Hypersensitivity of lymphocytes from chronic lymphocytic leukemia patientsto ultraviolet light-C radiation

Chronic lymphocytic leukemia (CLL) results in the accumulation of mature im munologically defective lymphocytes in G0 phase. Lymphocytes from CLL patie nts were exposed to UVC radiation to determine whether these cells are capa ble of undergoing apoptosis, as a response to DNA damage. Lymphocytes from CLL patients were found to be readily killed by ultraviolet light-C (UVC) r adiation. Cells from healthy donors were minimally affected by doses of UVC ten times higher then those which caused dramatic drops in the metabolism of CU cells. At four hours after irradiation, the reduction of 3-(4,5-dimet hylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) had dropped by 50% for CLL cells exposed to a dose of 10 J/m(2). In contrast, there was no sig nificant drop for healthy cells exposed to 100 J/m(2). Cell death was measu red by trypan blue staining, flow cytometry of Annexin V-PZ stained cells, and Wright staining. By 24 hours after irradiation, significant amounts of cell death were observed in CLL cells at doses which had no significant eff ects on viability of healthy lymphocytes. The extreme sensitivity of CLL ly mphocytes to WC indicates that phototherapy should be explored as a potenti al treatment for this neoplasm.