Cellular Infiltration and Cytokine Expression Correlate with Fistulizing State in Crohn's Disease

The purpose of this study was to determine the degree of infiltration of different cell subpopulations (tissue dendritic macrophages, T-helper cells, cytotoxic T lymphocytes, monocytes, neutrophils, and B cells) and the expression of the cytokines interleukin-12 (IL-12) and tumor necrosis factor alpha (TNF-α) in inflamed and noninflamed resected tissues from Crohn's disease (CD) and non-CD patients. Twenty-one resected full-thickness intestinal tissue specimens representing 13 subjects (8 CD and 5 non-CD patients) were included in this study. Sections of 20 μm in thickness were cut and then stained using immunohistochemistry. The sections were analyzed using confocal laser scanning microscopy (CLSM). Patterns of staining for inflamed CD and noninflamed CD tissues versus non-CD tissues demonstrated significant differences in the macrophage and T-helper subpopulations. Surprisingly, the T-helper subset was decreased significantly in the inflamed CD sections compared to the noninflamed CD and non-CD sections. The staining patterns also suggested differences in the expression of both IL-12 and TNF-α between the groups, with cytokine overexpression directly relating to the fistulizing state in CD patients. Cytokine expression is upregulated in chronic CD patients; therefore, the degree of inflammation and tissue damage in CD is dependent on the expression of specific cytokines within the tissue. Differentiation of cell subpopulations may be important for establishing a direct relationship with each state of CD (inflammatory, stricturing, and fistulizing states).