DNA-microarray analyses of the transcriptional changes within the salivary glands that occur following chronic activation of the IMD-pathway in these cells only. Cohorts of genes were identified that are either upregulated (additional file 3) or downregulated (additional file 4). Only those genes are included, where these differences are greater than twofold and the differences are statistically significant (evaluated with the SAM software package). Gene ontology analyses were performed with these cohorts of genes and compared to the complete set of Drosophila genes using the Fatigo software tool  revealed some statistically significant differences (A, top). Comparison of the set of upregulated genes with the complete set of Drosophila genes revealed some groups of genes that are highly enriched in this cohort (top). In addition, KEGG pathway analysis identified the oxidative phosphorylation as being significantly enriched in this cohort of genes. The cohort of downregulated genes includes two functional groups, being significantly different from the total number of genes (A, bottom). The corresponding lists are summarized in additional file 5. Venn diagram analyses showed that only a small minority of the up- or downregulated genes are classical immune relevant genes (additional file 1). Similarly, the intersection with those genes that are regulated upon an experimental infection with the insect pathogen Erwinia carotovora in two different epithelial tissues are rather small (B). In addition, small groups of genes are identical if compared with genes upregulated in the trachea following the same experimental manipulation (IMD-activation) and with susceptibility genes for gut infection (C), SG IMD up means the cohort of genes upregulated following IMD activation (see additional files 1, 2, 3, 4 and 5), gut and trachea Erwinia up means the groups of genes upregulated in the trachea or the gut following infection with Erwinia carotovora [9, 27], trachea IMD up means the list of genes upregulated following IMD activation in the larval trachea , gut infection susceptibility means those genes that have been identified as having an influence on oral infection in a genome wide RNAi screen .