Soluble levels of CD-95, CD 95-L and various cytokines after exposing human leukocytes to ionizing radiation.

Background: Local radiotherapy induces systemic effects and influences the immune system. Some of these effects can hardly be explained by direct cellular reactions, but might be triggered by humoral factors.
Materials and Methods: In seminoma patients we measured the influence of radiotherapy on various lymphocyte subsets by FACS-analysis. We analysed the release of cytokines, CD95 (Apo-1/Fas) and CD 95-L (Fas-Ligand) of human blood cells after exposure to ionizing radiation in vitro and in vivo by ELISA-technique.
Results: Although radiation leads to a differential and sustained reduction of all lymphocytes subsets in vivo no increase of cytokine levels, or of levels of CD95 or CD 95-L could be detected by ELISA in vivo or in vitro. On the contrary mitogen-induced cytokine production in vitro was inhibited by radiation.
Conclusions: Local radiation induced a significant systemic decrease of all lymphocyte subsets, but neither a systemic release of cell death mediators like CD95 or various cytokines, nor a release in the extracellular space in vitro were detectable.