**4.1 Biochemical signs of inflammation**

A typical western blot for MPO, NADPH oxidase, iNOS, nitrotyrosine, IL-1β and IL-6 are shown in figure 1A-F. A significant increase of MPO protein expression (ERD, p=0.0001, red streak, p=0.005) as well as a significant increase of nitrotyrosine expression (ERD, p=0.05, red streak, p=0.05) was detected in ERD-patients compared healthy controls using western blotting (figure 2A and D). No significant differences in expression of NADPH oxidase, iNOS (figure 2B and C), IL1β or IL6 were detected (data not shown). However at gene expression level using rt-PCR technique, IL6 was significantly increased in ERD-patients (p=0.01), whereas there was no difference in IL1β between the groups at gene level (data not shown).

Immunohistochemistry performed on endoscopically retrieved mucosal biopsies revealed a distinct staining for MPO in epithelial lymphocytes and also weak staining in the squamous epithelial cells (figure 3 A). Immunostaining for NADPH oxidase was detected in basal layer of the epithelium and papillae (figure 3B), whereas iNOS was localized mainly to the upper and mid-zone layer in the epithelium (figure 3C). Nitrotyrosin immunoreactivity was detected in the epithelium in both the basal and in the upper layer (figure 3D).
