In this study, mediators of inflammation were characterized in colonic and terminal ileum mucosa from subjects with ulcerative colitis. We considered the role of two different chemotactic factors (interleukin-8 and leukotriene B4) and of myeloperoxidase in the pathology of inflammatory bowel disease. Serial biopsy specimens were taken at different sites, washed in 0.02 M phosphate/saline buffer, homogenized, and then sonically disrupted. In both the proximal and distal regions of the colonic mucosa of ulcerative colitis patients, there was a more than 10-fold increase in interleukin-8 levels over that in control subjects (> 300 pg/mg protein vs. 30 pg/mg protein in controls, p < or = 0.01). However, terminal ileum levels of interleukin-8 were the same in ulcerative colitis and control groups (150 pg/mg protein). There was also a 3- to 5-fold increase in leukotriene B4 levels and a several-fold increase in myeloperoxidase levels throughout the colonic mucosa in patients with ulcerative colitis. This study demonstrates that 1) interleukin-8 may have an immunoregulatory role in the pathogenesis of inflammatory bowel disease, and 2) interleukin-8, myeloperoxidase, and leukotriene B4 may be useful markers for the biochemical identification of inflammatory bowel disease.