In vitro radiosensitivity of peripheral blood lymphocytes in multiple sclerosis patients.

PURPOSE: To assess the in vitro radiosensitivity of peripheral blood lymphocytes of secondary progressive multiple sclerosis (MS) patients in comparison to healthy individuals.
MATERIAL AND METHODS: Radiosensitivity of MS patients lymphocytes to in vitro irradiation of 2 Gy 60Co gamma-rays was studied in whole blood cultures and separated peripheral blood mononuclear cell (PBMC) cultures. Chromosomal radiosensitivity was investigated by means of the G0-micronucleus (MN) assay. The radio-induction of micronuclei was also studied in separated subsets of CD4+ (helper) and CD8+ (suppressor) T cells. Apoptosis was analysed in PBMC cultures using fluorescence microscopy techniques.
RESULTS: The spontaneous MN induction was significantly higher in MS patients compared to healthy controls for whole blood and PBMC cultures. After gamma-irradiation of whole blood cultures no difference in radiosensitivity was observed between patients and controls for MN induction. In irradiated PBMC cultures, the CD4+ lymphocytes of MS patients were less radiosensitive compared to healthy controls and this more resistant behaviour increased with increasing illness duration. Radiation induced apoptosis in G0 lymphocytes of MS patients was lower than in controls.
CONCLUSION: After gamma irradiation, a radioresistant behaviour in PBMC cultures of MS patients was revealed. This radioresistant behaviour was expressed by lower MN induction in CD4+ lymphocytes and by lower apoptosis induction in G0 PBMC cultures and may point to an adaptive response. The higher radiation response in whole blood cultures compared to PBMC cultures was significantly more pronounced in MS patients, suggesting special characteristics of the whole blood environment associated with this pathology.