EVALUATION AND MEASUREMENT OF COBALT-60 GAMMA-RAY FOR THE BLOOD LYMPHOCYTES INACTIVATION

Transfusion associated graft versus host disease(GVHD) is a serious clinical complication that occurs in some cases after blood and blood products transfusion. The mortality ratio of this disorder is very high and in over 90% of cases lead to patients’ death. The procedure routinely used to inhibit GVHD is inactivation of donor blood lymphocytes and prevention of their proliferation in recipients. Gamma radiation is currently the only recommended method for GVHD prevention. In spite of vast studies in this field,effective dose for completely inactivation of lymphocytes is not known. In this study, the effect of γ-ray of teletherapy cobalt machine (mean energy of γ-ray is 1.25 MeV) on lymphocytes viability and proliferation was investigated. Lymphocytes were isolated from normal donor blood and irradiated at doses ranging from 500 to 40000 cGy of γ-ray. Cell viability after 24 and 48 hours in each dose step, was evaluated by colorimetric tetrazolium method (MTT). MTT and BrdU assays were used to assess the response of lymphocytes proliferation with PHA mitogen. By inceasing dose of gamma radiation, cell viability and proliferation function were decreased. In high level of dose and longer time of culture, this effect was observed well. Do value estimation by MTT colorimetric assay was 1.44 Gy. Statistical analysis by t-test method was not significant (P>0.05) and decrease in irradiated cell proliferation was similar for two assays. By paying attention to decreased proliferative function in high level of irradiation, the range of 3000-4000 cGy of γ-ray is recommended for blood lymphocytes inactivation.