BackgroundInterleukin-11 (IL-11) is a well known anti-inflammatory cytokine that is associated with cell growth, and also participates in limiting X-ray irradiation induced intestinal mucosal injury. <br> AimThis study was performed to elucidate the effect of IL-11 in X-ray irradiated normal intestinal epithelial cells.<br> Materials and Methods Recombinant human IL-11 (rhIL-11) treated IEC-18 cells, normal rat ileum epithelial cells, were irradiated by X-ray and then examined for the cell viability. To evaluate the X-ray irradiation injury, we used trypan blue staining to detect the dead cells.<br> Results The viability of X-ray irradiated IEC-18 cells was up-regulated by rhIL-11 treatment and also resulted in the activation of p90 ribosomal S6 kinase (p90RSK) and S6 ribosomal protein (S6Rp). Wortmannin, a specific inhibitor of PI3K, suppressed the activation of S6Rp in rhIL-11 treated IEC-18 cells, and decreased the up-regulation of viability by rhIL-11 treatment in X-ray irradiated IEC-18 cells. We also performed TUNEL assay to estimate the rate of apoptosis in X-ray induced cell death. There was no difference in the result between in trypan blue staining and TUNEL assay. Further, rhIL-11 down-regulated the expression of cleaved caspase-3 in X-ray irradiated IEC-18 cells. ConclusionThese results suggest that rhIL-11 may play an important role to the protection of intesinal epithelial cell from X-ray irradiation injury.