THE ROLE OF CYTOKINES IN THE DEVELOPMENT OF NORMAL-TISSUE REACTIONS AFTER RADIOTHERAPY

Background: Cytokines are important for signaling between cells and ti ssues and constitute a humoral component of the response of cells and tissues to radiotherapy. Although several cytokines have been implicat ed in mediating radiation-induced reactions of normal tissues, the mec hanisms are only beginning to be elucidated. Methods: Published data o n radiation-induced cytokine expression from cell culture, experimenta l and clinical studies are reviewed. Current models of cytokine-mediat ed multicellular interactions in radiation-induced reactions of the lu ng, skin and intestinal mucosa are presented. Results and Conclusion: The major cytokines in the radiation response of non-hemopoietic tissu es include IL-6, IL-1, TNF alpha and TGF beta. Different cell types in teract via cytokines in a complex network of effector and receptor cel ls, including inflammatory cells, tissue-specific functional cells and fibroblasts. TGF beta appears to be of particular importance in the d evelopment of late reactions such as fibrosis.