationship and maintaining the dynamic ecosystem of the super-organism. There is emerging evidence that the mast cell plays an important role in microbiota host communication and in particular, that certain non-pathogenic microbes and components of the microbiota can influence the development and severity of allergic disease by modulating mast cell function. Furthermore, it appears that different non-pathogenic bacteria can utilize distinct mechanisms to stabilize mast cells, acting locally though direct interaction with the mast cell at mucosal sites or attenuating systemic mast cell dependent responses, likely thorough indirect signalling mechanisms. Further investigation of mast cell regulation by non-pathogenic or commensal bacteria will likely lead to a greater understanding of host microbiota interaction and the role of the microbiome in development of allergy and other diseases.