Microbiota and Type 2 immune responses.

The trillions of microbes that colonize mucosal surfaces are critical for educating the immune system and microbial-derived signals continually shape and set the tone of immune responses. Although Type 2 immune responses are important for mediating protection from helminth infection they also underlie atopy and allergy. Microbes modulate Type 2 immune responses through effects on Type 2 cytokines, dendritic cells and regulatory T cells. Microbial colonization in the gut, the lung and the skin during an early and critical time period in immune development appears to be of particular importance for tolerance induction and regulation of aberrant Type 2 immune responses. This is illustrated by studies showing microbial alterations in early life that are associated with allergies later in life.