Altered cellular response to UV irradiation in a patient affected by premature ageing.

An abnormal response to UV-irradiation was found in a patient affected by precocious senescence. A decreased level of unscheduled DNA synthesis (UDS) was present in 60% of Go lymphocytes and in fibroblasts after the fifth culture passage. Hypersensitivity of lymphocytes to UV-light was indicated also by a decreased rate of DNA synthesis after mitogen stimulation. The results of this study indicate that the defect which determines the premature ageing influences the capacity to repair UV-induced DNA damage.