Fig. 3.

A hypothetical model for how microbiota, based on genetic and environmental influences, may contribute to type 1 diabetes. In this model, the end result is the autoimmune destruction of pancreatic beta cells. However, for this to occur, there must be significant variations from the normal setting of development (i.e. healthy microbiota). Here, molecules produced by a given microbiota network, in response to a combination of environmental exposures and genetic susceptibility, influence proneness to type 1 diabetes. In a healthy microbiome, there is an optimal proportion of organisms, which provide signals to the developing immune system (controlled by genetic susceptibility and environmental events) that lead to a balance in immune regulatory activities that avoid, or provide susceptibility to, type 1 diabetes. At present, the list of potential means by which environment can influence microbiota development is large; with a variety of putative (i.e. unproven but previously noted) candidates listed. T1D, type 1 diabetes