Chronic activation of the epithelial immune system of the fruit fly's salivary glands has a negative effect on organismal growth and induces a peculiar set of target genes

Epithelial and especially mucosal immunity represents the first line of defence against the plethora of potential pathogens trying to invade via the gastrointestinal tract. The salivary glands of the fruit fly are an indispensable part of the gastrointestinal tract, but their contribution to the mucosal immunity has almost completely been neglected. Our major goal was to elucidate if the fly's salivary glands are able to mount an immune response and what the major characteristics of this immune response are. Ectopic activiation of the Immune deficiency pathway in the larval salivary glands using the Gal4/UAS-system of Brand and Perrimon. The activation was induced by the overexpression of the pattern recognition receptor PGRP-LCx using a driver line which was specific for the salivary glands.In general four replicates were performed including dye-swaps in two-colour arrays.