The expression of IL-12 p40 and its homologue, Epstein-Barr virus-induced gene 3, in inflammatory bowel disease

BACKGROUND: It has recently been suggested that Crohn's Disease (CD) is associated with an exaggerated T helper 1 cytokine response as manifest by increased production of interleukin-12 (IL-12) and interferon-gamma (IFN-gamma). Epstein-Barr virus-induced gene 3 (EBI3) encodes a 34-kDa glycoprotein that is 27% identical to the p40 unit of IL-12 and has recently been reported to be up-regulated in ulcerative colitis (UC). AIM: To determine whether mucosal expression of IL-12 p40 or EBI3 correlates with inflammatory bowel disease (IBD). PATIENTS/METHODS: mRNA expression in colonic mucosa from patients with UC, Crohn's disease (CD) and non-IBD controls was measured by reverse-transcribed real-time polymerase chain reaction (PCR). RESULTS: EBI3 was significantly increased in both involved and uninvolved colonic mucosa in patients with UC. Although IL-12 p40 was increased in some patients with CD relative to non-IBD controls, the increase was not statistically significant. However, 5-aminosalicylic acid (5-ASA) use was significantly correlated with reduced IL-12 p40 levels in the patients with CD, but not in UC cases. A similar reduction was not seen in 5-ASA-treated UC patients. CONCLUSION: IL-12 p40 expression in CD is heterogeneous. In contrast, expression of the IL-12 p40 homologue, EBI3, is up-regulated in nearly all UC cases and in a subset of CD.