Serum interleukin-8 in inflammatory bowel disease.

To investigate the relationship between serum concentrations of interleukin-8 (IL-8) and disease activity in inflammatory bowel disease, serum IL-8 concentrations were measured by enzyme-linked immunosorbent assay (ELISA) in 93 patients. Interleukin-8 levels were compared with plasma interleukin-6 (IL-6) levels in 80 of these patients. Interleukin-8 levels were also measured in ten patients with active Crohn's disease, before and after treatment with a defined formula polymeric diet. Of these patients, 70 out of 93 IL-8 concentrations were below the detection limit of the assay. Levels were higher in patients with active ulcerative colitis (median < 20 pg/mL, 75th centile value = 190) compared with inactive disease (median and 75th centile value < 20; P < 0.05). Interleukin-8 concentrations correlated with a combined score for disease severity and extent (P = 0.01). Thirty-eight per cent (8/20) of patients with active Crohn's disease also had high levels of IL-8 but there was no significant difference between active and inactive disease. There was no correlation between serum IL-8 and plasma IL-6; on the contrary, very few patients had raised blood levels of both cytokines. In the diet treated group, serum IL-8 fell significantly after treatment (median = 37 pg/mL, range < 20-4615 before treatment, median < 20, range < 20-104 after treatment; P = 0.03). The results suggest that although IL-8 may be involved in the inflammatory process in inflammatory bowel disease, it is a poor marker of disease activity.