Peripheral Blood Mononuclear Cells Promote Intestinal Epithelial Restitution in Vitro through an Interleukin-2/Interferon-gamma-Dependent Pathway

Acute intestinal mucosal inflammation is associated with recruitment of peripheral blood mononuclear cells (PBMN) into the mucosa and migration across the epithelium. It has recently been shown that several PBMN-derived cytokines, including transforming growth factor-beta (TGF-beta), tumor necrosis factor-alpha (TNF-alpha), interleukin-2 (IL-2), and interferon-gamma (IFN-gamma) may modify intestinal epithelial cell function, resulting in rapid improvement of wound repair. Our aim was to characterize the modulating effects of PBMN on intestinal epithelial restitution, the initial step of wound healing. PBMN were separated from whole blood, obtained from healthy volunteers, by using a density gradient. The effect of PBMN on intestinal epithelial restitution was assessed by using an in vitro coculture wounding model with non-transformed small-intestinal epithelial IEC-6 cells. Coculture of PBMN caused a significant enhancement of epithelial cell restitution in vitro. The modulatory effects of PBMN could be significantly blocked by adding immunoneutralizing anti-IL-2 or anti-IFN-gamma to the culture media, suggesting that PBMN may modulate intestinal epithelial migration through an IL-2- and IFN-gamma-dependent pathway. In contrast, PBMN-induced stimulation of intestinal epithelial restitution was not influenced by addition of anti-TGF-beta or anti-TNF-alpha, suggesting that these cytokines are not critical for the modulation of restitution by PBMN. These findings suggest that PBMN may promote intestinal epithelial wound repair by enhancing restitution through secretion of various cytokines, among them IL-2 and IFN-gamma, which are abundantly expressed in the course of several inflammatory diseases of the gut.