AN INTERLEUKIN 12-RELATED CYTOKINE IS UP-REGULATED IN ULCERATIVE-COLITIS BUT NOT IN CROHNS-DISEASE

Background & Aims: interleukin 12 (IL-12) is a heterodimeric, macropha ge-derived cytokine that is elevated in Crohn's disease (CD). Epstein- Barr virus-induced gene 3 (EBI3) is a recently characterized human gly coprotein that is homologous to the 40-kilodalton chain of IL-12 and f orms a heterodimer with the 35-kilodalton chain of IL-12. We investiga ted the expression of EBI3 in colonic mucosa of normal control subject s, patients with ulcerative colitis (UC), and patients with CD. Method s: Colonic tissue was analyzed for messenger RNA (mRNA) expression by quantitative polymerase chain reaction and for protein expression by i mmunohistology and Western blotting. Results: EBI3 mRNA was present in intestinal biopsy specimens from healthy subjects and patients with C D but was elevated only in active UC. EBI3 levels in UC specimens corr elated with histological scores of activity and T-cell infiltration. E BI3-positive cells that had a shape consistent with that of macrophage s were identified in the lamina propria, and protein was detected by W estern blotting. Conclusions: EBI3 is a novel IL-12-related cytokine t hat is expressed by macrophage-like cells in normal intestine and CD a nd has enhanced expression in active UC but not in active CD.