**2. Materials and methods**

### **2.1 Animals**

Swiss albino mice, were kept for a week under environmentally controlled conditions with access to standard food and water. Recommendations of the ethical Committee for the Purpose of Control and Supervision of Experiments on Animals (CPCSEA) instituted by the Animal Welfare Division of the Government of India were followed.

## **2.2 Irradiation**

 Gamma cell facility of Bhabha Atomic Research Centre, Trombay was used for irradiation. Whole body irradiation to mice was given to unanesthetized animals, which were kept in well-ventilated Perspex boxes and was exposed at a dose rate of 1 Gy/min. *Ex vivo* irradiation of human peripheral leukocytes was done in Junior Theratron unit with a dose rate of approximately 0.4 Gy/min. Chemicals were obtained from Sigma Chemicals (St. Louis, Missouri) and purchased from Merck India Ltd., Mumbai.
