Interferon γ Expressing Mucosal Cells in Pediatric Chronic Inflammatory Bowel Disease

The pathogenesis of Crohn's disease (CD) and ulcerative colitis (UC) is multifactorial and includes aberrations in the composition of gastrointestinal mucosal inflammatory cells. Accurate identification of CD and UC is important as treatment and prognosis differs; however, CD and UC may be difficult to differentiate. Interferon γ (IFNγ) expression appears to be increased in ileal mucosa from CD patients, implying that IFNγ could be a diagnostically useful marker to differentiate CD from UC. This study uses automated assessment of IFNγ immunohistochemical expression in archival GI mucosal biopsies from stomach, duodenum, terminal ileum, and colon in a pediatric population to address this possibility. IFNγ positive mucosal cells are increased in the colon in both CD and UC compared to normal colon and in the ileum of CD compared to normal and UC. The abundance of IFNγ positive cells is not correlated with the presence of active inflammation, indicating that active inflammation is not responsible for the variance in abundance of IFNγ positive cells between cohorts and sites. Overlap between CD, UC, and normal suggests that IFNγ immunohistochemistry may only be clinically useful in select situations such as undetermined inflammatory bowel disease and additional study in these areas is warranted.