Purpose:A significant reduction in the incidence of radiation-induced oral mucositis by Palifermin has been demonstrated. The underlying mechanisms, however, remain unclear. The aim of the present study was to assess the effect of Palifermin on inflammatory and immune processes during fractionated irradiation in mouse tongue. Materials and methods:Fractionated irradiation, 10×3Gy in two weeks, was given to the snout of the animals. In one group, a single injection of Palifermin (15mg/kg, s.c.) was given one day before the onset of radiotherapy. Groups of mice (n=3) were sacrificed from day 116 after the start of irradiation. Vasodilatation, endothelial expression of intercellular adhesion molecule 1 (ICAM-1) and the number of CD105-positive (CD105⁺) macrophages were assessed. Results:Compared to untreated control tissue, irradiation resulted in a significant vasodilatation and an increase in endothelial ICAM-1 staining intensity during the entire study period. Additionally, a significant increase in the number of CD105⁺ macrophages was detected. In contrast, with Palifermin treatment before irradiation, none of these changes were found within the first 10 days. Conclusion:Palifermin pre-treatment resulted in a long-lasting inhibition of radiation-induced inflammatory and immune changes in mouse tongue. This may contribute to the protective effect of this growth factor.