The four most highly up-regulated genes in the inflamed areas, compared to the non-inflamed areas, were IGLL5, SSR4, MZB1 and XBP1. The genes IGLL5 and MZB1 have previously been reported as up-regulated in gingival tissue from patients with aggressive or chronic periodontitis, compared to healthy controls19,20. This evidence concerns the gene XBP1 and chronic periodontitis.